| 摘要 |
PROBLEM TO BE SOLVED: To completely and surely reduce reflection at an unnecessary port and to stably obtain a large reflection attenuation quantity by covering the cut surface of a cut port with transparent resin and covering the transparent resin with opaque resin. SOLUTION: An optical branching/coupling part 14 formed by fusing and drawing two optical fibers is housed in a reinforcing device 15, ports 1 to 3 and the unnecessary port 4 are extended, and the port 4 is at a position near to the device 15. The cut surface of the port 4 is covered with the transparent resin 20, and further the resin 20 is covered with the opaque resin 21. The transparent resin whose light transmissivity of the used wavelength band of a coupler is >=80% and whose refractive index is approximate to that of glass constituting the optical fiber is used as the resin 20. The resin 21 is constituted of the resin whose attenuation quantity of the light in the used wavelength band of the coupler and the external light is 30dB and which has appropriate elasticity to cover and protect the port 4 and the port 3 adjacent to the port 4. |
