Mitigation of CD, PMD and Nonlinearity in Ultra High Speed Long Haul QAM-16 Coherent Fiber-Optic Communication System

The impacts of chromatic dispersion (CD), polarization mode dispersion (PMD), and nonlinearity have become very significant for ultra-high speed long-haul fiber-optic communication systems. We are considering a system with 160 km long fiber having a speed of 112 Gb/s employing QAM-16. This paper addresses the above challenges, focusing on the mitigation of PMD, a stochastic impairment caused by differential signal polarization propagation. We have employed a simulation-based methodology following the OCSim module to simulate the transmission system with these impairments. Furthermore, we have incorporated the Constant Modulus Algorithm (CMA), a popular adaptive equalization technique for PMD compensation, and a systematic dispersion management system. Our findings reveal a complex interplay between the CD, PMD, and nonlinearity. We have generally observed an increase in the BER due to CD, PMD, and nonlinearity. However, we demonstrate that it is possible to mitigate these effects by optimizing the system parameters and applying the CMA algorithm, Frequency-Domain Equalizer, and digital post-processing technique. Thereby, the system performance can be improved.