INTERFEROMETRIC NOISE IN OPTICAL CODE MULTIPLE ACCESS SYSTEMS

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Optical code-division multiple access (OCDMA) is a system approach able to support bursty, variable data rate traffic with a reduced network management overhead. The performance of OCDMA systems at the physical level is limited by a combination of noise sources, the more critical being multiple access interference (MAI) and interferometric beat noise. Interferometric beat noise (BN) occurs when different optical signals with identical (or nominally the same) frequencies are incident simultaneously on the same detector. Due to the square law receiver characteristic, the photocurrent attributed to BN is much greater than that owing to the incident optical (sum of intensities) power of the crosstalk signal alone, producing more severe performance degradation than otherwise would be expected. There are many studies that have considered beat noise in estimating performance of different OCDMA systems; frequency encoding (FE-CDMA), frequency hopping (FH-CDMA), coherence multiplexing (CM-CDMA), sequence-inversion-keyed (SIK-CDMA) and 2-D TW-CDMA. This travel grant aims to enable the establishment of meaningful interaction between two well respected research groupings to begin to experimentally characterise the effect of BN in representative OCDMA network scenarios. The output of the collaboration will be invaluable as input to the development of a theoretical framework to model more extensive implementations incorporating other physical layer impairments.