一种新的光码分多址多用户干扰抑制方法

A Novel Method for Suppressing Multi-User Interference of Optical Code Division Multiple Access System

目前光码多分址(OCDMA)系统多采用开关键控(OOK)调制,多用户干扰主要影响发送比特为“0”时的误码率,原因是发送比特“0”时信号中没有光脉冲。据此,提出了一种新的OCDMA多用户干扰抑制方法。研制了一种新型OCDMA系统,通过对比特“0”和比特“1”分别使用同一地址码和它的移位变形,来避免发送比特“0”时无光脉冲的问题,而且接收端采用最大值判决,进一步减小多用户干扰。阐述了其工作原理,系统采用最佳光正交码作为地址码,分析推导了新型系统的误码率表达式,进而对新型系统和常规系统进行误码性能仿真。仿真结果表明,新型系统比常规系统的误码性能改善10个数量级以上。

In order to restrain the multi-user interference that exists in optical code division multiple access（OCDMA） system,the on-off keying（OOK） is presently adopted as modulating method in most of OCDMA systems. Multi-user interference mainly has effect when bit 0 is transmitted ; the reason is that there is no optical pulse at that case. Based on this idea,a novel method to suppress multi-user interference in OCDMA is presented,which is a new OCDMA system. It avoids no optical pulse existing while bit 0 is transmitted by adopting a spread spectrum code and its shift as the address codes of bit 0 and bit 1, respectively,and using the maximum value decision instead of the threshold decision. The fundamental of the system is stated,the optimal optical orthogonal codes is applied as address codes,the bit error probability of the novel system is derived and analyzed. Simulations based on the expression are done. The results show that the bit error performance of the novel system can be ten orders better than that of conventional system.