ABSTRACT
This chapter explains the construction, properties, and performance of 1-D synchronous prime codes. The term synchronous usually refers to the requirement that transmissions of all simultaneous users originate at a certain reference frame, namely in time or wavelength, at all time. Synchronous coding can support more possible subscribers because cyclic-shifted versions of incoherent codewords can be treated as distinct codewords, substantially increasing code cardinality. Synchronous coding requires new optical codes with fixed, low, in-phase cross-correlation functions. In the synchronous prime codes, the peak of the cross-correlation function between any two codewords can be as high as the autocorrelation peak, but is never found at the expected autocorrelation-peak position of the codewords. In environments such as small-scale networks, where synchronization is relatively easy to achieve, synchronous coding is more attractive than asynchronous coding. In interexchange or long-haul networks, in which network synchronization is rather difficult to achieve, asynchronous coding becomes more attractive.
