Measurement of physical polarization parameters by system estimation

The system estimation by least squares optimization is employed to obtain physical polarization parameters of optical devices. The method is proved flexible and convenient for measuring polarization parameters in different systems where the input state of polarization (SOP) of the devices is either measurable or not, providing the analytical estimation equations and adequate measurements are available. The estimation error for the measurement system with a rotating wave-plate (WP) as the polarization state generator is analyzed and simulated. Better estimation precision can be obtained by involving more SOP measurements in estimations and choosing a WP with retardance around 3 pi/4. Two experiments are demonstrated. One is to estimate the polarization parameters of a fiber polarization controller with measurable input SOP, and the other is to measure the retardance of a glass quarter-wave plate whose input SOP is immeasurable. The standard deviations of estimated polarization parameters are within 0.0011-0.0103.