Influence of nondegenerate four-wave mixing on coherent transmission system using in-line semiconductor laser amplifiers

Three-channel coherent frequency-shift-keying (FSK) transmission experiments using in-line semiconductor laser amplifiers under the influence of nondegenerate four-wave mixing in laser amplifiers are discussed. The experiments show that the effect of four-wave mixing is reduced by applying modulation to the interfering carriers and enlarging the frequency separation of each carrier. However, transmission quality degradation becomes serious in multistage amplifier systems.<
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