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本文试从工程观点来计算数字光纤通信系统中接收机的三个主要参数,即给定误码率时所必须的最少输入光功率P_入、最佳雪崩增益G、最佳门限值r。文章叙述了光纤通信中接收机的各种噪声、给出一般的信噪比表达式。并用物理概念较为明确、计算较为简捷的高斯近似法求出P_入,得出采用APD后比PIN无倍增检出器灵敏度高3/G倍。文章讨论了高斯近似法在计算门限r时误差较大的原因,说明可用切尔诺夫上限法采计算给定P_入及G时的门限值r。因而避免了单纯用某一计算法求三参数时带来的复杂性或较大误差。
This article attempts to calculate from the engineering point of view digital optical fiber communication system receiver three main parameters, that is, given the minimum bit error rate required input optical power P_, the best avalanche gain G, the optimal threshold r . The article describes various kinds of noise in the receiver in optical fiber communication and gives a general expression of signal to noise ratio. And with a more explicit physical concept, the calculation of relatively simple Gaussian approximation method to find P_, obtained after APD than PIN without doubling the detector sensitivity 3 / G times higher. The article discusses the Gaussian approximation method in the calculation of the threshold error r larger reason, indicating the Chernobyl ceiling method can be used to calculate the given P_ and G when the threshold r. Thus avoiding the complexity or large error caused by simply using a certain calculation method for three parameters.