Prajapati Neha et.al; International Journal of Advance Research, Ideas and Innovations in Technology © 2018, www.IJARIIT.com All Rights Reserved Page | 739 ISSN: 2454-132X Impact factor: 4.295 (Volume 4, Issue 3) Available online at: www.ijariit.com A review article of WDM based optical fiber communication with WDM system evolution Amrita Soni amuujn@gmail.com Ujjain Engineering College, Ujjain, Madhya Pradesh Neha Prajapati prajapati.neha1910@gmail.com Ujjain Engineering College, Ujjain, Madhya Pradesh Dr. Neha Sharma nehatripathi@yahoo.com Ujjain Engineering College, Ujjain, Madhya Pradesh ABSTRACT “In the modern world, bandwidth and data rates are two most important parameters under consideration in any communication system. An optical fiber communication system is capable of transmitting the data at high bit rates and has a large bandwidth capacity. This high data rate and bandwidth capacity in an optical fiber communication system are further enhanced by using wavelength division multiplexing (WDM) in conjunction with the information transmission system, in which information from multiple sources are transferred using the same fiber, at the same time, but at different wavelengths. But the high capacity and data rates in optical WDM system is limited by nonlinear effects that occur in optical WDM system, which not only pose a limitation on the channel capacity and data rates but also degrades the performance of the data transmission system. In this paper, analysis has been done to investigate the efficiency of effect under the influence of different system parameters such as chromatic dispersion coefficient, channel spacing, transmission power level, effective area of fiber and fiber length in the form of input signals and output signals frequency spectrums”. Keyword: OFDM (Frequency Division Multiplexing), QAM, AWGN, etc. 1. INTRODUCTION Due to a massive increase in capacity demands inflicted upon the data transmission network by the rapid growth in information transmission rates in communication systems, the total number of channels in Wavelength Division Multiplexing (WDM) optical networks is increased [1]. The EDFA’s have limited gain-bandwidth. Hence in order to meet the requirement of increase in a number of channels, the spacing between the channels needs to be very small. A channels spacing of 100 GHz has been specified by current ITU grid, but these days systems with channel spacing of 50 GHz to 25 GHz are being considered. Such close spacing between the channels can give rise to many nonlinear effects such as Four-Wave Mixing (FWM), Cross Phase Modulation (XPM), Self- Phase Modulation (SPM), Stimulated Brillion Scattering (SBS) and Stimulated Raman Scattering (SRS) [3], [7]. These nonlinear effects, not just pose a serious limitation on the data transmission rate and channel capacity of an optical fiber WDM communication system, but also degrade the performance of the communication system. In FWM effect, two or more signals traveling in the same fiber interact with each other to produce new signals whose frequency lie within the same frequency range as that of original information signal [5]. This can lead to severe crosstalk and Intersymbol interference (ISI) and can lead to severe performance degradation of the system. In this paper, analysis has been done to investigate the efficiency of FWM effect at different simulation parameters such as channel spacing, transmission power level, effective area, chromatic dispersion coefficient and fiber length and results have been evaluated in the form of input signals and output signals frequency spectrums. 2. DIGITAL MODULATION TECHNIQUE WDM Wavelength division multiplexing is a kind of frequency division multiplexing – a technique where optical signals with different wavelengths are combined, transmitted together, and separated again. It is mostly used for optical fiber communications to transmit data in several (or even many) channels with slightly different wavelengths. In this way, the transmission capacities of fiber-optic links can be increased strongly, so that most efficient use is made not only of the fibers themselves but also of the active components