International Journal of Computer Science Trends and Technology (IJCST) – Volume 4 Issue 4, Jul - Aug 2016 ISSN: 2347-8578 www.ijcstjournal.org Page 19 Investigation of Fiber Non Linearity for Different Modulation Schemes in DWDM Networks S. Rajalakshmi [1] , Azaruddin Shaik [2] , Bangaru B.N.V. Chalam [3] Assistant Professor [1] (Senior) School of Electronics Engineering, Vellore Institute of Technology, University Vellore, 632014 Tamil Nadu –India ABSTRACT Nonlinear effects in optical fibers have become an area of academic research and of great importance in the optical fiber based systems. The employment of high bit rate multi wavelength systems together with optical amplifiers creates major nonlinear effects such as SRS, SBS, SPM, XPM and FWM in Dense Wavelength Multiplexing Division (DWDM) systems. Presence of these nonlinear effects in the optical fiber communication adversely effect the communication. Here we have investigated the Stimulated Raman effects (SR) and Stimulated Brillouin effects (SB) and Four Wave Mixing (FWM). We have designed and stimulated and analyzed the results using BER and Q factor for different data rates, distance, modulation formats and for different receivers. Keywords:- Stimulated Raman effects (SR), Stimulated Brillouin effects (SB), Four Wave Mixing (FWM). I. INTRODUCTION In some circumstances, the nonlinearity could counteract with the dispersion. In addition, when multiple channels are considered, the fiber nonlinearity results in interactions among channels. These nonlinear effects can be managed through proper system design. By increasing information spectral efficiency, which can be done by increasing channel bit rate, decreasing channel spacing or the combination of both, the effects of fiber non linearity come to play even more decisive role. Fundamental investigations have demonstrated the usefulness of Standard Monomode Fiber (SMF) for transmission of bit rate higher than 10 Gb/s over a single channel [1]. In the last few years, both dispersion and optical Kerr’s effects [2-4] have been studied together creating path ways to techniques called dispersion management techniques. The combined use of SPM and joint optimization of the bias and modulation voltages to increase the dispersion limited transmission distance at 10Gb/s was reported as high-speed transmission over SMF at 1.55ȝm suffers severely from the combined interaction of Kerr nonlinearity and dispersion. Several techniques have been developed to overcome these limitations[5]. The use of dispersion compensating fibers (DCF) has emerged as one of the most practical techniques to compensate for the chromatic dispersion in long-haul optically amplified standard fiber transmission systems.[6] II. FIBER NONLINEARITIES Even though optical networks are fast, robust, and error free, still nonlinearity exist. The nonlinear effects of the fibers play a detrimental role in the light propagation. Nonlinear Kerr effect is the dependence of the refractive index of the fiber on the power that propagating through it. This effect is responsible for self phase modulation (SPM), cross phase modulation (XPM) and four wave mixing (FWM). The other two important effects are stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS). 2.1 Four Wave Mixing FWM is a phenomenon that occurs in the case of DWDM systems in which the wavelength channel spacing are very close to each other. This effect is generated by the third order distortion that creates third order harmonics. In fact, these spurious signals fall right on the original wavelength which results in difficulty in filtering them out. In case of 3 RESEARCH ARTICLE OPEN ACCESS