Abstract: Provided is an optical coupler, which can allow the light to be branched off by the required amount when necessary, and a method of branching light using the optical coupler. Optical coupler 1 has optical fiber 10 that has small-diameter part 12, which is formed so as to have a relatively small outer diameter at a portion in the longitudinal direction, and that branches off the transmitted light by small-diameter part 12; and output optical fiber 20 that receives the light branched off from input optical fiber 10. Small-diameter part 12 of input optical fiber 10 is caused to contact with linear small-diameter part 22 of output optical fiber 20; a coupling length, which is the length along which small-diameter part 12 of input optical fiber 10 and small-diameter part 22 of output optical fiber 20 are made to contact with each other, or a propagation constant of the optical fibers is varied; and thus, branching ratio S of the light branched off from input optical fiber 10 into output optical fiber 20 is varied.

Abstract: To provide a tapered optical fiber having a good outer diameter accuracy and a high reproducibility, a manufacturing method of the tapered optical fiber, and a manufacturing system of the tapered optical fiber. The above-mentioned problem is solved by manufacturing system 1 of a tapered optical fiber comprising: shifter 11, 12 which reciprocates optical fiber 10 mounted at positions having a prescribed distance therebetween in the longer direction X of optical fiber 10 (the direction of the optical axis); and heating device 13 which heats the reciprocating optical fiber 10 at fixed position O, wherein shifter 13 includes a broadening unit which can increase the mounting distance (L1+L2) of the optical fiber while reciprocating the optical fiber. Shifter 11, 12 has at least two mounting unit which fix the optical fiber 10, and serves as a broadening unit controlling the two mounting unit independently or interlockingly.

Abstract: To provide a tapered optical fiber having a good outer diameter accuracy and a high reproducibility, a manufacturing method of the tapered optical fiber, and a manufacturing system of the tapered optical fiber. The above-mentioned problem is solved by manufacturing system 1 of a tapered optical fiber comprising: shifter 11, 12 which reciprocates optical fiber 10 mounted at positions having a prescribed distance therebetween in the longer direction X of optical fiber 10 (the direction of the optical axis); and heating device 13 which heats the reciprocating optical fiber 10 at fixed position O, wherein shifter 13 includes a broadening unit which can increase the mounting distance (L1+L2) of the optical fiber while reciprocating the optical fiber. Shifter 11, 12 has at least two mounting unit which fix the optical fiber 10, and serves as a broadening unit controlling the two mounting unit independently or interlockingly.