International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 05 Issue: 05 | May-2018 www.irjet.net p-ISSN: 2395-0072 © 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 2623 A Fast convergent frequency-domain MIMO equalizer for few-mode fiber communication systems Kovvuri Rakesh Reddy 1 , Prof. S.Revathi 2 1 Student, Dept. of Electronics and communication Engineering, VIT University, INDIA, 2 Prof, Dept. of Electronics and communication Engineering, VIT University, INDIA. ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Polarization-division multiplexing (PDM) has emerged as a next-generation technology to sustain the continuous traffic growth, in order to keep up with the future of Internet bandwidth requirement and one of the fundamental challenges in FMF transmission systems is the random inter-modal crosstalk between any two polarization modes. Another significant challenge is the large accumulated PMD, which can induce significant inter-symbol interference (ISI) on each polarized mode signal in PDM systems. The large accumulated PMD and an increasing number of multiplexed channels need very complex DSP hardware for MIMO processing and an urgent efficient solution is needed to mitigate the impact of booming internet penetration. We compare different mainstream blind and adaptive algorithms in order to find the algorithm that have better error convergence performance and efficient computational complexity. Key Words: Equalizers; Adaptive; Polarization Division Multiplexing, Chromatic Dispersion, Polarization Mode Dispersion 1. INTRODUCTION The data rates of optical communication networks have been widely increased but at data rates of more than 10 Gb/s, the performance of long-haul high-capacity optical fiber communication systems is significantly decreased by transmission impairments such as residual chromatic dispersion (CD), polarization-mode dispersion (PMD), laser phase noise and Kerr fiber nonlinearities. Generally, these linear impairments are compensated for in the optical domain, CD is compensated using dispersion compensating fiber or fiber Bragg gratings and PMD is avoided through fiber selection or compensated with an optical PMD compensator. Over the past four decades with the introduction and development of coherent detection, advanced modulation formats, and digital signal processing techniques these advancements promoted the growth of optical communication towards high-capacity and long-distance transmissions. With the entire capture of the amplitude and phase of the signals using coherent optical detection, the compensation and mitigation of the transmission impairments can be implemented using the digital signal processing in electrical domain this technique is generally called equalization which deals with inter-symbol interference in communication systems. There is no principal difference between a fiber optic channel and e.g. a radio channel in terms of ISI; the received baseband signal is distorted in a similar manner in both systems, i.e. symbols spread out over neighboring symbols as they propagate through the channel. Consequently, equalizer techniques used for radio and other systems should in essence be viable for fiber optic links as well. However, one important difference is that while a radio channel can usually be considered as linear, a fiber optic channel exhibits nonlinear characteristics which degrades the signal over transmission. So digital signal processing in optical communication enabled next-generation optical communication networks to achieve a performance close to the Shannon capacity limit to which we are closer than ever before. Long before we know we are touching the Shannon limit in order to solve this problem Polarization-division multiplexing (SDM) has emerged as a next-generation technology to sustain the continuous traffic growth, in order to keep up with the future of Internet bandwidth requirement. Among PDM technologies, PDM using few-mode fiber (FMF) transmission has been extensively explored [1]. and with the help of advanced DSP components it offered huge gains in data capacities that can be carried over optical networks [2]. In the digital coherent transmission systems, the output from the photodiodes are sampled and transformed into the discrete signals using high-speed analogue-to-digital convertors (ADCs), which can be further processed by the DSP algorithms. Figure (1.1): Schematic of coherent optical communication system with digital signal processing. In the early era of optical communication networks various methods have been developed to increase the communications system performance by reducing the effects of the ISI. In this project we compare and analyze the performance of different algorithms blind and adaptive that aid the DSP in 100 Gbps DP-QPSK optical communication system in reducing the ISI and the Polarization Mode Dispersion from the received de-multiplexed data that