Time dynamics of outage of fiber optic local system employing spread spectrum

A model is developed for ascertaining the robustness of operation of the random-carrier-code-division multiple-access (RC-CDMA) method of implementing optical frequency division multiple access. The unwanted wander (i.e. the supersensitivity of carrier frequencies to physical perturbations) of each channel is parameterized by sigma , of dimensions gigahertz per square root second. Channel outage comes about when, by chance, too many channels crowd into the same part of the optical band, causing overwhelming adjacent channel interference. In this study a lower bound is derived on the mean time between outages (units of years), as a function of bit rate ( approximately 10 Mbit/s), chip rate (units of gigabits per second), required signal-to-interference-ratio ( approximately 3-30 dB), population size (on the order of ten thousand), and sigma . While the technology has not matured to give a clear prognosis of the ability to limit sigma , the 'payoff', in terms of performance for a given sigma , is discussed. Constraints on sigma are found that, if met, imply that RC-CDMA can be used to achieve networks with throughput exceeding 100 Gbit/s.<
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