To Mitigate Dispersion Effects in Coherent Optical WDM System Using DSP

Abstract

Dispersion and attenuation of light signal are main hindrance in WDM optical communication system. Dispersion is spreading of pulse (wavelengths) without losing its original shape. This may cause of overlapping of pulses at output of fiber. Attenuation of signal can be overcome by using optical amplifier and dispersion can be compensated by using dispersion compensation fiber, fiber Bragg grating and optical phase conjugation. The performance of system can be enhanced by implementation for efficient digital compensation techniques in Coherent WDM system. This paper is analyzing the effect of linear impairments with existing techniques and proposed a digital mitigation technique for dispersion and polarization mode dispersion (PMD) in optical coherent system while ignore the nonlinear effects of optical transmission channel. The result of proposed digital technique shows clear constellation diagram i.e. clear symbols and indicate the improvement in Q-factor at bit error rate (about 10^-9) with advanced polarization multiplexed quadrature phase shift keying (PMQPSK) modulation at bit rate 100Gb/s. In addition, it also increases the achievable distance up to 200kms with DSP technique. This presented work shows improvement in both distance and quality of signal at minimum BER. It may consider the optimal solution to equalize the chromatic dispersion and PMD for coherent optical system.