Coherent optical PSK systems with Costas loop in multichannel environment for nonlinear PLL model

Using the nonlinear second order phase-locked loop (PLL) model the performance of the heterodyne coherent optical PSK systems with Costas loop in multichannel environment is considered in this paper for the first time. The shot noise of the corresponding photodiodes and adjacent channel interferences are described through the signal-to-noise ratio in the loop bandwidth, while the laser phase noise is described through the normalized frequency fluctuations instead of the phase ones. The theory and results presented in this paper can be applied when analyzing and optimizing the performance in the region where the linear PLL model is not good enough