Research On Polarization Orthogonality Loss Of Polarization Encoding Communication

Polarization encoding is one of the hot points in the field of high-speed optical fiber communication. Polarization encoding takes advantage of the polarization state of light carrying information, it is possible to completely solve the problem of power fluctuations, greatly reduces non-linear effects occur at 40Gb/s and higher speed optical fiber communication systems. This paper analyzes the impact of polarization dependent loss and gain of the entire system brings, and to further explore the impact of the loss of polarization orthogonality brings to BER. Applying the Muller-matrix method, we first obtain the measurable expressions for the polarization dependent gain (PDG) and the loss of polarization orthogonality (LPO), and put forward a maximum boundary value based on LPO; Secondly, for the long-distance single-mode optical fiber transmission, we measure its polarization dependent loss and loss of polarization orthogonality, comparing the experimental data with the theoretical values which confirm our conclusion, and do a detailed analysis with the sources of error, give the conclusion that the transmission fiber affect little to LPO. Last, for the first time, we experimentally demonstrate that nonlinear LPO creates in a semiconductor optical amplifier (SOA), and find that the LPO will slightly skim over the boundary nearby the threshold of injected current. Furthermore, an empirical formula has been achieved to gauge LPO induced power penalty, which has been proven to be valid in differential-polarization-shift-keying transmission by executing bit-error-rate measurement. Our conclusions are applicable not only to non-orthogonal polarization cases, but also valuable to polarization related communications even orbital angular momentum multiplexing.