| 摘要 |
PURPOSE:To lower the loss of the wavelength filter and to reduce its size by providing a diffraction grating having a periodic structure on the core of an optical fiber. CONSTITUTION:A clad 2 is removed in the prescribed part of the optical fiber 1 and the periodic structure, for example, rugged diffraction grating 4, is concentrically formed on the core 3 from which the clad 2 is removed. The diffraction grating 4 is then coated with a coating material 6 consisting of a material which does not absorb light to fill the part of the previously removed clad 2. A cylindrical heater 5 is concentrically disposed simultaneously therewith and is held by the coating material 6 by which the heater is covered. The diffraction grating 4 is formed without cutting the core 3 in such a manner and, therefore, the light propagating in the optical fiber 1 propagates in the diffraction grating 4 and is directly made incident on the other optical fiber element 1 after wavelength selection is made. The central wavelength of the area to block the transmission of the wavelength filter is varied by adjusting the heating by the heater 5. |
