Trellis-coded asynchronous optical CDMA systems

Since optical code division multiple access (CDMA) is an interference-limit ed system, we propose a system employing trellis-coded scheme and double op tical hardlimiters (TC-DHLs) to alleviate the adverse impact of multiple ac cess interference. For asynchronous transmission, optical orthogonal code ( OOC) is utilized as signature sequence, System performance is evaluated und er chip synchronous case among different users, and thermal noise, avalanch e photodiode (APD) noise, and interference are taken into consideration. Nu merical results show that our proposed scheme can further reduce the error floor up to several orders over systems that using only double optical hard limiters.