The optical coherent multi-carrier frequency (CMC) technique has progressed to a development level, where its application to switching techniques is discussed. Up to now point-to-point long distance transmission systems , the bidirectional subscriber line, TV/HDTV distribution systems and multipoint connections via a passive stair  were presented. These systems are characterized by signals on fixed optical carriers. Wavelength conversion was introduced by combining optical heterodyne receivers and transmitters .
© 1989 Optical Society of AmericaPDF Article