Performance of optical heterodyne PSK systems with Costas loop in multichannel environment for nonlinear second-order PLL model

Using the nonlinear second-order phase-locked loop (PLL) model the performa nce of the heterodyne coherent optical phase shift keying (PSK) systems wit h Costas loop in multichannel environment is considered in this paper for t he first time, The shot: noise of the corresponding photodiodes and adjacen t channel interferences are described through the signal-to-noise ratio (SN R) 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 opti mizing the performance in the region where the linear PLL model is not enou gh good.