CONTINUOUS LIGHT SOURCE

摘要

PROBLEM TO BE SOLVED: To provide a multi-wavelength continuous light source or a single- wavelength continuous light source with a favorable SN ratio. SOLUTION: By using a distributed Bragg reflector-accumulated mode-locked semiconductor laser 31, a large number of continuous light beams with a favorable SN ratio can be generated. By using a normal dispersion flat optical fiber 33, little degradation of the SN ratio is caused over the whole region of a spread spectrum, the intensity of the generated continuous light is made large, and the variation of the light intensity depending on the wavelength is minimized. The optical frequency spectrum of a repetitive light pulse train generated with the laser 31 consists of the longitudinal modes of a frequency interval corresponding to the repetition frequency. When this pulse train is amplified with a light amplifier 32 and sent into the normal dispersion flat optical fiber 33 by maintaining a large intensity, the optical spectrum turns into a broadband optical spectrum while the pulse train is propagating through the optical fiber. The single-wavelength- or the multi-wavelength continuous light source is obtained by taking out one or a large number of one longitudinal mode from the broadband optical spectrum by using a wavelength demultiplexer 34.