Patent ID: 7734185

Claim:
An optical transmitter for optically transmitting a plurality of electric signals, the optical transmitter comprising: an optical source operable to output an unmodulated optical signal; an optical branching section operable to split the optical signal into two signals; a multiplier section operable to multiply together an electric signal having a frequency fc and a plurality of electric signals having frequencies fo to ft (fo<ft); a filter operable to selectively extract signal components having frequencies fc to fc+ft from the signal obtained by the multiplication at the multiplier section; an optical intensity modulation section operable to subject one of the split optical signals from the optical branching section to an optical intensity modulation with an electric signal of a predetermined frequency extracted by the filter to thereby produce an optical intensity-modulated signal; an optical angle modulation section operable to subject the other one of the split optical signals from the optical branching section to an optical angular modulation with a plurality of electric signals having frequencies f 1 to fn (f 1 <fn) different from frequencies fo to ft to thereby produce an optical angle-modulated signal; an optical combining section operable to optically combine together the optical intensity-modulated signal and the optical angle-modulated signal; an optical detecting section operable to subject the combined optical signal from the optical combining section to a squared detection to thereby convert the combined optical signal to a modulated signal; and an optical transmitter section operable to convert the modulated signal from the optical detecting section to an optical signal and transmitting the obtained optical signal.