二维大气无线光码分多址通信系统

Atmospheric 2D-Wireless Optical Code Division Multiple Access Communication System

在无线光通信系统中采用光码分多址(OCDMA)技术,可以充分利用其丰富带宽,提高系统性能。考虑背景光噪声、探测器噪声、多用户干扰和大气闪烁等影响因素,给出了二维无线光码分多址(2D-WOCDMA)系统模型,在该模型中采用了脉冲位置调制(PPM)和光纤布拉格光栅(FBG)编解码器。通过数值分析,详细讨论了该无线光通信系统的性能。结果表明,大气闪烁是影响二维无线光码分多址通信系统性能的重要因素,当其对数方差较大时,系统难以实现通信,需要采用诸如多用户检测、信道编码及阵列接收等技术提高系统的性能;二维无线光码分多址通信系统适合采用1550 nm波段;该通信系统还受背景光、雪崩光电二极管(APD)增益和调制消光比等因素的影响。

Code division multiple access （CDMA） can be adopted to make full use of the broad bandwidth and effectively improve the system performance of wireless optical communication system. Considering the effects of background optical noise, multi user interference, avalanche photodiode detector （APD） noise, and atmospheric scintillation, the system model of atmospheric two-dimensional wireless optical code division multiple access （2D-WOCDMA） communication system with pulse position modulation （PPM） and fiber Bragg grating （FBG） encoder/ decoder is presented. And the bit error rate （BER） of this optical CDMA communication system is analyzed in detail. The results show that atmospheric scintillation is one of the important factors which affect the BER performance of this communication system, and the 1550 nm wave band is more suitable for this 2D-WOCDMA communication system. When the atmospheric turbulence is strong （σs^2≥0.2）, some new technologies, such as multi-user detection, channel coding and array reception, can be used to improve the system performance. The results also show that the performance of this communication system can be affected by background optical, APD gain and modulation extinction ratio.