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Proceedings Paper

Performance of a nonlinear receiver for the ultrashort-pulse optical CDMA system
Author(s): Bin Ni; James S. Lehnert
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Paper Abstract

At the receiver of an ultrashort-pulse optical code-division multiple-access (OCDMA) system, a nonlinear thresholder is needed to discriminate between the correctly decoded short pulse and the interference that appears to be a pseudorandom signal. It has been demonstrated that the self phase modulation (SPM) effect can be used to realize this nonlinear thresholder. The performance of a system that exploits this phenomenon is analyzed in this paper. If the spreading code is random, the electrical field of the interfering signal from the multiple users can be shown to be a complex Gaussian random process. The broadened power spectral density (PSD) function caused by the SPM effect can be calculated. When "1" is transmitted, the correctly decoded signal from the desired user, which is a deterministic waveform, is added to the Gaussian random process. Beating between the two signals causes random fluctuations in the power. Since the strength of the SPM effect is proportional to the variation rate of power, the broadened signal spectrum will appear random. The Monte Carlo method is used to obtain the properties of the decision statistic. Finally, the bit-error rate (BER) is calculated, and the simulation results are presented. The result reveals that the performance of the SPM-based nonlinear receiver can outperform the ideal linear receiver in some circumstances.

Paper Details

Date Published: 10 September 2005
PDF: 10 pages
Proc. SPIE 5908, Optical Information Systems III, 59080V (10 September 2005); doi: 10.1117/12.617457
Show Author Affiliations
Bin Ni, Purdue Univ. (United States)
James S. Lehnert, Purdue Univ. (United States)

Published in SPIE Proceedings Vol. 5908:
Optical Information Systems III
Bahram Javidi; Demetri Psaltis, Editor(s)

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