Patent ID: 6512619
Filing Date: 2003-01-28
Classification: H04B

Abstract:
A frequency modulation apparatus for converting an input electrical signal into an FM signal through optical frequency modulation and optical heterodyne detection using a first light source emitting first light and a second light source emitting second light, the first light and the second light having different optical frequencies from each other; the apparatus comprising:a first optical modulator for outputting said first light frequency-modulated with said input electrical signal as a first optical signal; a beat signal generating part for generating an unmodulated beat signal corresponding to a carrier component of a beat signal obtained from said first and second lights through optical detection based on a square-law detection characteristic; a frequency converter for generating the frequency-converted signal by converting frequency of said unmodulated beat signal; a second optical modulator for generating a second optical signal by optical-amplitude-modulating or optical-intensity-modulating any one of said first optical signal and said second light with said frequency-converted signal; and an optical receiver for receiving one of said first optical signal and said second light, which is not subjected to optical-amplitude-modulation or optical-intensity-modulation by said second optical modulator, and said second optical signal, and generating said FM signal through optical detection based on the square-law detection characteristic.