New fiber-optic ATM switching networks using optical code-division multiple access for broadband communication applications

We design new fiber-optic asynchronous-transfer-mode (ATM) networks which are based on incoherent optical code-division multiple access (CDMA). To eliminate the throughput bottleneck, optical signal processing is used in the proposed switching network to guarantee a high processing speed which is required by incoherent optical CDMA. This in turn can support real-time broadband communication services. Because strict optical orthogonal codes (OOCs) are employed, both cross-correlation and autocorrelation constraints are strictly limited to be "1" for variable-bitrate (VBR) and constant-bit-rate (CBR) data communications. In the VBR case, the use of strict OOCs can guarantee a lower bit error rate than using conventional OOCs. Moreover, the proposed ATM switching network can efficiently support CBR and VBR communications (e.g. HDTV and video conferencing with the MPEG-2 standard), with no increase of system bandwidth and no change of optical CDMA encoder/decoder. Simple theory and code construction of strict OOCs are presented. Moreover, error correction codes are used in fiber-optic CDMA networks to improve the system performance.