Patent ID: 7352783

Claim:
A tunable fiber laser light source, comprising: an optical fiber which serves as an optical path of a laser oscillation; a gain medium which is connected to said optical fiber and has a gain with respect to an oscillation wavelength; and a tunable optical filter which is connected to said optical fiber and continuously changes a bandpass wavelength, wherein said tunable optical filter includes: an optical beam deflector which periodically changes a reflection angle of an optical beam obtained from said optical fiber within a certain range; and a diffraction grating which inputs light deflected in said optical beam deflector and reflects light of a selected wavelength variable in accordance with an incident angle in a same direction as the incident angle; and a beam expander which enlarges a beam diameter of the optical beam deflected in said optical beam deflector, and said beam expander increases an enlargement rate as said selected wavelength is shortened so as to keep a bandwidth of an oscillated laser light constant.