Abstract: An object is to provide an optical fiber fusion splicing method in which splice loss can be reduced, and also to provide an arc-heating unit used for heating the fusion spliced part of an optical fiber. The method comprises a process of fusion-splicing together the end faces of two optical fibers and a process of continuously heating the fusion spliced part by arc while moving one pair of electrodes provided opposite to each other across the fusion spliced part. The arc heating process is performed with the operation for decreasing arc temperature.

Abstract: A method of fusion-splicing optical fibers having different mode field diameters or small mode field diameters is provided, which method is advantageous in that the splicing loss is smaller. The method comprises a fusion splicing process in which fusion splicing is performed by butting end faces of two optical fibers together and a heat treatment process in which the fusion spliced part of the optical fibers and the vicinity thereof are heated. The heat treatment process is performed by moving an arc heating unit in a direction other than the Y-axis direction (a direction perpendicular to the Z-axis direction and the opposing direction of arc electrodes) and Z-axis direction (the axial direction of the optical fiber), via the fusion spliced part in a Y-Z plane formed by the Y-axis direction and Z-axis direction.

Abstract: In a method of elongating a glass preform comprising the steps of holding both ends of the glass preform 1a with a first holding section 2 and a second holding section 3, respectively; moving the first holding section 2 and the second holding section 3 in a longitudinal direction of the glass preform 1a with the moving speed of the first holding section 2 faster than that of the second holding section 3 and, at the same time, heating and softening the glass preform 1a by a heating section 4 successively; and elongating the glass preform 1a by a tensile force applied thereto, so as to form an elongated body 1c; an electric furnace is employed in the heating section 4; and said method further comprising the steps of setting a reference value R1 with respect to an outside diameter at a specific position 1d in a tapered region 1b in the glass preform 1a in the process of elongating; acquiring an actually measured value R2 at the specific position 1d; and controlling the moving speed of the first holding section 2

Abstract: A molding die 1 is constituted by an upper die 1a and a lower die 1b which are made of a material transparent to an ultraviolet light, and has a cavity 3 constituted by grooves 2c, 2d, whereas a resin injection gate 4 and a resin exit gate 7 are provided so as to communicate with the cavity 3. A junction of an optical fiber 10 is inserted into the cavity 3. A UV-curable resin is injected into the cavity 3 surrounding an exposing portion of the glass optical fiber 11 from the resin injection gate 4 positioned at one of coating ends of the optical fiber 10, whereas a part thereof is discharged from the resin exit gate 7 positioned at the other coating end. The ultraviolet light is emitted through the lower die 1b so as to cure the resin, thereby forming a reinforcement resin coating. As a consequence, bubbles can be prevented from occurring due to the residual air within the reinforcement resin coating in the junction of the optical fiber 10.

Abstract: In a heating furnace which holds at least one end of a glass rod with a holding portion and elongates the glass rod by softening the glass rod successively from the other end portion thereof with heating while applying a tensile force thereto, the heating furnace comprises a tubular portion through which the glass rod to be elongated is inserted such as to be longitudinally movable; heater, positioned within the tubular portion such as to circumferentially surround the glass rod, for heating the glass rod; a moving portion through which one end of the glass rod is inserted; bellows the ends of which are respectively secured to the moving portion and the tubular portion and which is longitudinally expandable and contractible and composed of at least a double cylinder surrounding the part of the glass rod such as to block an outside air from flowing into the heating furnace; and gas supply line for supplying, for purging, an inert gas into a space within the tubular portion and the inner bellows as well as the

Abstract: A furnace body for a glass preform elongating apparatus which makes an elongated body by passing the glass preform through the furnace body and elongating the glass preform while heating the glass preform, the furnace body comprising a furnace core tube shaped like a cylinder through which the glass preform passes and having so adequate length in an axial direction that the elongated body may not bend or distort its form, a heating member disposed at an outer peripheral portion of the furnace core tube, a thermal insulator enveloping the furnace core tube and the heating member from outside in circumferential and axial directions thereof, and a furnace body outer shell holding the thermal insulator therein, wherein a through hole is disposed near the heating member downstream thereof in an advancing direction of the glass preform so as to penetrate through the furnace core tube, thermal insulator, and furnace body outer shell in the direction orthogonal to the furnace core tube.

Abstract: The present invention provides a method for manufacturing an optical fiber coupler in which an optical fiber is elongated and heated by using a heating source under a constant tension. The heat source is controlled based on the ratio of a target elongating speed and an actual elongating speed of the optical fiber.