Coherent optical CDMA (OCDMA) systems used for high-capacity optical fibernetworks-system description, OTDMA comparison, and OCDMA/WDMA networking

As the wavelength resource in mainstream wavelength-division multiple-acces s (WDMA) systems becomes exhausted, and the bit-rate Limitation within a si ngle wavelength bandwidth is reached, alternative approaches to implementin g a high-capacity optical fiber network need to be investigated. Coherent o ptical code-division multiple-access (OCDMA) systems, that can access many users simultaneously and asynchronously (or synchronously) across the singl e wavelength and same timeslot via spread spectrum techniques, are one alte rnative. In the longer term, the advantages of OCDMA in tandem with WDMA (O CDMA/WDMA) networks are compelling and worthy of further investigation in t he goal of realising an extensive, flexible, high throughput and easily man aged optical telecommunication infrastructure. In this paper, coherent OCDM A systems are introduced, and the issues of the system implementation withi n high-capacity optical fiber networks are discussed. A performance compari son between OCDMA and OTDMA systems is then carried out, both of them using narrow pulse laser sources. An optical fiber network utilizing coherent OC DMA techniques as one layer of a multiplexing hierarchy, in tandem with WDM A, is illustrated and a possible hybrid OCDMA/WDMA network architecture (an d its performances and advantages) is described.