| 摘要 |
PURPOSE: To realize an optical filter with a large loss ratio. CONSTITUTION: A loss part 2 and a reflection part 3 are arranged in an optical fiber 1. The loss part 2 is constituted by forming an optical waveguide type diffraction grating inclined to the optical axis of the optical fiber 1, and the reflection part 3 is constituted by forming the optical waveguide type diffraction grating orthogonal to the optical axis of the optical fiber 1. The loss part 2 is arranged on this side in the advancing direction of the transmitted light being incident light 4 with respect to the reflection part 3. The loss ratio of the loss part 2 is set to -20dB and the reflection loss of the reflection part 3 is set to 0.04dB. The incident light 4 of wavelength λ being 0dBm is attenuated by -20dB in the loss part 2 and the reflection part 3, and the transmitted light 5 becomes -40dBm. The reflected light 6 moves back and forth in the loss part 2, so that it is attenuated by -40dB and becomes -40.04dBm after adding the reflection loss -0.04dB of the reflection part 3 to the light 6. |
