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Genera l Photon ics Corporat ion 909.590.5473 www.genera lphoton ics .com -40-

ThePolaStay™polarization trackerautomaticallyadjusts thestateofpolarization(SOP)towardsareferenceSOP,counteractingcontinuousinputSOPvariationsasfastas0.7mswithnoresets.ThereferenceSOPisdeterminedbyafeedbacksignalwhichcanbeprovidedeitherinternallyorexternally.Theinternalfeedbackversion(POS-002-I)consists of a fiber squeezer polarization controller, in-line polarization monitor, digital andanalogcircuits,andproprietaryalgorithm.Theerrorsignalfromthepolarization

monitorisfedbacktothepolarizationcontrollertomaintainalinearSOPattheoutput.The external feedback version (POS-002-E) replaces the internal polarizationmonitorwith an

external analog electrical feedback signal of the user’s choice, such as a voltage proportional to the degree of polarization(DOP)measuredbyapolarimeter,thebit-errorrate(BER)fromaBERchip,theRFspectrumofadetectedsignal,ortheopticalpowerafterapolarizer.TheoutputfibercanbeeithersinglemodefiberorPMfiberwiththeSOPalignedtoitsslowaxis.ThismodulecanbeusedforPMDcompensation,polarizationdivisiondemultiplexing,eliminationofpolarizationfadingincoherentdetectionandfibersensorsystems,suppressionofnoisefigureinopticalamplifiers,andreductionofPDLeffects.

Notes:Unlessotherwisenoted,specifications listedabovearefor thestandardconfigurationwith internal feedbackoptionwithoutconnectors;specsmay be different for instruments with different wavelength or input power ranges.1. Other wavelengths and control algorithms may be available upon request. 2.TheoutputpowerfluctuationcausedbySOPfluctuationafterpassingthroughapolarizer.3.Requiresaspecialcable(included).

Features:.Resetfreeoperation. 0.7 ms recovery time. 47 π/s tracking speed. Plug and play

Applications:.PMDcompensation. Polarization demultiplexing.Eliminationofpolarizationfading. Coherent detection

OperatingWavelengthRange1 1310 or 1550 ± 50 nm

SOPRecoveryTime <2ms(0.7mstypical)

SOPRotationTrackingSpeed(ResetFree) 47 π/s

SOPAccuracy2 <0.1dB

Repeatability2 <0.1dB

InsertionLossInternalfeedback:0.8dBtypical,1.2dBmax.Externalfeedback:<0.1dB

ReturnLoss >50dB

IsolationinOrthogonalPolarization 20dB

OpticalInputPower-20dBmto20dBmstandard(lowpoweroptionavailable)forinternalfeedback version

ExternalFeedbackVoltage 0to4.6voltsforexternalfeedbackversion

OpticalPowerHandling 20dBmmax.,higherpossible

OpticalPowerDamageThreshold 300mW

OperatingTemperature 0to70°C

StorageTemperature -20to70°C

PowerSupply+12VDC/0.5A- 12VDC/0.15A

CommunicationsInterface 3 RS-232

Dimensions 0.75”(H)x3.8”(W)x7.25”(L)

Tech Info: p. 100, 215 FAQ: p. 228

Polarization Modules for Communications and Sensor Systems

Reset-Free Polarization Tracker – PolaStay™

Specifications:

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-41- Genera l Photon ics Corporat ion 909.590.5473 www.genera lphoton ics .com

Accessories:NoTailTMIsolator p.91NoTailTM Polarizer p. 90NoTailTM Coupler p. 85NoTailTMPMCouplers p.86NoTailTMPBC/S p.87NoTailTMCirculator p.92

Figure 2 POS-002-I compensation for a steppolarization change.

Figure3.POS-002-I trackingof sinusoidal polarizationmodulation.

Figure 4. POS-002-I tracking of half-wave platerotation at 45π rad/s.

OrderingInformation:

TypicalPerformanceData:

Figure1.PolaStay™polarization tracker functiondiagram.Either internal or external feedbackcanbeused.Diagramshows structure for internal feedback.

POS—002— — ——

OutputFiber:SMPM

ConnectorType:FC/PC,FC/APC,SC/PC,SC/APCOthers specify

FeedbackOption:I=internalE=external

Wavelength:13 = 1310 nm15 = 1550 nm

Polarization Modules for Communications and Sensor Systems

Reset-Free Polarization Tracker – PolaStay™

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Genera l Photon ics Corporat ion 909.590.5473 www.genera lphoton ics .com -42-

Application examples:

PMDcompensation

Scheme1: Using a polarimeter to obtain feedback signal. In thisscheme,apolarimeterisusedtodetectthedegreeofpolarization(DOP)ofthesignaltoindicatethePMDeffectonthesignal.TheDOPwillbemaximizedwhenthePMDisproperlycompensated.TheuserconstructsasimplecircuittoconvertDOPintoananalogsignalbetween0~5Vandfeeds thissignalback to thePOS-002-E. Thepolarization tracker thenautomaticallymaximizesDOPtoachievePMDcompensation.

Scheme2: Using the receiver toobtain the feedbacksignal. In thisscheme,theerrorsignalindicatingthePMDeffectcanbeaclocksignalfrom the receiver’sphotodetectororaBERdetectedbeforeFEC insidethe receiver. Theuserconverts theerrorsignal intoananalogsignalbetween0~5voltsandfeedsitbacktothePOS-002-E.Thepolarizationtracker then either maximizes or minimizes the error signal to achieve PMDcompensation.

PolarizationDemultiplexing

Scheme1:Pilot tonedetection. A lowfrequencypilot tonearound100kHz is injectedatoneof the transmitters. At thereceivingend,apilottone extraction circuit can be used to detect the strength of the pilot toneandconvertitintoa0~5VfeedbacksignalforthePOS-002-E.Thedetected pilot tone will be maximized when the two polarization channels are properly separated. The polarization tracker then automaticallymaximizes the feedback signal to separate the two polarization channels.

Scheme2:BERdetection. Thebit-error rate (BER)before the forwarderrorcorrection(FEC) in thereceiver isdetectedastheerrorsignal forpolarizationdemultiplexing. TheBERwillbeminimizedwhen the twopolarization channels are properly separated. A simple circuit can be usedtoconverttheBERintoa0~5VfeedbacksignalforthePOS-002-E:thebiggerthevoltage,thesmallertheBER.Thepolarizationtrackerthenautomatically maximizes the feedback signal to effectively separate the two polarization channels.

Scheme3:Low frequencyRFdetection. The low frequencycorrelationnoise between two polarization channels is an indication of the channel crosstalk.Thenoisewillbeminimizedwhenthetwopolarizationchannelsare properly separated. A low frequency photodetector followed by a bandpass filter can be used to detect the noise level. A simple circuit canbeusedtoconvertthenoiselevelintoa0~5VfeedbacksignalforthePOS-002-E: thebigger thenoise, thesmaller the feedbacksignal. Thepolarization tracker then automatically maximizes the feedback signal to effectively separate the two polarization channels.

Scheme4:Power imbalancedetection. The twopolarizationchannelsare set at different power levels and the detected power difference is an indication of polarization channel separation. A simple circuit can be used toconvertthenoisechannelpowerdifferenceintoa0~5VfeedbacksignalforthePOS-002-E.Thepolarizationtrackerthenautomaticallymaximizesthe feedback signal to effectively separate the two polarization channels.

CoherentDetection

Inacoherentdetectionsystem, thestatesofpolarizationof thesignaland local oscillator must be the same in order to maximize signal to noise ratio.APOS-002-IcanbeusedtostabilizetheSOPofthesignalafteritpropagatesthroughthetransmissionfiber.TheSOPoftheoutputofthepolarizationtrackerislinearandalignedwiththeslowaxisofthePMfiberpigtail and will beat with the local oscillator.

PolarizationTrackingforSensorSystem

Inan interferometricsensorsystem, thedetectionsensitivity isdirectlyrelatedtotheSOPsof thetwointerferingsignals.APOS-002-Ecanbeusedtoobtainthemaximumdetectionsensitivity.Inthisapplication,thevisibility of the sensor can be monitored with a phase modulator and can beconvertedintoananalogsignalof0-5voltstobefedbacktothePOS-002-E.Thepolarizationtrackerthenautomaticallymaximizesthevisibilityfor stable, optimized detection sensitivity.

Polarization Modules for Communications and Sensor Systems

Reset-Free Polarization Tracker – PolaStay™