Subcarrier multiplexing (SCM) is a convenient method of implementing multi-access in a lightwave system. Conventionally SCM receivers detect all channels using high speed optoelectronic components, each channel then being selected using heterodyne techniques in the electrical domain. Optical prefiltering is a novel technique where channel selection is accomplished optically. This method has the primary advantage that only a low bandwidth optical detector and receiver is needed to recover the baseband information.
Philip A. Greenhalgh,
Robin D. Abel,
Phillip A. Davies,
"Optical prefiltering in subcarrier systems", Proc. SPIE 1790, Analog Photonics, (26 February 1993); doi: 10.1117/12.141702; https://doi.org/10.1117/12.141702