Conventionally, optical CDMA systems with on-off keying (OOK) require a time duration equalling a signature sequence length to transmit only one bit. Since the crosscorrelation between the signature sequences results in multi-access interference (MAI), the signature sequences are designed so that their weight distribution is sparse for their long length, and then MAI rarely occurs. With this view, optical orthogonal codes (OOC) are investigated, which are characterized by a quadruple (L,W,/spl lambda//sub a/,/spl lambda//sub c/), where L and W are length and weight of sequences, respectively, and /spl lambda//sub a/, and /spl lambda//sub c/, are maximum off-peak autocorrelation and maximum crosscorrelation, respectively. Thus, the use of OOC makes the effect of MAI small, but has to spend a long duration for one bit. In this paper, we propose an embedded modulation scheme, where an asymmetric error correcting (AEC) code is embedded in an OOC used for identification in optical CDMA. We show that the proposed scheme achieves the same bit error rate (BER) as conventional systems, with less average number of photons.
展开▼
机译：传统上，具有开-关键控（OOK）的光学CDMA系统需要等于签名序列长度的持续时间以仅发送一位。由于签名序列之间的互相关会导致多址干扰（MAI），因此对签名序列进行设计，以使它们的权重分布在其较长的时间内稀疏，因此很少发生MAI。从这个角度出发，研究了光学正交码（OOC），其特征是四重（L，W，/ spl lambda // sub a /，/ spl lambda // sub c /），其中L和W是长度，序列的权重分别为/ spl lambda // sub a /和/ spl lambda // sub c /，分别为最大非高峰自相关和最大互相关。因此，使用OOC会使MAI的作用变小，但必须花费很长的时间持续一位。在本文中，我们提出了一种嵌入式调制方案，其中在光学CDMA中用于识别的OOC中嵌入了非对称纠错（AEC）码。我们表明，所提出的方案实现了与常规系统相同的误码率（BER），光子的平均数量更少。
展开▼
