Multilevel Optical CDMA Network Coding with Embedded Orthogonal Polarizations to Reduce Phase Noises

A spectral-amplitude coding optical code-division multiple-access (SAC-OCDMA) system with four-level intensities and polarization-division-multiplexing (PDM) is presented. Each encoder/decoder pair is shared by two subscribers in such a network. However, phase-induced intensity noise (PIIN) induced by high intensities deteriorates the system performance. To suppress PIIN, users sharing the same encoder transmit signals on mutually orthogonal polarizations, and the receiver structure with multiple balanced detectors is employed.