Patent ID: 7561811

Claim:
An optical device comprising: an optical path provided between an input port, which is connected to a first optical fiber, and to which signal light modulated at a frequency f s is supplied, and an output port; and an optical loop optically coupled to said optical path; said optical loop including: an optical amplifier for compensating for a loss in said optical loop so that laser oscillation of a continuous wave having a wavelength λ c occurs in said optical loop; an adjuster for adjusting an optical path length of said optical loop so that said frequency f s becomes equal to an integral multiple of the reciprocal of a recirculation period of said optical loop; an optical bandpass filter that allows light having said wavelength λ c to pass; and a nonlinear optical medium for mode-locking said laser oscillation according to said signal light, wherein said nonlinear optical medium includes a second optical fiber to which said signal light of said input port is inputted from said optical loop, and said continuous wave having said wavelength λ c is inputted from said optical loop, and generates amplitude modulated CW light having said wavelength λ c and including a component of said frequency f s by performing amplitude modulation of said continuous wave based on four-wave mixing by two lights between the signal light and the continuous wave generated by the laser oscillation, said signal light operating as pump light in the four-wave mixing by two lights between the signal light and the continuous wave; and wherein pulses including said wavelength λ c are generated by said nonlinear optical medium and output through the output port, and a wavelength λ s of said signal light of said input port is different from said wavelength λ c of said continuous wave.