Distributed Raman Fiber Amplifier

Due to the development of communications, the communication bandwidth has expanded from C band (1528-1562nm) to L band (1570-1610nm) and S band (1458-1520nm). Fiber Raman amplifier (FRA), based on Stimulated Raman Scattering, is the only amplifier that can work on the whole wave band from 1270nm to 1670nm. Meanwhile, FRA has become a hit recently because of its particular characteristics such as wideband and good noise performance. FRA has an extreme broad and attractive prospect Some numerical research work on FRA is discussed in this thesis, including numerical simulation method and the optimal design of a distributed FRA .The main research contents and results are given as follows:Firstly, The characters of several kinds of optical amplifiers are analyzed. And the developments and the existing state of affairs of fiber Raman amplifier are recounted. Then the meaning of this thesis is proposed.Secondly, The basic theory of Raman scattering and the function of stimulated Raman scattering in fiber are detailed. In succession, principles, characteristics, applications and classification of FRAs are summed up. The operation principle and function of the pump light source, Raman fiber and passive components, which build up the FRA communication system, are analyzed. And the functions of these devices are expressed in terms of corresponding figures and formulas. Then,such as gain property, noise property, polarization correlation and temperature stability, are discussed.Thirdly, a comprehensive analysis about mathematics'model of FRAs is presented firstly and the main numerical methods of FRA are discussed. In this thesis, on the basis of Runge-Kutta, an effective shooting algorithm is presented and used to solve the problem. For synthesizing all sorts of effects which may happen during the process of signal amplification, this algorithm is more adapted to the facts. After simplifying the mathematics'model of FRAs, the numerical method of backward-pumped FRAs is successfully accomplished. Based on all above, for the optimal design of FRAs, an effective computed method is accessible.Fourthly,A novel optimal design method for FRAs is presented. The propagation equations of FRAs pumped backward at multiple wavelengths are solved with two steps. Two fiber Raman amplifiers are designed with two pμmps and four pμmps,respectively. The relative gain flatnesses for the two-pump FRA and the four-pump FRA are all less than 1dB within the bandwidths of more than 50nm and 80nm,respectively. The calculational results verify that the proposed method is practicable and useful for designing FRAs with flat gain in broad bandwidth.