Research On Raman Fiber Amplifier Combining Multi-wavelength-pumped And Cascaded Fiber

All-optical amplifiers with large gain-bandwidth are developed extensively because of the increasing of the capacity of optical fiber communication systems and the development of wavelength division multiplexing(WDM) technologies. Fiber Raman amplifier(RFA) is full communication windows amplifier. The importance of RFA appears gradually because of its excellent features of distributed amplification, high gain, high output power,quick response speed, small non-linear influence, high signal noise ratio, et al.The main research contents and results are given as follows:Firstly, the development of fiber communication and the development and the existing state of affairs of fiber Raman amplifier are recounted. A basic requirement for the Raman fiber amplifier (RFA) used in the wavelength-division-multiplexing (WDM) optical fiber communication system is that its gain spectrum must be flat in the operation band. Several methods to design the gain flatness of RFA are analyzed. And the study on the gain flatness of RFA at home and abroad is summarized.Secondly, The basic of Raman scattering and characteristics are detailed. In succession, principles, characteristics, applications and devices are summed up. The Raman gain, gain bandwidth, the degree of polarization of gain and Raman threshold value relate to Raman fiber amplifier are detailed.Thirdly, A comprehensive analysis about mathematics'model of RFA is presented and a novel gain-flattened broadband Fiber Raman Amplifier (RFA) is presented. Several optimization methods of Fiber Raman amplifiers are discussed. A novel gain-flattened broadband Fiber Raman Amplifier (RFA) is presented by combining with multi-wavelength pumps and cascaded Fiber Raman Amplifier (RFA). The 100-channel WDM system is simulated and it has been received output power with gain-flattened broadband.Fourthly, Based on combination of the multi-pumps cascaded optical fiber, the paper optimized the pump power and the pump wavelength and the distance between two optical fiber using genetic algorithm. Then the changes of pump power and signal power are analyzed with the optical fiber distance. Then the RFA with two-wavelength pumps acting on two cascaded fibers combined silica fiber with phosphorus-doped silica fiber is simulated and achieve a bandwidth of 79.2 nm, gain flatness of 0.0197dB and a net gain of 5.3375 dB. And, the relation between gain and the change of wavelength, power of the two-wavelength pumps are simulated and analyzed in depth.The result show that the change of pump wavelength has little effect on the signal gain. However the power has much effect on the gain, the more power the more gain. At last, the Raman Fiber amplifier can get flat gain about the system with unequal signal inputting power by simulation.