| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to efficiently produce couplers having controlled and desired branching rations and having lessened excessive loss by thermally fusing the reduced diameter regions of multimode optical fibers and further, stretching these multimode optical fibers in the axial direction while thermally fusing the fibers and repeating these stages. SOLUTION: The multimode optical fibers fm are diametrally reduced in the outside diameter Dm of their clads by etching down to a prescribed diameter Dm' to form the reduced diameter parts fm'. Plural pieces of the multimode optical fibers are then arranged in parallel and the reduced diameter parts fm' are thermally fused in a thermally fusing stage. In succession, the thermal fusing and the stretching are simultaneously executed. The thermally fused regions of the respective multimode optical fibers are subjected to the thermally fusing in succession and are simultaneously subjected to stretching for the prescribed period of time under prescribed tensile force in the axial direction in this thermally fusing and stretching stage. Further, the multimode optical fibers are subjected repetitively to the thermally fusing stage and the thermally fusing and stretching stage by the prescribed number of times in succession. |
