JPS60171246A - Manufacture of covered optical fiber - Google Patents

Abstract

PURPOSE:To obtain a covered optical fiber having high adhesive strength between resin layers and superior resistance to lateral pressure by coating a semicured layer of a soft curable resin formed around an optical fiber with an uncured rigid curable resin and by completely curing both the resins. CONSTITUTION:A quartz preform rod 8 is spun into an optical fiber 2 in a spinning apparatus 7 composed of a rod feeder 5 and a spinning furnace 6. The fiber 2 is coated with an uncured soft curable resin by passing through a die type coater 9, and the resin is cured to a semicured state in a curing oven 10. The fiber 2 is then passed through a coater 11 to coat the semicured layer with an uncured rigid curable resin, and both the resins are completely cured in a curing oven 12 to obtain a covered optical fiber 1 having a buffer layer 3 of the soft resin and a protective layer 4 of the rigid resin formed successively around the optical fiber 2. The fiber 1 is wound around a bobbin 14 through a capstan 13.

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a coated optical fiber.

The coated optical fiber 1 shown in FIG. 1, which is called a cored optical fiber, generally includes an optical fiber 2 made of glass (for example, made of stone pod), which is composed of a core and a cladding, and a buffer layer 3 provided on the outer periphery of the optical fiber 2. Furthermore, it consists of a protective layer 4 provided on its outer periphery, the buffer layer 3 serving also as a primary coat and exhibiting the Knonyon effect, and the protective layer 4 exhibiting mechanical strength as a shell.

In the case of the above-mentioned coated optical fiber, it goes without saying that it is necessary to achieve low loss, but it is also necessary to ensure mutual adhesion between the buffer layer 3 and the protective layer 4 from the viewpoint of liquid tightness and strength. desirable.

Experimental examples regarding these will be described below.

A graded multimode optical fiber 2 with a core diameter of 50 μm, an outer diameter of 125 μm, and a relative refractive index difference of 1 inch, and an outer diameter of 023 μm.
In the coated optical fiber I IC, which consists of a buffer layer 3 of I++++++ and a protective layer 4 with an outer diameter of 04 mm, various coated optical fibers with different materials for the buffer layer 3 and the protective layer 4 are made,
We measured their transmission characteristics.

In addition, in this measurement, each coated optical fiber was 1 hour long and wound onto a bobbin with a body diameter of 340 fins while applying a tension of 150 g, and the difference in transmission loss before and after winding was measured at a wavelength of 1.3 μm. It was evaluated by

In the above-mentioned wound state, a lateral pressure=tension=7 bud radius-150 g/170+m is applied to the coated optical fiber, so the measurement results shown in the following table evaluate the contralateral pressure characteristics.

As is clear from the above table, the buffer layer 3 is made of thermosetting silicone rubber or a soft curable resin such as photocurable butadiene acrylate, silicone acrylate, or urethane acrylate, and the protective layer 4 is made of photocurable epoxy acrylate. It is preferable to use a hard curable resin such as , and by doing so, a coated optical fiber with excellent contralateral pressure properties can be obtained.

However, when a 1% screening test was carried out on coated optical fibers with contralateral pressure properties as described above, such as 46 and /I67 in the table, delamination occurred between the buffer layer 3 and the protective layer 4, and the It was found that there was a problem with adhesion.

This can be said to be due to the large difference in physical properties between the two layers when the buffer layer 3 is made of as soft a fibrous material as possible and the protective layer 4 is made of as hard a fibrous material as possible in order to improve contralateral pressure properties.

In order to address the above-mentioned problems, the present invention is designed to ensure not only contralateral pressure characteristics but also adhesion between the buffer layer and the protective layer. I will explain.

In FIG. 2, after spinning a quartz-based preform rod 8 and processing it into the optical fiber 2 using a known spinning machine equipped with a base material feeder 5 and a spinning furnace 6, the optical fiber 2 is is passed through a die-type coater 9, where an uncured (liquid and uncrosslinked) soft curable resin for the buffer layer 3 is applied to the outer periphery of the optical fiber, and a curing furnace 1o located next to the coater 9 is applied. Applying curing energy to the uncured soft curable resin, the resin becomes a semi-cured state (semi-crosslinked state).

The optical fiber 2 coated with the soft hardening resin in a semi-hardened state is guided into the next Gouiss-type coater 11, where a protective layer is applied to the outer periphery of the soft hardening resin (semi-hardened buffer layer 3). After applying the uncured (liquid and uncrosslinked) hard curable resin used in 4, the resin in the same state is subjected to the following curing treatment in the curing furnace 12 of the next stage.

In this curing furnace, a predetermined curing energy is applied to not only completely cure (crosslink) the curable resin for the protective layer 4, but also to completely cure (crosslink) the curable resin for the protective layer 4.
Complete curing (complete crosslinking) of the soft curable resin for use is also performed at the same time.

As a general matter regarding crosslink density, as shown in Figure 3,
Up to a certain curing energy Es, the crosslinking density increases as the energy increases, but once all unreacted groups are consumed, the crosslinking density does not increase even at curing energies of Es or more and is saturated at a constant value.

In the above-mentioned present invention, when crosslinking the soft curable resin for the buffer layer 3, the same resin is brought into a semi-crosslinked state by the curing energy of Eb, which is smaller than Es, and furthermore, the soft curable resin for the protective layer 4 is made into a semi-crosslinked state. After applying the curable resin, both resins are completely crosslinked using appropriate curing energy.When using this method, the curable resin reaction at this time becomes a radical reaction, and the reaction causes differences between the functional groups. As the reaction progresses regardless, a molecular link is generated between the buffer resin and the protective layer resin, thereby increasing the adhesion between the buffer layer 3 and the protective layer 4.

After the buffer layer 3 and the protective layer 4 are formed around the outer periphery of the optical fiber 2 in this way, the optical fiber 2 having these layers 3.4, that is, the coated optical fiber 1, is wound around the bobbin 14 via the capstan 13. It will be done.

Note that the soft curable resin forming the buffer layer 3 and the protective layer 4
The hard curable resin forming the buffer layer 3 may be thermosetting, but thermosetting resins require high temperatures during radical reactions when the bonding force between atoms is strong. As the resin for the protective layer 4, it is preferable to use a photocurable resin that is cured by ultraviolet irradiation, and specifically, butadiene acrylate, 7 silicone acrylate,
Urethane acrylate or the like is used for the buffer layer 3, and epoxy acrylate is used for the protective layer 4.

The hardness of the buffer layer 3 after curing is 1.0 K in terms of Young's modulus.
g/mrl or less, and the hardness of the protective layer 4 is Young's modulus of 5.
Q I (q/'- or more is better.

Furthermore, when the resin (photocurable) forming the above-mentioned both layers 3.4 is completely cured in the ultraviolet ray irradiation type curing furnace 12, the curing energy (light energy) may exceed the above Es, but it is too large. It is predicted that the resin will decompose when curing energy is applied, so it is preferable to keep the curing energy at this time to about several times Es.

In addition, when the buffer layer 3 is semi-cured in the curing furnace 10, the appearance and hardness do not decrease much compared to the cured state. Therefore, when covering the outer periphery of the layer 3 with a protective layer resin, No problems arise.

Next, a specific example of the method of the present invention will be described. When a coated optical fiber 1 similar to that described in the experimental example is manufactured by the method described in FIG. 2, the buffer layer 3 and the protective layer 4 are formed with the following specifications. Formed.

For buffer layer 3 Material: Urethane acrylate (curing characteristics Viscosity before curing: 2500 CP Young's modulus after curing: 0. I Kg/myl Energy during semi-curing: 1.5 units/crA For protective layer 4 Fiber material: Epoxy acrylate Viscosity before curing: 5500 CP Young's modulus after curing: 70 K9/crl The coated optical fiber 1 manufactured according to these specifications has a small increase in loss due to tension winding of 0.5 dB/Km. Even when a 1% screening test was performed, no delamination occurred between the buffer layer 3 and the protective layer 4.

Further, six coated optical fibers 1 are twisted together around a stainless steel tension member 16 of 04 diameter diameter as shown in FIG. By curing with ultraviolet rays, a solid layer 16 having a diameter of 1.3 mm was formed to form an optical cable unit 17.

This unit 17 is a completely filled liquid-tight type with no change in transmission loss, and since the Young's modulus of the solid layer 16 is three orders of magnitude higher than the Young's modulus of the protective layer 4, it is separated into each core. I was able to easily handle the useless terminals.

As explained above, the present invention provides a method for manufacturing a coated optical fiber in which a buffer layer is formed on the outer periphery of the optical fiber and a protective layer around the outer periphery of the buffer layer, wherein the material of the buffer layer is a soft curable resin, and the material of the buffer layer is a soft hardening resin. The material of is a hard curable resin, an uncured soft curable resin is applied to the outer periphery of the optical fiber, and curing energy is applied to the resin to make it into a semi-hardened state, and then semi-hardened soft curable resin is applied. The method is characterized in that an uncured hard curable resin is applied to the outer periphery and curing energy is applied thereto to completely cure the uncured hard curable resin and the semi-cured soft curable resin. A coated optical fiber that not only has good contralateral pressure characteristics but also excellent adhesion between the buffer layer and the protective layer can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a coated optical fiber, FIG. 2 is a diagram showing the relationship between crosslinking density and curing energy, FIG. 3 is a diagram schematically showing an embodiment of the method of the present invention, and FIG. FIG. 5, which is a diagram showing the curing characteristics of acrylate, is a sectional view of an optical cable unit composed of coated optical fibers manufactured by the method of the present invention. 1, 0, e-coated optical fiber 2 ■, self-optical fiber 3, 0, buffer layer 4, protective layer 9,11, die coater 10,12, - hardening Dear Commissioner of the Reactor Patent Office, Year 1. Indication of the case: Japanese Patent Application No. 58-2474872, title of the invention: Method for manufacturing coated optical fiber 3, person making the amendment Relationship with the case: Patent applicant: Furukawa Electric Co., Ltd. Column 7 of “Detailed description of the invention” of specification jlf Contents of amendment

Claims (2)

[Claims] (1) A method for manufacturing a coated optical fiber in which a buffer layer is formed on the outer periphery of the optical fiber and a protective layer around the outer periphery of the buffer layer,
The material of the buffer layer is a soft curable resin, and the material of the protective layer is a hard curable resin.The uncured soft curable resin is applied to the outer periphery of the optical fiber, and the resin is applied with curing energy. After that, an uncured hard curable resin is applied to the outer periphery of the semi-cured soft curable resin, and curing energy is applied to the uncured hard curable resin and the semi-cured soft curable resin. A method for manufacturing a coated optical fiber that completely cures a curable resin. (2) The method for manufacturing a coated optical fiber according to claim 1, wherein the soft curable resin for the buffer layer and the hard curable resin for the protective layer are made of a photocurable resin.