Analysis of optical communication systems employing dense wavelength division multiplexing in the presence of fiber nonlinearities.

摘要

There is a tremendous demand for cheaper and faster network services such as video, multimedia, data and voice-carried using Internet Protocol (IP). Optical communication networks need to provide more channels over a single fiber so as to increase capacity. The emerging multi-wave optical layer will have a profound impact on network architectures because it offers a simpler and less expensive way to carry high-speed data. Dense wavelength division multiplexing (DWDM) is a technology that transmits multiple data signals using different wavelengths of light through a single fiber. Therefore, DWDM technology gives the ability to expand the capacity of a fiber network rapidly to comply with the growing demands of transmission rates on the order of terabits (Tb/s). This high-speed, high-volume transmission is made possible by the optical amplifier. An optical amplifier is a section of fiber optic cable that has been doped with erbium to amplify the optical signal. Erbium-doped fiber amplifiers (EDFAs) have advantages compared to electronic amplifiers. They increase the strength of the optical signal without having to regenerate the signal, which offers new efficiency in the design and analysis of optical communication network systems.; The main objective of this dissertation is to analyze numerically how fiber nonlinearities can be compensated for in order to improve system performance of DWDM systems. As the transmission capacity increases, the signal-to-noise ratio (SNR) requirement increases, which requires that a high-power optical signal be inputted into a fiber. The use of high-power for large SNR leads to increased signal impairments due to the nonlinearity in the fiber. The narrow channel spacings in DWDM links give rise to crosstalk among the channels. Nonlinear crosstalk can be generated mainly by nonlinear effects such as: four-wave mixing (FWM), which increases the bit-error-rate (BER); self phase modulation (SPM), which overlaps with neighboring channels; and cross phase modulation (CPM), which changes the phases of pulses in other channels.; The traditional approach to the DWDM system design has been to employ a non-return to zero (NRZ) signal encoding technique for each wavelength. Optical soliton transmission technology is also investigated. This unique signal coding format takes advantage of fiber nonlinearity to increase the propagation distance.