Research And Application Of Third-order Fiber Raman Amplifier

With the development of optical fiber communications,the unrepeated optical transmission distance has been expanded from tens of kilometers to hundreds of kilometers.Because of the unrepeated optical transmission distance is limited by the attenuation,dispersion and non-linearity of optical fibers,when the transmission loss of optical fibers exceeds 90 dB,the traditional unrepeated optical transmission technology has been unable to achieve the breakthrough of the existing transmission loss,so new optical transmission technology need to be explored.Fiber Raman amplifier(FRA),which uses the transmission optical fiber as the amplifying medium to realize distributed amplification of signals,is one of the key technology of unrepeated optical transmission system because of the advantages of high gain,wide bandwidth and low noise.However,first-order and second-order FRA is still limited,but third-order FRA has lower equivalent noise figure(ENF)under the condition of same gain.So third-order FRA can obviously optimize the performance of system and expand the unrepeated optical transmission system.The focal point research in the thesis is third-order FRA.It mainly studies the mathematical model of the third-order FRA and analyses the key performance of the third-order FRA,such as noise and gain.A novel third-order FRA with multi-pumping wavelength based on semiconductor lasers is proposed,which optimizes the effects of laser lasing and relative intensity noise(RIN)on the system.Finally,experiments are carried out on high-speed ultra-long span unrepeated optical transmission system based on the new third-order fiber FRA.The specific research work is as follows:Firstly,based on the basic theory of stimulated Raman scattering(SRS)effect,the principle of third-order FRA is studied.According to the existing first-order,second-order and traditional third-order FRA structures,a novel third-order FRA structure with multi-pump wavelength based on semiconductor lasers is designed.Secondly,by studying the transmission equation of the first-order FRA with single pump and single signal,the mathematical models of pump light,signal light,Rayleigh Scattering,Double Rayleigh Scattering(DRS),Amplified Spontaneous Emission(ASE)noise of the third-order FRA are derived,and the solution methods of the mathematicalmodel of third-order FRA under initial and boundary conditions are given.Thirdly,by analyzing the noise sources and related parameters of FRA,the performance of first-order,second-order and traditional third-order FRA under the influence of DRS and ASE noise are simulated and analyzed.The conclusion is drawn that the traditional third-order FRA can improve the OSNR of system by 2.1dB compared with first-order FRA and 1.2dB compared with the second-order FRA,as well as the novel third-order FRA with multi-pumping wavelength based on semiconductor lasers can improve the OSNR of system by 0.9dB compared with the second-order FRA.Fourthly,a single-wave 50Gbit/s and 100Gbit/s high-speed ultra-long span unrepeated optical transmission system based on the new third-order fiber FRA is designed.The transmission of the total line loss 103.95 dB in 50 G single-wave system and 101.27 dB in 100 G single-wave system has been realized for the first time in China.