Impact of the physical layer impairments on optical fiber communication systems

High speed, long distance, and multi-wavelength transmission (or wavelength-division-multiplexing—WDM) has pushed optical fiber communication systems closer to their physical limits. This dissertation presented investigations on the impact of physical layer impairments on optical fiber communication systems and strategies to optimize the performance of these systems.; A realistic computer simulation tool was developed for this study. The tool simulates the propagation of WDM signals from source to destination, and was verified on an OC-48 (2.5 Gb/s) link of deployed optical network—the National Transparent Optical Network (NTON).; A few example systems were under investigation. The first example was an OC-192 (10 Gb/s) upgrade of the NTON link. It was confirmed that chromatic dispersion was the dominant impairment and that chromatic dispersion compensation was necessary for this upgraded system. Another example system under study was an 8 user, 2.5 Gb/s, 214 km, asynchronous optical code-division multiple access (O-CDMA) system based on flattened matrix codes. Chromatic dispersion was found to be the dominant impairment. But given full chromatic dispersion compensation at the mid-point wavelength of the transmission band, the non-uniform gain profile of the erbium-doped fiber amplifiers (EDFAs) and the chromatic dispersion-slope remains to degrade the signal to multi-access interference (MAI) ratio. In contrary, nonlinearities such as the Kerr and Raman effects have a negligible impact on these O-CDMA codes in the transmission range that the example system represents. Therefore, chromatic dispersion compensation, EDFA gain-equalization, and dispersion slope compensation are essential techniques in O-CDMA transmission. The last example system under study was a wavelength routed optical network. The impact of EDFA gain on the traffic performance of such a system was investigated. It was found that to obtain optimum traffic performance the EDFA small signal gain values should be chosen carefully so that the gain saturation can be adequately compensated while the amplified spontaneous emission (ASE) noise generation is kept under a reasonable limit.