Theoretical study on the stability of practical polarization transformers

sStability of practical polarization transformer (PPT) proposed by Huang is studied for the application of all-fiber optical current transformers (AFOCTs). The previous zero-order approximate solution ignores inter-mode coupling, which is one of the factors causing AFOCT instability. This paper develops a concise approximate solution to take into account the coupling between two local eigen-modes in the PPT. It is shown that power exchange of the two modes is determined by the internal coupling coefficient. Guidelines for designing spin rate profiles are given and verified with numerical results.