| 摘要 |
PURPOSE:To easily manufacture the wide-band optical fiber coupler without the need to control a difference in core diameter to give a propagation constant difference with high precision. CONSTITUTION:Two of optical fibers put on the market are taken out at random. The difference in propagation constant between the optical fibers 11 and 12 are normally about 0.4cm<-1> because of variance. Those optical fibers 11 and 12 fused and drawn to form a fusion-welded part 26. By this fusion drawing, the optical fibers 11 and 12 are only optically coupled. The branching ratio is measured and the fusion-welded part 26 is so controlled that the least branching ratio is about 40%. Namely, when the branching ratio is too small, the optical fibers are applied with tension, but the heating temperature is lowered to prevent drawing from being caused. Then, both the cores of the fusion-welded part are to become accurately parallel to each other with time and the interval becomes wide, so that the branching ratio increases. When the branching ratio is too large at the time of the fusion welding, on the other harnd, the tension is made greatly weak and the optical fibers are slacked to put both the cores of the fusion-welded part close to each other, thereby decreasing the branching ratio. |
