Investigations on Efficient Optical Fiber Communication System with Dispersion and Self Phase Modulation

Abstract

Optical fibers are not only used in telecommunication links but also used in the Internet and local area networks (LAN) to achieve high signaling rates. In this dissertation, fiber nonlinearities have been studied, and analyze the effect of various parameters on the received power. Optical amplifiers like EDFAs simply amplify the optical signal by several orders of magnitude without being limited by electronic speed. Transmission impairments, which are general not significant in a regenerative system, accumulate along the transmission link when amplifiers are used, so that they can not be simply ignored, and this puts a new challenge to transmission design engineers. The nonlinearities in optical fibers fall into two categories. One is stimulated scattering (Raman and Brillouin), and the other is the optical Kerr effect due to changes in the refractive index with optical power. Phase modulation due to intensity dependent refractive index induces various nonlinear effects, namely, self phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM). In the standard single mode fibers, the Polarization Mode Dispersion is the phenomenon that causes the hurdles to reach the high bit-rate-distance product of amplified light wave communication system. The impacts on eye opening, eye closing and output power due to dispersion variation are studied. The impacts of pre compensation, in high data rate transmission systems have been investigated at different bit rates. It is reported that pre compensation produces the adverse effect on the eye opening, eye closing. Due to pre compensation, the significant degradation in the performance of high speed optical transmission system with the increasing bit rate is also reported. At the bit rate of 40 Gb/s and above it is almost impossible to cope with pre compensation without the use of dispersion compensation. The fiber nonlinear characteristics are the Optical Kerr effect and the stimulated scatterings. The fiber nonlinearities produce the input power limitations on the system as well as maximum transmission distance. To mitigate their effects, the dispersion mappings are used. Pre, post and symmetrical compensation techniques are compared on the basis of bit error rate (BER). The dispersion compensation fiber (DCF) is used in the compensation techniques. It is demonstrated that the hybrid compensation is better to reduce the nonlinear effects than its counter parts.