Nippon Telegraph and Telephone Public Corporation

Sumitomo Electric Industries, Limited

Nippon Telephone and Telegraph Corporation

Sumitomo Electric Ind., Inc.

Sumitono Electric Inds., Ltd.

Takao Edahiro

Masao Kawachi

Toru Kuwahara

Gotaro Tanaka

Katsunari Okamoto

Shiro Kurosaki

Shoichi Suto

Tetsuo Miya

Minoru Watanabe

Michihisa Kyoto

Satoru Tomaru

Yutaka Sasaki

Akio Kawana

Hiroshi Yokota

Motohiro Nakahara

Juichi Noda

Nobuo Inagaki

Masaaki Yoshida

Fumiaki Hanawa

Tetsuo Miyajiri

Shiro Takahashi

Tadashi Miyashita

Masaharu Horiguchi

Kunio Masuno

Toshihito Hosaka

Katusunari Okamoto

An optical transmission fiber comprising (1) a core of high refractive index composed of SiO.sub.2 -based glass containing at least one of GeO.sub.2, As.sub.2 O.sub.3, Sb.sub.2 O.sub.5, SnO.sub.2, TiO.sub.2, PbO and Bi.sub.2 O.sub.3, (2) a clad of low refractive index composed of SiO.sub.2 -based glass containing at least one of F, F/B.sub.2 O.sub.3 and F/P.sub.2 O.sub.5, and (3) an outermost jacket layer composed of SiO.sub.2 and/or SiO.sub.2 -based glass containing at least one of Al.sub.2 O.sub.3, TiO.sub.2, ZrO.sub.2 and HfO.sub.2.

Optical transmission fiber and process for producing the same

A single-polarization single-mode optical fiber comprises a core made of silica glass, a clad surrounding the core and made of silica glass having a smaller index of refraction than the glass comprising the core, a pair of stress applying members symmetrically disposed on the clad and made of silica glass having different thermal expansion coefficient from that of the clad, spacers interposed between the stress applying members and made of silica glass having substantially the same thermal expansion coefficient as the clad, and a jacket surrounding the spacers, stress applying members. The jacket is also made of silica glass and has a smaller expansion coefficient than the stress applying members. The optical fiber of this invention has an excellent polarization preserving characteristic, low loss, long length, and stable characteristics.

Method for making single-polorization, single mode optical fibers

A process for producing an optical glass product having a predetermined distribution of refractive index in the interior of the product is disclosed. The process comprises the steps of:

Process for producing optical glass product

In a single mode optical fiber comprising a core made of glass and a cladding surrounding the core and made of glass, when a difference .DELTA. between refractive indices n.sub.1 and n.sub.2 of the core and cladding is expressed by (n.sub.1 -n.sub.2)/(n.sub.1).times.100%, the refractive indices n.sub.1 and n.sub.2 are determined to satisfy a relation 1.0&lt;.DELTA.&lt;3.6 and a diameter of the core is determined according to this value of .DELTA..

Single mode optical fibers

A single-polarization single mode optical fiber of the type comprising an elliptical core, a pair of stress applying parts on both sides of the minor radius of the elliptical core for applying asymmetrical stress thereto and a clad embedding therein the core and the stress applying parts, the stress applying parts being made of B.sub.2 O.sub.3 wherein a relative refractive index difference .DELTA. between the core and the clad satisfies a relation 0.004.ltoreq..DELTA..ltoreq.0.05, an ellipticity .epsilon. satisfies a relation 0.01.ltoreq..epsilon..ltoreq.0.9, the B.sub.2 O.sub.3 has a molar concentration of 1 to 25 mole %, ratio of thickness of the stress applying parts and the core is 5 to 15, a modal birefringence B expressed by an equation B=(.beta..sub.x -.beta..sub.y)/k satisfies a relation B=1.times.10.sup.-6 where (.beta..sub.x -.beta..sub.y) represents a propagation constant difference between HE.sub.11.sup.x and HE.sub.11.sup.y modes, and k a wave number in vacuum, whereby a polarization mode dispersion, that is a delay time difference between the HE.sub.11.sup.x and HE.sub.11.sup.y modes which are orthogonal with each other is zero.

Single-polarization single-mode optical fiber

A process for producing a porous optical fiber preform by hydrolyzing a gaseous glass forming material with a flame from an oxyhydrogen burner and depositing the resulting soot in a rod form in a muffle furnace is described, wherein the muffle furnace is supplied with a gas other than that from the oxyhydrogen burner, and said gas is maintained at a constant temperature.

Process for producing optical fiber preform

A core torch for fabricating a single-mode optical fiber preform wherein fine glass particles are produced eccentrically with respect to the center area of a flame stream, the core torch being so arranged as to blow the flame stream at an angle inclined to a seed rod. The porous glass body forming the core is grown on one end of the rod and in the direction of the axis of the rod. A cladding layer is formed on the periphery of the porous glass core body by at least one torch for forming the cladding. The obtained porous glass body is heated and vitrified into a transparent glass body, which is sealed in a silica tube for jacketting to form a single-mode optical fiber preform. At least one exhaust port is disposed within a distance of 1 mm to 50 mm from the periphery of the porous glass body and in the vicinity of the growing surface of the glass body to exhaust residual glass fine particles and undesired gases. A porous glass body having a diameter of 20 mm or less is easily formed. Single-mode optical fiber having a cladding-to-core-diameter ratio of 3 or more is fabricated by the VAD method. Accordingly, a long-length and low-loss single-mode optical fiber is mass-produced.

Core torch for fabricating single-mode optical fiber preforms

A process for producing high-purity silica glass wherein glass-forming chlorides, hydrogen gas, oxygen and an inert gas are supplied from a glass burner, the chlorides are decomposed by flame oxidation to form fine grains of glass which are deposited on a starting member and the glass deposit is sintered to provide a transparent vitreous substance, the volume ratio of oxygen gas to the sum of the chlorides and hydrogen gas being greater than about 0.6, preferably greater than about 1.0, and less than about 20.

Process for producing high-purity silica glass

A process for producing a glass perform for optical transmission fibers, which includes supplying a gaseous silicon compound, ammonia or a gaseous nitrogen compound, and an oxygen-containing gas as starting gases into a high temperature zone to produce fine particles of SiOxNy glass and depositing the fine particles in the form of a soot or a transparent glass on a starting member to produce nitrogen-doped silica glass.

Process for preparing glass preform for optical fiber

In a single mode optical fiber of the type comprising a core, a cladding surrounding the core and an intermediate layer, the refractive indices n1, n2 and n3 respectively of the core, the cladding and the intermediate layer are selected such that the following relations are satisfied

A method of fabricating an optical fiber preform wherein a synthesizing torch is inclined between 10.degree. and 60.degree. with respect to the rotation axis of a seed rod. Moving the rod while rotating it, a glass raw material gas and a flame forming gas are blown out individually from the torch to synthesize glass particles which are deposited onto one end of the rod, so that a cylindrical porous preform is grown in the direction of the rotation axis of the rod. Then the porous preform is heated at a high temperature to vitrify the porous preform into a transparent optical fiber preform. At least one exhaust port is disposed at a distance of 1 mm to 50 mm from the periphery of the porous preform and in the vicinity of the growing surface of the porous preform. In fabricating the porous preform the outer diameter fluctuations are small, and the preform is formed stably without formation of cracking on the periphery of the preform.

Method of fabricating multi-mode optical fiber preforms

A method of fabricating a single-mode optical fiber preform wherein a core torch produces fine glass particles eccentrically with respect to the center area of a flame stream, the core torch being so arranged as to blow the flame stream at an angle inclined to a seed rod. The porous glass body forming the core is grown on one end of the rod and in the direction of the axis of the rod. A cladding layer is formed on the periphery of the porous glass core body by at least one torch for forming the cladding. The obtained porous glass body is heated and vitrified into a transparent glass body, which is sealed in a silica tube for jacketting to form a single-mode optical fiber preform. At least one exhaust port is disposed within a distance of 1 mm to 50 mm from the periphery of the porous glass body and in the vicinity of the growing surface of the glass body to exhaust residual glass fine particles and undesired gases. A porous glass body having a diameter of 20 mm or less is easily formed. Single-mode optical fiber having a cladding-to-core-diameter ratio of 3 or more is fabricated by the VAD method. Accordingly, a long-length and low-loss single-mode optical fiber is mass-produced.

Fabrication method of single-mode optical fiber preforms

A process for producing a preform for glass fiber for optical transmission by heating supply gases to form fine particles that are deposited on a rotating starter member to form an aggregate of fine glass particles which are then sintered to give a transparent vitreous material, characterized by a first heating stage wherein the aggregate of fine glass particles is sintered by increasing the temperature at a constant rate in a gaseous atmosphere which contains a halogen or halide and which has dehydrating activity, followed by holding the aggregate for a given period of time at a temperature in the range that causes considerable shrinkage of the aggregate, and a second heating stage where said aggregate is heated to the vitrifying temperature.

Process for producing a glass preform for optical fiber

A process for producing an optical fiber preform which comprises forming a particulate glass rod in which the dopant concentration gradually increases toward the center of its cross section, and gradually heating the rod starting at a temperature below the minimum collapsing point of the fine glass particles in the center of the rod in such a manner that the softening of the rod proceeds from the center outward, to thereby produce a transparent glass rod.

An eccentric core optical waveguide comprising at least one glass core having relatively large refraction index disposed in an outer cylindrical glass jacket having larger diameter than that of the glass core and relatively small refraction index. The one or more glass core being so arranged as to made tangential contact with the inner wall of the glass jacket or a dielectric thin film coated inside the jacket at a small area. The space between the glass core and the outer glass jacket or said thin film is filled by air.

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Mito, Japan

Takao Edahiro