Research On Measurement Of Physical Polarization Parameters Of Optical Devices Based On Least-square Estimation

In the optical fiber communication and sensation system, Due to the inneranisotropic or external environmental factors influence of optical fiber and devices,all sorts of polarization related damage, such as polarization phase noise,polarization mode dispersion and diattenuation could be introduced into system. Onthe other hand, making good use of the polarization properties of the optical devicescould be another way to achieve the measurement of the devices and sub-systems.Thus, it is becoming a hot research filed to measure the polarization parameters ofthe optical devices or sub-systems. The polarization effects of the devices includes:depolarization effects, birefringence effects and diattenuation effects, and all ofthose effect could be represented by16independent physical polarizationparameters.In this paper, we propose to estimate physical polarization (PP) parameters ofoptical devices directly by solving nonlinear system estimation equations with leastsquare best-fit optimization. The system estimation method performs convenientlyand flexibly in obtaining the PP parameters of the device under test. Two schemesare proposed in this paper, the analysis of theory and simulation based on Matlab isshown and experiments are following.The first scheme is based on the all-fiber communication system. By way ofsystem estimation, the physical parameters of the DUT could be got. By simulation,it is found that a better estimation result could be got when the retardance of therotable wave plate is about3π/4and the rotation number is more than15. The resultof the experiment shows that the standard deviation is between0.002and0.01.The second scheme is aimed to the system that the input polarization andoutput polarization parameters could not be obtained directly. By the way of leastsquare optimized method, the polarization parameters of the DUT could be measured. The experiment shows that13-times measurement could get a consistentparameter of the measured QWP and HWP (half wave-plate). The estimatedbirefringence retardances of the QWP and HWP are89.03°and179.41°and thestandard deviation of the measured retardances are0.0836°and0.1092°respectively.