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本文阐述光纤数字通信中部分响应信号的特点,和适当地设置信号电平使平均误码率达到最小的方法。用高斯近似法导出部分响应系统的性能指标作为光纤和电路参数函数的解析公式,并且给出其波形参数的计算式。 本文对部分响应系统和全响应系统均在最佳信号电平设置条件下的性能作了比较,结果表明:(1) 部分响应系统的接收灵敏度优于全响应4电平系统1.7～3.0 dB。(2) 在使用PIN检测器的情况下,能够做到不论光纤的相对带宽如何,部分响应系统的接收灵敏度总优于NRZ系统。(3)在使用APD检测器的情况下,能够做到当光纤的全程3dB带宽小于数码率时,部分响应系统的灵敏度优于NRZ系统。 此外,本文还分析了部分响应系统进行误码监测的原理,并介绍了部分响应技术和其它码型结合应用的实例。在用PIN检测器的情况下,对部分响应系统和全响应系统进行了实验比较,实验结果和理论分析相符合。
This paper describes the characteristics of partial response signals in optical fiber digital communications and the method of setting the signal level to minimize the average bit error rate. Gaussian approximation method is used to derive the performance of partial response system as a function of fiber and circuit parameters analytic formula, and gives the waveform parameters of the formula. The performance of the partial response system and the full response system under the optimal signal level setting conditions are compared. The results show that: (1) The receiving sensitivity of the partial response system is better than 1.7 ~ 3.0 dB of the full response 4-level system. (2) With the PIN detector, it is possible to achieve a partial response system with better overall reception sensitivity than the NRZ system irrespective of the relative bandwidth of the fiber. (3) In the case of using the APD detector, the sensitivity of the partial response system is better than that of the NRZ system when the entire 3dB bandwidth of the optical fiber is smaller than the digital rate. In addition, this paper also analyzes the principle of bit error detection in some response systems, and introduces the application of partial response techniques in combination with other patterns. In the case of PIN detector, experimental comparison between partial response system and full response system is carried out. The experimental results are consistent with the theoretical analysis.