Use of subcarrier multiplexing/multiple access for multipoint connections in all-optical networks

Abstract

The use of subcarrier multiplexing/multiple access (SCM/SCMA) is a simple and cost effective alternative to time division multiplexing/multiple access (TDM/TDMA) for creating multipoint connections in lightwave networks. The SCM/SCMA technique can be used in all-optical networks to produce a significant increase in throughput and connectivity. However, when the signals from two or more lasers operating in a WDM/SCM system are combined at a detector, optical beat interference (OBI) occurring at a frequency equal to the difference in optical frequencies of the lasers can potentially severely interfere with the information being transmitted. Thus, to achieve satisfactory performance, the optical carriers must have the correct spacing, their individual wavelengths must be precisely controlled and the subcarrier frequencies carefully selected to minimize OBI. Our experimental work focuses in studying the OBI and its effect as the optical carriers are moved closer in frequency. Our results provide the minimum spacing needed to achieve a 10 -9 Bit Error Rate at both 3 Mbps and 200 Mbps. We also discuss an interesting application for the above scheme on the Optical Network Technology Consortium's all-optical testbed.