| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical wavegiude device having stably quality and transmission power by forming a diffraction grating of which diffractive index is changed periodically along the optical axis, on a core part and arranging a mode filter in the vicinity of the diffraction grating. SOLUTION: The core 2 with a nearly square section, and an upper part clad 4 and a lower part clad 5 surrounding the core 2, are provided on a substrate 1 such as silicon. The diffraction grating 3 having a diffractive index difference in the optical axial direction is formed on the core 2, and the mode filter 6 is arranged on the rear side of the diffraction grating 3. An optical waveguide device with such a constitution is inserted into a line network of an optical fiber, and monitoring light is sent in it, and by observing reflected light from the diffracting gradating 3, the condition of the line network is monitored. At this time, the monitoring light transmitting through the core 2 generates a high degree mode by the diffraction grating 3, and since the high degree mode is removed by the mode filter 6 even when the monitoring light transmits through the diffraction grating 3, the signal light isn't affected by the high degree mode. |
