Patent ID: 6208440
Filing Date: 2001-03-27
Classification: G02B,H04J

Abstract:
An optical filter comprising:a first coupler having a first port for receiving an input optical signal having a plurality of wavelength components, third and fourth ports for dividing the input optical signal received via the first port and outputting the divided outputs, respectively, and a second port for outputting optical signals which are reflected back from optical signals output from the third and fourth ports;a first optical wavelength reflector having an input port for receiving an optical signal from the third port of the first coupler, and an output port for reflecting an optical signal having a predetermined wavelength component from optical signals received via the input port backward from a light traveling direction, outputting the reflected optical signal to the third port of the first coupler, and outputting an output signal having wavelength components other than the predetermined wavelength component;a second optical wavelength reflector having an input port for receiving an optical signal from the fourth port of the first coupler, an output port for reflecting the optical signal having the predetermined wavelength component from optical signals received from the input port backward from the light traveling direction, outputting the reflected optical signal to the fourth port of the first coupler, and outputting the optical signal having wavelength components other than the predetermined wavelength component; anda second coupler having first and second ports for receiving optical signals from the respective output ports of the first and second optical wavelength reflectors, there being a -.pi./2 phase difference between the optical signals received by the first and second ports, and a third port for outputting the optical signals received by the first and second ports thereof, said third port having an optical coupling area for causing a -.pi./2 phase shift to one of said optical signals received by the first and second ports of the second coupler such that said optical signals output from said third port have the same phase and are thus coupled when output from the third port of the second coupler,the optical signal received from the second port of the first coupler being predetermined wavelength component of the input optical signal received from the first port of the first coupler and the output of the input optical signal, andthe optical signal received from the second coupler via the third port thereof having wavelength components except for the predetermined wavelength component of the input optical signal.