Calibration Research On Large Dynamic Range Optical Coherence Domain Polarimetry

Polarized devices,components and systems are widely used in the field of optical fiber sensing and optical fiber communications.In particular,optical fiber gyroscopes,optical fiber hydrophone and optical fiber current transformer paly an important role in the fields of aviation,aerospace and warships.Polarization devices are the basic components that make up a system or instrument.Their polarization properties are directly related to the performance of the system or instrument.Therefore,testing these basic components is critical.In the test of polarization devices,the polarization extinction ratio(also referred to as polarization crosstalk)is the main physical parameter and technical index that characterize polarization characteristics of various polarization devices,crystals,polarization-maintaining fibers,and optical systems.Taking the interferometric fiber optic gyro(FOG)as an example,the integrated waveguide modulator(Ywaveguide)and fiber-optic sensitive loop are important components of it.The polarization extinction ratio of the Y-waveguide chip determines the measurement accuracy of the FOG,and the overall polarization crosstalk of the fiber-optic sensitive loop determine the bias stability of the FOG.It can be seen that the polarization characteristics of these two critical devices affect the performance of the FOG.Therefore,it is of great significance to measure the polarization crosstalk accurately,which is related to the correct evaluation of the polarization performance of the device and the accurate prediction of the system performance.This paper focuses on the study of the calibration method of the white light interference based large dynamic range optical coherence domain polarimetry(OCDP),and the construction of the calibration device.The main contents are as follows:(1)To propose a calibration method of OCDP,the measurement principle of OCDP is studied.The calibration idea of using polarization crosstalk as a transmission carrier is clarified.By analyzing the formation process of polarization crosstalk and its superimposed characteristics,a calibration scheme using the first-order polarization crosstalk transfer standard and using high-order polarization crosstalk to expand the standard is proposed.(2)Based on the calibration scheme,the structure of the calibration device was studied,The structure of a polarization-maintaining fiber-based calibration device using a first-order polarization crosstalk transfer standard and scaling in the range of 0 to-40 dB,and the structure of a 0°polarizer based calibration device using a high-order polarization crosstalk expend standard and scaling in the range of-40 to-100 dB was proposed.(3)The errors caused by the device's own defects in the process of actually constructing the calibration device was studied,and an experiment was designed to verify it.The number of coupling points and their coupling strength,the length of the optical fiber,and the extinction ratio of the polarizer itself are the three factors that affect the performance of the calibration device,and their influence is given.Based on these factors,a method for selecting the optimal structure when constructing a calibration device is proposed,and a final calibration device is constructed.(4)Using the final calibration device to calibrate an actual OCDP system,the error correction formula is given by verifying and analyzing the error in the experiment,and the entire calibration method is improved.Based on the above work,we finally proposed a complete calibration method for a large dynamic range OCDP system,and constructed a calibration device based on this method,and successfully calibrated an optical coherent domain polarization system with a large dynamic range of 100 dB.