Shin-etsu Chemical Co., Ltd.

Hiroshi Oyamada

Hideo Hirasawa

Tetsuya Otosaka

Dai Inoue

Yuuji Tobisaka

Jun Abe

Hiroyuki Koide

Yuhei Urata

Yuichi Morishita

Go Ogino

Hitoshi Nakajima

Goh Ogino

An optical fiber curvature measuring method comprising rotatably holding an end of the optical fiber, irradiating two points at a prescribed distance from each other on a side surface of the fiber with a pair of parallel light beams orthogonal to an axial direction, measuring representative positions of scattered and reflected light beams scattered by the side surface as coordinate positions on an axis parallel to the optical fiber axis, calculating a difference between the two coordinate positions, rotating the fiber by a prescribed angle, repeating the calculation of the difference a plurality of times, calculating a positive representative value for amplitude Sfrom the difference obtained at each angle, calculating curvature from the amplitude Sas a first curvature of a first optical fiber longitudinal position, changing positions of the beams irradiating the fiber in the longitudinal direction, and calculating first to m-th curvatures by repeating this process.

Optical fiber curvature measuring method

A method for manufacturing deuterium-treated silica glass includes exposing silica glass to a deuterium-containing atmosphere for a predetermined period of time to diffuse deuterium molecules within the silica glass, maintaining the silica glass at 40&#xb0; C. or higher, and cooling the silica glass to room temperature. The silica glass is a silica glass-based optical fiber having a core made of silica glass, where the core is positioned at a center of the optical fiber and contains at least germanium, and a clad made of silica glass, where the clad surrounds the core and has a lower refractive index than the core. A surface of the silica glass is covered with a resin coating.

Optical fiber and method for manufacturing silica glass

An optical fiber comprising a first core, a second core, a third core, and a cladding, wherein with a refractive index of the cladding as a reference, &#x394;1 is a maximum value of a relative refractive index difference of the first core, &#x394;2 is a maximum value of a relative refractive index difference of the second core, &#x394;3 is a minimum value of a relative refractive index difference of the third core, 'a' is a half-value radial width for the relative refractive index difference (&#x394;1&#x2212;&#x394;2) of the first core, 'b' is a radius of a second core/third core boundary, and &#x201c;c&#x201d; is a radius of a third core/cladding boundary, the expressions 0.30%&#x2266;&#x394;1&#x2266;0.45%, &#x2212;0.05%&#x2266;&#x394;2&#x2266;0.05%, &#x2212;0.6%&#x2266;&#x394;3&#x2266;&#x2212;0.3%, 2.85&#x2266;b/a, 10 &#x3bc;m&#x2266;b&#x2266;15 &#x3bc;m, and 3 &#x3bc;m&#x2266;c&#x2212;b&#x2266;5.5 &#x3bc;m are satisfied, and transmission loss for a wavelength of 1550 nm when the optical fiber is wound around a mandrel with a diameter of 10 mm is no greater than 0.2 dB/turn.

Optical fiber

An optical fiber comprising a first core, a second core, a third core, and a cladding, wherein the expressions 0.30%&#x2266;&#x394;1&#x2266;0.45%, &#x2212;0.05%&#x2266;&#x394;2&#x2266;0.05%, &#x2212;0.35%&#x2266;&#x394;3&#x2266;&#x2212;0.15%, 2.5&#x2266;b/a, 3.5 &#x3bc;m&#x2266;a&#x2266;4.2 &#x3bc;m, 9 &#x3bc;m&#x2266;b&#x2266;13 &#x3bc;m, and 4.5 &#x3bc;m&#x2266;c&#x2212;b&#x2266;7.0 &#x3bc;m are satisfied, a zero-dispersion wavelength is no less than 1300 nm and no greater than 1324 nm, and transmission loss increase for a wavelength of 1550 nm when the optical fiber is wound around a mandrel with a diameter of 10 mm is no greater than 1 dB/turn.

Provided is an optical fiber including: a core at a center thereof; a first cladding adjacent to the core to cover a circumference of the core; and a second cladding adjacent to the first cladding to cover a circumference of the first cladding, where 0.35%&#x2266;(&#x394;&#x2212;&#x394;)&#x2266;0.65%, 0.30%&#x2266;&#x394;&#x2266;0.55%, &#x2212;0.20%&#x2266;&#x394;&#x2266;&#x2212;0.05%, 0.22&#x2266;a/b&#x2266;0.34, and 4&#x2266;b&#x221a;|&#x394;|&#x2266;10 hold, and loss increase resulting when the optical fiber is wound on a mandrel having a diameter of 20 mm is 0.5 dB/turn or smaller at a wavelength of 1550 nm, where &#x394;(%) is a specific refractive index difference of a maximum of a refractive index distribution of the core with reference to a refractive index of the second cladding, &#x394;(%) is a specific refractive index difference of a minimum of a refractive index distribution of the first cladding with reference to the refractive index of the second cladding, a(&#x3bc;m) is a radius of a boundary between the core and the first cladding with respect to a center of the core, and b(&#x3bc;m) is a radius of a boundary between the first cladding and the second cladding with respect to the center of the core.

Provided is an optical fiber including: a first core at a center thereof; a second core adjacent to the first core to cover a circumference of the first core; a third core adjacent to the second core to cover a circumference of the second core; and a cladding adjacent to the third core to cover a circumference of the third core, where conditions of 0.28%&#x2266;&#x394;&#x2266;0.4%, &#x2212;0.05%&#x2266;&#x394;&#x2266;0.05%, &#x2212;1.0%&#x2266;&#x394;&#x2266;&#x2212;0.5%, 3.8 &#x3bc;m&#x2266;a&#x2266;4.5 &#x3bc;m, 12 &#x3bc;m&#x2266;b&#x2266;21 &#x3bc;m, and 1.5 &#x3bc;m&#x2266;c-b&#x2266;10 &#x3bc;m hold, and loss increase resulting when the optical fiber is wound on a mandrel having a diameter of 20 mm is 0.1 dB/turn or smaller at a wavelength of 1625 nm, where &#x394;is a specific refractive index difference of the first core from the cladding refractive index, &#x394;is a specific refractive index difference of the second core from the cladding refractive index, &#x394;is a specific refractive index difference of the third core from the cladding refractive index, 'a' is a radius of a boundary between the first core and the second core with respect to a center of the first core, 'b' is a radius of a boundary between the second core and the third core with respect to the center of the first core, and &#x201c;c&#x201d; is a radius of a boundary between the third core and the cladding with respect to the center of the first core.

A method for manufacturing a preform having a core and a multilayer clad, includes covering a circumference of a rod including at least the core and an inner clad layer with a first tube including at least a high viscosity clad layer, and unifying the rod and the first tube by heating and contracting the first tube.

Optical fiber preform, method for manufacturing thereof, and optical fiber obtained by drawing thereof

A glass base material, which is a base material of an optical fiber, comprising: a core; and a clad surrounding the core; wherein: a rate of change in a relative-refractive-index-difference between the core and the clad in a longitudinal direction of the glass base material is substantially 6% or less.

Method of manufacturing a glass based material with defect removal

A method for measuring non-circularity of a core portion of an optical fiber base material includes a distribution measuring step of (i) moving the optical fiber base material in a direction parallel to a central axis of the core portion while light is irradiated, in a direction perpendicular to the central axis, to the optical fiber base material which is immersed in the matching oil, and (ii) recording a variation in a width of a portion of the irradiated light which transmits through the core portion in association with a moved distance of the optical fiber base material, thereby measuring a distribution of relative values of an outer diameter of the core portion in terms of a longitudinal direction of the optical fiber base material, a distribution storing step of performing the distribution measuring step each time the optical fiber base material is rotated about the central axis by a predetermined angle, thereby recording a plurality of distributions of the relative values of the outer diameter of the core portion each of which is associated with the predetermined angle, and a non-circularity calculating step of calculating a plurality of values, in terms of the longitudinal direction of the optical fiber base material, each indicating non-circularity of the core portion, based on the plurality of distributions of the relative values of the outer diameter stored in the distribution storing step.

Method for measuring non-circularity at core portion of optical fiber parent material

An optical fiber includes a clad portion and a core portion surrounded by the clad portion. Here, the clad portion is formed by substantially pure quartz, and the core portion has a higher refractive index than the clad portion. The optical fiber is characterized in that a relative refractive index difference of a center of the core portion falls within a range from 0.15% to 0.30%, and a maximum relative refractive index difference of the core portion falls within a range from 0.4% to 0.6%. Here, it is preferable that an average relative refractive index difference of the core portion falls within a range from 0.30% to 0.40%. Here, a mode field diameter of the optical fiber falls within a range from 8.6 &#x3bc;m to 9.5 &#x3bc;m at 1310 nm, and a cable cutoff wavelength of the optical fiber is equal to or lower than 1260 nm. Note that, after the optical fiber is subjected to hydrogen aging, a loss of the optical fiber is preferably equal to or lower than 0.4 dB/km at 1383 nm.

Glass base material, optical fiber, method for manufacturing thereof, and method for determining cause of defect thereof

Proposed is an improvement in the VAD process for the preparation of a porous silica glass preform for double-core optical fibers by using three oxyhydrogen flame burners installed one above the other in a flame hydrolysis chamber in which a porous silica glass body consisting of the center core portion formed by the lowermost burner, side core portion formed by the middle burner and the cladding layer formed by the uppermost burner is gradually pulled up as it grows under rotation. Different from conventional procedures in which the extension of the nozzle axis of each of the burners intersects with the rotation axis of the growing body, the extension of the nozzle axis of the middle burner for the side core is displaced in a horizontal direction by a limited distance not to intersect nor to be in parallel with the rotation axis in the invention. By this means, an improvement is obtained in the uniformity of distribution of the refractive index in the side core which otherwise is remarkably disordered.

Method for the preparation of a porous silica glass preform for optical

An improvement is proposed, in a method for the preparation of a step-index silica glass preform as a precursor of optical fibers by completing the cladding layer of the secondary preform by the outer deposition on and around a primary preform consisting of the center core and side core, to conduct the outer deposition for the cladding layer in such a way that the inequality

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Gunma, Japan

Hiroshi Oyamada