Shin-etsu Chemical Co., Ltd.

Hitachi Cable, Inc.

Kokusai Denshin Denwa Co., Ltd.

Other

Rikagaku Kenkyusho

Kazuo Koya

Jun Abe

Tsuneo Mori

Tadakatsu Shimada

Kiyoshi Yokokawa

Noboru Edagawa

Katsuyuki Imoto

Yoshihiro Yoshida

Minoru Taya

Nobuyasu Mantoku

Masaaki Shirota

Masayasu Nagaoka

Toshiyuki Suzuki

Masatoshi Suzuki

Kunio Itoh

Yoshiharu Konya

Itsuro Morita

Seiki Ejima

Ichirou Yamaguchi

Tetuo Yoshida

Tadakatsi Shimada

Yukio Fujimaki

Syouji Hosino

Sayuri Maeda

A grating optical fiber comprises a core, a first clad layer formed around the core, and a second clad layer formed around the first clad. Germanium is doped in the core, while germanium and fluorine are doped in the first clad layer. Gratings are formed on both the core and the first clad layer. The difference between the indexes of refraction between the first and second clad layers is smaller than the difference between the indexes of refraction between the core and the first clad layer.

Grating optical fiber, and optical fiber base material suitable for grating

The soliton pulse compression optical fiber comprises a core and a clad that surrounds the core for compressing the injected light pulse in width. The maximum relative index difference between the core and the clad is between about 1.2% and 2.5%. The core diameter of the soliton pulse compression optical fiber varies along the length of the soliton pulse compression optical fiber and the core has a step-like refractive index distribution. The optical fiber perform of the soliton pulse compression optical fiber comprises a core preform, which is to be a core of the soliton pulse compression optical fiber, and a clad preform that surrounds the core preform. The maximum relative index difference between the core perform and the clad preform is also between about 1.2% and 2.5%.

Soliton pulse compression optical fiber and method for making soliton pulse compression optical fiber

A mask having a center hole for passing through a center fiber, which is one of multiple fibers, and multiple surrounding holes for passing through surrounding fibers, which are the remainder of the multiple fibers, and a stress adjusting unit for holding stresses generated in the center fiber and surrounding fibers to a desired constant value, respectively, are installed. The surrounding fibers are rotated around the center fiber by rotating the mask. The center fiber and the surrounding fibers that have been twisted around the center fiber are heated with a heating apparatus and drawn. The center fiber and the surrounding fibers are fixed using a clamp installed between the stress adjusting unit and the heating apparatus.

Apparatus and method for making multi-branching optical coupler

Grating optical fiber, and optical fiber base material suitable for

A rare earth element-doped multiple-core optical fiber has an outer cladding layer and a plurality of cores each covered with a primary cladding layer. The cores are positioned substantially on a central axis of the outer cladding layer and separated with a predetermined spacing S from each other by the primary cladding layer. The outer cladding layers are made of SiO.sub.2, or SiO.sub.2 added with a dopant like F, Ge, etc. The primary cladding layer is made of SiO.sub.2 doped with Er, or SiO.sub.2 doped with Er and F together and formed to have a predetermined thickness of 1.0 .mu.m.about.1.5 .mu.m to form the predetermined spacing S. The Soot glass rods for cores and primary cladding layers are immersed in an Er-compound solution, then picked up, dried and consolidated to form Er--Al co-doped SiO.sub.2 --GeO.sub.2 transparent glass rods. The glass rods are inserted into a quartz tube and collapsed by heat to fabricate an optical fiber preform rod, then heated to be drawn to provide an Er-doped multiple-core optical fiber.

Rare earth element-doped multiple-core optical fiber and method for

An Er-doped multiple-core optical fiber amplifier has an Er-doped multiple-core optical fiber. A signal light of 1.5 .mu.m wavelength band is input through an optical isolator at front stage, and excitation lights of 0.98 .mu.m or 1.48 .mu.m wavelength emitted from excitation light sources are injected through a WDM coupler at front stage and a WDM coupler at rear stage, respectively. An amplified signal light is output through optical isolator at rear stage. A length L.sub.M of the Er-doped multiple-core optical fiber is set to obtain a substantially maximum saturated output power of the amplified signal light.

Rare earth element-doped optical fiber amplifier

The object of the present invention is to provide a wide-band optical fiber coupler whose light-branching ratio is independent of the wavelength of light rays to be transmitted therethrough as well as a method for preparing the wide-band optical fiber coupler. When an optical fiber 1 having zero-dispersion at 1.55 .mu.m band and an optical fiber 2 having zero-dispersion at 1.3 .mu.m band are fused and drawn to form a coupled portion 3, a light beam 15 is incident upon the optical fiber 2 and the intensity of the light beam outgoing through either of these optical fibers 2 or 1 is measured to detect the light-branching ratio observed at the coupled portion 3. The drawing operation is interrupted at an instance when the detected light-branching ratio falls within the range of 50.+-.5%.

Wide-band optical fiber coupler and method for preparing the same

At least three elementary optical fibers are covered with a jacket layer. Each of the elementary optical fibers has a core of a first refractive index doped with at least one rare earth element and Al, and a cladding layer of a second refractive index lower than the first refractive index for covering the core. A value of (1+2t/Dw) is ranged to be 1.1 to 2.5, where t is a thickness of the cladding layer, and Dw is an outer diameter of the core, and a doping amount of Al is at least 1 weight %. The at least three elementary optical fibers are inserted into a jacket tube, and the elementary optical fibers and the jacket tube are heated to be welded at contact surfaces thereof by vacuum-drawing air from interstices of the elementary optical fibers and the jacket tube. Thus, a preform is obtained, and the preform is heated to be drawn. Consequently, a rare earth element-doped multiple-core optical fiber is fabricated. The rare earth element-doped multiple-core optical fiber is used to amplify a signal light to be propagated therethrough by receiving an excitation light.

Rare earth element-doped multiple-core optical fiber, method for

Herein disclosed is an optical amplifier which permits sufficient reduction of light-transmission loss when it is incorporated into an optical communication system as a part thereof. The optical amplifier comprises an optical fiber 8 for amplification having a length sufficient for stimulated emission through excitation by an excitation laser beam and sufficient for amplifying a transmitted laser beam; an optical fiber 17 for transmission; and an optical wavelength division multiplexer 6 formed by partially fusing, under drawing conditions, the optical fibers 8 and 17 at a portion in the proximity to the light-incident end of the fiber 8 for amplification. The optical amplifier comprises the optical wavelength division multiplexer 6 formed from a part of the optical fiber 8 for amplification and, therefore, permits substantial reduction in the number of fused portions required for the connection thereof to an optical communication system upon incorporation thereof into the system. For this reason, the connection loss of light can substantially be reduced and accordingly the overall efficiency for amplification is substantially increased.

Optical amplifier

A wide wavelength range-coupler whose light-branching ratio shows low wavelength-dependency, which is provided with a well-shaped light-coupling portion and excellent optical properties and which can easily be connected to other optical fibers as well as a method for the production thereof are herein provided. The light-coupling portion 3 of the optical fiber coupler is formed by fusing and orientating a plurality of single mode optical fibers 1 and 2 partially arranged parallel to one another and these optical fibers 1 and 2 have cores 1a and 2a which are different from one another in diameter, but are substantially identical in the outer diameter of the clad and in the mode field diameter. Each single mode optical fiber as a material for the coupler has a core diameter and a mode field diameter which are correlated through a quadratic function and therefore, there can be selected two optical fibers 1 and 2 which are identical to one another in the mode field diameter, but differ in the core diameter.

Wide wavelength range-optical fiber coupler and method for the

The inspection apparatus for determination of the degree of ellipticity of an optical fiber perform and the eccentricity of the core thereof comprises optical system 12 for projecting a light beam from light source 10 through optical fiber preform 1 to video camera 11; and signal processing circuit 17 for converting the image of the optical fiber preform 1 photographed by the video camera 11 into a numerical value and the apparatus is connected to driving device 14 for rotating the optical fiber preform 1 traversing the optical path of the optical system 12 around the central axis of the preform 1. The curve showing the external shape of the optical fiber preform 1 is represented by the formula: v=(a-b)Sin2.theta. and the line showing the external shape of the core represented by the formula: w=nU Sin.theta.+(n-1)(a-b)Sin(2.theta.+.alpha.). The eccentricity of the core can be calculated from these values.

Apparatus and method for inspecting elliplicity and eccentricity of

A method and an apparatus for accurately, thoroughly and automatically inspecting an optical fiber preform for the presence of bubbles and/or inclusions are herein provided. The inspection apparatus comprises light source 2 for making light rays incident upon the end face 1a of rod-like optical fiber preform 1 as a subject to be inspected, video camera 7 for photographing the side face of the optical fiber preform 1 and image-processing circuit 11 for discriminating and detecting bubbles and/or inclusions present in the preform 1 through processing of image signals outputted from the video camera 7 and inputted to the circuit 11.

Method for detecting bubbles and inclusions present in optical fiber

In an optical fiber coupler comprising a plurality of optical fibers bundled together and a light-coupling portion which is formed by partially fusing and drawing these bundled fibers and which permits branching of light rays incident upon one of these fibers into the other fibers at a predetermined branching ratio, the optical fiber coupler has a difference between the branching ratio thereof determined immediately after the fusing and drawing operation and that determined after accommodating the coupler in a protective case and then adhering it to the case, equal to or less than 5%. Such an optical fiber coupler can be produced by bundling a plurality of optical fibers 1 and 2, fusing and drawing a part of the bundled optical fibers with heating, fixing the relative positions of these optical fibers 1 and 2 immediately after the fusing and drawing operation and then accommodating in and fixing to a protective case. If the foregoing difference in the branching ratio is not more than 5%, the difference between the branching ratios determined after the fusing and drawing operation and determined after the coupler is subjected to a thermal shock test is reduced to a level of not more than 2%. Therefore, the coupler does not suffer from any substantial change in properties even after the thermal shock test and thus can practically be used with high reliability.

Optical fiber coupler and method for preparing same

An improvement is proposed for decreasing the variation in the coupling ratio of an optical fiber coupler after a heat shock test. In an optical fiber coupler which is an elongated intergral body formed by fusing a plural number of optical fibers side-by-side consisting of two straightly columnar parts and a biconical part therebetween formed by drawing and adhesively bonded to a reinforcing base with a coating layer of an adhesive therebetween, the improvement can be achieved by limiting the zone where the coating layer of an adhesive to the surface of each of the straightly columnar parts within a range from the boundary between the straightly columnar part and the biconical part to a point 8 mm apart from the boundary.

Optical fiber coupler

Herein provided is a support member for supporting an optical fiber coupler formed by arranging a plurality of optical glass fibers parallel to one another, then welding and drawing a part thereof wherein a long and thin reinforcing material of quartz whose external is at least partially formed into a circular shape is accommodated in a cylindrical metal case while coming the material into contact with the inner wall of the case; the optical fiber coupler is arranged along the reinforcing material; a portion of the optical fiber coupler which is not welded and drawn comes in contact with the reinforcing material and a part of the contact portion of the optical coupler is fixed to the material with an adhesive.

Growing community of inventors

Gunma, Japan

Kazuo Koya