Transmission approaches for services of variable bit-rate and differentiated QoS using OCDMA

The technology of optical code division multiple access (OCDMA) has been considered as a competitive candidate for constructing future high-speed fiber-optic networks, especially the passive optical access networks (PON). Future PON should be able to provide multiservices. In an on-off keying (OOK) OCDMA network, different bit-rates can be implemented through varying lengths of subscribers´ address codes while bit-error-rates of the systems can be changed by adjusting codeweights in user´s address codes. In this regard, we proposed a new family of two-dimensional variable-weight on the basis of the proposed one-dimensional variable-weight-OOCs. When this new code is employed for encoding different services, differentiated QoS for distinct services can be supported. In doing so, the demands of differentiated QoS for different services and distinct subscribers can be met and the usage of optical network resources can be optimized. It is shown by analysis that the cardinality of this type of codes is larger than that of constant-weight 2-D OOCs and is close to its theoretical upper bound. The subscriber with heavier codeweight outperforms the user with lighter codeweight in the bit-error-rate performance in an OCDMA network.