| 摘要 |
PURPOSE:To reduce energy loss due to coupling by making the cores of some of optical fibers less in refractive index than clads of other optical fibers. CONSTITUTION:The optical fiber coupler 5 is constituted by twisting and fusing plural optical fibers and the core of one optical fiber 1 is made less in refractive index than the clad 2b of the other optical fiber 2. Then multi-mode light is made incident on the optical fiber 1 whose core 1a is lower in refractive index and single-mode light is made incident on the other optical fiber; and the multi- mode light enters the optical fiber where the signal-mode light is made incident at the twist fusion splicing part, and then the signal-mode light and multi-mode light can be coupled. An in-line optical amplification system which uses the single-mode light as transmitted light and the multi-mode light as pump light is completed. Consequently, the energy loss due to the coupling is reducible. |
