JPH0725639A - Production of core fiber of optical fiber having high strength - Google Patents

Abstract

PURPOSE:To obtain the core fiber even if flaw, crack, breaking, etc., exists on the surface of an optical fiber by heating and melting an optical fiber preform, drawing the preform, applying a gelling substance containing titanium to the preform before superposing and applying different thermosetting resins to the preform. CONSTITUTION:A gel-like viscus substance containing titanium is uniformly applied to the surface of an optical fiber 110 obtained by spinning a preform 100 by a die 11 while heating a drawing apparatus 10. The viscus substance is a solution, etc., obtained by adding, e.g. an alcohol and a small amount of an acid to Ti(OC2H5)4. Then, this fiber is heated in a heating furnace 12 and coating of the viscus substance is dried and subjected to solation to afford TiO2 coating film. A thermosetting resin is applied onto this film by a primary coating die 13 and primary coating is applied to the film-coated optical fiber by curing this resin in a curing furnace 14 and other thermosetting resin is applied thereon by a secondary coating die 15 and this resin is cured in a curing furnace 16 to apply secondary coating to the coated optical fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an internal mounting method, an external mounting method,
The present invention relates to a manufacturing method of an optical fiber core wire, in which a preform made by an axis attachment method or a plasma method is spun and subjected to a primary coating and a secondary coating, and particularly, scratches on the surface of the preform, adhesion of foreign matter, etc. The present invention relates to a method for manufacturing a high-strength optical fiber core wire, which enables to obtain an optical fiber core wire having higher strength than a conventional optical fiber core wire even when spun in a state where it cannot be completely removed.

[0002]

2. Description of the Related Art Generally, in an optical fiber, light propagates in the core while being totally reflected at the boundary surface between the core and the clad constituting the optical fiber. This propagation method differs depending on the refractive index distribution of the core, and the core diameter is several tens of μ in both the step index type and the graded index type.
When the length is more than m, the light path varies depending on the incident angle of light, and many light paths occur. Moreover, the outer diameter of the core is 5 to 15 μm.
With a certain degree, the light does not reflect at the boundary surface between the core and the clad, and goes straight through the core to form one optical path. Such an optical fiber is a single mode optical fiber.

In such an optical fiber, it is ideal that the intensity of the incident light is emitted without being attenuated, but while the light propagates through the core of the optical fiber, various kinds of light are emitted. Transmission loss occurs due to the cause. The degree to which the intensity of light becomes weaker while propagating in an optical fiber is the transmission loss of the optical fiber. The transmission loss of an optical fiber is mainly due to absorption by electron transition in the ultraviolet region, absorption by molecular vibration in the infrared region, Rayleigh scattering inversely proportional to the fourth power of the wavelength, and impurities, especially water (hydroxy ion / OH group) absorption. However, even if a minute scratch is formed on the surface of the optical fiber or a minute foreign substance adheres to the surface of the optical fiber, it occurs.
The minute scratches on the surface of the optical fiber and the minute foreign matter that adheres to the surface of the optical fiber remain on the surface of the optical fiber when the scratches on the surface of the preform, which is the base material of the optical fiber, are spun. It was found that it appears as a minute scratch on the surface of the optical fiber or a minute foreign substance adhering to the surface of the optical fiber. Therefore, conventionally, before spinning a preform manufactured by an internal attachment method, an external attachment method, an axial attachment method, or a plasma method, the scratches formed on the preform surface and the foreign matter adhering to the preform surface are removed. ing. Methods for removing scratches formed on the surface of the preform and foreign matters adhering to the surface of the preform include chemical polishing and flame polishing. Chemical polishing, as shown in FIG.
This is a method in which the preform 100 is immersed in the hydrofluoric acid solution 200 contained in the container 150 to melt the surface of the preform 100 to remove scratches on the preform surface and foreign substances adhering to the preform surface. Further, in the flame polishing, as shown in FIG. 6, the preform 100 is sandwiched by two lathe chucks 250, and the flame 300 is rotated by the arrow B while rotating the preform 100 as shown by the arrow A.
Move as shown in C to move preform 100 to flame 300
It is a method of removing scratches on the surface of the preform 100 and foreign matters adhering to the surface of the preform 100 by exposing to light.

After performing the chemical polishing or flame polishing in this way, an optical fiber core wire is manufactured by the method shown in FIG.
That is, the preform 100 is spun in the drawing furnace 400 to manufacture the optical fiber 110. The surface of the optical fiber 110 is coated with a thermosetting resin in the primary coating die 410, and is thermally cured in the curing furnace 420. Further, the secondary die 43 is placed on the optical fiber 110 coated with the thermosetting resin.
At 0, a thermosetting resin is coated and thermoset in a curing oven 440. After that, by coating a thermoplastic resin such as nylon in the extrusion process, the optical fiber core wire 120 is manufactured and taken by the take-up capstan 500.

[0005]

However, large scratches formed on the surface of the preform and foreign matters adhering to the surface of the preform cannot be completely removed by conventional chemical polishing or flame polishing. For this reason, even if the preform produced by the internal attachment method, the external attachment method, the axial attachment method, and the plasma method is treated by chemical polishing or flame polishing before being spun, the preform surface scratches and remaining that cannot be completely removed and There is a problem that the influence of foreign matter adhering to the surface of the preform appears as a transmission loss of the optical fiber formed by spinning.

Further, the silica glass constituting the optical fiber is apt to be scratched, cracked, chipped, etc., and in the process of manufacturing the optical fiber by spinning from the preform, the surface of the optical fiber is not scratched, cracked, chipped or the like. If this happens, there is a problem that the strength of the optical fiber is significantly reduced.

According to the present invention, the surface of an optical fiber is scratched, cracked,
It is an object of the present invention to provide a method for manufacturing a high-strength optical fiber core wire, which can increase the strength of the optical fiber core wire even if there are chips and the like, and can obtain long-term reliability.

[0008]

In order to achieve the above object, in a method for producing a high-strength optical fiber core wire, an optical fiber preform is melted by heating in a heating furnace and drawn, and then a gel containing titanium is used. -Like viscous substance is coated to form a heat-dried sol, the sol-ized viscous substance is coated with a thermosetting resin and cured by heating, and a thermosetting resin of different composition is further applied on the thermosetting resin. It is formed by coating and curing.

In order to achieve the above object, in the method for producing a high-strength optical fiber core wire, after chemically polishing or flame polishing the surface of the optical fiber preform, it is heated and melted in a heating furnace to draw. The drawn optical fiber is coated with a viscous substance containing titanium to form a heat-dried sol, and a thermosetting resin is coated on the sol-ized viscous substance to be heat-cured. It is formed by coating a resin with a thermosetting resin having a different composition and curing the resin.

Further, in order to achieve the above object, in a method for producing a high-strength optical fiber core wire, a gel-like viscous substance containing titanium is prepared by heating and melting an optical fiber preform in a heating furnace to draw it. To heat and dry the sol,
A UV-curable resin is coated on the solified viscous substance to be UV-cured, and a UV-curable resin having a different composition is coated on the UV-curable resin and cured to form it.

[0011]

The optical fiber preform is heated and melted in a heating furnace to be drawn, and then a gel-like viscous substance containing titanium is coated to form a heat-dried sol, and a thermosetting resin is applied on the solified viscous substance. Since it is coated and heat-cured, and then a thermosetting resin of different composition is coated on the thermosetting resin and cured to form, there are scratches, cracks, chips, etc. on the surface of the optical fiber. Also, the strength of the optical fiber core wire can be increased, and long-term reliability can be obtained.

Further, after chemically polishing or flame polishing the surface of the optical fiber preform, it is melted by heating in a heating furnace and drawn,
The drawn optical fiber is coated with a viscous substance containing titanium to form a heat-dried sol, and a thermosetting resin is coated on the sol-ized viscous substance to be heat-cured,
Furthermore, because a thermosetting resin of different composition is coated and cured on the thermosetting resin, it is manufactured by pulling even if there are large scratches, cracks, chips, etc. on the surface of the optical fiber preform. It does not leave large scratches, cracks, chips, etc. on the surface of the optical fiber, reduces the effect on the surface of the optical fiber, and even if small scratches, cracks, chips, etc. remain on the surface of the optical fiber. The strength of the optical fiber core wire can be increased, and long-term reliability can be obtained.

Further, in order to achieve the above object, in a method for producing a high-strength optical fiber core wire, a gel-like viscous substance containing titanium is prepared by heating and melting an optical fiber preform in a heating furnace to draw it. To heat and dry the sol,
The sol-form viscous substance is coated with a UV-curable resin to be UV-cured, and the UV-curable resin is coated with a UV-curable resin having a different composition to be cured. Even if there are scratches, cracks, chips, etc. on the surface, the strength of the optical fiber core wire can be increased and long-term reliability can be obtained.

[0014]

EXAMPLES Examples of a method for manufacturing a high-strength optical fiber core wire according to the present invention will be described below. FIG. 1 is a process flowchart showing an embodiment of a method for manufacturing a high-strength optical fiber core wire according to the present invention, and FIG. 2 is an optical fiber core for manufacturing the high-strength optical fiber core wire shown in FIG. A wire manufacturing device is shown. A method for manufacturing a high-strength optical fiber core wire will be described using the optical-fiber core wire manufacturing apparatus for manufacturing the high-strength optical fiber core wire shown in FIG. 2 according to the processing procedure shown in the figure.

First, in step 1, the preform 100 produced by the internal attachment method, the external attachment method, the axial attachment method, and the plasma method is spun while being heated by the drawing device 10 to produce the optical fiber 110.

In this step 1, the preform 10
When the optical fiber 110 is manufactured by spinning 0 while heating it with the drawing device 10, the viscous substance (gel-like) containing titanium (Ti) is uniformly formed on the surface of the optical fiber 110 by the coating die 11 in step 2. To cover. The viscous substance containing titanium is coated on the surface of the optical fiber 110 to a thickness of 3 μm or less. The coating thickness of this viscous substance containing titanium is 3μ.
A thickness of m or less is sufficient. This viscous substance containing titanium is, for example, Ti (OC ₂ H ₅ ) ₄ which is obtained by adding water, alcohol and a small amount of acid to homogenous Ti (OC ₂ H ₅ )
₄ solutions. When water, alcohol and a small amount of acid are added to this Ti (OC ₂ H ₅ ) ₄ , Ti (OC ₂ H ₅ ) ₄ + 2H ₂ O → TiO ₂ + 4C ₂ H
Hydrolysis / polymerization reaction of ₅ OH occurs and Ti (OC ₂ H ₅ )
_{The 4th} solution is a solution that has undergone this hydrolysis / polymerization reaction. In the substances other than the viscous substance Ti (OC ₂ H ₅ ) ₄ containing titanium used in this example, Ti was used.
_{(OCH 3) 4, Ti (} OC 4 H 9) 4, Ti (i-O
C ₃ H ₇ ) ₄ etc. Examples of alcohol solvents include methanol, ethanol, propanol, butanol, ethylene glycol, ethylene oxide, triethanolamine and xylene. Further, acid catalysts include sulfuric acid, stripping, acetic acid, hydrofluoric acid and the like.

In step 2, the surface of the optical fiber 110 is coated with a coating die 11 to form a gel Ti (O).
When the C ₂ H ₅ ) ₄ solution is uniformly coated, in step 3, the Ti coated on the surface of the optical fiber 110 is coated.
The (OC ₂ H ₅ ) ₄ solution is heated and dried to form a sol. That is, the coating die 1 is formed on the surface of the optical fiber 110.
Gel Ti (OC ₂ H coated with 1)
₅ ) The ₄ solution is heated by the heating furnace 12, dried and solized to form a gel coating film, which is about 500 ° C to 80 ° C.
It is heated to 0 ° C. and becomes a TiO ₂ coating film. The thickness of this TiO ₂ coating film is gel (Ti (OC)
It can be freely adjusted within the range of 3 μm or less depending on the viscosity of the ₂ H ₅ ) ₄ solution and the heating temperature.

When the Ti (OC ₂ H ₅ ) ₄ solution coated on the surface of the optical fiber 110 is solized in step 3, the TiO ₂ coating film formed on the surface of the optical fiber 110 is thermally cured in step 4. With a transparent resin. That is, the optical fiber 110 having the TiO ₂ coating film formed on the surface discharged from the heating furnace 12 is supplied to the primary coating die 13, and the primary coating die 13 is coated with the thermosetting resin. When the thermosetting resin is coated in step 4, in step 5,
The thermosetting resin is cured. That is, the optical fiber 110 in which the thermosetting resin is coated on the TiO ₂ coating film discharged from the primary coating die 13 is supplied to the curing furnace 14 and heated in the curing furnace 14 to be coated with the TiO ₂ coating. The resin coated on the membrane cures. This is the so-called primary coating.

When the thermosetting resin is cured in step 5, in step 6, the thermosetting resin is coated on the thermosetting resin with another composition. That is, the curing furnace 1
The optical fiber 110 on which the thermosetting resin film is discharged from the No. 4 is the secondary coating die 15
Supplied to this secondary coating die 15
In, the thermosetting resin having a composition different from the composition of the thermosetting resin already coated is coated on the thermosetting resin film. When the thermosetting resins having different compositions are coated on the thermosetting resin in step 6, the thermosetting resin is cured in step 7. That is, the optical fiber 110 coated with the thermosetting resin discharged from the secondary coating die 15 is heated in the curing furnace 16 and the thermosetting resin having a different composition coated on the thermosetting resin is heated. Harden. This is the so-called secondary coating. In this way, the optical fiber core wire 120 is manufactured. When the thermosetting resin is cured in step 7, it is taken up and wound around a drum or the like in step 8. That is, the optical fiber core wire 120 discharged from the curing furnace 16 is taken up by the take-up capstan 500 and wound on a drum or the like.

FIG. 3 is a processing flowchart showing another embodiment of the method for manufacturing a high-strength optical fiber core wire according to the present invention. A method of manufacturing a high-strength optical fiber core wire will be described according to the processing procedure shown in the figure. This embodiment is different from the embodiment shown in FIG. 1 in that a preform 100 manufactured by an internal attachment method, an external attachment method, an axial attachment method, or a plasma method is spun while being heated by a drawing device 10 while being spun. Prior to manufacturing the fiber 110, the preform 10
The point is that chemical polishing or flame polishing is performed in order to remove scratches formed on the surface of No. 0 and foreign matters attached to the surface of the preform 100. That is, in step 20, the preform 100 manufactured by the internal attachment method, the external attachment method, the axial attachment method, and the plasma method is subjected to chemical polishing or flame polishing. As a result, scratches formed on the surface of the preform 100 and foreign substances attached to the surface of the preform 100 are removed. Step 21 is Step 1 shown in FIG. 1, and Step 22 is Step 2 shown in FIG.
1, step 23 is step 3 shown in FIG. 1, step 24 is step 4 shown in FIG. 1, step 25 is step 5 shown in FIG. 1, step 26 is step 6 shown in FIG. Step 27 is step 7 shown in FIG.
Since step 28 is the same as step 8 shown in FIG. 1, description thereof will be omitted here.

FIG. 4 is a processing flowchart showing another embodiment of the method for manufacturing a high-strength optical fiber core wire according to the present invention. A method of manufacturing a high-strength optical fiber core wire will be described according to the processing procedure shown in the figure. The present embodiment is different from the embodiment shown in FIG. 1 in that the resin coated on the TiO ₂ coating film is U instead of the thermosetting resin.
The point is to use a V-curable resin. That is, step 3
3, Ti formed on the surface of the optical fiber 110.
A UV curable resin is coated on the O ₂ coating film.
That is, TiO is formed on the surface discharged from the heating furnace 12.
_The optical fiber 110 on which the ₂ coating film is formed is supplied to the primary coating die 13, and the primary coating die 13 is coated with the UV curable resin. When the UV curable resin is coated in step 33, the UV curable resin is cured in step 34. That is, the optical fiber 11 in which the UV curable resin is coated on the TiO ₂ coating film discharged from the primary coating die 13
0 is supplied to the UV curing furnace, and in this UV curing furnace, the resin coated on the TiO ₂ coating film is heated and cured. This is the so-called primary coating.

When the UV curable resin is cured in step 34, the UV curable resin having a different composition is coated on the UV curable resin in step 35. That is, the optical fiber 110 having the UV-curable resin film formed thereon, which is discharged from the UV-curing furnace, is supplied to the secondary coating die 15, and the composition of the UV-curable resin already coated on the secondary coating die 15. A UV-curable resin having a different composition from is coated on the already-cured UV-curable resin film. When the UV curable resin having a different composition is coated on the UV curable resin in Step 35, the UV curable resin is exposed in Step 36.
The curable resin is cured. That is, the optical fiber 110 discharged from the secondary coating die 15 and coated with the UV curable resin is heated in the UV curing furnace, and the UV curable resin having a different composition coated on the UV curable resin is heated. Harden. This is the so-called secondary coating. In this way, the optical fiber core wire 120 is manufactured. Step 30 is the same as step 1 shown in FIG. 1, step 31 is the same as step 2 shown in FIG. 1, step 32 is the same as step 3 shown in FIG. 1, and step 37 is the same as step 8 shown in FIG. Therefore, the description thereof is omitted here.

[0023]

Since the present invention is constructed as described above, it has the following effects.

After the optical fiber preform is heated and melted in a heating furnace and drawn, a gel-like viscous substance containing titanium is coated to form a heat-dried sol, and a thermosetting resin is applied on the solified viscous substance. Since it is formed by coating and heat-curing, and then coating and curing a thermosetting resin of different composition on the thermosetting resin, there are scratches, cracks, chips, etc. on the surface of the optical fiber. However, the strength of the optical fiber core can be increased and long-term reliability can be obtained.

Also, after chemically polishing or flame polishing the surface of the optical fiber preform, it is melted by heating in a heating furnace and drawn.
The drawn optical fiber is coated with a viscous substance containing titanium to form a heat-dried sol, and a thermosetting resin having a different composition is coated on the sol-ized viscous substance to be heat-cured. An optical fiber manufactured by pulling even if there are large scratches, cracks, chips, etc. on the surface of the optical fiber base material because it is formed by coating a thermoplastic material on a thermosetting resin and curing it. It does not leave large scratches, cracks, chips, etc. on the surface of the optical fiber, reduces the effect on the surface of the optical fiber, and small scratches, cracks,
Even if chips or the like remain, the strength of the optical fiber core wire can be increased and long-term reliability can be obtained.

Further, in the method for producing a high-strength optical fiber core wire, the optical fiber preform is heated and melted in a heating furnace to be drawn, and then a gel-like viscous substance containing titanium is coated to form a heat-dried sol. , UV-curable resin is coated on the sol-ized viscous substance, and UV-cured.
The UV curable resin of different composition is coated on the curable resin and cured to form a strong optical fiber even if there are scratches, cracks, chips, etc. on the surface of the optical fiber. Therefore, long-term reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a process flowchart showing an embodiment of a method for manufacturing a high-strength optical fiber core wire according to the present invention.

FIG. 2 is a view showing an optical fiber core wire manufacturing apparatus for manufacturing a high strength optical fiber core wire based on the method for manufacturing a high strength optical fiber core wire shown in FIG.

FIG. 3 is a process flowchart showing another embodiment of the method for manufacturing a high-strength optical fiber core wire according to the present invention.

FIG. 4 is a processing flowchart showing another embodiment of the method for manufacturing a high-strength optical fiber core wire according to the present invention.

FIG. 5 is a diagram showing a conventional method for polishing a preform surface by chemical polishing of a preform.

FIG. 6 is a diagram showing a method of polishing a preform surface by flame polishing of a conventional preform.

FIG. 7 is a diagram showing an optical fiber core wire manufacturing apparatus for manufacturing an optical fiber core wire based on a conventional method of manufacturing an optical fiber core wire.

[Explanation of symbols]

10 ……………………………………………… Drawing device 11 ……………………………………………… Coating die 12 ………………………… ……………………… Heating furnace 13 ……………………………………………… Primary coating die 14,16 …………………………………… Curing Furnace 15 …………………………………………………… Secondary coating die 100 ………………………………………… Preform 110 ………………………… …………………… Optical fiber 120 ………………………………………… Optical fiber core

Claims (3)

[Claims] 1. An optical fiber preform is heated and melted in a heating furnace to be drawn, and then a gel-like viscous substance containing titanium is coated to form a heat-dried sol, and the sol-ized viscous substance is heat-cured. A method for producing a high-strength optical fiber core wire, which is characterized in that a high-strength optical fiber core wire is formed by coating a thermosetting resin and heat-curing it, and then coating and curing a thermosetting resin having a different composition on the thermosetting resin. 2. A surface of an optical fiber preform is chemically polished or flame-polished, and then heated and melted in a heating furnace to be drawn, and the drawn optical fiber is coated with a viscous substance containing titanium. Formed by heating and drying to a sol, coating a thermosetting resin on the solified viscous substance and heating and curing, and then coating and curing a thermosetting resin of a different composition on the thermosetting resin. A method for manufacturing a high-strength optical fiber core wire. 3. An optical fiber preform is heated and melted in a heating furnace to be drawn, and then coated with a gel-like viscous substance containing titanium to form a heat-dried sol, which is UV-cured on the solified viscous substance. UV-curable resin coating, UV curing, U
A method for producing a high-strength optical fiber core wire, which is formed by coating a V-curable resin with a UV-curable resin having a different composition and curing it.