Experimental optical code-division multiple access system for visible light communications

An optical code-division multiple access system (OCDMA) is presented for visible light communications (VLC). The OCDMA scheme is based on the recently proposed random optical codes (ROC), which do not present optimal correlation properties but are characterized by their ease of generation when large number of simultaneous users are considered. The synchronism mechanism when using ROCs is an important issue which is adequately addressed and solved by the designed system. An experimental prototype has been developed which allows us to transmit medium-quality audio data from several emitting sources simultaneously through different channels (using different codes), obtaining a practically error-free reception (imperceptible by the human ear) which perfectly agrees with the theoretical analysis.