| 摘要 |
PROBLEM TO BE SOLVED: To widen a controllable wavelength range and improve accuracy in wavelength detection by selecting one of a plurality of wavelength detection means and adjusting an oscillation wavelength of a laser according to a wavelength detection signal. SOLUTION: Light 12 output from a laser 11 is split to a signal light 13 output to the outside and monitor light 14 for wavelength control. The monitor light 14 is selected by a switch 15 and is input to one of a plurality of wavelength detection means 161 to 163. At first, a wavelength detection means 31 of the widest wavelength detection range is selected. Then, a wavelength detection signal output from the wavelength detection means 161 is input to a wavelength adjustment means 19, a wavelength is adjusted to reduce a difference between a set wavelength and a wavelength of a laser by the wavelength adjustment means 19. At the same time, an absolute value of a wavelength detection signal is monitored by a signal monitoring means 18 and is fed back to a switch 15. According to this method, it is possible to control a wavelength highly precisely near a set wavelength after a controllable wavelength range is widened. |
