WDM-subcarrier FDMA lightwave networks: optical beat note interference

It is shown that the introduction of subcarrier frequency-division multiaccess (SFDMA) into a wavelength-division multiplexing (WDM) network provides an increase in throughput which is limited significantly by beat-note-interference-induced channel outage. The reduction of throughput prevents the network capacity from growing unabated as more subcarrier channels are added. The analysis is useful for studying the tradeoffs associated with adding subcarrier channels to a WDM network, specifically in terms of key parameters such as laser modulation format and optical and subcarrier channel bandwidths. It is found that for a WD/SFDMA network with N optical channels each having M subcarrier channel, i.e., NM concurrently accessible channels, using a slotted-Aloha-like protocol, there is a maximum throughput corresponding to an optimum offered load, and these values decrease as more subcarrier channels are offered.<>