Fiber Raman Amplifier (fra)

The Fiber Raman Amplifiers (FRAs) are more and more attractive for its particular virtues such as on-line, wide band, and low noise etc, and they are very fit for dense wavelength division multiplexing (DWDM) system of next generation charactered by its super large capacity and long transmission distance. FRAs are unsubstitutable in the fields such as optical fiber communication over the ocean, long haul transmission and exploitation of the entire low-loss band of fiber. In this thesis, the main study of FRAs includes:First, the numerical algorithm is developed to solve the coupled Raman equations, and implemented in MATLAB (noises are neglected). The equations describing the single wavelength and multi-wavelength forward pumping FRA are solved through numerical methods by dividing fiber into many small sections. The single wavelength backward pumping problem, which is in principle a two-boundary value problem, is solved by the common shooting method. Finally, for the multi-wavelength backward pumping FRA problems, which are very hard to cope with, we proposed multi-dimension parallel shooting method. The simulation results demonstrate that this method is very useful in solving the Raman coupled equations, which are representative of the highly nonlinear problems. The shooting can be converged in short time (the shooting deviation can be less than 10-8 after 6 shooting when there are 8 pumping wavelengths).Secondly, novel genetic algorithm is developed to optimize the wavelength and power value of the pumping sources in the mutli-wavelength backward pumping FRA to get the best gain flatness. In this algorithm decimal coding (which is suit for multi-dimension search) is adopted, the arithmetic crossovering and adaptive mutation are also introduced. Then the genetic algorithms are implemented in MATLAB. On the basis of numerical simulation, C band (1530～1570nm) and C+L band(1530～1610nm) FRA are designed and optimized.Thirdly, the principle of Fiber Raman Laser (RFL) and its analysis method aregiven. The optimization method is qualitatively analyzed.Finally, a C+L band optical fiber communication system amplified by FRA is simulated on the platform of PTDS (Photonic Transmission Design Suite), which is a commercial simulation package developed by VPI Inc. of German. The influence of FRA on system performance is discussed and according optimization schemes are given.