Synchronous versus asynchronous CDMA for fiber-optic LANs using optical signal processing

Synchronous spread-spectrum code division multiple access (S/CDMA) for fiber-optic local area networks using optical signal processing is investigated. Compared to time division multiple access (TDMA), CDMA can provide some degree of immunization against fiber dispersion. Moreover, S/CDMA can accommodate more subscribers and a larger number of simultaneous users than asynchronous CDMA (A/CDMA). A/CDMA is a more suitable protocol in fiber-optic interexchange or long-haul networks where the number of users is less and network synchronization cannot easily be achieved. The design of the code sequences, suited for asynchronous access and incoherent optical signal processing, is studied. A two-user S/CDMA system demonstration at 500 Mbit/s is reported.<
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