JPS58196502A - Reinforced optical fiber - Google Patents

Abstract

PURPOSE:To assure not only tensile strength but bending strength and compressive strength as well by laminating and forming two kinds of reinforcing layers differing in the form of fibrous materials from each other on the outside of an optical fiber. CONSTITUTION:A buffer layer 2 formed on the outside of an optical fiber 1 consists of a solft or hard plastic such as polyurethane or silicone and there are a reinforcing inside layer 3 and a reinforcing outside layer 4 formed successively on the outside of said layer, each of which layers consists of a composite material of long fibers 5, 6 and thermosetting resins 7, 8. The layer 3 is so formed that the respective long fibers 5 are placed along the longitudinal direction of the fiber 1 on the outside of the layer 2 and the layer 4 is so formed that the respective long fibers 6 intersect with the fibers 5 on the outside of the layer 3. The content of the fibers 5, 6 in both layers 3, 4 is made 60-85wt% in terms of both strength and flexibility and if the layer 3 is designated as A and the outside layer 4 as B, B/A+B is made preferably 7-40wt%.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reinforced optical fiber in which the reinforcing layer on the outer periphery of the optical fiber is made of a composite material of resin and fiber material.

As a means to strengthen the optical fiber, after the primary coating layer, buffer layer, etc. have been formed, glass fibers in a roving state are longitudinally attached to the outer periphery of the optical fiber, and the long fibers are impregnated with thermosetting resin. It has already been carried out to form a reinforcing layer around the outer periphery of the optical fiber by curing it using a suitable heating means.

In the case of the above-mentioned reinforced optical fiber, the temperature characteristics and tensile strength are improved by providing a reinforcing layer with long fibers, but the long fibers of the reinforcing layer are arranged in the longitudinal direction of the optical fiber. Therefore, vertical tearing easily occurs in the reinforcing layer when subjected to bending load, compressive load, etc.

Of course, in the above case, it is not that the long fibers in the longitudinally spliced state are bad, but that this fiber material mainly provides only tensile strength,
Therefore, reinforcing means that can withstand bending loads and compressive loads is required.

Normally, the seven stages adopted to cope with bending loads and compressive loads involve randomly entangling short fibers with longitudinally attached long fibers, and a considerable reinforcing effect can be expected from this.

However, in the case of short fibers, not all of them intersect and become entangled with long fibers, and fibers along the longitudinal direction of the long fibers, that is, those that do not have the above-mentioned longitudinal tear prevention IF effect, also account for a considerable amount of weight. Therefore, it can be said that the loss of fiber material seen from reinforcement F is large.

Another possibility is to wrap medium fibers, which are longer than short fibers, so as to intersect with the long fibers. In view of this, medium fibers with a small finite range of length cannot handle long ones, and even if they are added, the strength of the joint becomes a problem.

In order to solve these problems, the present invention has two types of reinforcing layers with different types of fiber materials laminated around the outer periphery of an optical fiber to improve not only tensile strength but also bending strength and compressive strength. The structure is explained below with reference to the illustrated embodiment.

In FIGS. 1 and 2, (1) is an optical fiber on which a thin primary coating layer (not shown) of thermosetting resin such as silicone resin is formed, and (2) is the optical fiber (11).
This buffer layer (2) is made of a soft or hard synthetic resin such as polyurethane or silicone.

Furthermore, in the figure, +31 (41 is the buffer layer (2)
) are sequentially formed on the outer periphery of the reinforcing inner layer and the reinforcing outer layer.
51 (51+51..., (6X6) +61・
...and a thermosetting resin (71+81).

Long fiber in the above (5+ +5) +51...
, +61 (61 (61... is one or two of these, such as glass fiber, carbon fiber, aramid fiber, metal fiber, fused silica fiber, ceramic fiber, etc.)
A combination of the following is used.

In addition, these long fibers (51 + 51151..., +
61 +61 (61... is in a roving state (fiber diameter 20 μm or less, number of fibers = several tens to hundreds) or yarn state, and depending on the case, long fibers +6+ +6j +61・Due to the relationship between the outer diameter of the reinforcing optical fiber and the covering layer thickness, the fiber diameter of ... is determined by the other long fibers + 51
(Sometimes a smaller value than 51+51... is used.

On the other hand, unsaturated polyester resin, epoxy resin, etc. are used as the resins +71 and +81, and these are made of the same material in order to obtain mutual chemical adhesion (integration) between the two layers [31F41].

The reinforcing inner layer (3) is made of long fibers (51 [51F5+...) and a resin (7) impregnated therein and cured.
In the outer periphery of the buffer layer (2), each long fiber [51L
51 (51... is formed along the longitudinal direction of optical fiber (11), and long fibers 161 +6
1 (61... and the resin impregnated into it and cured) 8
), each long fiber (6)+6) (6)... intersects with the long fiber +51 (51+51...) on the outer periphery of the reinforcing inner layer (3). As a specific example of fiber intersection, one straight long fiber +51 +51 +51...
On the other hand, the other long fiber (61 + 61 + 6)...
is spirally wound as shown in Fig. 1〇 In this case, the long fiber +61 +61 +61... can be wound in one thread or in multiple threads, and the optical fiber (1)
The long fiber (6) based on the axis of +61 [6
The wrapping angle θ of 1... is set within the range of 900<θ (1800).

Furthermore, in the above, both layers (long fibers in 31+41+51 (51+51..., (61(6116)
The content of 1... is preferably 60 to 85% by weight for both layers f31 (41) in view of the balance between strength and flexibility. Outer circumference (4)
When B is B, B/(A + B) is preferably 7 to 40% by weight.Next, specific examples will be explained using a table.

In addition, each sample (reinforced optical fiber) in the above table has an outer diameter of the reinforcing coating of 2wnφ in FIG.
The outer diameter of the optical fiber (1) is 125 μm1. The buffer layer (
The outer diameter d of 2) is 400 μm, and the reinforced inner layer (3) and the reinforced outer layer (4) have long fibers +51 +51 +51..., +61 +61
Adopts roving glass as +61...
Unsaturated polyester resin was used as resin [7] and (81).

Furthermore, the eccentricity α occurs when both layers (31(4)) are hardened through the drawing die, and this α was calculated from a and b in FIG. 3 as shown in the following equation.

The amount of increase in transmission loss (dB/h) is ta+ (41
It was determined from the difference between before and after coating.

The wavelength used in this case is 0.85′” −+
160
1 On the other hand, the crushing strength is an example 10 reinforced optical fiber without the reinforcing outer layer (4), that is, reinforced with only the reinforcing inner layer (3), with the crushing strength of 1 being 1, and the remaining crushing strength on each side is shown as a relative value to this. Ta.

The sample length at the time of crushing was 50 mm, and the crushing speed was 0.5 mm/
m, and was measured using a testing machine manufactured by Instron, USA.

Hereinafter, each side in the table will be explained. Since the case of Example 1 did not have the reinforcing outer layer (4), the bend easily caused longitudinal tearing due to the load, and it was confirmed that the case was defective.

Although the strength of Example 2 was somewhat higher than that of Example 1, some of them suffered from vertical tearing to the same extent as Example 1, so the strength was still insufficient.

It was confirmed that the material of Example 3 had considerably improved crushing strength compared to Example 1, and could sufficiently withstand bending in practical use. Of course, there is no interlayer function between the reinforcing inner layer (3) and the reinforcing outer layer (4).

In Example 4, the effects described in Example 3 are more pronounced, and there are no adverse effects that are inversely proportional to the strength.

In Example 5, although it was observed that the strength of Example 4 was -E, there was a tendency for the eccentricity α to increase. However, the eccentricity remains at a level that does not pose a practical problem.

Although examples 6 and 7 have no problem in terms of strength, the eccentricity α is considerably large, and this is a drawback.

In the above, if we make a comprehensive judgment on each side except for example 1,
Example 4 is good, Example 3 and Example 5 are good, Example 2.6.7
is normal or lower.

As explained above, the reinforced optical fiber of the present invention has a reinforcing inner layer and a reinforcing outer layer formed around the outer periphery of an optical fiber having a buffer layer, and both of these layers are formed by impregnating long fibers between the long fibers. It is made of hardened resin, and the long fibers of the reinforcing inner layer are stretched along the longitudinal direction of the optical fiber.
, characterized in that the long fibers of the reinforcing outer layer intersect with the long fibers of the reinforcing inner layer.

Therefore, in the case of the present invention, the reinforcing inner layer not only provides tensile strength and good temperature characteristics, but also the reinforcing outer layer provides bending strength and crushing strength that do not cause longitudinal tearing. The mechanical properties of the fiber are improved overall.

In particular, since the reinforcing fiber materials are all long fibers, they are easily compatible with long optical fibers from the manufacturing point of view, and have uniform strength in the longitudinal direction.

[Brief explanation of the drawing]

FIG. 1 is a cutaway front view showing the essential parts of the reinforced optical fiber of the present invention, FIG. 2 is a sectional view of the same, and FIG. 3 is an explanatory diagram of eccentricity. (1) ...Optical fiber +21 -----Buffer layer (3) ...Reinforcement inner layer (4) ...Reinforcement outer layer (Fil (61...Long fiber +71) +81・・・Resin patent applicant representative Patent attorney Makoto Ito

Claims (4)

[Claims] (1) A reinforcing inner layer and a reinforcing outer layer are formed on the outer periphery of an optical fiber having a buffer layer, and both of these layers are made of long fibers and a resin impregnated and hardened between the long fibers, and the reinforcing inner layer long fibers in the longitudinal direction of the optical fiber.
A reinforced optical fiber characterized in that the long fibers of the reinforcing outer layer intersect with the long fibers of the reinforcing inner layer. (2) The reinforced optical fiber according to claim 1, wherein the reinforcing inner layer and the reinforcing outer ring are chemically bonded at their interface. (3) Reinforced outer layer/(reinforced inner layer + reinforced outer layer) is 7 to 4
The reinforced optical fiber according to claim 1, which has a strength of 0 tonne. (4) The reinforced light according to any one of claims 1 to 3, wherein the long fibers of the reinforcing outer layer intersect with the long fibers of the reinforcing inner layer in a spirally wound state along the longitudinal direction of the optical fiber. fiber.