Optical CDMA Systems in High-Speed Telecommunications

摘要

Boulder Nonlinear Systems (BNS) and the University of Colorado at Boulder (CU-Boulder) have developed a novel spectral optical code division multiple access (OCDMA) system with bipolar code capability for use in ultra- high-speed communication applications. By using liquid crystal spatial light modulators (SLMs), BNS and CU-Boulder have successfully fabricated and demonstrated a reconfigurable 2-user encoder-decoder system based on a fiber test bed using three arrayed liquid crystal SLMs. A broadband Superluminescent Diode (SLD) source amplified by an erbium-doped fiber amplifier (EDFA) was spectrally encoded and decoded. The bipolar correlations of the codes were verified. Good contrast between the autocorrelation and cross-correlation values shows that a binary information symbol can be recovered by an appropriate threshold operation. BER (bit-error-rate) measurements also show the ability of this system to perform MAI (multiple-access-interference) rejection. The system can be made very compact, even with large numbers of subscribers, when large format, two-dimensional SLMs are used. Due to its programmability and two-dimensional operations in the optical domain, the system is suitable for implementing optically transparent routings in an ultra- fast Asynchronous Transfer Mode (ATM) switch.