Abstract: Methods for connecting two optical fibers having different mode field diameters ((MFD) with low connection loss is proposed. One method comprises steps of preparing the third fiber (Fiber 3), a short length and MFD being smaller than that of the first fiber (Fiber 1) and larger than that of the second (Fiber 2), connecting the Fiber 1 to 3, connecting Fiber 2 to 3, and increasing MFD of Fiber 3 near the part connected or to be connected to Fiber 1, or MFD of Fiber 2 near the part connected or to be connected to Fiber 3 by heating the corresponding part. The other method comprises steps of preparing a short length Fiber 3 having smaller MFD than that of Fiber 1, increasing MFD of Fiber 3 near the part to be connected to Fiber 1 by heating the corresponding part, and then connecting Fiber 1 to 3, and 3 to 2 in that order.

Abstract: An object of the present invention is to provide a method and apparatus for producing a glass particles deposit in which a soot body having less fluctuation in the outer diameter in a longitudinal direction can be produced without increasing an ineffective portion formed at an end portion of the soot body.

Abstract: Two optical fibers to be spliced are prepared, coatings of resin are removed from end portions of the respective optical fibers to expose glass fibers, the glass fibers are aligned to each other, an a fusion step is carried out to heat the end faces of the glass fibers to cause fusion thereof to form a fusion-spliced portion. After that, an additive-diffusing step is carried out to diffuse an additive added in the glass fibers around the fusion-spiced portion, by a heat treatment around the fusion-spliced portion, by a heat treatment around the fusion-spliced portion at a first temperature of not less than 800° C. nor more than 1500° C. Further after the additive-diffusing step, a thermal-strain-removing step is carried out to remove thermal strain by a heat treatment of a wider region than heated regions in the fusion splice step and in the additive-diffusing step of the fusion-spliced portion, at a temperature of not less than 500° C. nor more than 1200° C.

Abstract: Three or more glass particle synthesizing burners are arranged to be opposed to a rotating glass rod. The glass rod and the glass particle synthesizing burners are reciprocated in parallel and relatively to deposit glass particles synthesized by the burners on the surface of the glass rod, thereby producing a soot body. The glass particle synthesizing conditions of the burners arranged at both ends are changed to have a greater deposition amount of glass particles per unit time in part or all of its movement range than other burners.

Abstract: The present invention relates to a dispersion-compensating optical fiber which can transmit, with a low loss, light signals having a high power; and an optical transmission system including the same. This dispersion-compensating optical fiber is insured its single mode at a wavelength of 1.55 &mgr;m, and comprises, about the optical axis, at least a first core having a refractive index n1, a second core having a refractive index n2 (>n1), and a cladding having a refractive index n3 (<n2). Also, this dispersion-compensating optical fiber has a chromatic dispersion of −10 ps/nm/km or less at the wavelength of 1.55 &mgr;m, whereas the ratio 2a/2b of the outside diameter 2a of the first core with respect to the-outside diameter 2b of the second core is 0.05 or more.

Abstract: Vent holes are provided on a reaction vessel in the vicinity of burners which are placed in the reaction vessel. The gas of different flow rate and/or temperature is supplied through the vent holes toward a soot body in a length direction of the soot body.

Abstract: In an apparatus for producing glass particles deposit according to the present invention, a plurality of glass particle synthesis burners are placed on a front face of a reaction vessel, and at least one exhaust port is provided on a rear face of the reaction vessel. Two wall faces extending from both sides of the exhaust port and being in contact with two side faces of the reaction vessel are provided so that its contained angle is 90 degrees or less. Assuming that the shorter distance between the shortest distance from a rotation axis of a target rod to the side face of the reaction vessel and the shortest distance from the rotation axis of the target rod to the wall face is L, and the outer diameter of the glass particles deposit deposited on the target rod is d, L is greater than d.

Abstract: In a method in which a rotating starting rod and glass particle synthesizing burners are relatively reciprocally moved in parallel with each other, so that while a turn-back position of the relative movement is shifted in a predetermined direction, glass particles (soot) are deposited on a surface of the starting rod to thereby produce a glass particles deposit, the deposition of soot is performed under a condition that an interval between a burner located at any one of both ends in a direction of the relative movement and a burner located adjacent thereto is shorter than another interval between any two of intermediate burners other than the two burners located at the both ends.

Abstract: A magnetic recording element is composed of a first magnetic film to generate spin vortex by an external magnetic field and a second magnetic film having a magnetization perpendicular to the surfaces thereof, and also an insulating layer to control (repress) a current through the magnetic recording element which is formed between the first magnetic film and the second magnetic film. A given external magnetic field is applied to the magnetic recording element, to generate a spin vortex in the first magnetic film and then, generate a vertical magnetization at the center of the spin vortex. Then, a given data is written on the vertical magnetization.

Abstract: An optical fiber splicing method capable of fully reducing the splice loss at room temperature is provided. In the optical fiber splicing method in accordance with the present invention, respective end faces of optical fibers are fused together in a splicing step (S101). In a condition setting step (S102), a set value &agr;0 is set. Thereafter, a heating step (S103), a measuring step (S104), and a termination determining step (S105) are carried out repeatedly. In the heating step, a region including the fusion-spliced point is heated under a predetermined heating condition. In the measuring step, splice loss is measured. In the termination determining step, the splice loss &agr;n measured in the measuring step and the set value &agr;0 set in the condition setting step are compared with each other in terms of magnitude.

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: A plurality of glass particles synthesizing burners are arranged at a predetermined burner interval opposite to a rotating starting rod. The starting rod and the glass particles synthesizing burners are relatively parallely reciprocally moved, and the soot deposition is conducted. A reciprocating speed v(mm/minute), axis rotating speed r (rpm), and burner interval L (mm) are set so that a value A expressed by the expression A=(r/v)×L is in a range 40≧A≧8.

Abstract: A method of making an optical fiber preform in which a starting member prepared by fusing dummy rods to both end portions of a core preform is axially reciprocated relative to a glass synthesizing burner while being rotated about its axis, so that fine particles of glass synthesized by the burner are sprayed and deposited onto the outer periphery of the starting member, whereby a soot body is formed.

Abstract: A method for producing an optical fiber preform is provided in which the variation of the outer diameter in the longitudinal direction is minimized and a target quantity of glass is accumulated as a whole. Based on a predetermined relationship between three variables: the outer diameter of a starting rod being a first variable, the outer diameter of an optical fiber preform a second variable, and the timing for ending the glass particles depositing process a third variable, the starting rod and burners are subjected to relative reciprocating movement so as to deposit glass particles on the starting rod until the timing for ending the depositing process, and then the resulting deposit body is vitrified. The third variable may be the traverse velocity, the glass particles deposition time, or the weight of a soot glass deposit body.

Abstract: A concentric multi-tubular burner for synthesizing glass particles having a center port group constituted by a combination of jet ports of raw material gas, combustible gas and oxygen gas, wherein an outer wall of the oxygen gas jet port in the center port group protrudes more toward a burner head than an inner wall of the oxygen gas jet port. The flow rate of oxygen gas jetted from the oxygen gas jet port of the center port group is controlled to be in a proper range.

Abstract: A plurality of glass particle synthesizing burners are disposed opposite to a rotating starting rod. The starting rod and the glass particle synthesizing burners are relatively reciprocally moved to each other in parallel to the axial direction, so that glass particles synthesized by the burners are sequentially deposited on the surface of the starting rod. The movement is stopped and restarted repeatedly once or more than once during one reciprocal movement.

Abstract: Methods for connecting two optical fibers having different mode field diameters ((MFD) with low connection loss is proposed. One method comprises steps of preparing the third fiber (Fiber 3), a short length and MFD being smaller than that of the first fiber (Fiber 1) and larger than that of the second (Fiber 2), connecting the Fiber 1 to 3, connecting Fiber 2 to 3, and increasing MFD of Fiber 3 near the part connected or to be connected to Fiber 1, or MFD of Fiber 2 near the part connected or to be connected to Fiber 3 by heating the corresponding part. The other method comprises steps of preparing a short length Fiber 3 having smaller MFD than that of Fiber 1, increasing MFD of Fiber 3 near the part to be connected to Fiber 1 by heating the corresponding part, and then connecting Fiber 1 to 3, and 3 to 2 in that order.

Abstract: The present invention relates to an optical fiber device having a structure for effectively restraining the splice loss from increasing between two kinds of optical fibers having respective mode field diameters different from each other. The optical fiber device comprises first and second optical fibers fusion-spliced to each other, which are partly heat-treated such that both of their respective ratios of change in mode field diameter in the longitudinal direction become a predetermined value or less after fusion-splicing. When the ratios of change in mode field diameter in the vicinity of the fused point are appropriately controlled as such, the increase in splice loss at the fused point between the first and second optical fibers is effectively suppressed.

Abstract: In a process for producing an optical fiber preform, a starting member and a glass synthesizing burner are reciprocated relative to each other so that fine glass particles synthesized with the burner are deposited layer by layer on the starting member, and a heating power of the glass synthesizing burner in a nonsteady outside diameter portion at either end of the soot preform is adjusted to control the temperature of the nonsteady outside diameter portion at either end against local elevation. The starting member is formed of a transparent glass rod that is held within a vessel and rotatable about its own axis, the burner is fitted on a lateral side of the vessel at right angles to the rotating axis of the starting member and is movable towards or away from the starting member.