sagnac interferometry

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SagNAC Interferometry. Matt Boggess and Devon Sherrow -Groves. Overview. Intro Theory Improvements Problems Final Iteration Data Conclusions Future prospects. Introduction. Sagnac effect used in fiber optic gyroscopes Used for navigation in planes and boats - PowerPoint PPT Presentation


Muhfuckin SAGNAC

SagNAC InterferometryMatt Boggess and Devon Sherrow-GrovesOverviewIntroTheoryImprovementsProblemsFinal IterationDataConclusionsFuture prospectsIntroductionSagnac effect used in fiber optic gyroscopesUsed for navigation in planes and boatsLightweight alternativeAble to make measurements inside an inertial frameBasic SetupSource1550 nm50/50Detector2 km loopOIDiscuss the setup as well as a small amount about connectorization and polishing.4TheoryCounter propagating wavesDifference in path length due to rotationCauses a phase shift, which causes interference

In/out at t=0In/out at t=tSecond IterationConfine inertial frameAdd polarization controllerOptimize detection schemeSource1550 nm50/50Detector2 km loopPolarization ControllerRotational StageOI

Second Iteration of Sagnac InterferometerImprovementsQualitative vs. quantitativePhase shift measurementRotational rate measurementPhase ModulatorWrapped PZT cylinderExpansion causes the fiber to stretchr = d33 (V)Path length changes, causing a phase shiftCharacterize with a Mach-ZehnderoutRadial Expansion+-inNonzero voltageZero voltageD33- radial tensor element, property of the PZT9Mach-Zehnder InterferometerDetects interference due to phase difference between two armsSource1550 nm50/50Detector50/50Phase ModulatorVoltage Driver

OIPM ObstaclesEpoxy (20 coil, hand-wrapped)Weak bondNo phase shift visible

PM Obstacles Cont.Cyanoacrelate (122 coil, lathe-wrapped)Bonding to the plastic coatingStill no phase shift

PM Obstacles Cont.Tensile testBreaking fibersFree space phase shifter test

Third IterationImproved design considering 50/50 couplersFiber Loop consolidation Error minimizationSource1550 nm50/50DetectorTerminated ends

50/502 km loopPolarization Controller

Rotational StageOIFinal Iteration of Sagnac Interferometer

DataMeasuring relative intensity change under rotational influenceRotational rate measurement, V measurement

System LossesLosses in optical power due to 50/50 coupling, backscattering, etc.CW Rotation

Slow rotational rate (0.10 rad/s)V = 0.800mVRegular rotational rate (0.15 rad/s)V = 1.20mVFast rotational rate (0.22 rad/s)V = 1.52mVCCW RotationSlow rotational rate (0.079 rad/s)V = 0.720mVRegular rotational rate (0.11 rad/s)V = 1.28mVFast rotational rate (0.20 rad/s)V = 2.48mV

Data Cont.

Stable CCW stable CW stableSwinging motionLower limit of detectable CCW rotation0.0416 rad/s (~2 degrees per sec)Rotational Rate and Intensity ShiftConclusionsAble to discern Sagnac effect in a fiber optic setupIntensity change is linearly related to rotational rateVibrational noise plays a large roleWithout a phase modulator, limited range of rotation ratesPhase modulator progress

Moving ForwardImplementation of phase modulatorExamine intensity shift dependence on phase differencePhase shift nullingIntegrated feedback circuit (PID loop) to control piezoelectric phase modulatorComplete FOG setupQuestions?


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