| 摘要 |
PURPOSE:To automatically correct the central wavelength shift of a demultiplexing characteristic by providing a thin film heater in or on the clad film of a directional coupler which is formed with nearly square core waveguides on a low-refractive index layer and is formed with the clad layer thereon and applying a voltage thereto. CONSTITUTION:The directional coupler 9 is constituted by laminating the core waveguides 3-1, 3-2 (refractive indices nc, nc>nb) and the clad 4 (refractive indices nr, nr<nc) successively on the low-refractive index layer 2 (refractive index nb). The thin film heater 5 is provided in or on the clad 4. The clad 4 is constituted of SiO2 contg. at least one of dopant Ti, etc., so that the refractive index thereof changes with temp. A temp. detecting element 7 detects the deviation in the central wavelength of the demultiplexing characteristic when said wavelength deviates with a change in the temp. The input voltage to the heater 5 is then controlled, by which the specified temp. is maintained, i.e., the deviation in the central wavelength is automatically corrected. |
