| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 94 === The importance of optical fiber communication is increasing in modern world. In optical fiber communication system networks, the application of optical amplifiers can avoid the signal distortion from transformation between electrical and optical signals and then provide even longer transmission span and permit even more components regardless of the loss increment. At present, the dominant optical amplifiers are erbium-doped fiber amplifiers (EDFAs), which have a characteristic of fixed amplification bandwidth. With the rising of internet popularization, wider bandwidth is required to satisfy the increasing requirement of the data quantity. This demand is limited by EDFAs’ characteristic. Another optical amplifier, fiber Raman amplifier (FRA), which has the characteristic of flexible amplification bandwidth, is a candidate to fulfill this demand. The lack of high power Raman pump light in the past, is solved with the development of high-power semiconductor and fiber lasers. Now the application of FRAs attracts people’s attention again.
The demand of high-power Raman pump light in FRAs is due to the low gain coefficient of the existing optical fibers. To achieve a suitable gain level, this demand of high-power pump is unavoidable. However, the higher the pump power is, the more severe the nonlinearity problem will be introduced. The performance of Raman pump light will greatly affect the performance of FRAs. In this thesis, we first focus on the relationship between Raman pumping schemes and the noise performance of FRAs. We further propose a combined pumping scheme to achieve better performance.
Although FRAs are often used in long-haul systems, we believe they can also benefit metropolitan networks with its better noise performance. In this thesis, we also investigate the appropriate application of FRAs in passive optical ring networks. We find that the performance of FRAs is very sensitive to the component loss. Because in metropolitan networks, many passive components should be included in addition to optical fibers, they introduced additional losses. In practice, the components have different losses. We investigate the impact of component losses and provide a way to optimize the performance of the Raman amplifier through proper arrangement of these components with different losses.
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