The Simulation Research Of Few-mode Erbium Doped Fiber Amplifier

With the advent of the mobile Internet, the network traffic presents the exponential growth, which has exceeded the growth of the single mode optical communication system capacity. At the same time, the single mode optical system capacity is approaching the nonlinear Shannon limit. So it is necessary to introduce a new physical dimension to cater to the demand of network traffic.Space division multiplexing based on mode division multiplexing and core division multiplexing is one of the most promising technologies. Inline optical amplifiers of high performance and low energy consumption are the key in long distance transmission. Erbium doped fiber amplifier(EDFA) greatly promote the development of optical fiber communication, as a result of higher gain bandwidth and good gain performance over the C band. However, the single mode EDFA will not be suitable for the mode division multiplexing systems where the signal mode is more than one. The large difference of the modal gain would lead to the signal distortion and the increase of BER, thus it would lead to the decrease of system capacity and the increase of outage probability. So the equalization of modal gain becomes an important target for measuring the mode division multiplexing amplifier systems.Based on the optical fiber mode theory and the model of few mode erbium doped fiber amplifier theory, the details of modal gain and noise figure are presented. Some ways to realize the equalization of modal gain were demonstrated in detail. The scheme of reconfigurable pump mode to control the modal gain of two and four signal mode groups was proposed. An optimized erbium doped distribution with using genetic algorithm to realize the equalization of four mode groups was devised, which provided technical support to fabricate the few mode erbium doped fiber.