| 摘要 |
PURPOSE:To provide an photodetector, and an optical communications network employing it, having a demultiplexing function taking advantage of the fact that the angle of diffracted light radiated from an optical waveguide having a diffraction grating to the outside depends on the wavelength of the light. CONSTITUTION:Means for controlling the quantity of light, e.g. an optical amplifier 20, having optical damping function and/or optical amplifying function for sustaining the intensity of incident light to a waveguide 21 having a diffraction grating 9 is provided on the incident side of the waveguide 21. The light quantity control means is controlled to restrain the wavelength demultiplexing function from degrading due to the equivalent refractive index variation of the waveguide 21 caused by the variation of the intensity of incident light. The incident light may contain a continuous light at all times or laser oscillation may take place at the Bragg wavelength of the diffraction grating in the waveguide with no incident light. An photodetector array 11 which has not a wide dynamic range may also be employed. |
