Opt Quant Electron (2007) 39:723–734 DOI 10.1007/s11082-007-9134-0 Multiple access interference cancellation in Manchester-coded synchronous optical PPM-CDMA network H. Ghafouri-Shiraz · M. M. Karbassian · F. Liu Received: 12 April 2007 / Accepted: 31 October 2007 / Published online: 11 December 2007 © Springer Science+Business Media, LLC. 2007 Abstract A new interference cancellation technique for direct-detection optical code- division multiple-access (OCDMA) network employing pulse-position modulation (PPM) is proposed in this paper. The multiple access interference (MAI) estimation is achieved by pre-reserving one of optical spreading code sequences at the receiver based on the cor- relation property of padded modified prime codes (PMPC). The estimated interference is then cancelled out after photo-detection process. Additionally, the transmitted signal is Manchester-coded to further improve the system performance. Based on this proposed inter- ference canceller in a shot-noise limited regime, we have obtained an expression for the upper bound of the bit-error probability (BEP) taking into account effects of both MAI and shot- noise. This BEP is compared with that of a PPM-OCDMA without cancellation. Finally, the receiver structure of the proposed optical network unit (ONU) is fairly simple to compare with the conventional cancellation schemes. Keywords Multiple access interference · Prime code families · Synchronous optical CDMA 1 Introduction The optical code-division multiple-access (OCDMA) technique, as a potential candidate for multiplexing in high-speed local area networks (LAN) have lately attracted considerable H. Ghafouri-Shiraz (B ) · M. M. Karbassian Department of Electronic, Electrical and Computer Engineering, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK e-mail: h.ghafouri-shiraz@bham.ac.uk F. Liu ZTE Co. Ltd., Keji Road South, Hi-Tech Industrial Park, Nanshan District, Shenzhen, China e-mail: liu.fulei@zte.com.cn M. M. Karbassian e-mail: mmk404@bham.ac.uk 123