CENTER WAVELENGTH STABILIZING DEVICE FOR OPTICAL FILTER

PROBLEM TO BE SOLVED: To provide a center wavelength stabilizing device for an optical filter having a wide control band to make a center wavelength of the optical filter used for a cross connector and coping with a wide band noise in an input light. SOLUTION: The center wavelength stabilizing device 3 is made up of an optical distributor 4, a photo detector 5, a multiplier 6, an oscillator 7, and a control circuit 8. The oscillator 7 modulates an output wavelength of light sources 231 -23M. A CW light of one wavelength selected by a wavelength variable filter 2811 branches part of intensity at an optical distributor 4 and given to a photo detector 5, in which the signal is converted into an electric strength signal. The electric strength signal is synchronously detected with a modulation signal from the oscillator 7 at the multiplier 6 and demodulated. The signal is an error signal in response to a relative wavelength error between a transmission center wavelength of the wavelength variable filter 2811 and an output wavelength from the light source 231 . The control circuit 8 processes the error signal and applies negative feedback to the processed signal to the variable filter 2811 to act like a loop making the relative wavelength error zero.