Improvement of optical CDMA communication systems with coherent pulse and time coding

We propose optical code-division multiple-access (CDMA) communication systems with coherent pulse and time coding to improve the system performance for future optical networks. CDMA is one of the multiple-access schemes capable of sharing a common optical channel among many users by using address codes, which leads to high efficiency of channel bandwidth. We use the coherent pulse and the time coding to generate optical bipolar codes in time domain as the address codes, which offer better performance than unipolar codes. We theoretically analyze the bit error rate (BER) of the proposed system, and compare it to the BER of optical CDMA system with "incoherent pulse" and time coding. The numerical results show that our proposed system offers much smaller BER to a larger number of user pairs than the CDMA with the incoherent pulse. The proposed system is worthy of practical use in high-speed optical fiber network.