Experimental evaluation of parallel transmission using optical ZCZ-CDMA system

In the high speed parallel transmission of optical wireless communication, shifting of optical axis is important problem. An optical CDMA system using the optical ZCZ code is proposed as a method with the possibility that this problem can be solved without complicating hardware. The optical ZCZ code, which is a set of pairs of binary and bi-phase sequences with zero correlation zone, can provide optical code division multiple access (CDMA) communication system without co-channel interference. We proposed the compact construction of a code generator and a bank of matched filters for this code . In this paper, we verified that this system can remove co-channel interference even if an optical axis is shifted, by experiment of parallel transmission using an optical ZCZ-CDMA wireless communication system, consisting of a infrared light emitting diode(LED), an avalanche photo diode(APD) module and field programmable gate array( FPGA) boards corresponding to 400,000 logic gates. Desired to undesired signal ratio (DU ratio) in correlation output whose shiftings of optical axis are 0° and 45° are improved about 61.9 dB and 39.1 dB, respectively. As a result of experiment on the optical parallel transmission, it was proved that this system was able to suppress interference by shifting of optical axis.