Multiple-access interference suppression in an optical DS-CDMA LAN using fractionally-spaced equalization

We present a new adaptive equalization scheme for an optical direct-sequence code-division multiple-access/wavelength-division multiple-access local area network system based on a star architecture. Differentially-coherent demodulation of differential-phase shift keying (DPSK) signals is used at the receiver, which comprises a matched filter followed by a fractionally-spaced equalizer to suppress multiple-access interference. The system performance is evaluated via simulations with simultaneous asynchronous users employing length 127 Gold sequences. Mean-square error and bit-error rate results show that this scheme outperforms the conventional single-user receiver, even without a training sequence.