Patent ID: 8494378

Claim:
A synchronous optical signal generating device, comprising: optical phase detecting means for comparing a phase of a reference optical signal with a phase of an optical beat signal to generate a phase error signal; shaping means for shaping the phase error signal; and voltage controlled optical signal generating means for generating an optical beat signal based on the shaped phase error signal and outputting the optical beat signal while feeding the optical beat signal back to the phase detecting means, wherein the voltage controlled optical signal generating means includes: voltage controlled electrical signal generating means for generating an electrical signal corresponding to the shaped phase error signal and outputting the electrical signal; optical comb generating means for generating an optical comb signal having optical spectrum lines with frequency intervals corresponding to the electrical signal generated by the voltage controlled electrical signal generating means; 2-mode selecting means for selecting optical signals having optical spectrum lines of two different wavelengths from the optical comb signal; and 2-mode multiplexing means for multiplexing the selected optical signals having two different wavelengths and outputting the multiplexed signal as the optical beat signal while feeding the optical beat signal back to the phase detecting means, wherein a loop band width is not less than 10 kHz and not more than 1 MHz, a total length of a fiber composing a loop is shorter than a fiber length given by a loop band limited by a voltage controlled oscillator (VCO), and the reference optical signal and the optical beat signal are controlled so that phases thereof are synchronized, the optical comb generating means includes a first laser light source for outputting laser light having a single wavelength, and light modulating means for modulating the outputted laser light to generate the optical comb signal based on the electrical signal generated by the voltage controlled electrical signal generating means, the light modulating means being light phase modulating means for modulating a phase of the laser light to generate the optical comb signal.