Multi premises network based on spectral amplitude coding optical CDMA systems

The aim of this article is to introduce multi downstream passive optical network based on optical code division multiple access (OCDMA) technique, which is considered as a next-generation optical access network. Hence, incorporating this technique with passive optical network (PON) will enable the system to support higher bandwidth compared to the standard PON. The decoder is configured based on spectral coding because of its good noise suppression properties. Since the most important aspect of PON architecture is its simplicity, a multi PON access network each PON comprises 9 users encoded by modified quadratic congruence (MQC) codes at the C band for downstream signals with channel spacing 25/50 GHz is simulated. In this article low error rate transmission at high data rate for distances up to 28 km is demonstrated. Variation in the results was studied when varied fiber length, data rate and different effective power were applied. It has been shown that OCDMA is capable of providing gigabit-per-second for each user. The receiver sensitivity is affected by the multi premises system, where the best system performance can only be achieved when the effective power is -1dBm. Nevertheless, the results have indicated that the proposed PON based on spectral amplitude coding OCDMA technique is capable to support multi premises network

Proposal of successive interference cancellation scheme in optical code-division multiple access systems

Proposes one of the multiuser detection schemes, a new technique that has the potential to reduce interference or suppress multiple-access interference and, therefore, increase the capacity of optical code-division multiple access (CDMA) systems. It is a successive interference cancellation (SIC) scheme known as a low-complexity multiuser detection method for direct sequence CDMA systems. A SIC scheme is analyzed using an optical orthogonal code, with a different power for each user, that takes into account the impact of imperfect interference cancellation. (C) 2008 Society of Photo-Optical Instrumentation Engineers

Analytical comparison of optical code-division multiple-access systems with and without a successive interference cancellation scheme using modified prime-sequence codes

We analyzed direct-sequence code-division multiple-access system using a successive interference cancellation (SIC) scheme. Modified prime-sequence codes are utilized as signature sequences, and the performance measure studied in this paper takes into account the the effect of imperfect interference cancellation. The basic principle of the SIC scheme is to subtract the strongest received signals from the original signal one by one till all users have been detected and demodulated. In this analysis we have compared optical code-division multiple-access systems with and without the cancellation scheme, and it is shown that the SIC scheme with -20-dBm effective power can suppress multiple-access interference better than the system without cancellation. (C) 2008 Society of Photo-Optical Instrumentation Engineers