Abstract: Disclosed is a low bend loss optical fiber including: a core; an inner layer disposed at outside of the core, which has a refractive index lower than a refractive index of the core, the refractive index of the inner layer gradually decreasing as it becomes farther from the core; and a trench layer disposed at outside of the inner layer, which has a lowest refractive index.

Abstract: Disclosed herein is a novel gluconacetobacter strain having cellulose producing activity. Specifically, the present invention relates to a novel gluconacetobacter strain producing nano-structured cellulose in a highly efficient manner. The cellulose produced by the strain, due to its superb thermodynamic properties, can be characterized as nano-structured bacterial cellulose and therefore utilized as a bio-nano-fiber. Particularly, the cellulose can be impregnated with a resin to form a cellulose-based resin which can be effectively adapted for a substrate for a liquid crystal display (LCD).

Abstract: Disclosed is a low bend loss optical fiber including: a core; an inner layer disposed at outside of the core, which has a refractive index lower than a refractive index of the core, the refractive index of the inner layer gradually decreasing as it becomes farther from the core; and a trench layer disposed at outside of the inner layer, which has a lowest refractive index.

Abstract: The present invention relates to a preflux composition having excellent heat-resistance suited for the formation of a film on the surface of copper or copper alloy, and more precisely, a preflux composition having enhanced heat-resistance, compared with the conventional preflux composition, and capable of selectively coating a copper plating circuit. The preflux composition with high heat-resistance of the present invention is characteristically composed of 0.1-5 weight part of benzimidazole derivative, 0.5-20 weight part of organic acid or inorganic acid, 0.001-1 weight part of iron compound, 0.001-1.5 weight part of chelating agent, 0.0001-1 weight part of nickel compound and 0.01-1 weight part of iodine compound for 100 weight part of water.

Abstract: Disclosed is an optical fiber, which includes: a core positioned at the center of an optical fiber to have the maximum refractive index within the optical fiber; an inner clad surrounding the core to have the minimum refractive index within the optical fiber; and an outer clad surrounding the inner clad to have a refractive index lower than that of the core and higher than that of the inner clad, wherein a difference ?ncore-inner—clad between the refractive index of the core and the minimum refractive index of the inner clad is within the range of 0.00615 to 0.00645, and a difference ?nouter—clad-inner—clad between the refractive index of the outer clad and the minimum refractive index of the inner clad is 0.0006 or more.

Abstract: Disclosed is a method for fabricating an optical fiber preform. The method includes: (a) growing a first soot preform on a starting member along a lengthwise direction of the starting member by a soot deposition; (b) dehydrating the first soot preform; (c) sintering the dehydrated first soot preform, to obtain a first glassed optical preform; and (d) elongating the first optical fiber preform by heating the first optical fiber with a heat source that excludes hydrogen, wherein the first glassed optical fiber is elongated by means of only a heat source that excludes the use of hydrogen.

Abstract: A method for dehydrating and consolidating a porous optical fiber preform in a heating apparatus is provided. The apparatus includes a muffle in which the porous optical fiber preform is placed and a plurality of multi-stage heaters attached to an outer circumference of the muffle in a longitudinal direction of the preform. The preform is placed in the muffle such that the multi-stage heaters surround a total length of the preform. The preform is heated and dehydrated in a state in which a temperature of the multi-stage heaters reaches a dehydrating temperature of the preform. A temperature of one heater selected from the heaters is raised to a consolidating temperature of the preform. The dehydrated preform is moved and is passed through a high temperature zone formed by the selected heater in the muffle. The dehydrated preform is consolidated.

Abstract: An apparatus for heating an optical fiber preform and a method for manufacturing the optical fiber preform are disclosed, in which the optical fiber preform aligned in a vertical direction is heated by stacked heating sources. The apparatus for heating the optical fiber preform includes a muffler accommodating the optical fiber preform therein, and at least two heating sources aligned lengthwise along the optical fiber preform.

Abstract: A method for fabricating large aperture optical fiber preform using a sintering apparatus for gel tube, includes the steps of: forming a uniform sol by mixing/dispersing for mixing fumed silica with deionized water, and adding a dispersing additive to form uniform sol; injecting the sol into a mold with a certain tubular form, and then gellifying the sol; demolding the tube-shaped gel from the mold; drying the tube-shaped gel; processing (or Binder burn-out & Purification) organic compounds including remaining moisture, alkali metallic impurities, and hydroxides in the gel; inserting a primary preform into the tube-shaped gel and then fastening the preform; and after arranging the gel with the primary preform therein into a sintering apparatus, sintering/over cladding the gel with the primary preform therein under vacuum atmosphere at high temperature.

Abstract: A silica product, method and apparatus for manufacturing a tube-shaped silica glass product using a molded green body having a hollow rod structure. A molded green body having a hollow rod structure has a uniform outer diameter and has a bore having an inner diameter increasing gradually from one end to the other. When sintered in a vertically movable sintering furnace, a tube-shaped silica glass product having a longitudinal cross section distribution less than a tolerance limit may be obtained. Optical fiber manufactured using the silica glass tube according to the present invention may have a uniform longitudinal geometrical structure, thereby exhibiting superior transmission characteristics.

Abstract: Disclosed is an apparatus and method for sintering an over-jacketing tube in the zone sintering phase of an optical fiber preform fabrication process using a sol-gel process. The sintering apparatus includes: a processing tube; a gel tube assembly connected to a top rotation cap positioned at the top opening of the processing tube and being rotated at a predetermined rate, a ceramic pin extending downwardly from the center axis of the rotation cap, and a gel tube suspended from the bottom of the ceramic pin and suspended along the same axle of the processing tube; and a movable furnace initially positioned at the bottom of the processing tube and translating in a vertical direction along the processing tube for thermally treating the gel tube.

Abstract: A method of a fabricating silica glass by sol-gel process is provided. The method includes mixing silica, a binder, a dispersing agent and a gelling agent, and forming a sol without air bubbles; injecting the sol into a mold, the injection of the sol into the mold being controlled by the pressure of an inert gas; gelating the sol injected into the mold and demolding the gel; and drying the demolded gel, and thermally-treating the dried gel. Therefore, incorporation of impurities and air bubbles during injection of a sol into a mold is minimized, and injection amount and injection rate of the sol can be controlled.

Abstract: A method of a fabricating silica glass by sol-gel process is provided. The method includes mixing silica, a binder, a dispersing agent and a gelling agent, and forming a sol without air bubbles; injecting the sol into a mold, the injection of the sol into the mold being controlled by the pressure of an inert gas; gelating the sol injected into the mold and demolding the gel; and drying the demolded gel, and thermally-treating the dried gel. Therefore, incorporation of impurities and air bubbles during injection of a sol into a mold is minimized, and injection amount and injection rate of the sol can be controlled.

Abstract: Disclosed is an apparatus and method for sintering an over-jacketing tube in the zone sintering phase of an optical fiber preform fabrication process using a sol-gel process. The sintering apparatus includes: a processing tube; a gel tube assembly connected to a top rotation cap positioned at the top opening of the processing tube and being rotated at a predetermined rate, a ceramic pin extending downwardly from the center axis of the rotation cap, and a gel tube suspended from the bottom of the ceramic pin and suspended along the same axle of the processing tube; and a movable furnace initially positioned at the bottom of the processing tube and translating in a vertical direction along the processing tube for thermally treating the gel tube.

Abstract: A silica glass composition and a method for manufacturing silica glass using the silica glass composition are provided. The silica glass composition includes: pyrogenetic silica having an average particle diameter of 5.times.10.sup.-3 to 1.times.10.sup.-1 .mu.m and a specific surface area of 50 to 400 m.sup.2 /g; and heat-treated silica, as an agglomerate of the pyrogenetic silica, having an average diameter of 2 to 15 .mu.m and a specific surface area less than that of the pyrogenetic silica. A high purity silica glass tube, in which cracking after drying rarely occurs and the shrinking ratio is remarkably decreased, can be obtained by using the silica glass composition according to the present invention. Also, a large silica glass tube can be manufactured by using the composition.

Abstract: A silica glass monolith fabricating method using a sol-gel process. In the method, a first sol is formed by mixing 100 parts by weight of high-density silica containing powder with 100-300 parts by weight of water, and rapidly dried, while the pH of the first sol is being controlled in the range between 9 and 11. The dried first sol is powdered and then thermally treated at or above 600.degree. C., and a second sol is formed by mixing the thermally-treated powdered first sol with 100-200 parts by weight of deionized water and a aqueous organic binder. The second sol is gelled in a mold, dried, thermally treated, and sintered. Thus, a high-purity silica glass monolith is obtained.

Abstract: There are provided tube-shaped glass monolith fabricating apparatus and method using a sol-gel process. In the tube-shaped glass monolith fabricating method using a tube-shaped glass monolith fabricating apparatus which has an upper mold including cylindrical portions of different sizes, a lower mold including a first lower cylindrical portion inclined toward the center thereof by a predetermined degree and a second lower cylindrical portion having a vacuum releasing hole, a cylindrical central mold for forming a tube-shaped glass, and a rod-shaped rod, the lower mold, the central mold, and the rod are assembled and a sol is poured in the central mold. Then, an unmixable liquid is poured on the sol, and the upper mold is assembled to the central mold. The sol is gelled in the central mold, the upper mold is removed, a cap is opened to release vacuum, and the rod is removed.

Abstract: There is provided a high-purity silica glass fabricating method using a sol-gel process. In the method, a first sol is formed by mixing 100 parts by weight of fumed silica powder with between 100 to 300 parts by weight of deionized water. The first sol is gelled, dried, powdered, and thermally treated. A second sol is formed by mixing the thermally-treated first sol with between 100 to 200 parts by weight of deionized water and 20 to 50 parts by weight of non-thermally treated original fumed silica powder. The second sol is gelled, dried, and sintered. Thus, a high-purity silica glass is formed.

Abstract: A method of fabricating a dispersion shifted optical fiber with a smooth annular ring refractive index profile has the steps of heating a quartz tube with an external oxygen or hydrogen burner and supplying the quartz tube with raw materials including SiCl.sub.4, GeCl.sub.4, POCl.sub.3 and CF.sub.4. O.sub.2 is later supplied. Then, the quartz tube is heated in nine passes of decreasing temperature from 1920.degree. C. to 1890.degree. C., so as to deposit a core section. In the nine passes, the quantity of SiCl.sub.4 feed flow decreases from 380 milligrams per minute to 260 milligrams per minute, the quantity of GeCl.sub.4 feed flow increases from 20 milligrams per minute to 195 milligrams per minute, and the quantity of O.sub.2 feed flow is kept constant at 1500 cubic centimeters per minute.