Patent ID: 7120361

Claim:
A wavelength tunable multiplexing and demultiplexing filter device which demultiplexes and multiplexes arbitrary wavelength components from wavelength-multiplexed light, comprising: an optical filter element having a transparent substrate with two sides parallel to each other, said optical filter element having multiple filter chips arranged in two straight line arrangements, said multiple filter chips respectively transmit at least one of the wavelength components of the wavelength-multiplexed light and said multiple filter chips including a pair of filter chips with the same wavelength characteristic, said pair of filter chips being disposed in mutually corresponding positions on respective sides of said transparent substrate; a first light emitting unit which emits the wavelength-multiplexed light into said optical filter element from a specific direction; a second light emitting unit which inputs arbitrary wavelength components of the wavelength-multiplexed light into said optical filter element from a specific direction; a first light receiving unit which is located on the same optical axis as said first light emitting unit and receives the light transmitted through said optical filter; a second light receiving unit which is located on the same optical axis as said second light emitting unit and receives the light from said second light emitting unit, which has been transmitted through said optical filter element, and the light from said first light emitting unit, which has been reflected at said pair of filter chips on said optical filter element; a moving unit which moves said optical filter element in the direction of said multiple filter chips so that the light from said first light emitting unit and light from second light emitting unit enter different filter chips; and a controller which controls said moving unit in accordance with the wavelength to be multiplexed and demultiplexed.