Optical wavelength/spatial coding system based on quadratic congruence code matrices

This letter proposes a wavelength/spatial optical code-division multiple-access system based on quadratic congruence code matrices (QCCM). According to the in-phase cross-correlation of the QCCM, multiple-access interference can be fully eliminated by using balanced photodetectors (PDs). Moreover, this proposal provides greater signal power than does the modified quadratic congruence (MQC) coding system. Compared with the maximal-area matrices (M-matrices) and MQC coding system, the simulated results indicate that the proposal can remarkably improve the system performance in the receiver PDs.