FI94048B - Process for manufacturing an optic fibre item and use of a fibre product containing silica in the manufacture of an optic fibre item - Google Patents

Description

94048

The present invention relates to a process for producing an optical fiber preform, in which a fiber is grown on a primary blank of pure or doped silica by winding a layer of silica glass by winding. The invention also relates to the use of a silica-containing viscose fiber in the manufacture of an optical fiber blank.

The fabrication of an optical fiber is basically a two-step process in which the first step comprises the fabrication of an optical fiber preform and the second step the drawing of the preform into a fiber. The main industrial manufacturing processes of the fiber preform are based on gas phase growth: MCVD (Modified Chemical Vapor Deposition), VAD (Vapor-Phase Axial Deposition) and OVD (Outside Vapor Deposition). Finished preform. ···, consists of alloyed or pure silica glass • · .JJI. a core blank and a sheath having a lower fold • • · “130 action, which is also doped or pure silica glass. A typical fiber blank is about 1 m in length and 20-50 mm in diameter, and the yield of one blank is in the order of 10-50 km of optical fiber.

···; The optical fiber has a core portion which is pure or doped amorphous silica and a shell which is also: silica glass, but which is doped so that its refractive index is less than the refractive index of the core. As well as. the core and the shell contain alloying elements having refractive index values, softening temperatures, etc. for different parts of the fiber which are important for the use and manufacture of the fiber; '**; desired. The fiber core forms the actual optical • · · transmission path in which the signals propagate. The shell acts as a refracting surface to prevent light scattering from the core. Thus, the fiber blank must have the materials required for the core and shell layers in proportion to 3594848 so that the core and shell layers of the fiber are formed in the desired manner simultaneously during the fiber drawing process.

The drawing of the optical fiber takes place by slowly feeding the preform into a tubular oven, where the fiber is drawn from the end of the softened preform at a high speed and wound on a drum after various processing steps.

All manufacturing methods have in common high costs due to the high purity requirements that have been solved in the known solutions for the growth of the blank by means of gaseous raw materials. In addition, most gas formation processes are difficult to control and have a modest production rate.

It is an object of the present invention to provide a method for growing an optical fiber preform which reduces raw material costs and significantly increases production speed. To achieve this, the method according to the invention is characterized in that. - a viscose fiber containing silica is wound on the initial blank to form a blank, • · · “'^ 0 - the formed blank is heated to burn the organic material of the fiber product and to melt the silica contained therein, or to sinter into a silica • · · • · * glass layer on top of the initial blank.

According to the invention, the optical fiber blank is grown in a completely new way by winding a silica-containing fibrous product around the initial blank, after which the obtained blank is sintered or melted into a uniform fibrous material. ground, whereby the silica-based fiber product is converted into • · · h. ’silica glass. The fibrous product used as a raw material is • · * ·; * 3θ cheap, and the necessary winding equipment does not require a large investment, because the silica rod as a preform ·: ··· or tube can be simply attached to a rotating spindle and the wire containing silica wound evenly with vertical control Number of layers on the bar 35.

94048 3

The various embodiments of the method according to the invention and the use of the fiber product according to the invention are characterized by what is stated in the claims below.

The invention will now be described in more detail by way of example and with reference to the accompanying drawings, in which Figure 1 shows an optical fiber as a finished product, Figure 2 shows an apparatus for making a blank 10, Figure 3 shows an optical fiber drawing apparatus, Figure 4 shows a refractive index measured from a blank according to the invention. .

According to Figure 1, the optical fiber 1 consists of a core-15 core 2, a core shell 3 and a protective sheath 4. The fiber diameter is typically about 125 μπκ. The core material consists of high-purity amorphous silica glass. ta, which is doped as desired and has a high • · .1 !!. refractive index of light. The shell 3 consists of pure, e.g.

»·· ·» · · ‘’ * ^ 0 from fluorine-doped silica glass with a lower refractive index than the core. The ·· * signals passing through the core of the optical fiber are then completely reflected from the interface between the core and the shell, so that the light travels along the core • ··: with minimal losses. The protective sheath 4 consists of 25 e.g. conventional plastic insulation.

Figure 2 shows the production of an optical fiber blank according to the invention. It has very pure silica. the initial blank 5 is rotatably attached e.g.

• · on the spindle 7 of the lathe 6. The wire 8 containing the silica is guided -; · 3θ from the spool 9 through the guide 10 and the guide tube 12 to the initial 5. ** guide tube 12 is guided in the axial direction of the initial blank by a power device 11 to form a uniform wire layer alkuaihiolle. The required number of rounds is formed, typically several dozen. When the required layer thickness is reached, the preform is heated

__ ___I_____I II - -. . .. ». . -., 1 T —WW »OV-JI

4,94048 either in a sintering furnace or by flame melting to burn the organic material of the fibrous product and form the silica contained therein into a solid layer of silica glass on top of the initial blank.

Figure 3 shows a fiber drawing apparatus in which fiber 14 is drawn from a blank 13 made in accordance with the invention through a processing apparatus. The apparatus consists mainly of a heating furnace 15 of a blank 13, a diameter adjusting device 16, a sheath forming nozzle 17, a heat-treatment furnace 18, guides 19 and a winding drum 20.

Figure 4 shows the refractive index profile measured from a fired blank made according to the invention. It is observed that the relative refractive index is relatively uniform (near zero) in the region of the core material (weather-15 de ± 10 mm), and decreases sharply in this case in the area of the boron-doped shell (radius> 10 mm).

The silica-fiber-containing fiber used in the process of the invention is preferably a silica-viscose material made by pressing a homogeneous solution of silica-viscose containing 20 dimonomers and viscose into a nozzle. through to the polymerization and regeneration solution.

Thus, the fiber or filament of silica viscose material is prepared by polymerizing monomeric silica in a cellulose matrix. This results in a fibrous product, i.e. a silica-viscose material fiber, which can be washed and dried in the same way as in a conventional viscose process. Tä- • · · ·; ”*; The method of making pine-type fibers has been described. See, e.g., FR Patent 1364238 and GB Patent Publication 1155292.

* · * ••• * 30 Made of viscose silica fiber can be easily *: ** '; ti spin yarn with properties very similar to those of viscose yarn. Thus, a yarn with a completely homogeneous structure is provided, from which a yarn can be wound on the initial blank or used as a suitable textile product or ribbon, such as 94048 fabric, knit, braid, fabric, felt or nonwoven.

The following are some of the results of empirical experiments performed within the scope of the invention on the treatment and preform formation of a silica-containing fibrous product.

Example 1 In this case, a quartz bar was used as the initial blank, which was attached to a lathe acting as a winding device. 1C The silica-based fiber product was wound on a quartz rod using an automatic, pneumatically operated divider as shown in Figure 2. A 2x25 tex yarn with a silica content of 30-35% was used as the fiber product. After spooling, the fiber product was melted as such with a hydrogen-burner (about 2000 ° C) on the surface of a quartz rod.

It was found that only a thin layer of unalloyed fiber product is made to melt.

• * t • · * ·

Example 2 »·· · • · ·” * ’20 The silica-based fiber product was purified »· as follows: • · '··· * The fiber product was wound on a perforated, conical • · ·. * Starting spool. The polish on which the fibrous product was placed was • · · ·. * · Immersed in hot water and rinsed with deionized water.

A 0.5M oxalic acid solution was pumped through the spool and the fibrous product, followed by a pump · · · · * · * through the spool and the fibrous product; a solution containing 1M ammonium chloride solution containing. 2% hydrogen peroxide had been added. The pH of the solution was adjusted to 9 with ammonia. Deionized water was then pumped through the spool and the fiber product, after which the spool and the fiber product were dried at 70 ° C. After this treatment, the fiber product was wound on a quartz rod into a blank as shown in Fig. 2. The fibrous product was blended by immersing the preform in 0.5M boric acid solution until the fibrous product based on silica was wetted. The fiber product 6 94048 was then dried, remixed and dried again. The blank was then fired into a solid blank as in Example 1.

As a result of the doping, the softening point of the silica glass was significantly reduced, and the fibrous product melted into a homogeneous layer on top of the initial blank.

Example 3

The fiber product was pretreated as in Example 10, but instead of boric acid, the fiber product was blended using diammonium hydrogen phosphate (DAP) as a 0.5 M solution. The results were similar to Example 1, although the melting of the fiber product was slower.

15 Example 4

The fiber product was pretreated and blended as in Example 2, but the fiber product was sintered in an oven. At 1450®C in the form of a fabric on top of the initial blank • · • HI. screwed. The fibrous product formed a shell in the desired manner on the initial blank, although the homogeneity of the layer was not in the same order as in the results obtained in Example 2. The inhomogeneities have been estimated to reach Ϊ. · With better attachment of the fiber product to the initial blank throughout the ···: .Σ: process. Repetition of Example 4 with phosphorus doping of fiber product 25 (cf. Example 3) gave similar results.

• · · ·

It will be apparent to one skilled in the art that the invention is different. embodiments are not limited to the above examples, but may vary within the scope of the following claims.

• · · • · »· • ♦ · ·· · · 2 • ·

Claims (5)

1. A process for the manufacture of an optical fiber blank, in which a silica oxide glass coating (5) is constructed by means of a pure or doped silicon oxide component (5), characterized in that: - on the blank (5) the viscose fiber is flushed ( 8) containing silica to form a substance (13), 10. The formed substance is heated to burn the organic material in the fiber product and to melt or sinter the silica oxide contained in the fiber product into a layer of silica gel on the substance. 2. A process according to claim 1, characterized in that the doping agent which lowers the softening point of the silica, such as boric acid (B203), is added to the fibrous product (8) containing silica. . ···. 3. A process according to claim 1 or 2, characterized in that the fiber product (8) containing silica is purified with ion-exchanged water, oxalic acid solution and ammonium chloride solution before being flushed onto the substance (5). Method according to any one of claims 1-3, "mm * ·" characterized in that the fiber product (8) which pours in silica is spun or promoted as a textile or a textile belt. JJ *: 5. Use of viscose fiber (8) containing silica in the manufacture of a substance (13) for optical fiber. In which a silica oxide compound (5) is formed, a layer of fiber which burns or sinters forms a silica-coated mantle glass layer on said blank. · · T r «• · · 1 ·« · # ·