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PXA-1000 User Manual

1. Exit Check that the optical power is at an appropriate level Power 1mW or so usually works well If the power is too high or too low change the attenuator setting range 0 to 30 dB and check the power again 6 Set the amplifier gain Low gain is recommended for most applications High gain can be used for fiber systems with very high loss 7 Click the Run button at the bottom of the screen or press the F2 function key on the computer keyboard to start the measurement During measurement the message Measuring birefringence will be displayed in the message box at the bottom left of the screen 8 When the measurement is finished the message Birefringence measurement is done is displayed and the dialog box shown below appears Enter the length of the PM fiber and click OK Input the length of fiber 1 meter 9 After the fiber length is entered the birefringence will be calculated Go to the Fiber tab on the right side of the screen to view the data The Fiber Birefringence box shows the fiber length measured delay between input and output connectors measured birefringence and estimated beat length The user can change the fiber length used for birefringence calculation by selecting the value in the fiber length box and typing in a new value then clicking the Recalculate button On the plot Marker 1 and Marker 2 indicate the PXA 1000 input and output conn
2. Atak measurement is done PER Calibration Recalculate M S nianze RY Et Click Set Marki as Zero Position at the bottom of the Setup tab 5 You will be prompted for a password reference Enter the password and click OK The Marker 1 position will be set as the system x PXA 1000 User Guide PER Reference General Photonics can provide an optional O dB PER calibration artifact for users to verify and if necessary re establish the PXA 1000 s PER reference The procedures are as follows PER Verification 1 Connect the 0 dB PER artifact as the DUT Make sure connectors are clean connections are good and fibers are stationary 2 Run the PER measurement If the measured system PER is lt 0 2 dB the PXA 1000 does not require PER calibration Re establish the PER reference 1 Click PER Calibration at the bottom of the Setup tab PER Calibration Set Markl As Zero Position 2 You will be prompted for a password Please Input Password 3 Enter the password and click OK You will be prompted to connect the 0 dB PER artifact Please connect PER 0 Calibration Cable to input amp output of PAA 1000 4 Connect the 0 dB PER artifact as the DUT Make sure connectors are clean connections are good and fibers are stationary Click OK 5 The PXA 1000 will perform a measurement and recalibrate its PER reference When it is finished the progress bar and messa
3. Garcons Displays removes cursor 1 When the cursor is present its coordinates on the active curve selected at top right of screen are displayed next to it Displays removes cursor 2 When the cursor is present its coordinates on the active curve selected at top right of screen are displayed next to it Options to insert or remove markers 1 and 2 The selected marker is Mark inserted at the active cursor s position Marker coordinates are displayed in the Curve Analysis tab on the right of the screen Note Cursor must be on screen to insert marker GP UM PXA 1000 V21 Page 16 of 68 PXA 1000 User Guide Curve options include Curves Copy one trace to another Clear one or more traces Display Display or hide one or more curves Sets x position of active cursor as x reference zero point for active Set X position of active cursor as X reference for trace B Sets y position of active cursor as y reference value set by the system for active trace Set Y position of active cursor as Y reference for trace B Measured optical power at interferometer input DUT output Power Monitor 1 18717 mW Exit Measurement Setup Options tab on right side of screen Select curve A B or C for Setup Curve Curve Selection l acain 0 Fiber information or Events Measurement Xtalk Distribution Sets system to _ measure a crosstalk distribution aos Sets system to measure birefringence of Birefringence
4. 53 207 044 58 558 ee Quasi continuous couplings SF 187 287 190 191 192 193 55 207 330 58 169 56 207 669 58 874 l z fiber length v He Sorted by xtalk lt from hig ah to low Sorted by position from low to high PER including internal fibers 16 80 dB Estimated PER of Coil 45 52 dB ce ee Calculation method C Set fiber START 188 287 Set fiber END 194 224 Calculate PER of Coil O Peak Area v Exit Figure 31 a X talk measurement of a 340 meter long fiber coil Two significant sections labeled A and B are marked b Closeup view of section A showing both discrete and quasi continuous coupling peaks The table on the right of the screen lists the magnitudes of discrete x talk peaks larger than 60 dB Note that the shape and width of discrete x talk peaks are determined by the coherence function of the light source X talk caused by continuous polarization coupling This category includes polarization coupling that accumulates gradually over a section of fiber induced by a line stress or by fiber internal imperfections where the length of the affected section of fiber is comparable to or larger than the resolution of the measurement instrument as shown in the center section of Figure 30a The crosstalk measurement result of such continuous coupling is a broad dome with a width and shape determined mainly by the length of the section of fiber under stress as shown in Figure 30b In general crosstalk caused by
5. Each button has a status indicator in its upper left corner which turns green when that option is enabled Cursor Movement Tool graph only Allows cursor or marker to be dragged on the display Zoom dZooms in and out of the display Cursor i Panning Tool Picks up the plot and moves it movement tool around on the display The Zoom tool middle button on the graph palette allows the user to zoom in or out on the graph When the Zoom tool is clicked a pop up menu of zoom options appears This menu is shown below Zoom by selection rectangle Only the area in the a pa i selected rectangle is displayed Zoom by rectangle with zooming restricted to x data the y scale remains unchanged Zoom by rectangle with zooming restricted to y data the x scale remains unchanged Undo last zoom Resets the graph to its previous setting Zoom in about a point If you hold down the mouse on a specific point the graph continuously zooms in until you release the mouse button PIE Zoom out about a point If you hold down the mouse on a specific point the graph continuously zooms out until you release the mouse button GP UM PXA 1000 V21 Page 42 of 68 PXA 1000 User Guide Graph Scale Options Linear Crosstalk Ko a v O k O ua 100 125 225 242 156 Fiber Length w Delay lt Fiber Length Figure 23 Graph scale options The y axis parameter is always crosstalk or inte
6. multiple densely packed stress points spaced on the order of or less than the resolution of the instrument X talk caused by discrete polarization coupling points This category includes polarization coupling induced by a sharp stress a splice point or multiple stress splice points separated by distances much larger than the resolution of the measurement instrument as shown on the left side of Figure 30a These types of discrete coupling result in sharp distinct peaks in the x talk measurement trace with the width of the peak determined by the spatial resolution of the instrument as shown in Figure 30b For this type of coupling the peak x talk value for each coupling point conveys useful information The x talk values listed in the table at the right of Figure 31b result from such discrete coupling points GP UM PXA 1000 V21 Page 62 of 68 Crosstalk faenonst Dor tnciens Shed BFE 5 IIF ELFEDI Crosstalk 5 22 2012 12 33 22 PM Discrete couplings 42 30 peaks found Top 1 41 39 187 434 60 344 40 187 738 60 048 3940 Threshold 60 dB 43 41 189 446 58 891 a L A A 42 189 799 55 103 A 43 192 605 60 303 44 193 370 59 836 45 194 316 57 201 46 194 640 55 866 _ J r 47 196 742 60 326 Hr 48 198 085 59 336 A VN 49 198 777 _ 59 967 N i J j 50 199 423 58 380 51 204 420 59 744 VY 52 206 601 60 297
7. Calibrates the system using a O dB PER Calibration Set Mark1 As Zero Position Position Curve Analysis tab on right side of screen o Setup Cure Analysis Fiber Events Cursor positions Marker positions Amplitude 0 0001 STDV Center Ut Bandwidth 0 089 Residue Gaussian Results Third Order Polynomial Moving Average Smoothing Method Third order polynomial Moving Average Set Marki as Zero Sets Marker 1 position as x reference 0 position for the system The top block summarizes the x coordinates and corresponding y coordinates on the selected curve of cursors 1 and 2 Y coordinates on other curves can be displayed by selecting another curve at the top of the screen The next block summarizes the x coordinates and corresponding y coordinates of markers 1 and 2 as well as the x and y distances between them Markers are placed on specific curves Displays the fit results with Gaussian fit x w O model a exp where a is the amplitude o is the standard deviation STDV and Xp is the center Bandwidth is the 3dB bandwidth of the Gaussian fit curve The fit residual is 1 N I defined by FO m Pa i 0 order polynomial intercept method Obtains a smooth curve using the moving average method yliJ yli y it 1 y it n n where n is the average number GP UM PXA 1000 V21 Page 18 of 68 PXA 1000 User Guide Moving Average Sets the average number for m
8. PM fiber Sets system to measure the coherence Coherence length length of an input light source Ran eeren Sets system to measure and display raw interference signal data vs delay Measures the system s polarization extinction ratio quick check for system wera Delay Scan Range Scan paree Set up scan a aa for variable delay line Start Position Position 0mm Omm by default default sateen Position Set end position depending on length of en or waveguide to be measured 2 Set attenuation _ internal VOA GP UM PXA 1000 V21 Page 17 of 68 Setup Cure Analysis Fiber Events SLD switch Xtalk Distribution Birefringence Coherence Length Raw Interference Stop Position 50 Attenuation An of PM fiber SLD ns PXA 1000 User Guide Software switch turns light source on or off Running a measurement will automatically turn on the light source Sets the amplifier gain to low or high When input optical power is low setting the amplifier gain to high will increase SNR and system measurement sensitivity The low gain setting is the default it works well for most measurements Sets the birefringence of PM fiber under test This value is used to calculate the positions of coupling points on the PM fiber To change the value click on the number and type in the desired value then press ENTER i System calibration functions Calibration may not be available to all users l
9. X talk peak of height between 15 and 40 dB from the X talk peak induced by the input connector zero position GP UM PXA 1000 V21 Page 56 of 68 PXA 1000 User Guide Appendices Appendix 1 0 Comparison of PXA 1000 to Traditional White Light Interferometer It is well known that only the two eigenpolarization modes HE and HE4 can propagate in polarization maintaining fiber HE is polarized along the slow axis and Hes along the fast axis of the fiber After traveling through a piece of PM fiber an input wave packet is split into a series of small wave packets separated in time because of the birefringence and mode coupling of the PM fiber This section describes a simple model to simulate the wave packets aligned to the slow and fast axes of the fiber Assume that the light input to the PM fiber has no fast axis component and that there are three coupling points x1 X2 and x3 along the fiber see Figure 28 It should be emphasized that light is coupled not only from the slow axis to the fast axis but also from the fast axis to the slow axis at each coupling point therefore the resulting wave packet series will include wave packets caused by multiple couplings Input wave packet polarized along slow axis x X X X Xout S13 S23 S12 Slow axis Optical path length fo fs fi fast D E N Optical path length PM fiber So Figure 28 Wave packet sequence generated by coupling between slow and fast axis Figure 2
10. changing measurement settings e g fiber length GP UM PXA 1000 V21 Page 19 of 68 PXA 1000 User Guide Events tab on right side of screen The Events tab provides a table summarizing the position and amplitude of all measured crosstalk peaks between the designated start and end points specified on the Fiber tab that exceed the user defined threshold and width settings Crosstalk peaks can be sorted by Sort by ve position or amplitude m Lists position and amplitude of all peaks Setup Curve Analysis Fiber Events Table between Marker 1 and Marker 2 that Sort by Position meet the threshold criteria Lists average crosstalk value calculated using peaks listed in the table Lists the maximum crosstalk from peaks listed in the table Saves data in peak table to a file Pave EVENS Saved data includes index position and amplitude of listed peaks Define threshold parameters for table Peak Detection listings To change a parameter select Parameters it type the new value and press ENTER The table will update automatically Threshold rejects peaks that are too small The peak detection function Threshold ignores any peak found whose fitted amplitude is less than the specified Xtalk Average 40 519 dB threshold Xtalk Maximum 19 232 a Width specifies the number of r consecutive data points to use in the quadratic least squares fit The width is Width coerced to a value greater
11. coupling during the winding process so as to remove the induced stress as it occurs The distributed polarization crosstalk analyzer PXA 1000 can reveal the location and magnitude of polarization coupling induced by both intrinsic and external stresses PXA 1000 System Schematic A B C Z Az An PM fier coil polarizer 45 deg alignment Y PM fiber Coupler S SLD T T E Mirrors og Digital AG i L a Amplifier PD Variable delay line lt H I Delay line control Figure 7 PXA 1000 system schematic GP UM PXA 1000 V21 Page 21 of 68 PXA 1000 User Guide As shown in Figure 7 the PXA 1000 system consists of three main parts light source interferometer and light detection processing circuit The light input to the DUT is linearly polarized and aligned to the slow axis of the PM fiber with a 30nm bandwidth and 1310nm or 1550nm center wavelength Its power can be adjusted by a variable optical attenuator VOA After passing through the DUT the light aligned to the fast and slow axes are mixed together through an analyzer generating interference peaks in a fiber based interferometer as the delay line is adjusted Distributed Polarization Crosstalk Measurement Principle slow axis force Fixed mirror fast axis A B 45 oriented polarizer Figure 8 Polarization crosstalk measurement principle As shown in Figure 8 when light enters the PM fiber at position A it has only one polarization component aligned to
12. detailed structure of quasi continuous couplings The cumulative x talk of the region between the two cursors is 26 46 dB Capabilities and limitations of the PXA 1000 The PXA 1000 can take crosstalk measurements at spatial intervals of about 4 6 mm much finer than the specified x talk resolution of the instrument on the order of 5 cm The exact Spacing between two adjacent data points is dependent on the birefringence of the fiber it is defined as the ratio of the delay resolution of the variable delay line used in the PXA 1000 to the PXA 1000 User Guide fiber birefringence However depending on the type of the polarization coupling a given x talk reading may not represent the true x talk value at that point in space as will be discussed below For X talk induced by discrete polarization coupling points the PXA 1000 is able to display the corresponding discrete x talk peaks to provide an accurate x talk value for each x talk peak and to list in a table all peak values above a defined threshold as shown in Figure 31b Note that each peak has a Gaussian shape corresponding to the coherence function of the light source used however only the peak value is meaningful and represents the x talk value at the point in space at which the x talk occurs The other points on the Gaussian curve are due to the light source s coherence function and do not represent meaningful x talk values for the corresponding points as shown in Figure 34 Not
13. of data points if the scale is set to fiber length 8 Click the Run button at the bottom of the screen or press the F2 function key on the computer keyboard to start the measurement During measurement the message Measuring xtalk will be displayed in the message box at the bottom left of the screen and the progress bar will indicate the status of the measurement Progress bar Message box 9 When measurement is finished the x talk vs position trace will be displayed see below The x position of the PXA light input connector which connects to the DUT output is zero on the plot Marker 1 To the left of that is a peak corresponding to an internal input reference point Marker 2 is placed at the PXA 1000 light output connector DUT in To the right of that is a peak corresponding to an internal output reference point Section 3 5 provides more details on analysis of the measured results GP UM PXA 1000 V21 Page 25 of 68 i I PXA 1000 vi n Crosstalk rs cua fase per Curve C etup urve Analysis vents Fitting nae connector Smooth 4 Output connector PER Including Internal Fiber 16 86 GES aNput gence Estimated PER of FUT 35 Cursor 1 62 38 Set Fiber START 0 Cursor 2 Set Fiber END 2 98196 Crosstalk Marks Calculation Method Curves Peak Area Display Noise floor Calculate PER of FUT i i Length of Fiber m NaN LAN J y LA w Da S
14. test to a PM pigtailed polarizer then connect the polarizer s PM output to the PXA 1000 s input connector 2 On the measurement information section on the right side of the screen select the curve A B or C on which to display measured data setup Curve Analysis Fiber Events talk Distribution Birefringence Coherence Length Raw Interference PER stop Position 50 Attenuation 5 SLD An of PM Fiber 3 81E 4 3 Select Coherence Length from the Measurement menu on the Setup tab 4 The coherence length measurement uses the default delay range settings 5 Check the light source power level a Click the Power Monitor button on the lower left side of the screen 1 18717 mW Exit Check that the optical power is at an appropriate level Power 1mW or so usually works well If the power is too high or too low change the power level of the light source if possible and check the power again 6 The coherence length measurement uses the default gain setting 7 Click the Run button at the bottom of the screen or press the F2 function key on the computer keyboard to start the measurement During measurement the message Coherence GP UM PXA 1000 V21 Page 36 of 68 length is being measured will be displayed in the message box at the bottom left of the screen and the status of the measurement will be indicated by the progress bar 8 When the measure
15. the software interface Individual features and functions are described in more detail in the following sections Function Keys bottom line of screen or corresponding keys on keyboard F1 About Displays the PolaX software version Features and interfaces described here correspond to PolaX v 2 2 F2 Run Executes the selected measurement F3 Load Loads saved data from file This function does not require connection to the PXA 1000 Resets system parameters to default values Delay Start 0mm Delay End 50mm i DerAUIt Attenuation 5 dB Gain Low An 5 x 10E 4 F6 Save Stores measured data to file F8 Initialize Delay line initialization resets position to zero Exits PXA 1000 control software PolaX F9 Exit The PXA 1000 will run through an exit sequence before exiting the program Do not disconnect or power down the instrument during this process Plot Options top left side of screen lt Plot Visible Cune A gt Common Plots p CuveB Color Curve C Line Style p Fitting ee Line Width gt Anti Aliased Bar Plots b Fill Base Line d Curve Titles Interpolation gt Point Style Curve Icons gray hidden X Scale b Y Scale a Export Export Data To Clipboard Export Data To Excel GP UM PXA 1000 V21 Page 15 of 68 PXA 1000 User Guide The plot options allow the user to customize curve appearance as well as to export data from the selected plot To cus
16. to prevent the zero order second order and most higher order interference signals from being generated as the delay line scans see Table 1 Consequently the PXA 1000 is able to achieve higher position measurement accuracy higher dynamic range and higher sensitivity than traditional white light interferometers Table 1 Interference peaks for PM fiber model shown in Figure 28 Traditional White light Interferometer PXA 1000 zero order interference So So S12S 12 S23 gt S23 S13 S43 None frofi hofa fsf Interference from first Sofi Sof Soof3 Sofi Sofa Soof3 order coupling Interference from So S12 Som 53 S09 S 13 second order coupling fi lt fo ficf3 foof3 Interference from higher S12f3 S129 S23 S12 gt S13 most higher order order coupling Si2ef2 Sif couplings are eliminated f3 lt gt S23 f3 lt gt S13 S23 gt S13 S230f2 Sa3hi Si30f2 Si30f1 GP UM PXA 1000 V21 Page 58 of 68 PXA 1000 User Guide Appendix 2 0 Spatial Resolution of PXA 1000 According to interference theory the full width at half maximum FWHM of an interference single envelope can be calculated by 2In2 A Ae lwm 0 44 9 m AA AA where A and AA are the center wavelength and spectral width respectively of the light source used for measurement Thus the spatial resolution of a PM fiber measurement can be obtained by ly WHM 9 resolution An where An is the birefringence of the PM fiber For example when Ap 1310n
17. 50 60 Hz Communication Interfaces USB 2 0 Display Laptop control computer supplied Software PolaX polarization X talk measurement program Identifies polarization X talk magnitude location Zoom in function X talk related calculations GP UM PXA 1000 V21 Page 55 of 68 PXA 1000 User Guide Physical and Environmental Dimensions 2U 34 19 rack mount size 14 L x 14 W x 3 5 H Fiber Type PM fiber Fiber Input Output Connectors FC PC narrow key standard Weight 13 5 Ib Operation temperature 10 to 50 C Storage Temperature 20 to 60 C Notes Specifications listed in table apply for standard 1550 or 1310nm operation at 235 C 1 Defined as the system noise displayed on the polarization X talk curve if the input power is disconnected during a measurement for which the DUT output power is gt 5dBm 2 Defined as the standard deviation of twenty successive measurements of the amplitude of an X talk peak between 15 and 40 cB 3 At 23 5 C Guaranteed by design and calibration in manufacturing process 4 Average speed for full length scan 5 Defined as the minimum resolvable distance between two polarization X talk points of equal amplitude based on Sparrow Criterion two peaks of equal height overlap at 3dB point resulting in a flat top curve and measured when the peaks are between 15 and 40 cB 6 Defined as the standard deviation of twenty successive measurements of the distance of an
18. 7 M J A J j i AM vi yo Fiber Length w lt Output connector Output reference generated by pigtailed polarizer just after SLD source Noise floor K N r urnag ha Ma hameas AN m v TA FE R WEAN FE R OF hs Le sr mF 6 BD i HY He AF FA Xtalk measurement is done Figure 25 Measurement example 1 3m PM patchcord PER Including Internal Fiber 16 86 Estimated PER of FUT 62 38 Set Fiber START 0 Set Fiber END 2 98196 Calculation Method Peak Area Calculate PER of FUT Length of Fiber m NaN 1 0735 Delay Between Input amp Output mm Measured Birefringence Beat Length mm NaN Recalculate Cuve A A OA B ec Curve B dB Crosstalk y Curve C Fitting 20 Sort by Position v index position Amplitude im ab 0 000 1 312 29 074 8 326 49 630 299 629 47 520 299 920 44 768 AS 300 169 _ 42 118 Setup Cure Analysis Fiber Events Smooth w 25 z 18 378 Gaussian ae 1 2 en 3 Cursor1 40 F Cursor w 300 515 42 622 50 8 325 248 49 500 325 98 55 e 3 N Beeren Curves 10 386 244 EENE Marks Crosstalk ECZ i 60 11 387828 26454 Display 5 X Ref 70 E Y Ref 75 80 Xtalk Maxi Power 10 0 25 50 75 100 125 4150 175 4200 225 250 275 300 325 350 alk Maximum Monitor F Fiber Len
19. 8 shows the significant output wave packets at the end of the fiber Xo ut So is the principal wave packet aligned to the slow axis f f2 and f are wave packets aligned to the fast axis generated by first order coupling S 2 S23 and S 3 are wave packets aligned to the slow axis generated by second order coupling GP UM PXA 1000 V21 Page 5 7 of 68 PXA 1000 User Guide So i f f2 f3 i ih i ii Mixed wave packet i sequence in fixed arm i i So i f 3 i i fi Sa Sa S12 Mixed wave packet sequence i in moving arm 4 AEE E EET Figure 29 Wave packet sequence in traditional interferometer after passing a 45 oriented analyzer After passing through a 45 oriented analyzer the wave packets aligned to the slow and fast axes will be mixed together see Figure 29 If this mixed light is input to an interferometer a series of interference peaks can be observed as the delay in one arm of the interferometer is changed Table 1 lists all possible interference peaks for the example shown in Figure 28 Only the peaks generated by the interference between Soefi Somfs2 and Sof represent the coupling points X X2 and x3 The other peaks listed in Table 1 are ghost peaks that can cause errors in the identification of coupling points They can also be superimposed on the real peaks reducing the x talk measurement accuracy In order to minimize the number and magnitude of ghost peaks the PXA 1000 uses a patented technique
20. HT FROM A HIGH POWER LASER IS HARMFUL TO HUMAN EYES Follow industry standard procedures when operating a high power laser source Since the light from the PXA 1000 is invisible it is safer to turn it off before changing connections and when the light source is not in use OPERATION CONSIDERATIONS e To ensure measurement accuracy allow 10 minutes warm up time before taking measurements e When powering the instrument off wait at least 20 30 seconds before powering it back on to avoid damage to electrical components e The PolaX software program should be closed before powering off the PXA 1000 GP UM PXA 1000 V21 Page 3 of 68 PXA 1000 User Guide GP UM PXA 1000 V21 Page 4 of 68 PXA 1000 User Guide Section 1 0 OVEJITA EEEE EEA 7 Section 2 0 FS aeeoea 9 2 1 Front Panel and Optical Inputs sssssssnususuunnnususuunnnnnnnnnnnnnnnnnn 9 FiDi CONNECLOTS srinrrini iinn nania AA 9 Ferrule Cleaning Procedure s sssssss22222222222222222202 220222 2 2 22 2 10 2 2 Rear Panel Electrical and Remote Control Interfaces 11 Section 3 0 Operation Instructions ssss2s2s 5 252 13 3 1 Unpacking sssini aaa aa 13 32 SETUD EE A E EE E 13 3 3 Software Interface Quick Reference sssssusss2usuu2u222222uu2u n 15 3 4 M asurementS sisssisrisisssissrdaaa naaa aaan 21 Distributed Polarization Crosstalk Measurement PM fiber 21 Polarization Extinction Ratio PER Measurement PM fibe
21. Making Light Work Lighter X Genera Photonics Corporat i on PXA 1000 Distributed Polarization Crosstalk Analyzer Polax User Guide Version 2 1 Date March 9 2015 PXA 1000 User Guide General Photonics Corporation is located tn Chino California For more information visit the company s website at www generalphotonics com or call 909 590 5473 GP UM PXA 1000 V21 Page 2 of 68 PXA 1000 User Guide SAFETY CONSIDERATIONS The following safety precautions must be observed during operation of this product Failure to comply with these precautions or with specific warnings elsewhere in this manual violates safety standards of design manufacture and intended use of the product General Photonics assumes no liability for customers failure to comply with these requirements Before operation the user should inspect the product and review the manual carefully Properly ground the chassis and work space using the chassis ground terminal Use only in a safe work environment in terms of temperature humidity electrical power and risk of fire or shock The product is designed for indoor use Avoid exposure to liquids or water condensation Provide adequate ventilation for cooling Operate the product on a stable surface Avoid excess vibration Standard laser safety procedures should be followed during operation Never look into the light source fiber connector when the light source is turned on THE OUTPUT LIG
22. Measurement of PM Fiber Birefringence Measurement Principle slow axis fast axis A B PXA 1000 G o fe light output p Figure 14 Birefringence measurement principle As shown in Figure 14 when light enters the PM fiber under test from the PXA 1000 light source output position A two polarization components aligned to the slow axis and fast axis respectively of the fiber are launched because of the misalignment between the PM fiber output of the PXA 1000 light source and the fiber under test Due to the birefringence of the PM fiber the two polarization components travel at different group velocities and experience a delay difference at the end position B of the fiber under test Delay gow fast NL n L AnL 4 where L is the length of the fiber under test The delay siow fast generated by the PM fiber under test can be measured by adjusting the delay line in the PXA 1000 s interferometer The birefringence of the PM fiber can therefore be calculated by An n n Delay stow fast as 5 L It should be noted that the delay measured by the PXA 1000 is related to the group velocity of light in the fiber not the phase velocity Therefore the measured birefringence is group birefringence not phase birefringence and the beat length calculated by A An is consequently only an approximate value Setup for Birefringence Measurement The recommended setup for measuring the birefringence of PM fiber is shown in F
23. The effects can be compared by placing a cursor at the peak in the center of the plot and switching the curve selection between A B and C Cursors can also be used to update the fiber range to be used for PER calculation and peak detection After a crosstalk measurement is made the PER will be calculated for the FUT between Marker 1 and Marker 2 PXA 1000 input and output connectors respectively This is also the range used for peak detection for the Events table The user can select a more limited range to be used for the PER measurement and peak detection by dragging a cursor to the desired position on the plot then clicking on Set Fiber START or Set Fiber END on the Fiber tab on the right side of the screen Then click Calculate PER of FUT to recalculate the PER over the new range The Events table will also update to cover the new range Marker Options Marks Create Mark 1 Create Mark 2 Clear Marks GP UM PXA 1000 V21 Page 45 of 68 PXA 1000 User Guide The marker pull down menu on the left side of the screen allows the user to add or delete markers Selecting Create Mark x from the menu adds or moves if the marker is already on screen the specified marker at the current active cursor position If both cursor 1 and cursor 2 are on screen the active cursor position is the position on the selected curve of the cursor that was most recently moved The coordinates of the markers are displayed in th
24. a section of imperfect fiber is very small in amplitude on the order of 60 dB or lower Because of this curve structure low amplitude wide peak the peak x talk value for crosstalk resulting from continuous polarization coupling is not meaningful However the cumulative coupling occurring in a section of fiber can be obtained by defining the starting and ending positions of the continuous coupling section of fiber using the PXA 1000 software s cursors as shown in Figure 32 In this example the Cumulative value is 61 32 dB Continuous Discrete Crosstak 75 1 L7 i 220 105 220 2 x 220 8 H oR fiber length v PER including internal fibers 15 23 dB i tritcisus eee iMG 3 Mees Calculation method Set fiber START 220 788 Set fiber END Calculate PER of Coil See OOOO Dee dee eee et O OO rr Figure 32 Closeup view of section B of the x talk measurement plot shown in Figure 31a in which two continuous or quasi continuous x talk peaks are identified b Cumulative x talk value of a continuous quasi continuous coupling is obtained by setting the locations of cursors Z and Z and calculating the integrated PER of the corresponding fiber section The resulting value 61 32 dB is shown at the bottom right of the screen PXA 1000 User Guide X talk caused by quasi continuous polarization coupling This category includes polarization coupling induced by multiple stress points spaced on the order of or less than the resolut
25. aks by redefining the start and end points for fiber PER measurement zmo LL CuveA OA Crosstalk ET Setu Curve Analysis iber Events Curve C 7 p d Fitting Smooth v E 4 Cursor 4 Cursor A PER Including Internal Fiber 16 59 Gaussian w Estimated PER of FUT Cursor 1 35 63 Set Fiber START 14 987 Cursor 2 Set Fiber END 372 647 Crosstalk Marks Calculation Method Curves Peak Area Calculate PER of FUT Display X Ref Length of Fiber m NAN Y Ref Delay Between Input amp Output mm 139 59 Power 200 MEERMEG Monitor Birefringence Fiber Length w Beat Length mm General Potta FE E E EA A A S kk ld ek kk a a pe mm NaN General Photons Xtalk measurement is done Recalculate PER of DUT recalculated with new start and end points PER Including Internal Fiber 16 59 Estimated PER of FUT 32 63 Start point Cursor 1 position End point Cursor 2 position Peak threshold setup from Events tab used for PER calculation Set Fiber START 14 987 Set Fiber END 372 647 Threshold dB Calculation Method Width points Peak Area Calculate PER of FUT Click Calculate PER of FUT button to recalculate PER after changing setup parameters fiber range peak threshold etc Figure 13 PER measurement of same 388m fiber coil as in Figure 11 with different fiber range PXA 1000 User Guide Birefringence
26. circumstances the PXA 1000 places Marker 1 at the input connector position and references the x axis of the plot such that the input connector position corresponds to X 0 If the x reference becomes corrupted such that the PXA 1000 consistently misidentifies the position of the input connector the user can re establish the x reference using the Set Mark1 as Zero Position function in the Calibration block at the bottom of the Setup tab on the right side of the screen The procedure is as follows 1 Connect a good PM patchcord for which the input connector peak can be easily identified as the DUT 2 Follow the standard procedure for a distributed polarization crosstalk measurement GP UM PXA 1000 V21 Page 51 of 68 3 Identify the peak corresponding to the input Currey Cume E EA Cure C Fatir Smooth Gawssian Cursor 1 Cursor 2 Marks Gunes Display A Rel Y Rel Power Monita connector and place Marker 1 on that peak EE Ee Crosstalk A 5 ar i salu j Cure Analysis Fiber PER Including intemal Fiber 16 86 Falimabed PER of FUT 624 36 Set Fiber START U Sel Fiber END 86 OB TOR Calculation hbethod Peak Area Calculate PER al FUT Length of Fiber im NaN Deky Behn Input amp Output rm 1 0739 Minse Birefringence Fiber Length w Pl i 5 BESS RS ERS SSS RE SREP BSR SSE SEE PR TRARRE BS Be ee ee eS SS ee eee eee a EN MaN Set Mark As Zero Position
27. e PXA 1000 sssssss22222 GP UM PXA 1000 V21 Page 6 of 68 PXA 1000 User Guide Section 1 0 Overview The Distributed Polarization Crosstalk X Talk Analyzer PXA 1000 is a white light interferometer designed to obtain space resolved stress information by analyzing stress induced polarization cross coupling along a length of polarization maintaining PM fiber Its unique optical design eliminates the strong zero order interference and reduces the multi coupling interference common in traditional white light interferometers as a result the PXA 1000 has higher measurement sensitivity higher dynamic range and higher spatial measurement accuracy than traditional white light interferometers The PXA 1000 enables the use of the PM fiber itself as the sensing medium eliminating the need to place multiple fiber gratings along the fiber It can therefore obtain higher spatial resolution of the stress distribution than grating based systems Because no discrete sensing elements are required the system is easy to install and calibrate making it ideal for monitoring space resolved structural changes along bridges tunnels dams oil pipes or buildings It can also be used as an intrusion detection system because any mechanical disturbances to the PM fiber will cause polarization coupling Another important application is PM fiber quality inspection The PXA 1000 easily identifies defective sections of PM fiber enabling the manufactur
28. e table at the top right of the screen The coordinate differences between the two markers are automatically calculated and displayed in the bottom line of the table on the Curve Analysis tab on the right side of the screen Unlike the cursors the marker coordinates do not change with curve selection In fact the two markers can be placed on different curves This is also useful for calculating differences in position or amplitude of crosstalk events on different curves Curve Smoothing In most cases curve smoothing is not necessary but occasionally it can be useful to help enhance hard to resolve crosstalk features The bottom section of the Setup tab allows the user to select the smoothing method to be used and for the moving average method to specify the moving average number Smoothing can be applied to or removed from one or more curves from the pull down menu at the left of the screen omooth All Curves Gaussian A only B only n C only Curse Cancel Smooth Cen All curves Cursor 2 ToN B only Cony Smoothing method selection on Setup tab Curves Smoothing pull down menu Display Third Order Polynomial Moving Average X Ref Power Monitor The third order polynomial method is useful to resolve detailed features of peaks It fits the peaks with no changes to peak widths GP UM PXA 1000 V21 Page 46 of 68 CurvveA eN Curve B The moving average method can change the widt
29. e that the instrument s x talk accuracy specification is based on measurement of the peak values of such discrete x talk points For discrete coupling only the peak value is meaningful For continuous or quasi continuous coupling only the integrated x talk value over a distance is meaningful meaningless Z Z Figure 34 Left Illustration of a crosstalk peak caused by discrete coupling with peak and off peak values marked The off peak values are artifacts caused by the coherence function of the light source they have no relation to real x talk points on the fiber Right Illustration of a x talk dome induced by continuous or quasi continuous polarization coupling A point on the dome does not correspond to a x talk point on the fiber In this case only the integrated cross coupling between the points Z and Z2 is meaningful Points Z and Z can be defined in the software interface For X talk induced by the continuous or quasi continuous coupling shown in Figure 30 the x talk value of any single point on the broad x talk composite peak is not meaningful The PXA 1000 is unable to give an accurate x talk value for such a point although the x talk data file includes data points every 4 6 mm For a x talk composite peak caused by continuous or closely packed quasi continuous coupling points only the cumulative cross talk value is meaningful as shown in Figure 32b and Figure 33b The PXA 1000 s data display and analysis softwa
30. ector positions respectively The default x axis for the plot is delay so the distance between the markers is the measured delay D n ns L where L is the fiber length GP UM PXA 1000 V21 Page 33 of 68 i 2B PXA 1000 vi Curve Curve B Setup Curve Analysi Fiber Event etup urve Analysis vents Curve C Fitting Smooth w 25 PER Including Internal Fiber 16 89 Estimated PER of FUT Gaussian w 30 35 Cursor 1 63 28 40 Set Fiber START 0 Cursor 2 4S Set Fiber END 1 06788 Marks 50 Crosstalk Calculation Method 55 Curves Peak Area 0 Calculate PER of FUT Display 65 X Ref 70 l im f N I li h Y Ref 75 Ay 4 rar AA 3 J LA ny p wad Length of Fiber m 302 A Auna AAA rn A if Delay Between ig 5 Input amp Output ini 1 0679 80 Power Measured Monitor i j Dela i i l i Birefringence 2 y v Beat Length LS SG A A A ON S PG S O N A a AN a N E a PE 4 38 neral Photonics Birefringence measurement is done Recalculate Figure 16 Birefringence measurement of a 3m PM fiber Default plot shows crosstalk dB vs delay mm Coherence Length Measurement of a Light Source Measurement Principle The interference pattern generated by the PXA 1000 is shown in Figure 17 It has the form of an amplitude modulation signal The modulation frequency is a constant determined by the center wavelength of the light source and the swe
31. edure Make sure light source is off before cleaning connectors Each connector ferrule is contained in a universal connector interface consisting of a front piece that connects to the external fiber connector and a base piece that is mounted on the front panel of the instrument as shown in Figure 3 To clean a connector ferrule first make sure no external connector is connected to the universal connector interface Then using a Phillips screwdriver remove the two small screws connecting the front and back parts of the adapter and carefully pull the front flange straight out Note never remove the adapter base from the front panel The ferrule end should now be exposed Clean the ferrule using standard cleaning procedures compressed air or a fresh lint free tissue and alcohol or other connector cleaning solvent taking care to avoid scratching the ferrule surface Finally replace the front flange position it so that the key notch faces up and the small alignment pin lines up with the hole in the base piece before pushing it in and the screws Hole for alignment pin Remove screws Adapter base Front flange do not remove Ferrule end Figure 3 Diagram of universal connector interface GP UM PXA 1000 V21 Page 10 of 68 PXA 1000 User Guide 2 2 Rear Panel Electrical and Remote Control Interfaces The rear panel of the PXA 1000 is shown in Figure 4 Figure 4 Rear panel Rear Panel Features Cooling fan a
32. ep speed of the delay line The amplitude of the envelope represents the x talk magnitude and its full width at half maximum FWHM is related to the linewidth of the light source 2In2 A Ae 0 44 m AA AA where Ao is the center wavelength of the input light source and AA is the FWHM of the FWHM 6 power spectrum of the light source The coherence length of the light source can be calculated by t l FWHM 2 266 FWHM 7 In2 PXA 1000 User Guide TA Z Z aa 7 Envelope of interference signal Interference signal of coupling after demodulation circuit point when delay line is moving Figure 17 Interference signal and its envelope Setup for Coherence Length Measurement The recommended setup for coherence length measurement of a light source is shown in Figure 18 If the degree of polarization DOP of the light source under test is very low the interference signal can be too small to be detected by the PXA 1000 It is therefore recommended that a polarizer be placed between the light source and the PXA 1000 input A PM pigtailed polarizer is preferred because SM pigtail fiber may result in coupling between different interference peaks and reduce the measurement accuracy Light source under test Polarizer Figure 18 Setup for coherence length measurement GP UM PXA 1000 V21 Page 35 of 68 PXA 1000 User Guide Coherence Length Measurement Procedure 1 Connect light source under
33. ers or users to remove them Furthermore the PXA 1000 is ideal for quality inspection and screening of PM fiber coils since it can pinpoint the locations of imperfections or areas of local stress on the fiber coil induced during the fiber winding process The software displays the location and polarization coupling ratio of each stress point as a function of distance It also generates a table listing the locations and polarization coupling strengths of all crosstalk peaks above a user defined threshold Other applications of the instrument includes measuring the extremely high polarization extinction ratio of a polarizing waveguide obtaining the autocorrelation function of a light source measuring the birefringence of a PM fiber and the lengths of PM and SM fibers and matching the optical path lengths of an interferometer More detailed information on measurement principles is provided in section 3 Polak OS TRATED MARATON TALE aA TER A General Pantons PXA 1000 a s _ Figure 1 PXA 1000 Distributed Polarization Crosstalk Analyzer GP UM PXA 1000 V21 Page 7 of 68 PXA 1000 User Guide GP UM PXA 1000 V21 Page 8 of 68 PXA 1000 User Guide Section 2 0 Features 2 1 Front Panel and Optical Inputs The front panel of the PXA 1000 is shown in Figure 2 LIGHT j ii Seneral Photoies gt PXA 1000 Polax DISTRIBUTED POLARIZATION X TALH ANALYZER POWER im i E he re eE T 2 EDP 7
34. ew value then pressing ENTER d From the Gaussian pull down menu on the left of the screen select the Gaussian fitting option for the active curve curve A in the example above The calculated coherence length will be displayed in the message box at the bottom of the screen The corresponding Gaussian fitting curve is displayed as a red line on the plot and the fitting parameters are displayed in the Curve Analysis tab on the right of the screen r LLL CuveA OA Linear Crosstalk i Curve B hi Setup Cure Analysis Fiber Events Curve C 5 Fitting 0 0028 0 0026 Smooth w C oe a 0002 INA NA _ Gaussian 0 0022 0 000 2 054E 2 1 084 3 598E 3 Cursor 1 0 002 core t Measured data white 1084 1 09552 0 0016 Cursor 2 WEILS Crosstalk 0 0014 AL i a Amplitude 0 001824 A be STDV 0 0245 0 0012 of ye Curves VA N Center 1 1538 ai A P Bandwidth 0 0479 Display 0 0008 Residue 1 1149E 9 0 0006 X Ref Y Ref Third Ordbr Polynomial Moving Average Power 1221 Sbi Monitor 1 19 1 18 1 17 1 16 115 1 14 113 1 12 111 11 1 093 General Piotta TEA FES ER E ee E Fe S E SA E DA C S E R D E S S E S S F A A A E S A F F E E S E S S E E E E E E S S E E E E F E S A E S E E E S S E A E Estimated Coherence Length is 108 5 micron Estimated coherence length Gaussian fitting parameters Figure 20 Coherence length measurement results after curve f
35. ffects of particular connectors or splice points In addition the measured value is heavily dependent on the alignment of the input light at its launch point into the FUT which limits both the accuracy and repeatability of the measurement As described in the previous section the PXA 1000 measures crosstalk at all points along the fiber under test The PER of a particular section of the FUT can be calculated by integrating the effects of all crosstalk events between the designated points on the fiber When a distributed polarization crosstalk measurement is done the PXA 1000 provides measurement results for system PER and PER of the fiber under test on the Fiber tab Figure 11 PER including Internal Fiber is the PER of the entire system including the effects of internal fibers and reference points in the PXA 1000 Estimated PER of FUT is the PER of the fiber under test FUT calculated using the crosstalk contributions from all crosstalk events that meet the threshold conditions as listed in the events table between the designated start point and the designated end point for the calculation When the distributed crosstalk measurement is first completed the algorithm automatically identifies and excludes the contributions of misalignments at the FUT input and output connectors The start point for the PER measurement is denoted by Marker 1 which is automatically placed at the PXA 1000 input connector FUT output and the end poin
36. ge box at the lower left of the screen will indicate that the process is finished GP UM PXA 1000 V21 Page 53 of 68 PXA 1000 User Guide 3 7 Troubleshooting The following table lists some common issues and probable causes Symptom Probable Cause Program shows PXA 1000 not connected Plot shows inaccurate fiber length or peaks not at expected positions Noise floor of plot is too high Program shows Detector saturated message in the message box Program shows estimated PER of FUT as Inf Markers incorrectly placed after measurement of a long coil ora waveguide GP UM PXA 1000 V21 Check the USB connection Reconnect the cable and wait for the device detected message before running the control program If necessary restart the PXA 1000 and the control computer before reconnecting Check An of fiber If the value used is not the actual An of the fiber the displayed fiber length will be incorrect Check that the DUT connector keys are aligned to the slow axis of the FUT DUT If the DUT output power is too low the noise floor of the plot may increase Generally it should be 10 dB below the lowest crosstalk peaks to be measured Use the Power Monitor function to check the DUT output power and if necessary adjust the attenuation DUT output power is too high Use the Power Monitor function to check the DUT output power and increase the attenuation as needed There are no
37. gn LIGHT UT LIGHT Figure 2 PXA 1000 front panel Front panel features Power Power on off switch Light Light source safety key Light Out Adapter narrow key PM FC PC standard for SLD output to FUT Light In Adapter narrow key PM FC PC standard for interferometer input from FUT The recommended default connector type is a narrow key FC PC PM connector although other connector types are available by customer request The connector keys are aligned to the slow axis of the PM fiber Fiber Connectors The front panel adapters are universal connector interfaces UCI which feature a male type adapter top piece that can be removed for direct access to the ferrule end for routine cleaning and maintenance without removing the entire adapter from the panel This feature helps avoid high insertion loss high return loss and measurement instability caused by dirty or contaminated connectors External fiber connectors should be cleaned using industry standard cleaning methods before connection to the PXA 1000 If this procedure is followed before each connection the instrument s internal connector ferrules should not need regular cleaning However high insertion loss or measurement instability that does not improve after cleaning the external connectors may indicate that the instrument s internal connector ferrules require cleaning GP UM PXA 1000 V21 Page 9 of 68 PXA 1000 User Guide Ferrule Cleaning Proc
38. gth w z Save Events Xtalk Average 39 277 dB 18 378 dB General Photonics Xtalk measurement is done Threshold dB Width points E Figure 26 Measurement example 2 PM fiber coil Figure 26 shows the results of a distributed polarization crosstalk measurement of a fiber coil Marker 1 and Marker 2 show the positions of the input and output connectors of the coil Between them are several smaller crosstalk peaks at semi regular intervals possibly due to winding defects The table in the Events tab on the right of the screen summarizes the crosstalk peaks within the analysis area defined by Markers 1 and 2 that meet the threshold conditions The Sort by pull down menu at the top of the table allows the user to sort peaks by position or amplitude In this example the table lists the amplitudes and locations of all crosstalk peaks gt 50 dB Clicking on the index number of any peak in the table causes a cross shaped marker to appear at that peak the marker is at peak 6 in this example The average and maximum crosstalk calculated from the peaks listed in the table are shown below the table The threshold level can be changed by typing in the text box After changing the threshold press ENTER or click outside the text box to update the table to include peaks above the new threshold The peak analysis region can be redefined by moving Markers 1 and 2 on the curve to be analyzed The table will update automatically The
39. h and amplitude of crosstalk peaks so it is not recommended for detailed analysis of individual peaks However it is useful for separating crosstalk features from noise when the noise is too high Gaussian Fit The Gaussian Fit function was described in the Coherence Length Measurement section Besides its use for light source coherence length measurement it is also useful for characterizing individual crosstalk peaks It can be used to determine the center and width of a particular peak Data Interpretation Figure 25 shows a typical x talk measurement curve Marker 1 and Marker 2 show the x talk peaks generated by the input and output connectors respectively of the PXA 1000 The curve between the two markers represents the x talk distribution of the PM fiber under test There are also some small peaks outside the region bounded by the two markers These are caused by x talk reference points built into the system for x talk calibration and from the misalignment between the polarizer chip and the pigtailed PM fiber Estimated PER of FUT DUT without connectors PER of entire system including PM fiber in PXA 1000 QA a 2 Crosstalk e Setup Curve Analysis Fiber hd Events Curve C Fitting Smooth w 25 Gaussian 35 Cursor1 40 Cursor w 45 Crosstalk Marks om 50 55 Curves 60 Display X Ref Y Ref Power Monitor NAS aN J LAN J x talk reference i
40. he Di a aa osama Delay Between l hi Input amp Output mm 1 0735 Power 2 5 a i Measured Monitor Birefringence E Fiber Length w m 7 Beat Length mm NEI General Piina SM p S B i ti tt it tk tt nt dk tt eo e a a General Photons Xtalk measurement is done Recalculate Figure 10 Crosstalk measurement of a 3m PM fiber Default plot shows crosstalk dB vs fiber length m PXA 1000 User Guide Polarization Extinction Ratio PER Measurement PM fiber PER Determination from Distributed Polarization Crosstalk Measurement Polarization extinction ratio PER is the ratio between the power in the principal polarization component of a light beam and the power in the orthogonal polarization component expressed in dB It is a measure of the linearity and degree of polarization of a polarized light source or of the polarization preserving or suppressing properties of a fiber or optical component It is one of the principal parameters used to evaluate the quality of a PM fiber When evaluating a PM fiber or PM fiber system the principal polarization component is usually the one aligned to the slow axis of the PM fiber In this case the PER can be expressed as PER 10log P P 3 where P is the total power in the slow axis and P is the total power in the fast axis Most PER meters and measurement systems can only measure the total PER of the fiber or system under test Because of this it is impossible to isolate the e
41. igure 15 The slow axis of the PM fiber under test should be aligned to the connector key GP UM PXA 1000 V21 Page 31 of 68 PXA 1000 User Guide PM fiber under test Light output DUT in Light input DUT out Figure 15 Setup for birefringence measurement of PM fiber Birefringence Measurement Procedure for PM fiber 1 Precisely measure the length of the PM fiber under test then connect it to the PXA 1000 as shown in Figure 15 2 On the measurement information section on the right side of the screen select the curve A B or C on which to display measured data 3 setup Curve Analysis Fiber Events talk Distribution Birefringence Coherence Length Raw Interference PER stop Position 50 Attenuation 5 SLD Low High Select Birefringence from the Measurement menu on the Setup tab Set the delay scan range The start position is fixed at Omm Set the Stop Position to the desired value For short fibers up to several tens of meters the default value of 50mm should be sufficient For longer fibers the delay range should be increased 5 Check the attenuation setting GP UM PXA 1000 V21 Page 32 of 68 PXA 1000 User Guide a Make sure the light safety key is in the on position b If the SLD on off button is red click the button to turn on the SLD c Click the Power Monitor button on the lower left side of the screen 1 18717 mW
42. information in the table index position and amplitude of crosstalk peaks can be saved to a file by clicking on the Save Events button The user will be prompted for a filename and location to which to save the data The saved data file will have file extension pks to avoid confusion with other types of data files but it can be opened using applications such as Notepad or Excel OA Js c Pressure applied at this point Setup Curve Analysis Fiber on the fiber Crosstalk PER Including Internal Fiber 16 01 Estimated PER of FUT 53 76 Set Fiber START 0 Set Fiber END 2 89681 Calculation Method Crosstalk Peak Area Calculate PER of FUT Length of Fiber m NaN Delay Between Input amp Output mm 1 1037 90 Measured 0 238 0 i 15 2 Birefringence HEO Fiber Length w men MEURE SN ai i Beat Length mm NaN Xtalk measurement is done Recalculate F2 Run Figure 27 Measurement example 3 PM patchcord with 900um loose tube with different amounts of pressure applied over a 1cm section of fiber Curve A blue no pressure applied Curve B green 1kg applied Curve C red 500g applied Figure 27 illustrates how the PXA 1000 can detect changes in crosstalk in a fiber due to environmental factors It shows 3 consecutive crosstalk measurements of a PM patchcord with 900um jacket with different weights placed over a particular 1cm section of the fiber Curve A blue i
43. ion of the measurement instrument as shown in Figure 30a This type of polarization coupling appears in polarization crosstalk measurements as a broad composite peak with height variations with a width and shape determined by the number of stress points their relative positions and their relative strengths as shown in Figure 30b Quasi continuous coupling cannot reliably be distinguished from continuous coupling As in the case of continuous coupling it is not meaningful to give a peak x talk value for quasi continuous coupling However the cumulative coupling occurring in a section of fiber can be obtained by defining the starting and ending positions of the continuous coupling section of fiber using the PXA 1000 software s cursors aS shown in Figure 33b GP UM PXA 1000 V21 Page 65 of 68 Curve A Crosstalk Fitting curve Curve B Crosstalk iso 309 264 fiber length Y PER including internal fibers dB Estimated PER of Coil dB Set fiber START E Set fiber END Calculation method Calculate PER of Coil Curve 4 Crosstalk Yy Fitting curve Curve B Qqasi continuous Crosstalk 275 239 025 242 p fiber length PER including internal fibers dB Estimated PER of Coil 26 46 Wels Calculation method Set fiber START 241 377 Set fiber END 243 104 Calculate PER of Coil Figure 33 a X talk measurement of a low quality PM fiber coil of length 309 meters b Closeup view of the boxed section in a showing more
44. ir intakes Line External AC input connector The PXA 1000 uses a USB interface to communicate with the control computer The control program and USB driver are pre installed on the control computer Fuse location Figure 5 shows the location of the fuse compartment under the power cord plug There are two fuses in the compartment the one in use and a Spare The fuse further inside the compartment is active The one closer to the compartment opening is the spare Replace the fuse with one with the exact rating of the original Figure 5 Fuse compartment GP UM PXA 1000 V21 Page 11 of 68 PXA 1000 User Guide GP UM PXA 1000 V21 Page 12 of 68 PXA 1000 User Guide Section 3 0 Operation Instructions 3 1 Unpacking Inspect PXA 1000 for any physical damage due to shipping and transportation Contact carrier if any damage is found Check the packing list to see if any parts or accessories are missing Packing List pan 000 2 Powered 7 1 2 C o en 3 2 Setup 1 Connect instrument power cord and plug it into wall receptacle Make sure the ground pin of the power cord is connected to earth ground 2 Power on control computer Connect instrument to computer with USB cable Wait for device detected message to appear USB 6216 detected gt X Click here to use this device 4 Connect input and output fibers see next several sections for details on measurement setups Make s
45. itting Polarization Extinction Ratio PER Measurement System In addition to the PER measurement from the crosstalk data the PXA 1000 has a quick system PER measurement function that can be used to check a measurement setup before doing crosstalk characterization of a device or fiber under test In general this function gives the same PER value as the PER including internal fiber calculated from the distributed polarization n crosstalk measurement Measurement Principle For the quick PER measurement the PXA 1000 uses an optical switch to block or transmit slow axis aligned light Assuming that the measured light powers are Piota and Prast respectively when the slow axis is unblocked or blocked the PER of the system including the PM fiber under test can be calculated by Post PER 10 log _ 8 total fast PXA 1000 User Guide It should be noted that the measured PER includes the x talk generated by the misalignment at both the input and output connectors so the measured PER is not equal to the PER of the PM fiber under test Setup for PER Measurement OPS TRURUTED PO ARLLATION K T R ANALYZER uor P aia Pradon fi Polax E PM fiber so under test Light output DUT in Light input DUT out Figure 21 Setup for PER measurement PER Measurement Procedure 1 Connect DUT as shown in Figure 21 2 Select PER from the Measurement menu on the Setup tab Setup Curve Analy
46. lysis or comparison with other curves by using the Load button F3 The software can be used for display and analysis of saved data without the PXA 1000 connected to the computer GP UM PXA 1000 V21 Page 50 of 68 PXA 1000 User Guide 3 6 PER and Position Reference Calibrations Optional Feature To ensure maximum accuracy and repeatability General Photonics recommends periodic factory calibration of the PXA 1000 However an option is available for users to quickly re establish the PER measurement and input connector position references Note These user calibrations write to the system file so they must be done carefully X Position Reference X talk and position references in the PXA 1000 In order to calibrate the x talk in the PXA 1000 a standard coupling point is built into the optical path just after the input connector Its position and coupling ratio x talk have been factory calibrated and stored in the PXA 1000 system files After every x talk measurement the PolaX control software automatically locates the reference point position and adjusts the y position of the measured trace such that the x talk at the reference point matches the calibrated value Then the software automatically locates the input connector and sets its x axis position to zero Therefore the x position of a coupling point indicates its distance from the input connector of the PXA 1000 Re establishing the X 0 position reference Under normal
47. m AA 30nm and An 5x10 then the spatial resolution of the PXA 1000 will be about 5cm GP UM PXA 1000 V21 Page 59 of 68 PXA 1000 User Guide GP UM PXA 1000 V21 Page 60 of 68 PXA 1000 User Guide Appendix 3 0 Polarization Crosstalk in PM Fiber Classification of Polarization Crosstalk by Cause Polarization crosstalk in a PM fiber arises from three principal causes 1 Fiber axis misalignment at fiber connection interfaces such as connectors or fusion splices typically causes extremely localized large amplitude crosstalk The amplitude depends on the misalignment angle Examples are shown on the left side of Figure 30 Figure 30a shows crosstalk sources along a fiber and Figure 30b shows the resulting crosstalk measurement plot 2 PM fiber imperfections such as local birefringence variations internal shape variations or internal stress cause polarization coupling that is generally small in amplitude and occurs gradually over a certain length of the PM fiber see center section of Figure 30 3 External mechanical stresses on sections of the fiber such as fiber bending fiber crossing fiber squeezing or pressure on the fiber can cause complicated composite crosstalk effects that can include polarization couplings that occur at sharp points in space as well as some that occur gradually along a length of fiber with varied amplitudes that depend on the stress orientations with respect to the slow axis and on the stress inten
48. ment is finished the message Coherence length measurement is done is displayed in the message box at the bottom left of the screen BB PXA 1000 vi CuveA A A OA e Curve B dB wv Crosstalk v EG ean z Setup Curve Analysis Fiber Events Cuvee AN t b Set scale to linear Fitting 20 02 Set y SC le imi Xtalk Distribution Birefringence Gaussian Coherence Length 35 j Cursor 1 i d Fitt j Smooth v Bi Raw Interference Cursor 2 PER pea E ES Stop Position 50 Curves a Select zo Dp in on nr ar A Attenuation 8 7 X Ref ppo l a AG et VW IM 1 Nay bapaan Power High Monitor i j i j i PER Calibration HE o Delay FEH FER E nk in ti i fl EE E A S E E E i a tt A R kt lt E E E E General Photonics Coherence length measurement is completed Crosstalk Marks Set Mark1 As Zero Position Figure 19 Initial data display after coherence length measurement Plot shows crosstalk dB vs delay mm 9 The plot will show the crosstalk dB vs delay mm a Select and zoom in on one peak from the measured curve see section 3 5 for details on zooming the graph For best results choose a peak with a good shape that does not overlap with other peaks b Set the y scale to linear using the y scale pull down menu at the top left of the plot c If necessary change the y scale limits by selecting the value of the upper y scale limit and typing in a n
49. n the measurement should be PM fibers with connector keys aligned to their slow axes The external connectors should be carefully cleaned before connecting to the PXA 1000 Light output FUT in Light input FUT out Figure 9 Distributed polarization crosstalk measurement setup Distributed Polarization Crosstalk Measurement Procedure for PM fiber 1 Connect fiber under test FUT as shown in Figure 9 GP UM PXA 1000 V21 Page 23 of 68 PXA 1000 User Guide 2 On the measurement information section on the right side of the screen select the curve A B or C on which to display measured data a Setup Curve Analysis Fiber Events Xtalk Distribution Birefingence Coherence Length Raw Interference PER stop Position 50 Attenuation E 5 SLD Low High An of PM Fiber 3 81E 4 Select Xtalk Distribution from the Measurement menu on the Setup tab Set the delay scan range The start position is fixed at Omm Set the Stop Position to the desired value range is 0 to 700 mm for the 1 3 km PXA 1000 or 0 to 1500 mm for the 2 6 km PXA 1000 Generally the Stop Position should be longer than the minimum delay calculated by Minimum Delay fiber length An 1000 mm 2 The Stop Position can be changed either by using the up down arrow buttons next to the value or by selecting the value and typing in a new number 5 Check the attenuation setting a Make sure the ligh
50. oving number average method Fiber tab on right side of screen Fiber measurement data Fiber PER Analysis PER including Measured PER of the entire system internal fiber including internal fiber in the PXA 1000 5 Estimated PER of Calculated PER of the fiber under test Sa Toms as Fw lE FUT FUT over the designated range etup urve Analysis Iber vents lt p Set Fiber START Sets start point for PER calculation and events table PER ami Internal Fiber Set Fiber END Sets end point for PER calculation and 15 89 events table Estimated PER of FUT Select calculation method for PER 49 40 measurement Peak Include all peaks threshold value within designated range in the Set Fiber START Calculation Method Set Fiber END 2 88217 calculation Calculation Method Area Integrate over area under the Peak Ame curve within the designated range to calculate PER PEE Recalculate PER after changing settings Calculate PER of FUT calculation method fiber range or peak threshold Fiber Data summary for birefringence Length of Fiber m NaN Birefringence measurement ea enn EOB Venath of Fiber Length of fiber under test input by Measured user Birefringence ee pu Measured delay for fiber under test Beat Length mm NET and Output mm Measured Measured birefringence of fiber under Recalculate Birefringence test Beat Length ee beat length of fiber under Recalculate birefringence and beat Recalculate length after
51. r 27 Birefringence Measurement of PM FIDE ssssus2us22222 2 31 Coherence Length Measurement of a Light SOUFCeE ssssssss22 34 Polarization Extinction Ratio PER Measurement System 38 3 5 Advanced Data AnalySiS sssssssss2ususuu2222222ununuununnnnnnnnnnnnnnnnnn 41 Graph ODErati NS sicisnssiccdsesscbecsuccsasccescuasssnecbivsswensastunnseandsesesawseenes 41 Data Interpretation wissccssciicwiincteccctnctiesviveteawesecitestinetesessewabneesnvantes 47 Savino D lia a 50 3 6 PER and Position Reference Calibrations Optional Feature 51 X POSITION R CTE FENCE iscecace wexeceewsscotnensevececcatcusaseasvenatesecoseesseewsacwwens 51 PER IRC OE CINGG sesaaccnccnccn sacevetsseewveuusacuescuawousesuavesutssceuveweweentetimsuwaness 53 3 7 Troubleshooting sicicurrsccccucsincineterssousinenioucnessionnsedetanensssisueenain 54 Section 4 0 SPECHICIGON S arr E 55 GP UM PXA 1000 V21 Page 5 of 68 PXA 1000 User Guide PO DCN GICES anana E O A EE E 57 Appendix 1 0 Comparison of PXA 1000 to Traditional White Light LnterferomMmetl e riisiin asa a 57 Appendix 2 0 Spatial Resolution Of PXA 1000 sssssss22222222 59 Appendix 3 0 Polarization Crosstalk in PM Fiber ssssssssusnnnnnnnnnnn 61 Classification of Polarization Crosstalk by CaUSe s ssss222 61 Classification of Polarization Crosstalk by Measurement Results Ia O Capabilities and limitations of th
52. re PolaX has a function that calculates the cumulative x talk from point Z to point Z2 where Z and Z gt are defined by the locations of the cursors as shown in Figure 32b and Figure 33b In general the distance between Z and Z should be much larger than the spatial resolution of the instrument in order to obtain an accurate result In addition the two points should also be chosen at valleys on the x talk curve and the Area calculation method should be selected as shown at the bottom right of Figure 32b and Figure 33b GP UM PXA 1000 V21 Page OW of 68 PXA 1000 User Guide Note that the primary purpose of the PXA 1000 is to obtain accurate x talk measurements of discrete x talk peaks the accuracy of a cumulative x talk calculation is not guaranteed However the instrument records measurement data every 4 6 mm and this data is available to users to optimize the calculation for specific cases where higher accuracy is required Data is available to the user in two forms the raw interferometer signal data as a function of the relative delay between the two arms of the interferometer Interferometer Only data and the x talk data as displayed on the screen The x talk data is the raw interferometer data with the horizontal and vertical axes shifted according to internal position and x talk references GP UM PXA 1000 V21 Page 68 of 68
53. rference amplitude The scale of the plot can be log scale dB or linear The default is log scale because smaller peaks may not be visible in linear scale however linear scale is useful for viewing some data and for curve fitting The x axis parameter can be the position along the fiber fiber length or the delay The default parameter depends on the measurement being made If the x parameter is fiber length it will be expressed in meters If the x parameter is delay it can be displayed in terms of length mm or time ps Both the x and y scale limits can be edited by selecting the text and typing in new values This can be a more precise way of rescaling the plot than using the zoom options GP UM PXA 1000 V21 Page 43 of 68 Cursor Options Cursor 1 Cursor 2 Cursor pull down menus Create Cursor 1 Delete Cursor 1 Create Cursor 2 Delete Cursor 2 Curve A is selected OA d d Setup Curve Analysis Fiber Events 53 659 53 709 114664 0000 102 233 176 1 844E 3 233 1 6 8 625E 3 Curve Analysis Figure 24 Cursor control The cursor pull down menus on the left side of the screen allow the user to add or delete cursors Selecting Create Cursor x from a cursor menu causes the corresponding cursor to appear on the plot With the cursor movement tool HH selected the cursor can be moved to different positions on a measured curve using the mouse The coordinates x y of the c
54. s the baseline measurement with no weight applied Curve C red shows the same fiber with a 500g weight placed on it The weight causes crosstalk of about 55 dB at the point where it was applied but the rest of the curve is relatively unchanged Curve B green shows the same fiber with a 1kg weight placed on it at the same point The crosstalk at that point increases to almost 35 dB Note that many factors can affect the amount of crosstalk caused by pressure on a fiber including the axis along which the pressure is applied for example pressure applied along the Slow or fast axis of a fiber will have a different effect than the same pressure applied along an axis 45 between the fiber axes how much the fiber is insulated from the pressure jacketing etc and whether the pressure is applied to a discrete point or distributed over a longer length of fiber PXA 1000 User Guide Saving Data Data from any completed measurement can be saved to a file using the Save button F6 The user will be prompted to specify which curve is to be saved Select the desired curve and click OK The user will be prompted for a filename and location to which to save the data The saved data file will have file extension pxa to avoid confusion with other types of data files but it can be opened using applications such as Notepad or Excel Saved curve data with file extension pxa can be loaded for display further ana
55. ser Guide Fiber Range for PER Measurement The user can choose to calculate the PER between any two points on the FUT for example to exclude the effects of connectors splice points etc by changing the start and end points used for the PER calculation Figure 12 shows some examples Output connector l Input connector seveeeeees PER calculation ising DPXA data excluding T A0 Fi PER calculation using DPX A data excluding bowed contributions from two connectors contributions from two connectors and two splices 0 2 4 6 8 10 12 0 50 100 150 200 250 a Fiber length Z m b Fiber length Z m Figure 12 Polarization crosstalk curves of a 13 m jumper with two FC APC connectors a and a 250 m PM fiber coil spliced with two FC APC connectors PER measurement with a commercial PER meter always includes the contributions of the input connector and two splices while the PXA 1000 has the ability to identify and eliminate the polarization crosstalk contributions of all connectors and splices in the measurement system Note that fiber length in the horizontal axis is obtained by dividing the fiber delay line distance AZ by the average birefringence obtained using the procedure described in Section 3 2 of the referenced paper Start or end points can be set to an active cursor position place cursor drag to desired position and click Set Fiber START or Set Fiber END or can be set to particular values by selecting the val
56. sis Fiber Events Xtalk Distribution Birefringence Coherence Length Raw Interference PER a 3 Click the Run button at the bottom of the screen or press the F2 function key on the computer keyboard to start the measurement During measurement the message PER is being measured will be displayed in the message box at the bottom left of the screen 4 When the measurement is finished the measured PER will be displayed in the message box at the bottom left of the screen Measured PER Is 16 62dB GP UM PXA 1000 V21 Page 39 of 68 PXA 1000 User Guide GP UM PXA 1000 V21 Page 40 of 68 PXA 1000 User Guide 3 5 Advanced Data Analysis Graph Operations Using the graph operation functions shown in Figure 22 the user can zoom in and out in the data plot use cursors to read the coordinates of measured points place two markers on the curves and measure the coordinate differences between the two markers Markers Cursor and marker coordinates DD PxA 100001 Trace Display and Fitting Options Graph palette Figure 22 Graph operations interface GP UM PXA 1000 V21 Page 41 of 68 PXA 1000 User Guide Graph Palette The graph palette can be used to move cursors and to zoom and pan the graph display Click the corresponding button in the graph palette to enable cursor movement display zooming or display panning
57. sities as shown in the right section of Figure 30 Classification of Polarization Crosstalk by Measurement Results In general the PXA 1000 distributed polarization crosstalk analyzer can accurately measure the strength of polarization crosstalk occurring at different locations along a fiber with a Spatial resolution of a few centimeters Although the causes of the crosstalk cannot always be identified from measurement results educated guesses can be made based on the shape and strength of the measured crosstalk at each location It is also feasible to classify the crosstalk based on the shapes of the measured curves as discussed below GP UM PXA 1000 V21 Page 61 of 68 PXA 1000 User Guide Point Splice or Line Multiple point stress connector stress stresses Internal fiber a l variations a Discrete coupling Continuous Quasi continuous coupling coupling Figure 30 Illustration of different types of polarization crosstalk a Different sources of polarization crosstalk b The resulting crosstalk peak profiles Left discrete polarization x talk peaks induced by a point stress or a splice Each such peak is a Gaussian curve with a shape determined by the coherence function of the light source The spatial resolution is also determined by the width of the coherence function Center continuous polarization x talk induced by a line stress and by internal fiber imperfections respectively Right quasi continuous x talk induced by
58. t enough detected peaks to calculate a PER Either change the PER calculation method to Area or change the threshold level used for peak detection for Peak method PER calculation for example from 50 to 60 dB Check that the delay range for the MDL is set correctly If the measurement curve does not include a peak at the right corresponding to the output connector the MDL scan range may be too short to measure the entire DUT and the PXA 1000 software will not be able to place Marker 2 correctly Check the required scan length for the DUT and adjust the MDL stop position accordingly Page 54 of 68 PXA 1000 User Guide Section 4 0 Specifications Optical lt 75 dB for DUT output power gt 5dBm sensitivity 80dB typical noise floor Polarization X talk repeatability 0 5 dB Polarization X talk accuracy 0 5 dB 4 Measurement or sensing range 1 3 km or 2 6 km standard Assuming PM fiber An of 5 x10 3 1 km optional Measurement speed 8 s 100 m with fiber An 5 x10 Spatial resolution 6 cm assuming no fiber dispersion birefringence An 5x10 PER measurement range gt 30 dB Spatial accuracy 20 cm with fiber An 5x10 Waveguide polarization dependent Up to 75dB for DUT power output gt 5dBm attenuation LiNbO waveguide spatial 0 75 mm resolution SLD Power gt 10 dBm SLD bandwidth gt 30 nm SLD PER gt 20 dB Electrical Communication Power Supply 100 240VAC
59. t for the PER measurement is set at Marker 2 which is automatically placed at the PXA 1000 output connector FUT input GP UM PXA 1000 V21 Page 27 of 68 GB BB PXA 1000 vi rcs L OA e Crosstalk Setup Cure Analysis Fiber Events Smooth h PER Including Internal Fiber 17 68 Estimated PER of FUT Cursor 1 26 50 Set Fiber START 0 Gaussian Cursor 2 Set Fiber END 388 214 Marks Calculation Method Crosstalk Curves j Peak Area z Calculate PER of FUT Display X Ref Length of Fiber m NAN Y Ref Delay Between Input amp Output mm 139 16 Power i Measured Monitor Birefringence Fiber Length w m Beat Length a kt St ah i Sa at a a ak ere ma at NaN General Phatontcs Xtalk measurement is done Regalculate PER Including Internal Fiber System PER includes the effect of gt 17 68 I fi in the PXA 1 ema EDK ia Estimated PER of FUT PER of DUT calculated using the gt eu measured crosstalk from the designated start point _ _ __ Set Fiber START to the designated end point Ree Set Fiber END 386 714 Calculation Method Peak Area Calculate PER of FUT Figure 11 Results of polarization crosstalk measurement of 388m fiber coil with closeup of PER results section on Fiber tab CP_IIM_ PX A_1NNN_ 9 Dana 72 af FQ Crosstalk dB PXA 1000 U
60. t safety key is in the on position b If the SLD on off button is red as in the example above click the button to turn on the SLD c Click the Power Monitor button on the lower left side of the screen 1 18717 mW Exit Check that the optical power is at an appropriate level Power 1mW or so GP UM PXA 1000 V21 Page 24 of 68 PXA 1000 User Guide usually works well although higher power may be necessary for sensitive measurements If the power is too high or too low change the attenuator setting range 0 to 30 dB and check the power again d If the measurement is run with the power level too high the detector may saturate and the resulting data may not be accurate In this case the PXA 1000 s message box will show Detector is saturated Please increase attenuation of VOA e The optical power level affects the position and width of the noise floor of the measurement If the noise floor is too high or too broad the optical power may be too low 6 Set the amplifier gain Low gain is recommended for most applications High gain can be used for fiber systems with very high loss 7 Set the birefringence of the PM fiber under test If the birefringence is not known measure it by following the procedure described in the next section The birefringence setting can be changed by selecting the value and typing the new value in the box The fiber birefringence setting determines the x positions
61. than or equal Threshold dB EO to 3 The value should be no more than Width points Cy about 1 2 of the half width of the peaks and can be much smaller but gt 2 for noise free data The peak analysis region can be modified by changing the values of Fiber START and Fiber END on the Fiber tab GP UM PXA 1000 V21 Page 20 of 68 PXA 1000 User Guide 3 4 Measurements The PXA 1000 can perform several types of measurements related to polarization crosstalk Measurement principles setup descriptions and results analysis for each type of measurement are described in this section Distributed Polarization Crosstalk Measurement PM fiber Polarization maintaining PM fiber is widely used in fiber optic sensor systems The performance of such a sensor system is directly limited by the quality of the PM fiber coil especially by the magnitude of cross coupling between the two principal polarization modes The PM fiber itself may have imperfections such that the local intrinsic stresses may cause polarization cross coupling External stress on the PM fiber during the fiber winding process may also cause polarization cross coupling In order to optimize PM fiber coil quality one would first select PM fiber with low intrinsic polarization cross coupling and then wind the fiber so as to minimize externally induced cross coupling In practice one would also like to identify the exact stress points which cause polarization
62. the slow axis red Stress at position B induces polarization coupling and produces a polarization component aligned to the fast axis blue Because the two polarization components travel at different group velocities at the output of the fiber position C the two components will experience a delay difference Az n zZ n Z Anz 1 where n and n are the refractive indices of the slow and fast axes respectively their difference An is the birefringence and z is the distance between the coupling point B and the output point C If a polarizer oriented at 45 degrees from the slow axis is placed at the fiber output half of the power in each of the polarization components will pass through the polarizer and emerge with the same polarization state linear aligned to the polarizer axis Consequently they will interfere in the Michelson interferometer shown in Figure 8 to produce interference peaks as the delay is adjusted The distance between the two adjacent interference peaks is Anz therefore from Eq 1 the location of the coupling point is z Az An The coupling point can therefore be located using the interference graph The coupling ratio can also be calculated from the strength of the interference peaks GP UM PXA 1000 V21 Page 22 of 68 PXA 1000 User Guide Setup for Distributed Polarization Crosstalk Measurement The recommended distributed polarization crosstalk measurement setup is shown in Figure 9 All fibers used i
63. tomize the appearance of a plot click on the icon for that plot to bring up a customization pull down menu Plot Visible hides or displays the plot The pull down menu also gives options to copy that curve s data to the clipboard or export it to an Excel file Trace Display and Fitting Options left side of screen sss ANI Curves omooth 1 Gaussian A only Pp Fitting Curve A B only Enean Fitting Curve B C only Create Cursor 1 Fitting Curve C Cancel Smooth Cursor 1 Delete Cursor 1 Clear Fitting Curve All curves SESE A only Create Cursor 2 C only Marks Delete Cursor Marks Create Mark 1 Curves Fen cs Create Mark 2 AtoB Clear Marks Display AtoC Bto A Display A X Ref BtoC Display B CtoA Display C Ref CtoB Display All Clear Curves Hide A Power Clear Curve A Hide B Monitor Aa eE Hide C Clear Curve C Hide All Options to apply or remove smoothing from one or more curves Curve smoothing method can be selected from the Curve Analysis tab on the right side of the screen Once smoothing is applied original data and curve are replaced by smoothed version Fits selected curve using Gaussian function for coherence length measurement or general peak characterization The fitting curve is Gaussian displayed in the graph window for comparison to the raw trace and the fitting parameters are displayed in the Curve Analysis tab on the right of the screen
64. ues in the start or end point boxes and typing in new values Note either cursor 1 or cursor 2 can be used to reset the fiber start or end position If both cursors are on the screen the active cursor is the one most recently moved PER Calculation Method There are two methods available for PER calculation Peak uses all crosstalk peaks within the designated range that meet the user defined peak threshold criteria defined on the Events tab on the right side of the screen This method is generally more suited to a FUT that includes multiple discrete crosstalk peaks for example from multiple connector interfaces splice points or localized stress points on the fiber Area uses the integrated area under the curve to calculate the PER This method is generally better for a single length of fiber or a system with more continuous or quasi continuous coupling rather than discrete crosstalk events If this method is selected when the distributed crosstalk measurement is made the initial PER measurement is made from the input connector to the output connector and will include half of the area under the peaks for the input and output t Zhihong Li X Steve Yao Xiaojun Chen Hongxin Chen Zhuo Meng Tiegen Liu Complete characterization of polarization maintaining fibers using a distributed polarization crosstalk analyzer Preprint paper GP UM PXA 1000 V21 Page 29 of 68 connectors The user can choose to exclude these pe
65. ure SLD source is turned off while cleaning connectors and making connections Power on PXA 1000 Turn on the safety key for the internal light source if applicable Note The safety key enables control of the internal SLD light source It does not by itself GP UM PXA 1000 V21 Page 13 of 68 PXA 1000 User Guide un m turn on the light source Once the safety key is in the on position the PolaX measurement software is able to turn on the light source 7 Run the program PXA 1000 from the desktop or Start menu shortcuts The program files are in the folder C DPXA The user interface screen shown in Figure 6 will appear 8 The PXA 1000 will run through an initialization sequence which takes about 1 minute During this time a System is initializing message will be displayed in the system message box on the bottom left of the screen and the progress bar immediately above the message box will show the status of the process Once initialization is complete the system is ready for measurement and the message box contents will change to System is ready to test Data Display Window Setup and Analysis Powe Monitor ae Fiber Length oe m v Trace Display and Fitting Options System message box Progress bar Function keys Figure 6 Main program interface GP UM PXA 1000 V21 Page 14 of 68 PXA 1000 User Guide 3 3 Software Interface Quick Reference This is a quick reference guide for
66. urrent cursor position will be displayed next to the cursor The x y coordinate display can also be moved with the mouse The cursor coordinates are also shown in the table on the Curve Analysis tab on the right side of the screen Linear w 0 0022 0 002 0 0018 0 0016 0 0014 0 0012 0 001 a7 ms zZ O 0 0008 0 0006 0 0004 0 0002 0 Crosstalk 0 16 Delay 0 14 Y OA EET Curve Analysis Fiber Events Amplitude 0 001877 STDV 0 021 Center 0 1217 Bandwidth 0 0411 Residue 1433E 10 Third Order Polynomial Moving Average PXA 1000 User Guide If there is data for more than one curve on screen the user can select which curve s coordinates will be displayed for a particular cursor position In the example shown in Figure 24 curve A is selected so the cursor coordinates displayed on the plot and in the curve analysis table are the coordinates on curve A that correspond to the current positions of cursor 1 and cursor 2 If the user selects curve B the coordinates displayed will be those that correspond to the cursor positions on curve B This is useful for comparing peak heights or widths on different curves Crosstalk Yv v 2 O O 15 Fiber Length For example in the plot above curves A B and C are the measured crosstalk in the same test fiber with different amounts of pressure applied at a particular point

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