Patent ID: 9586852
Date: 2017-03-07
CPC Classifications: C03B,G02B

Claim:
1. A method of manufacturing a preform for a multicore fiber, comprising: a preparation process of preparing for a plurality of core rods, a plurality of clad rods, and a clad tube, the respective core rods include a core element layer having a refractive index higher than the clad rods; an arrangement process of arranging the plurality of core rods and the plurality of clad rods in a tube of the clad tube, in a state in which distances between center axes of the adjacent core rods become equal to each other and a state in which parts of outer circumferential surfaces in the adjacent rods contact; and an integration process of integrating the clad tube and the plurality of core rods and the plurality of clad rods arranged in the tube, wherein, in the arrangement process, a ratio of a total cross-sectional area of a direction orthogonal to a length direction in the plurality of core rods and the plurality of clad rods with respect to an internal cross-sectional area of the tube of a direction orthogonal to a length direction in the clad tube is 0.84 or more, wherein the internal cross-sectional area of the tube is an area of a region surrounded by an inner circumference of cross-section of the tube, and the total cross-sectional area in the plurality of core rods and the plurality of clad rods is a sum of a cross-sectional area of all of the core rods arranged in the tube and a cross-sectional area of all of the clad rods arranged in the tube, wherein, in the preparation process, first clad rods having a diameter equal to a diameter of the core rods and second clad rods having a diameter smaller than the diameter of the first clad rods are prepared, and in the arrangement process, the plurality of core rods and the first clad rods are arranged in a state in which a cross-sectional shape coupling centers of the three adjacent rods becomes a triangle and a state in which parts of the outer circumferential surfaces in at least the two core rods of the plurality of core rods contact an inner circumferential surface of the clad tube and the second clad rods are arranged in a state in which the second clad rods contact parts of the outer circumferential surfaces in the core rods which are contacting the inner circumferential surface of the clad tube, parts of the inner circumferential surface in the clad tube, and parts of the outer circumferential surfaces of the core rods sandwiched by the core rods contacting the inner circumferential surface of the clad tube.