二维非相干光码分多址系统信息侦听技术

Interception of 2D incoherent optical code division multiple access system

以二维非相干光码分多址(OCDMA)系统为例,设计不同的信息侦听方案,开展了信息侦听技术探讨。假设窃听者对整个系统的编/解码方式,地址码字的构造方式,系统的传输速率以及采用的频率片数量、大小等信息有足够的了解,利用光电检测技术获取OCDMA系统中光信号在不同波段、不同时间的能量分布情况;利用获取的能量分布矩阵有效地破译出系统中存在的地址码字。分别将两种侦听方案在利用Optisystem和MATLAB软件搭建的采用了7个用户和7组二维地址码的二维非相干OCDMA软件平台上进行分析。分析结果表明,两种侦听方案均能有效地破译出用户的地址码字,实现对整个系统的信息窃取。由此可见,二维非相干OCDMA系统仍然存在安全性问题。

Two different information intercepting schemes were designed to resolve the security problems on a 2D incoherent Optical Code Division Multiple Access（OCDMA） system. Firstly, it was assumed that the interceptors knew enough information such as the mode of en/decoding, the constructing mode of address code, the transmission rate of the system, the value and quantity of wavebands, etc. Then, the energy distributions of optical signals at different time and wavebands in the OCDMA system were achieved using an advanced optoelectronic detection technique. Finally, the address codes existing in the OCDMA system could be deciphered effectively employing the energy distributions. The functions of the two intercepting schemes were simulated on the software platform of an incoherent OCDMA system with seven users and seven Reed-Solomon （R-S） codes received randomly,experimental results show that the interceptors can decipher the user signature codes effectively when the two-code keying is employed as the modulation way of the OCDMA system or the multi-users are in existence simultaneously. The results indicate that the security problem still exists in the 2D incoherent OCDMA system.