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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Performance analysis of WDM-based coherent time-spreading optical CDMA system

Jianhua Ji, Zhiwen Chen, Ming Xu

Published Oct 20, 2008• 1 citation
Publisher

Abstract

The performance of WDM-based coherent time-spreading OCDMA system is studied. Upper bound and lower bound of normalized throughput are obtained with 8 wavelength channels and 127 length and 511 length Gold codes. It is shown that when all simultaneous users are equally allocated to different wavelength channels, WDM+ TS OCDMA has much better performance. However, if there is no central control to allocate wavelength channels equally, WDM+ TS OCDMA system has the in-between performance of normalized throughput.

DOI
10.1117/12.802763

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Religación•Jul 19, 2019•0 citations
The performance of WDM-based coherent time-spreading OCDMA system is studied. Upper bound and lower bound of normalized throughput are obtained with 8 wavelength channels and 127 length and 511 length Gold codes. It is shown that when all simultaneous users are equally allocated to different wavelength channels, WDM+ TS OCDMA has much better performance. However, if there is no central control to allocate wavelength channels equally, WDM+ TS OCDMA system has the in-between performance of normalized throughput.
We propose a novel quasi-synchronous coherent time-spreading optical CDMA (TS-OCDMA) system, where the synchronization among users can be controlled within permissible time delay. Relationship between the system performance and code parameters is analyzed. In quasi-synchronous coherent TS-OCDMA system, beat noise (BN) and multiple-access interference (MAI) are depend- ent on the mean intensity of aperiodic cross-correlation within permissible time delay. LA sequence is employed in this network, and code performance is analyzed. Within permissible time delay, the mean intensity of aperiodic cross-correlation equals zero, and hence the BN and MAI can be eliminated in quasi-synchronous coherent TS- OCDMA system. When the time delay is out of zero correlation zone, crosstalk value of LA sequence is less than that of Gold sequence. Therefore, quasi-synchronous coherent TS-OCDMA using LA sequence is beneficial in a low-user-load OCDMA network.
The performance of coherent time-spreading (TS) and asynchronous TS phase coding optical code division multiple access (OCDMA) systems is investigated and analyzed. Particular consideration is given however to both beat noise (BN) and multiple-access interference (MAI) effects, and the impact of decision threshold on the bit-error-rate (BER) performance is evaluated. Improvement of the BER performance can be obtained by use of optimum threshold detection, and the improvement is more apparent in the asynchronous TS OCDMA scheme for a low number of simultaneous users with long code length.
OCDMA) is an alternative method, which performs encoding and decoding through an optical signature code, in order to allow the selection of a desired signal so that different users can share the same bandwidth.In such a systems, data signal overlap both in time and wavelength.Tradeoffs between security and performance in optical CDMA are presented.Confidentiality against eavesdropper interception strategies for optical CDMA is considered.Coherent detection and combining signals shows better confidentiality than the incoherent one.Spectral amplitude optical CDMA based on Modified Double Weight (MDW) systems, with different code dimension, is investigated.Increasing the network system capacity or maximizing authorized specified SNRs will lead to eavesdropper to detect high SNRs.
(OCDMA) is an alternative method, which performs encoding and decoding through an optical signature code, in order to allow the selection of the desired signal so that different users can share the same bandwidth. In such a system, the data signal overlap both in time and wavelength. Tradeoffs between security and performance in optical CDMA are presented. Confidentiality against eavesdropper interception strategies for optical CDMA is considered. Coherent detection and combining signals shows better confidentiality than the incoherent one. Spectral amplitude optical CDMA based on Modified Double Weight (MDW) systems, with different code dimension, is investigated. Increasing the network system capacity or maximizing authorized specified SNRs will lead to eavesdropper to detect high SNRs.