Disk shaped tunable optical filter

摘要

A reference wavelength light generation apparatus, comprising: a single mode wavelength tunable semiconductor laser light source; a disk shaped optical filter having such a filter characteristic that a transmission central wavelength varies linearly with respect to a rotation angle, through which optical beams from the light source pass; and a servo motor for rotating the disk shaped optical filter in synchronization with a clock; and a control circuit for detecting an error between an oscillation wavelength of the light source and a specified wavelength, and generating a negative feed-back control signal to control the light source so as to cancel out the error.