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给出了时域相位光码分多址系统(OCDMA)的噪声模型,提出了由码间串扰(ISI)所引起的自差拍噪声(SB)概念。利用鞍点近似法分析了多址干扰(MAI)、码间串扰、自差拍等噪声对系统性能的影响,给出了系统误码率公式。对最佳门限接收系统以及采用光硬件限幅器的系统性能进行了仿真研究,表明“1”码的误判概率是影响系统的决定性因素,也是开关键控(OOK)系统难以克服的主要问题。最后给出一种采用双编/解码器平衡检测系统的原理框图,分析其性能,并与传统OOK系统比较,结果表明其性能有较大的提高。
The noise model of OCDMA system is given and the concept of self-beat noise (SB) caused by inter-symbol cross-talk (ISI) is proposed. The effects of multiple access interference (MAI), crosstalk between codes, self-beat and other noise on system performance are analyzed by using the saddle point approximation method. The system error rate formula is given. Simulation results show that the misjudgment probability of “1 ” code is the decisive factor affecting the system, and it is also hard to overcome by the OOK system main problem. Finally, a block diagram of the balanced detection system with dual encoder / decoder is given, and its performance is analyzed. Compared with the traditional OOK system, the performance of the system is greatly improved.