Theoretical And Experimental Research Of Broad-Band Fiber Raman Amplifiers

Fiber Raman amplifier (FRA) has been recognized as an ideal choice for the next-generation optical amplifiers. Because Raman amplification has many merits, such as low noise and flexibility in bandwidth design etc., it has been proved to be one of the key technologies to expand the span transmission reach and improve the capacity of optical communication systems. It is now a hot subject in the research area of optical amplifiers.In this dissertation, FRA and it design techniques are studied both theoretically and experimentally. The main points are as follows:1. The gain and noise properties of FRAs have been characterized systematically. The influence of the design parameters, such as pumping geometry, gain level, fiber length, and input signal power level, on the performance of FRAs have been analyzed.2. An efficient and stable algorithm for FRA design has been proposed. Based on the simple-shooting method and by introducing a modified-Newton method and the Broyden's rank-one method, for the first time, the simulation efficiency has been improved more than 4 times compared with the conventional shooting algorithms. This algorithm can be used to the performance evaluation of all kinds of FRAs.3. An efficient method for the gain or noise optimization of FRA has been proposed. This method deals with the optimization problem as a constrained nonlinear programming problem. The sequential-qudratic-programing method has been used to solve this problem. The efficiency of the method has been improved about 9 times compared with the conventional methods based on the genetic-algorithm.4. A novel method for the gain adjustment of FRA without changing the gain profile has been proposed and experimentally verified, for the first time, to our knowledge.5. The first domestic discrete dispersion-compensating C+L band FRA model machine has been successfully realized and experimentally tested. The bandwidth of the amplifier is 75 nm (1530-1605 nm). It can provide a net-gain higher than 10 dB. The gain flatness is about 0.9 dB and the noise figure is lower than 7 dB at the net-gain level about 10 dB.