CS271642B1 - Method of drawn fibre surface finish - Google Patents

Abstract

The method of the surface finish of the stretched fibre is solved, while the overlay of oxides can serve as the sealing layer for the increase of the long-term durability of optical fibres. The merit of the solution lies in the fact that a layer of the solution of the oxidic precursors, which are under physically standard conditions in the solid state, with the thickness of 0.1 to 5 micrometers, is laid on the stretched fibre. Afterwards, the stretched fibre is conducted for a maximum of 30 seconds through a space with 40 to 100 percent of relative humidity, whereupon the stretched fibre is heated for a maximum of 2 minutes until it reaches a temperature of 300 to 1,000 degrees C.

Description

The invention relates to a method of surface treatment of a drawn fiber, used in particular in optical communications or as sensors.

The known and most widespread protection of optical fibers is implemented by organic polymers. Primary protection of optical fibers with metals is also known, which is used both for forming the hermetic sheath and for forming the electrically conductive layer. Furthermore, ceramic primary protection of optical fibers is known which is accomplished by a variety of techniques - suspension coating, magnetic dusting, pyrolysis decomposition and the like, as disclosed in VB Patent No. 216494 or EP 0095729.

The disadvantage of organic polymers is that they are not able to protect the fiber against atmospheric moisture and limit the temperature range of the fiber to a maximum of 350 ° C. layers when temperature changes and rapid corrosion of thin metal layers due to air humidity. The disadvantage of ceramic protection is that the application and / or sputtering devices are often very complex and expensive.

These drawbacks are overcome by the method of surface protection of the drawn fiber according to the invention. SUMMARY OF THE INVENTION The present invention is characterized in that a layer of a solution of precursors of oxides, which are physically normal in solid state, with a thickness of 0.1 to 5 µm is applied to the drawn fiber, then the drawn fiber is guided for a maximum of 30 The 100% RH solution is preferably prepared by controlled hydrolysis of the oxide precursors, preferably alkoxides or inorganic salts, in a common solvent, preferably an alcohol. A complexing agent, preferably β-diketones, may be added to the solution of the oxide precursor. In addition, a viscosity enhancing agent, preferably glycerin, hydropropylcellulose or polyvinyl alcohols, may be added thereto.

According to the method of the invention, a solution of precursor oxides of the desired composition and suitable viscosity is applied to the drawn fiber to form a layer of desired thickness and composition. The fiber passes through a container filled with an alkoxide solution after passing through a soft nozzle whose diameter determines the layer thickness. from 40 ° C up to 1000 ° C. During this heating, hydrolysis, condensation, evaporation of solvents and water occur. In this way, an oxide layer of 0.1 to 5 µm thick is formed on the drawn fiber surface, depending on the diameter of the nozzle and the drawn fiber, the drawing speed, the composition and the viscosity of the solution. In this way, several layers may be applied to the drawn fiber and may be overlaid with a thermally or radiation curable organic polymer. The advantage of this process against deposition of alkoxide solutions by spraying or magnetic dusting and pyrolytic decomposition thereof is that a thicker layer of any oxide composition can be deposited without a special device enclosing the deposition area. The coating solution is prepared by the controlled hydrolysis of oxide precursors, usually alkoxides, in a common solvent, usually an alcohol, and optionally with the addition of complexing agents such as diketones, and viscosity enhancing agents such as glycerin, hydroxypropylcellulose, etc. Compounds that are difficult to prepare , such as alkoxides, can be added to the solution as inorganic salts. The application of the flow is carried out by means of a soft nozzle, which makes it possible to apply a layer less than 1 µm thick without significantly reducing the strength of the drawn quartz fiber. The advantage of this procedure is that <.

The oxidized layers are applied directly to the drawn fiber and can have very different softening temperatures. A further advantage of the process according to the invention over conventional solution-drawing application is that a solution of the desired thickness can be applied more rapidly with a soft nozzle.

The invention is illustrated by way of example, but not by way of limitation.

CS 271642 Bl

Example 1

A solution of 100 g tetra-n-butoxyortotitanate, 53.5 ml n-butanol, 10.5 ml water, 44 ml 1,4- was poured into a 25 [deg.] C container terminated with a soft conical nozzle with 150 µm outlet. of pentadienone and 20 ml of concentrated hydrochloric acid. The quartz fiber immediately after being withdrawn from the preform was coated with this solution at a speed of 10 m / min. After passing through the filament nozzle and deposited layer, it passed through a 2.5 m long furnace system in which the temperature was gradually increased from 40 ° C to 700 ° C and at its upper part a 100% relative humidity was maintained at 40 ° C. By this procedure, a continuous, non-cracked titanium dioxide layer of 0.1-0.2 µm was applied to a 145 µm diameter fiber,

During the drawing, the titanium dioxide layer was coated with a 50 µm UV curable polymer.

Example 2

Under the conditions given in Example 1 (except for the relative humidity, which was 50% and a temperature of 900 ° C), a solution of 116 g tetra-n-butoxyortosirconate, 39 ml water, 32 ml n-butanol, 28 ml 1,4 pentodienol was applied. , 8 ml of 1N hydrochloric acid, 10 ml of glycerin. A continuous layer of 0.4 to 0.6 µm thick zirconia was deposited on a 140 µm diameter fiber.

Example 3

Under the conditions of Example 2, a fiber drawn from a multi-component glass having a refractive index of 1.5 and a diameter of 200 µm was applied by passing through a container filled with a solution of 38.2 g tetraethoxy-ortho-silicon, 3.3 ml water, 8.3 ml. g of ethanol, 3.6 ml of 0.5 N hydrochloric acid, through a soft nozzle with an outlet of 200 µm and a 2 m long furnace with a gradually increasing temperature, a 0.5 µm thick silica layer. The drawing speed was 5 m / min.

The deposited oxide layer may serve as a hermetizing layer to increase the longevity of the optical fibers to form an optical coating or layer affecting the modal structure of transmitted light by thickness and refractive index or electrical conductivity.

Claims (2)

SUBJECT OF THE INVENTION 1. A method of surface treatment of a drawn fiber, characterized in that a layer of a solution of precursors of oxides, which are in the physical normal state in solid state, with a thickness of 0.1 to 5 µm, is applied to the drawn fiber, then the drawn fiber is guided for 30 with a space of 40 to 100% relative humidity, then the drawn fiber is heated to 300 to 1000 ° C over a maximum of 2 minutes. » 2, The method of surface treatment of the drawn fiber of claim 1, wherein the solution of the precursor oxide is prepared by controlled hydrolysis of the precursor oxide, preferably alkoxides or inorganic salts, in a co-solvent, preferably an alcohol. CS 271642 Bl 2. The method of surface treatment of a drawn fiber according to claims 1 and 2, characterized in that a complexing agent, preferably .beta.-diketones, is added to the oxide precursor solution. 4. 2. The method of surface treatment of a drawn fiber according to claims 1 to 3, characterized in that a viscosity enhancing agent, preferably glycerin, hydropropylcellulose or polyvinyl alcohols, is added to the solution of the oxide precursor.