4 Gb/s Subcarrier Multiplexed Transmission over 30 km Using Microwave QPSK Modulation

With recent advances in optoelectronic components, particularly high-speed lasers and optical amplifiers, subcarrier multiplexing emerges as a potentially important multiplexing technique [1-4], in addition to time-division multiplexing, wavelength-division multiplexing, and coherent frequency-division multiplexing. Among the advantages of subcarrier multiplexing are its relative simplicity and flexibility, as one can combine and separate information channels of different formats in the RF domain without synchronization and coordination.