OPTICAL DEMULTIPLEXING FOR SUBCARRIER MULTIPLEXED SYSTEMS

Subcarrier multiplexing (SCM) is an attractively simple technique for establishing multiple independent channels over a single fiber. At the receiver, electrical mixing converts a selected channel to baseband. The photodiode, oscillator, mixer, and preamplifier must, however, ope rate up to the highest subcarrier frequency. The use of an optical fil ter for channel selection allows any subcarrier to be accessed with on ly baseband electronics. To obtain the best performance with this appr oach, sub-subcarrier modulation is needed. In this paper we propose a method suitable for externally modulated CATV systems and show that th e sensitivity is comparable to the best conventional receivers.