| 摘要 |
PROBLEM TO BE SOLVED: To prevent occurrence of an unnecessary mode hop at an unexpected position. SOLUTION: A calibration mode is designated to detect an angular shift of a diffraction grating 3 with respect to an output wavelength, and an angle setting means 23 continuously varies the angle of the diffraction grating 3, while a mode-hop-angle detection means 30 detects an angle to cause a laser- diode mode hop, from the level changes of output light from a laser diode 2. Calculation means 36 calculates a correction angleΔϕfor correspondence between an output wavelength and the angle of the diffraction grating 3 in a normal mode, based on the detected mode hop angle. In the normal mode, the diffraction grating 3 is controlled in accordance with the angle corrected with the correction angleΔϕwith respect to a designated wavelength.
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