受扰陆上级联掺铒光纤放大器系统的特性分析

PEKFOKMANCE ANALYSIS OF PEKTURBED TERRESTRIAL CASCADED ERBIUM-DOPED FIBER AMPLIFIER SYSTEMS

通过引入描述扰动程度的参数Ｘ和描述掺饵光纤放大器（ＥＤＦＡ）饱和特性陡度的参数Ｔ，本文推出了一个归一化的ＥＤＦＡ增益表达式，并据此对系统受扰后的信号恢复特性和误码率变化进行了分析。结果表明：对ＥＤＦＡ饱和程度较浅的陆上光纤通信系统，出现小于１ｄＢ（Ｘ≥０．８）的微扰时，光功率经一级ＥＤＦＡ即可恢复其原值的９０％；系统经３ｄＢ扰动（Ｘ＝０．５）后，光功率（信号和噪音功率之和）经过三级ＥＤＦＡ方能恢复到原值的９０％，但系统误码率（ＢＥＲ）的恶化则在两个量级以上，且随着扰动开始点的后移而更加恶化。这说明为保证系统受扰后能正常工作，其光信噪比应有相当大的裕量。ＥＤＦＡ饱和越浅，系统受扰动的影响就越严重。

By introducing two parameters,X(describing the perturbation)and T(descibing thesteepness of EDFA ain under saturation),an improved normalized Erbium-Doped Fiber Amplifier(EDFA)gain formula is derived.For terrestrial systems where EDFAs work under light saturation,results show that the optical power could regain 90 per-cent of its original value after one stage ofEDFA under perturbation of less than 1 dB(≥0.8).When the system suffers a 3 dB(X=0.5)perturbation,3 stages is needed to achieve the same degree of optical power restoration. On the otherhand,the corresponding system Bit-Error-Rate(BER)will deteriorate by more than two～orders ofmagnitude,and the later the perturbation starts,the more degradation in BER. Less saturatedEDFAs would result in worse BER under perturbation.