A novel asynchronous hybrid duty-cycle division multiplexing/optical code division multiple access system

The growing demand for larger optical bandwidth and new services rises the need for efficient multiplexing techniques. Recently, hybrid optical code division multiple access (OCDMA) systems have been developed in order to expand the capacity of optical networks. In this paper a new asynchronous hybrid duty-cycle division multiplexing (DCDM) spectral amplitude coding (SAC) OCDMA system is proposed. In the proposed system, each code-word of SAC-OCDMA carries 2-channel DCDM where each user is operating at data rate of 622 Mb/s which forms 3 × 2 × 0.622 Gb/s optical system. In hybrid DCDM/OCDMA system, users are first electrically multiplexed using different duty-cycles and then optically coded using multiple wavelengths. The performance of users with different duty-cycles are optimized by controlling the electrical amplitude levels. Results show that the bit error rate of 10^-9 for worst user is achieved at received power per chip of-22.5 dBm. Performance of proposed DCDM/OCDMA system operating at high speed data rate (i.e. 40 Gb/s per OCDMA channel) is also demonstrated.