Fiber Raman Amplifier Optimization Algorithms And Software Design

With the fast development of Internet and other data communication, the capability demand of long-haul fiber communication system is increasing dramatically. Dense wavelength division multiplexing(DWDM )technique and optical amplifier are two milestones in fiber communication field. To obtain even higher capacity, it will be necessary to increase the spectral efficiency of these C- and L-band systems or utilize wavelength bands outside the erbium_doped fiber amplifier(EDFA)window. Fiber Raman Amplifier (FRA) based on stimulated raman scatter(SRS)effect in the transmission fiber to obtain amplification enable the capacity of future high-capacity systems to be increased using both those approaches.Raman fiber amplifier(FRA)is a kind of optical amplifier that can amplify signal light directly through nonlinear interaction of high intensity pump and signal light in fiber. Whereas the spectrum of Raman gain coefficient of optical fiber is not flat, the gain of signal light with different wavelength induced by a single pump is rather different。In this case , we must optimize the wavelength and the power of the pumps to get flat-gain of the signals.The main research contents and results are given as follows:(1) The characters of several kinds of optical amplifiers are compared. And the properties, applications and developments of fiber Raman amplifier are recounted.(2) The basic theory of Raman scattering and the characteristics of stimulated Raman scattering in fiber are detailed. The properties of fiber Raman amplifier are discussed, including gain property, noise property, polarization correlation and temperature stability.(3) The numerical model of fiber Raman amplifier is given first. Optimizing to the wavelengths and powers of pumps with an improved genetic algorithm and shooting method is actualized on FRA based on the numerical model and the simulation is actualized to amplify C+L band (approximately 100nm ) signals. The result is that when we chose suitable number and power range of pumps , according to wavelength and power the optimize software computed, the signal gain flatness is less than 1 dB. It is showed that the algorithm can be applied to the optimized designing of FRA.(4) On the base of MFC programming , the videotex Windows interface design of FRA optimizing software is particular described by the method of object-oriented programming. After enter the parameters on the interface, the wavelengths and powers of pumps can be obtained. At the same time, the gain flat, power evolvement and noise figure can be analysed.