A Channel Model to Deal with Distributed Noises and Nonlinear Effects in a Fiber System with Distributed Raman Amplifiers

Nowadays, the distributed fiber Raman amplifier (FRA) has become more and more popular in long-haul fiber systems, owing to its lower noise figures and weaker nonlinear effects in the link. The critical issue in distributed FRAs is the presence of various kinds of noises and their interactions with the signal. However, the existing Raman channel models and their numerical solving methods can only partially describe how the randomly distributed noises interact with the signal. This causes the difficulties in analyzing the distributed FRA precisely and the inconveniences for the applications and the maintenance of FRA systems. In this paper, we propose a modified Raman channel model to describe more comprehensively the interactions between the distributed noises and the signal under the influence of loss, distributed gain, dispersion, and nonlinear effects in the distributed FRA systems. With the comparisons of the error–vector magnitude (EVM) curves, our model can get lower errors in the experimental results regarding bidirectional pumped FRA single-span fiber systems and multi-span systems with backward-pumped FRAs.

Optimal Design and Performance Study of Optical Fiber Raman Amplifier with Flat Gain

Optical fiber communication is favored by many communication manufacturers because of its low interference, large capacity, long distance and low consumption. Extending the transmission distance of optical fiber communication system will result in attenuation loss. Therefore, it is necessary to improve the incident power of the initial optical fiber, but it will be affected by Raman scattering effect, thus reducing the performance of the overall optical fiber communication system. In order to overcome the above problems, Raman amplifier is used to pump high-power short-wavelength light wave and amplify long-wavelength and low-power signals, but the flattening of signal gain needs to be considered. In this study, the working principle of Raman amplifier is introduced, the Raman pump module is optimized, the system architecture of the module is studied, and the module circuit is designed. It mainly covers the structure design, driving circuit design and auxiliary circuit design of the module. In the experimental process, based on the transmission coupling equation of the fiber Raman amplifier, the distribution of pump and signal power on the fiber is calculated by numerical analysis. By optimizing the pump module, the gain flatness of the amplification system is optimized, and the signal gain of the whole fiber communication system is reduced by more than 80%. It proves that the optimal design of fiber Raman amplifier proposed in this study is effective and can achieve the overall stability of signal reception in the application of optical fiber communication system.