Abstract: A core part of a multimode optical fiber including the core part and a cladding part has a structure composed of a plurality of concentric layers in which a refractive index is decreased stepwise from a first core layer as an innermost layer to a third core layer as an outermost layer. The structure having the plurality of layers is formed by adjusting a quantity of addition of fluorine to silica glass. Fluorine is added to the cladding part so that a refractive index is lower than that of the third core layer as the outermost layer of the core part.

Abstract: A communication cable having a communication wire and an armor including at least two synthetic resin layers, and protects the communication wire in a loose state. The communication wire protecting tube includes at least two synthetic resin layers, and inserts the communication wire in a loose state. The most hard resin layer of the armor has a crosswise or spiral annular groove or cut portion continuous in the longitudinal direction to reach the radially inner face, and the outermost layer of the armor is formed of a protective layer made of a softer resin than the hard resin layer. The adjoining edge portions of the annular groove or the cut portion come, when the communication wire is to be bent, into contact with each other so that it may be prevented from being bent to a predetermined or smaller bend radius.

Abstract: [Problems to be solved]A communication cable and a communication wire protecting tube, which can be easily bent to a predetermined bend radius by a low force but which requires such a higher force for the bend of a smaller diameter that it may be hard to bend. [Means for solving the Problems]The communication cable 10,10A comprises a communication wire 11,11A and an armor 13A including at least two synthetic resin layers, and protects the communication wire 11,11A in a loose state. The communication wire protecting tube comprises at least two synthetic resin layers, and inserts the communication wire 11,11A in a loose state. The most hard resin layer 13a, 13aA of the armor 13,13A has a crosswise or spiral annular groove 14 or cut portion 14A continuous in the longitudinal direction to reach the radially inner face, and the outermost layer of the armor 13,13A is formed of a protective layer 13b,13bA made of a softer resin than the hard resin layer 13a, 13aA.

Abstract: A self-supporting cable includes a main cable constructed by covering a cable core with an inner cover layer and installing one or more strength members inside the inner cover layer such that they lie on a plane passing through the central axis thereof; a support member; and an outer cover layer formed so as to cover the main cable and the support member while they are arranged in parallel. A support member portion including the support member and a part of the outer cover layer and a main cable portion including the main cable and a part of the outer cover layer are connected by connecting portions, which are also a part of the outer cover layer, in the longitudinal direction thereof. The main cable portion is made longer than the support member portion so that there is an allowance in the length thereof.

Abstract: A plurality of optical fibers are arranged in parallel and peripheries of the plurality of these optical fibers are integrally formed using a sheath. Here, the sheath is formed over the entire length of optical fiber ribbons and a flat portion of the sheath is formed substantially parallel to a common tangent of the neighboring optical fibers. A maximum value of a thickness of the optical fiber ribbons is set to a value which is larger than an outer diameter of the optical fibers by 40 &mgr;m or less. Due to such a constitution, it is possible to easily branch the optical fibers from the integrally formed optical fiber ribbons.

Abstract: The present invention relates to a wide-band, low-loss, submarine optical cable excellent in productivity, an optical fiber unit employed in the submarine optical cable, and a method of making the optical fiber unit. The optical fiber unit employed in the submarine optical cable comprises a loose structure in which one or more coated optical fibers are accommodated together with a soft resin in a space formed within a plastic support. In particular, one or more compression members are embedded in the plastic support along the space accommodating the coated optical fibers. The compression members closely in contact with the plastic support prevents the shrinkage of the plastic support from occurring due to temperature changes before forming a cable utilizing the optical fiber unit.

Abstract: An optical fiber cable having excellent workability and long-term reliability. The cable comprises at least one optical fiber, a plastic jacket covering the optical fiber or optical fibers, and at least one anti-shrink member embedded in the jacket. The jacket has a longitudinal shrinkage of at most 0.5% when heated at 110° C. for two hours. The cable has a remaining bend with a radius of curvature of at least 100 mm when wound on a 50-mm-radious mandrel and heated at 85° C. for two hours. The deflection of a 30-cm-long cantilever made of the cable is at least 50 mm. In one aspect of the cable, the cable is specified by the conditions of ESt/ESj≧0.7, EIt/EIc≧0.1, and EIc/Mc≦8×106 mm3 (E: Young's modulus; S: cross-sectional area; t: total of anti-shrink members; j: jacket; I: geometrical moment of inertia; c: cable; and M: mass).

Abstract: A self-supporting cable includes a main cable constructed by covering a cable core with an inner cover layer and installing one or more strength members inside the inner cover layer such that they lie on a plane passing through the central axis thereof; a support member; and an outer cover layer formed so as to cover the main cable and the support member while they are arranged in parallel. A support member portion including the support member and a part of the outer cover layer and a main cable portion including the main cable and a part of the outer cover layer are connected by connecting portions, which are also a part of the outer cover layer, in the longitudinal direction thereof. The main cable portion is made longer than the support member portion so that there is an allowance in the length thereof.

Abstract: An optical fiber cable having excellent workability and long-term reliability. The cable comprises at least one optical fiber, a plastic jacket covering the optical fiber or optical fibers, and at least one anti-shrink member embedded in the jacket. The jacket has a longitudinal shrinkage of at most 0.5% when heated at 110° C. for two hours. The cable has a remaining bend with a radius of curvature of at least 100 mm when wound on a 50-mm-radious mandrel and heated at 85° C. for two hours. The deflection of a 30-cm-long cantilever made of the cable is at least 50 mm. In one aspect of the cable, the cable is specified by the conditions of ESt/ESj≧0.7, EIt/EIc≧0.1, and EIc/Mc≦8×106 mm3 (E: Young's modulus; S: cross-sectional area; t: total of anti-shrink members; j: jacket; I: geometrical moment of inertia; c: cable; and M: mass).

Abstract: A self-supporting cable includes a main cable constructed by covering a cable core with an inner cover layer and installing one or more strength members inside the inner cover layer such that they lie on a plane passing through the central axis thereof; a support member; and an outer cover layer formed so as to cover the main cable and the support member while they are arranged in parallel. A support member portion including the support member and a part of the outer cover layer and a main cable portion including the main cable and a part of the outer cover layer are connected by connecting portions, which are also a part of the outer cover layer, in the longitudinal direction thereof. The main cable portion is made longer than the support member portion so that there is an allowance in the length thereof.