Novel subcarrier multiplexing technologies for optical communication

Microwave subcarrier multiplexing (SCM) has recently emerged as a potentially important multiplexing technique for wideband lightwave systems. By using a double beam modulation technique (DBM), in which the information is modulated onto an optical coherent pair instead of a single optical beam, a novel SCM system is proposed. The system, with multi-division and multi-channel capability (encompassing the multiplexing of both multi-channel analog and/or digital signals), potentially has an information bandwidth (IBW) of tens of GHz and is particularly suitable for optical fiber and free-space communications.;The principle of the proposed system was first demonstrated by using a standing-wave surface-acoustic-wave optical modulator (SWSAW). The modulator was fabricated on the top of a Ti - LiNbO;The more advanced way of implementing the proposed SCM is utilizing a frequency-locked-laser (FLL) pair, which has virtually no upper frequency limitation and is readily FM modulated. We have demonstrated, to our knowledge, the first FM modulated FLL pair for optical communication. The subcarrier (locked) frequency of 15 GHz is also believed to be the highest reported today. The multi-channel video signals and high frequency sinusoidal modulations up to 1 GHz, after being FM modulated onto and demodulated from a 15 GHz subcarrier, are displayed directly on standard TV receivers and oscilloscopes.;Another novel SCM, with ultra high millimeter-wave frequency subcarriers of up to one hundred GHz, based upon the self-sustained-pulsation (SSP) of the laser diode, was also proposed. A preliminary optical link test with multi-channel transmission on a 6 GHz subcarrier has demonstrated the feasibility of using SSP. (Abstract shortened with permission of author.).