Trellis-coded asynchronous optical CDMA systems

Since optical code division multiple access (CDMA) is an interference-limited system, we propose a system employing trellis-coded scheme and double optical hardlimiters (TC-DHLs) to alleviate the adverse impact of multiple access interference. For asynchronous transmission, optical orthogonal code (OTC) is utilized as signature sequence. System performance is evaluated under chip synchronous case among different users, and thermal noise, avalanche photodiode (APD) noise, and interference are taken into consideration. Numerical results show that our proposed scheme can further reduce the error floor up to several orders over systems that using only double optical hardlimiters.