| 摘要 |
PROBLEM TO BE SOLVED: To easily check the direction of an optical cable at the time of its connection construction by providing a specific coated optical fiber among coated optical fibers with a fiber diffraction grating of a wavelength band that causes no hindrance to signal light. SOLUTION: Specific coated optical fibers 2-1 to 2-3 are provided with parts where light of specific wavelength is reflected. Fiber type diffraction gratings formed by irradiating the cores of the coated optical fibers 2-1 to 2-3 are optimum to the reflection parts, the reflection parts 3-1 to 3-3 are provided respectively, and a range which causes no hindrance to the wavelength band of signal light is selected as the reflection wavelength band of the reflection parts 3-1 to 3-3. By this connecting method, both ends of specific coated optical fiber 2-1 to 2-3 of the ribbon of optical fibers 1 are connected to constitute the serial optical cable 9. Then light of specific wavelength is made incident on the input end by using OTDR and reflected light from each of the reflection part 3-1 to 3-3 is detected. |
