JPS6066214A - Coated optical fiber - Google Patents

Abstract

PURPOSE:To prevent increase of transmission loss or the like even if a high tension test is executed, by setting the adhesive strength between a glass optical fiber and a coating of a coated optical fiber, where the glass optical fiber is coated with high polymer materials, to a prescribed value of higher. CONSTITUTION:The glass optical fiber is coated with high polymer materials to constitute the coated optical fiber. The adhesive strength between this glass optical fiber and the coating is set to >=0.15kg/mm.<2>, desirably, >=0.25kg/mm.<2>. Thus, degradation of the strength due to a proof test is reduced.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention coats a glass optical fiber with a polymeric material.

[Prior art]

Generally, optical fibers made of quartz glass or multi-component glass have physical and chemical protection from the external environment.
A coating of polymeric material such as a thermosetting resin, a UV curable resin or a thermoplastic resin is provided. Usually, such a coated optical fiber is subjected to a bruising test in which a predetermined tension is applied over its entire length to confirm that it will not break below that tension (the broken portion is removed). However, conventional coated optical fibers have the problem of increased transmission loss and strength deterioration when subjected to high-tension Bruch tests.

The Bruf test is performed on the supply reel 3 as shown in Figure 1.
This is done by winding the coated optical fiber 1 drawn out from the coil onto a winding wheel 11 through a bonded cag stan 5, a tension applying wheel 1, and a take-up capstan 9. The applied tension is set by a lever 15 that supports the tension application wheel 7 and has a fulcrum 13 in the middle. When such a Blue 7 test is performed, the inner portion 21a of the coating 21 is subjected to compressive force at the tension applying wheel 7 due to the tension of the glass optical fiber 19, as shown in FIG. Such a phenomenon also occurs in the delivery cab stun 5 and the take-up cab stun 9. Furthermore, at the J-feeding capstan 5 and take-up capstan 9, there is a difference in the amount of strain between the glass optical fiber and the coating, and the bonded portion between the glass optical fiber and the coating is subjected to shearing force. For this reason, when grouthisting is performed under high tension, the coating is subjected to compressive and shearing forces and is destroyed to a considerable extent, reducing its original ability to protect the optical fiber, increasing the transmission loss of the coated optical fiber, and increasing the strength of the coated optical fiber. This is thought to lead to deterioration.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art as described above and to provide a coated optical fiber that does not substantially cause an increase in transmission loss or deterioration in strength even when subjected to a proof test.

[Structure of the invention]

In order to achieve the above objective, the present inventors conducted numerous studies and found that the increase in transmission loss and deterioration in strength in the Blue 7 test were correlated with the adhesive strength between the glass optical fiber and the The present invention was completed based on this.

That is, the present invention provides a coated optical fiber formed by coating a glass optical fiber with a polymer material, in which the adhesive strength between the glass optical fiber and the target α is 0.15 kvmm2 or more, preferably 0.25 kg/mm2 or more. It is characterized by Nishi Takoto. As will become clear from the examples described below, the adhesive strength between the glass optical fiber and the coating is 0.15 kg.
If it is smaller than /mm2, the increase in transmission loss and deterioration in strength in the proof test will be large, but if it is more than that, both the increase in transmission loss and deterioration in strength will be small.

In particular, setting the adhesive strength to 0.25 kg/mm2 or more is effective in sufficiently minimizing strength deterioration in the Blue 7 test. In addition, the adhesive strength between the glass optical fiber and the coating is 0.6 kg/mm mainly from the viewpoint of manufacturing technology.
``It is desirable to set the value below.This is because if the adhesive strength is made larger than this, the transmission loss in the coating process (the process of coating the glass optical fiber) increases rapidly.The transmission loss in this coating process increases. In order to almost eliminate the increase in adhesive strength, it is preferable that the adhesive strength is 0.50 kg/mm2 or less.

The adhesion strength between the glass optical fiber and the coating in the damaged optical fiber is measured as shown in FIG.

The sample has a length IQ on one end side of a coated optical fiber 1 of a suitable length.
The glass optical fiber 19 is exposed by leaving the l1lln coating 21 and removing the other coatings. The glass optical fiber 19 side of such a sample is passed through a drawing chair 25 having a hole 23 slightly larger than that, and the glass optical fiber 19 is pulled out at normal temperature and humidity at a drawing speed of 100 mm/rn. Measure the load at the time. The adhesive strength is determined by dividing this load by the adhesive area between the glass optical fiber 19 and the coating 21. When the outer diameter of the glass optical 7 eyelid 19 is 125 μm, the diameter of the hole 23 of the drawing die 25 is suitably 180 μm.

When measuring the strength, it is around 0.08 kg/mm' for optical fibers coated with silicone resin and nylon, and 0.07 to 0.13 kg for optical fibers coated with ultraviolet curable resin.
/Inm''. Conventional coated optical fibers have weak adhesion to glass optical fibers in order to make it easier to remove the coating at the end when connecting optical fibers to each other or connecting optical fibers to equipment. However, this resulted in increased transmission loss and reduced strength during proof testing.

As the glass optical fiber in the coated optical fiber of the present invention, a silica glass optical fiber and a multicomponent glass optical fiber can be used. In addition, thermosetting resin, ultraviolet curable resin, thermoplastic resin, etc. can be used for the coating, but basically a material with a low elastic modulus is used near the glass optical fiber, and a material with a high elastic modulus is used on the outside. It is appropriate to use materials. In terms of the fact that suitable adhesion strength with the glass optical fiber can be easily obtained, the UV-curing resin used for the coating is generally composed mainly of polybutadiene acrylate, urethane acrylate, or epoxy acrylate. In general, polybutadiene acrylate has an elastic modulus of 0.5 kg/mm" or less and is suitable for inner layer coating near the glass optical fiber. Urethane acrylate has an elastic modulus of 0.05 to several tens of kg/m+n2 and is suitable for inner layer coating and reinforcement. Epoxy acrylate has an elastic modulus of several kg/ry++n' to several 100
kg/mm” and is suitable for outer layer coating.

Various grades of polybutadiene acrylate and urethane acrylate used as inner layer coatings are commercially available, but the smaller the molecular weight and the larger the amount, the higher the adhesive strength, so any adhesive strength can be obtained. It is.

Note that no suitable means for measuring strength deterioration using the Blue 7 test has been proposed so far. Therefore, we adopted the following measures. In other words, when the same coated optical fiber is repeatedly subjected to the Bruch test with the same tension, the breakage that occurs in the second and subsequent Blue 7 tests can be considered to be due to deterioration caused by the Bruch test. Repeat the Blue 7 test with the same tension on the optical fiber 10 times, add up the number of breaks A from the second to the 10th time, and calculate it by the unit length (] Om) and the number of test times B (sample length/unit length). Divide and accumulate, rupture rate (-
X100%) was determined and used as an index of strength deterioration by the Bruch test.

〔Example〕

First, a silica-based glass optical fiber with an outer diameter of 125 μm was used.
An inner layer coating with an elastic modulus of 0.05 to 3 kg/mm2 and an outer diameter of 200 to 300 μm, consisting of a resin whose main component is ultraviolet curable polybutadiene acrylate-urethane acrylate or epoxy acrylate, and an elastic modulus of 2 to 200 μm.
kg/mm2, outer diameter 4 with higher elastic modulus than the inner layer coating
Various coated optical fibers having different adhesion strengths between the glass optical fiber and the coating were manufactured by applying an outer layer coating of 00 μm.

Figure 4 shows the relationship between the cumulative breakage rate (unit length 1Qrn) from the 2nd to the 10th test (unit length 1Qrn) and the above adhesive strength when the Bruch test is repeated with a tension of 2 kg using these coated optical fibers. As described above, there is a strong correlation between the cumulative breakage rate (proof test) (strength deterioration due to K) and adhesive strength, and when the adhesive strength is set to 0.15 kg/mm2 or more, the cumulative breakage rate (proof test) It can be seen that the cumulative rupture rate becomes sufficiently small, especially when it is 0.25 kg/mm' or more, the cumulative rupture rate becomes even smaller and stable.

Next, a proof test (1
We investigated the change in the transmission loss of light with a wavelength of 1.3 μm (comparison with before the Bruch test) after conducting the test. As a result, it was revealed that the transmission loss changes as shown in FIG. 5 depending on the adhesive strength between the glass optical fiber and the coating.

In other words, the increase in transmission loss caused by the Blue 7 test almost disappears when the adhesive strength is increased to 0.15 kg/mm or more, and increases rapidly when the adhesive strength is lower than that. In fact, losses tend to decrease.

From the results shown in Figures 4 and 5, in order to reduce strength deterioration and transmission loss increase due to proof tests, K is set so that the adhesive strength between the glass optical fiber and the coating is 0.15 kg/mm" or more, preferably 0.25 kg/mm". It can be seen that it is sufficient to have a value of 1 kg/snm or more.

Next, when manufacturing various coated optical fibers by applying a coating similar to the above to a silica glass optical fiber with a core diameter of 50 μm and a cladding diameter of 125 μm, we investigated the change in transmission loss before and after applying the coating. saw. The wavelength of the light is 1.3 μm. The results are shown in Figure 6, and the adhesive strength is
It can be seen that below 0.6 kg/mm2, the increase in transmission loss due to the covering is small, and when it exceeds 0.6 kg/mm2, the increase in transmission loss i increases rapidly.Especially, the adhesive strength When the weight is 0.5 kg/mm" or less, there is almost no increase in transmission loss (it is seen that it is stable).

Therefore, considering the increase in transmission loss in the coating process, it is necessary to consider the increase in transmission loss in the coating process.
It is appropriate to set the weight to less than 0.5 kg/mm, preferably 0.5 kg/mm. However, as shown in Figure 5, when the adhesive strength is greater than 0.6 kg/mm, the transmission loss tends to decrease in the proof test, so there is a possibility that the increase in transmission loss in the coating process will be canceled by the proof test. However, it does not mean that adhesive strength greater than 0.6 kg/mrn2 cannot be used.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain a coated optical fiber that hardly causes any increase in transmission loss or deterioration in strength even when subjected to a high-tension proof test.

[Brief explanation of drawings]

Figure 1 is a front view showing the Blue 7 test equipment for colored optical fibers, Figure 2 is a cross-sectional view of the optical fiber to be contacted at the tension applying wheel section of the equipment, and Figure 3 is a glass optical fiber and a coated optical fiber. What about the adhesive strength? l? Fig. 4 is a partially cut-away front view showing the method for determining adj.
The figure is a graph showing the relationship between the adhesive strength and the change in transmission loss determined by the proof test, and FIG. 6 is a graph showing the relationship between the adhesive layer strength and the increase in transmission loss during the coating process. Figure 1 Figure 2 Figure 3 Figure 4 0 0.1 0.2 0.3 0.4 0.5 Adhesive strength (kg/mm2)

Claims (1)

[Scope of Claims] (1) In a coated optical fiber formed by coating a glass optical fiber with a polymeric material, the adhesive strength between the glass optical fiber and the coating is 0.15 kg/mm” or more. A coated optical fiber characterized by: (2) The coated optical fiber according to claim 1, wherein the adhesive strength is 0.25 kg/mm2 or more. (3) Claim 1 The optical fiber to be compensated according to item 1 or 2, wherein the adhesive strength is 0.6 kg/mm2
Those that are less than or equal to. (4) The coated optical fiber according to claim 1 or 2, wherein the adhesive strength is Q, 5 kg7fnm.
“What is less than.