Abstract: An evaluation method for insulation performance includes: a step ? of applying a DC voltage to a first insulator and measuring an integration value of a current flowing through the first insulator from a start of application of the DC voltage after a prescribed time period; a step ? of applying a DC voltage to the second insulator on an applying condition that is identical to that in the step ? and measuring an integration value of a current flowing through the second insulator from a start of application of the DC voltage after a prescribed time period; and a step ? of comparing (i) a first graph obtained in the step ? and (ii) a second graph obtained in the step ?, to evaluate a difference between insulation performances of the insulators.

Abstract: An evaluation method for insulation performance includes: a step ? of applying a DC voltage to a first insulator and measuring an integration value of a current flowing through the first insulator from a start of application of the DC voltage after a prescribed time period; a step ? of applying a DC voltage to the second insulator on an applying condition that is identical to that in the step ? and measuring an integration value of a current flowing through the second insulator from a start of application of the DC voltage after a prescribed time period; and a step ? of comparing (i) a first graph obtained in the step ? and (ii) a second graph obtained in the step ?, to evaluate a difference between insulation performances of the insulators.

Abstract: In an optical fiber coupler fabricating process where couplers are successively formed by heating, elongating and cutting a plurality of long optical fibers, light is led into the first end of the fiber, reflected at the second end of the coupler, and the reflected light is monitored by photodetectors. In this manner, an exact splitting ratio can be obtained. Techniques for minimizing measuring errors caused by the inter-reflected-light interference, the inter-Rayleigh-scattering-light interference, and the interference between the reflected light and the Rayleigh scattering light, while exploiting the advantageous feature of the reflection monitor method that the fiber connection work for each fiber coupler fabrication is not required are disclosed.

Abstract: In a method of producing an optical fiber coupler, in which glass portions of a plurality of optical fibers are heated so as to be fusion bonded to each other and then, are heated so as to be stretched, the improvement comprising: a gas burner which acts as a heat source and has a plurality of gas nozzles arranged in an axial direction of the optical fibers so as to be fixed in position during heating of the glass portions.

Abstract: A method for manufacturing a fiber type coupler of the present invention by fusing and elongating a plurality of optical fibers is characterized in that a multi-wire optical fiber wire is used as the plurality of optical fibers.

Abstract: An optical fiber coupler constructed of single-mode optical fibers having claddings of differing refractive indices. The fibers are fused together and the fused portion is elongated in order to achieve the desired coupling and branching characteristics.

Abstract: A method of fabricating an optical branching and coupling device includes the steps of preparing at least a pair of coated optical fibers; partly stripping the coating of the optical fibers; and fixedly inserting the coating stripped portions of the optical fibers into a pair of comb-shaped grooves under a condition prior to a unification step which is free from tension and torsional stress in an optical axial direction to bring the coating stripped portions into contact with each other between the comb-shaped grooves. The method also includes the steps of melting the coating stripped portions thus contacting each other by heating to unify the coating stripped portions and extending the coating stripped portions in the optical axial direction while in the melted state.

Abstract: A mode scrambler is interconnected between a light source and an optical fiber coupler made of a plurality of graded index multi-mode optical fibers. The mode of the input light signals can be converted to a random pattern mode through the mode scrambler, so that a steady excitation state of the input light can be realized, including not only dominant lower modes but also higher modes of the input light signals, resulting in enabling to divide the input light signals without any irregularity of the output light power.

Abstract: A method for manufacturing a fiber type coupler or the present invention by fusing and elongating a plurality of optical fibers is characterized in that a multi-wire optical fiber wire is used as the plurality of optical fibers.

Abstract: This invention is the method for manufacturing the fiber type coupler by extending at least two optical fibers having coatings thereof removed, along an optical axis while fusing the optical fibers to form a coupler member, is characterized by a step of adding a tension to the coupler member along the optical axis before the coupler member is fixed to a protective member.

Abstract: Disclosed is an optical fiber cable which prevents water from running or spreading toward the cable interior. The optical fiber cable comprises at least one optical fiber unit, an outermost sheath member, and a water absorbing and swelling member. The optical fiber unit includes a central spacer formed with grooves, and at least one coated optical fiber or optical fiber tape disposed in each of the grooves. The outermost sheath member surrounds the optical fiber unit, and the water absorbing and swelling member is filled in spaces defined between the optical fiber unit and the outermost sheath member. The water absorbing and swelling member comprises a non-water absorbing and non-swelling base and water absorbing and swelling material fixed to a surface of the base. In another embodiment of the invention, the water absorbing and swelling member is in the form of a tape in which a layer of water absorbing and swelling material is bonded to one or both surfaces of a film like flexible base.