Temporal and statistical analysis of ultrashort light pulse code-division multiple access communications network

A technique for encoding and decoding coherent ultrashort light pulses is analyzed. In particular, the temporal and statistical behavior of pseudonoise bursts generated by spectral phase coding of ultrashort optical pulses is discussed. The analysis is motivated by recent experiments, which demonstrate high-resolution spectral phase coding of picosecond and femtosecond pulses and suggested the possibility of ultrahigh-speed code-division multiple access (CDMA) communications using this technique. The evolution of coherent ultrashort pulses is traced into low-intensity pseudonoise bursts as a function of the degree of phase coding. For random coding it is found that the encoded pulse obeys Gaussian statistics and that the intensity probability distribution function is a negative exponential. These results are utilized to calculate the performance (bit error rate) of a proposed ultrashort-pulse CDMA communications system as a function of data rate, code length, number of users, and receiver threshold. It is found that performance improves drastically with increasing code length.<
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