Bias control approach based on VMD and LIA demodulation of a lithium niobate polarization controller.

A bias control approach is an automatic lock working point algorithm based on variational mode decomposition (VMD) and lock-in amplification (LIA) demodulation for a lithium niobate polarization controller (LNPC). Commonly, the dither voltage applied to the LNPC is much smaller than the bias voltage to avoid the influence of the dither signal on the output light, which reduces the polarization control accuracy of the LNPC. In this paper, we use VMD and LIA, with which the polarization control accuracy of LNPC can be improved, to extract and amplify the dither signal to compensate the drift half-wave of LNPC. The light intensity fluctuations of the output polarized light in vertical or horizontal directions are less than 0.017%.