| With the construction and development of the Global Energy Internet,the increase of projects such as trans-regional UHV construction and transoceanic submarine optical cables,optical fiber communication systems have put forward new requirements for transmission capacity and transmission distance.In a long-distance optical fiber communication system,several relay stations are usually used to regenerate and amplify the signal to ensure the quality of the optical signal.However,the setting of the relay station will increase the cost and maintenance difficulty,especially in the harsh natural environment,the relay station is difficult to lay,so it is necessary to extend the transmission distance of the single-span optical fiber communication.When dealing with long-distance transmission,the traditional hybrid gain technology is difficult to provide sufficient gain,and high-order Raman amplifiers have become a research hotspot in the amplification technology of long-distance optical fiber communication systems due to their high gain,low noise,and large bandwidth.This dissertation investigates the key principles of distributed fiber Raman amplifiers and remote pump amplifiers.On this basis,the noise characteristics and gain characteristics of high-order Raman amplifiers,the optimization method of high-order Raman gain spectrum flattening,and the joint optimization method of remote pumping and Raman gain spectrum are studied,and the long-distance optical fiber transmission system is solved.The problem of uneven gain spectrum,the main research work of the paper is as follows:This dissertation studies the key principles of distributed fiber Raman amplifiers and remote pump amplifiers.On this basis,the noise characteristics and gain characteristics of high-order Raman amplifiers,the optimization method of high-order Raman gain spectrum flattening,and the joint optimization method of remote pump and Raman gain spectrum in the process of long-distance optical fiber transmission are mainly studied.(1)Aiming at the noise characteristics of high-order Raman amplifiers,a comparison scheme of the noise characteristics of different Raman pumping orders is designed,and the first-order to third-order Raman pumping order pairs are simulated and analyzed in a 100km transmission system.The effect of the equivalent noise figure,the research results show that the average ENF of the third-order pump is improved by about 1.78dB compared to the first-order pump.(2)Aiming at the problem of uneven gain spectrum of the third-order Raman amplifier,a method for optimizing the gain spectrum of the thirdorder Raman amplifier based on the differential evolution algorithm is proposed,and the optimization performance of the method under the transmission distance of 100km is simulated and studied.The research results show that the proposed method can obtain a flat gain spectrum with a gain fluctuation of 0.51dB;compared with the genetic algorithm,the proposed method has higher efficiency and stability.(3)Aiming at the problem of the deterioration of the gain spectrum caused by the introduction of the remote pump in the long-distance optical fiber communication system,a joint optimization method of the bidirectional third-order Raman and the remote pump gain spectrum is proposed.The simulation study shows that the gain is obtained in the transmission system with a fiber span of 260 km Gain spectrum with fluctuation of 0.7398dB;compared with direct introduction of remote pump,the system gain flatness is improved by 0.634dB. |
