Abstract
Direct sequence Code Division Multiple Access (CDMA) provides a method of exploiting the wide bandwidth offered by optical fibres without the added complexity of wideband electronics. Each data bit is encoded with a code sequence (of N chips) which represents the destination address of each data bit. The correct selection of orthogonal codes allows the data bit destined for a given receiver to be extracted in the presence of noise (i.e., interference from other users in the system). Due to the uni-polar nature of light, coding schemes used in conventional CDMA cannot be applied directly to optical CDMA. Coding schemes have been proposed for optical CDMA [1] [2] but they have a number of limitations which include high bandwidth expansion factors and significant cross-talk levels. These problems can be overcome by employing complementary correlation detection which generates bi-polar electrical signals from received uni-polar optical ones [3]. Correctly selected codes (Alberta codes) are truly orthogonal for complementary correlation detection.
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