卫星光网络中分光信息损耗研究

Study on information expenses of beam splitting in optical satellite networks

分析了由星间并行M-ary激光链路分光引起的能量损耗和由此导致的信息损耗。采用Lagrange乘数法得到了量子噪声极限下的最佳分光比与各符号发送概率和发送能量的关系。当用先验等概率和等能量发送时,最佳分光功率比为1:1:…:1,与相同平均发送功率OOK相比,M-ary各支路接收功率下降到了OOK的(log2M)/M量级。基于分光能量损耗的分析结果,推导了链路接收误码率恶化和信息损失,并做了相应的数值分析和Monte-Carlo仿真。仿真结果表明:4-ary受分光影响最小;随着M-ary分组数的增加,链路性能恶化,当分组数从4增至32时,由分光损耗造成的信息损失与5dB的接收功率损耗相当。

The expenses of energy and information on beam splitting in parallel M-ary optical inter-satellite links are analyzed.The optimum splitting ratio with the relation between transmitting probability and transmitting energy of each distinct symbol is obtained using Lagrange multiplier method.Under the circumstance of equal transmitting probability and equal transmitting symbol energy,the optimum splitting is equal power splitting,and the average energy received in each branch of parallel M-ary links decreases to an order of （log2M）/M compared to OOK with similar average transmitting power.Based on the expenses of energy,the BER degradation and information lost due to beam splitting are calculated using Monte-Carlo method.According to both results,when M increases from 4 to 32,information loss caused by beam splitting is the same as an attenuation of received signal by more than 5dB.