Recently, the transmission capacity of fiber-optic communication system has been increased rapidly by using the wavelength-division-multiplexing (WDM) technology. However, to increase this capacity to beyond Tb/s, broadband optical amplifiers are indispensable. There have been substantial interests in Raman amplifiers due to their extremely broad bandwidth and low noise figure. However, the performance of Raman amplifier depends mostly on the fiber characteristics since it utilizes the transmission fiber itself as a gain medium. Thus, for the design of a high performance Raman amplifier system, it is essential to analyze the effects of various optical fiber characteristics.
In this thesis, we compared the performances of Raman amplifiers using various types of optical fibers and analyzed the desirable characteristics of optical fibers for Raman amplifiers. In addition, we analyzed the effects of the dispersion-managed fiber link for Raman amplification. The results show that it should be possible to maximize the optical signal-to-noise ratio (OSNR) of WDM signal by optimizing the dispersion management. For example, the OSNR of the WDM signal Raman amplified in a 100-km long dispersion-managed fiber link was 1.3 dB higher than that obtained by a homogeneous fiber link with the same length
