We have implemented an automated, nonmechanical approach to the measurement of polarization dependent loss (and, equivalently, gain). We use a deterministic fixed-states method to derive Mueller matrix elements from intensity measurements at specific polarization states. Voltage-modulated liquid-crystal variable retarders set the polarization states. Synchronous detection is employed to increase the signal-to-noise ratio (SNR) of the system and thereby allow measurement resolution to better than 0.001 dB. We present polarization-dependent loss measurements from 0.0016 to 0.56 dB at 1550 nm to verify performance.
Rex M. Craig, Sarah L. Gilbert, and Paul D. Hale, "High-Resolution, Nonmechanical Approach to Polarization-Dependent Transmission Measurements," J. Lightwave Technol. 16, 1285- (1998)