A spatial-spectral holographic correlator at 1536 nm using 30-symbol QPSK and QPSK codes optimized for secure communications

摘要

Direct sequence spread spectrum is employed for non-centralized, multiple access, secure, coherent optical communication. Finding a family of phase codes with optimal correlation properties is challenging; processing them at multi-gigahertz rates is even more challenging. Spatial-spectral holographic devices combine spectral hole burning with conventional holography to perform correlations and other signal processing and memory functions in real time and are ideally suited to process multi-phase encoded information. Such devices can operate at bandwidths greater than 10GHz, have time-bandwidth products of 10{sup}3 to 10{sup}5 and can potentially enhance optical telecommunications capabilities. Employing Er{sup}(3+) : Y{sub}2SiO{sub}5, we demonstrate excellent signal fidelity in the important telecommunications band around 1550 nm. We further believe this to be the maximum number of symbols yet achieved for correlations with optimized codes.