Square wave frequency modulation in a coherent optical FSK TV-transmission/distribution system

The transmission of a square wave frequency modulated signal via a coherent optical frequency shift keying-system combines the advantages of the high sensitivity of the coherent heterodyne system with the simplicity of the SWFM codecs. This paper describes the implementation of SWFM codecs in a digital coherent optical multichannel TV-transmission/distribution system. The authors obtained a sensitivity of -51 dBm for a video signal to noise ratio of 56 dB (weighted).