| 摘要 |
PURPOSE:To use both a single mode fiber and a multi-mode fiber as a fiber for transmission line by constituting a common port fiber of a double core structure having coaxially a core part which becomes a single mode waveguide and a core part which becomes a multi-mode waveguide. CONSTITUTION:The title device is provided with a double core part 13, a single mode waveguide art 14 and a multi-mode waveguide part 15 of a common port fiber 1a, and the single mode waveguide part 14 and the multi-mode waveguide part 15 are formed coaxially. An input fiber 1b and lenses 4a, 4b are adjusted in advance so that a light beam of wavelength lambda1 which has been emitted from the input fiber 1b is coupled efficiently with the single mode waveguide part 14 of the common port fiber 1a. Also, in a coupling system of the common port fiber 1a and an output fiber 1c, a lens 4c and the output fiber 1c are adjusted so that said system is coupled efficiently against a light beam of wavelength lambda2 which has been propagated through the multi-mode waveguide part 15 of the common port fiber 1a. In such a way, both the single mode fiber and the multi-mode fiber can be used. |
