JP2835228B2 - Optical fiber screening method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for screening and testing optical fibers to ensure the mechanical strength of the optical fibers.

[0002]

2. Description of the Related Art In order to guarantee the mechanical strength of an optical fiber, as shown in FIG.
A so-called screening test has been conventionally performed in which the film is unwound from the roll 2, wound on a winding bobbin 20 via a fixed roll 14, a movable roll 16, and a fixed roll 18, and a constant load 22 is applied to the movable roll 16.

In this case, if the optical fiber has no coating, the optical fiber comes into direct contact with each of the rolls 14, 16, and 18, so that the surface of the optical fiber is scratched and its mechanical strength is reduced. A screening test is performed with the fiber coated with an ultraviolet curable resin or a thermosetting resin. At this time, the load is also shared by the coating of the optical fiber. If the Young's modulus of the coating is 70 kg / mm ² , this load sharing ratio is about 3 to 15%. The load to be applied is determined in consideration of the load sharing ratio of the coating.

[0004] By the way, recently, a plan to introduce an optical fiber into ordinary households has been promoted. At that time, reduction of cable cost and installation test is a major goal. A high-density optical fiber cable has been developed. In this high-density type optical fiber cable, it is necessary to accommodate as many optical fiber cores as possible within a predetermined outer diameter. Optical fiber cores have been developed.

[0005]

However, when a screening test is performed on an optical fiber having such a thin coating, the probability of breakage of the optical fiber is significantly increased even if the same optical fiber is used up to now. . In general, the reason why an optical fiber breaks in a screening test is that (1) the case where the strength of the optical fiber itself is originally low, and (2) the case where the strength of the optical fiber itself is inherent but the coating strength is low, for example. As described above, there is a case where the fiber is broken due to a secondary cause other than the optical fiber. If the optical fiber breaks due to the latter secondary cause, the screening of the optical fiber cannot be performed accurately even if the same optical fiber is used.

[0006] It is an object of the present invention to provide a method capable of avoiding the above-mentioned drawbacks and accurately screening an optical fiber even if the coating of the optical fiber is reduced.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an optical fiber formed by arranging a plurality of optical fibers in parallel on a plane and covering the plurality of optical fibers collectively. An object of the present invention is to provide an optical fiber screening method characterized by performing a screening test in a state of a fiber ribbon.

[0008]

According to the present invention, as described above, as a result of various investigations assuming that it is highly probable that the breakage of the optical fiber is caused by a secondary cause such as the thickness of the coating, various studies have been conducted. The estimation was confirmed to be correct. Therefore, when a plurality of optical fibers having a small coating thickness are arranged on a plane and coated collectively to form a tape core wire, the coating thickness becomes large as a result with respect to a screening roll. Since the number of optical fibers can be reduced, the optical fibers can be accurately screened, and a plurality of optical fibers can be collectively tested, so that the working efficiency is improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, in which the details of the present invention are described together with the embodiments, the optical fiber 30 subjected to the screening test according to the method of the present invention has a thin optical fiber 32 as shown in FIG. According to the method of the present invention, when performing the screening test, the optical fiber 30 is arranged in parallel on a plane and covered with a tape material 36 as shown in FIG. The optical fiber tape is coated to obtain a state of the optical fiber ribbon 38. As described above, when the optical fiber 30 is screened in the state of the optical fiber ribbon 38, the coating of the optical fiber 30 becomes thick as a result, and the optical fiber is broken due to a secondary cause due to the coating. The factors were eliminated and the screening test could be performed accurately, but it was confirmed.

Next, a screening test is performed on the optical fiber in the state of the tape by the method of the present invention.
The reason why the test is performed correctly is described in detail below.
FIG. 4 shows the probability of breakage of the optical fiber strand by varying the thickness of the coating of the optical fiber strand 30. With the fracture probability as P, the reciprocal 1 / P is plotted on the vertical axis, and the outer diameter of the coating of the optical fiber is plotted. Shows the breaking characteristics of the optical fiber represented by the horizontal axis. In this case, the screening load was changed for each coating outer diameter so that the same load was applied to the optical fiber itself in consideration of the load shared by the coating.

Since the same optical fiber is used, in the above screening test, 1
Although / P should be the same, as shown in FIG. 4, 1 / P increases in proportion to the coating outer diameter when the coating outer diameter within the range of the test is 0.25 to 0.5 mm. The result was obtained.

The present inventors have estimated the result as follows. That is, when the coated optical fiber (the optical fiber) comes into contact with the screening rolls 14, 16, 18, the coated portion that comes into contact with these rolls is loaded on the optical fiber as shown in FIGS. Is partially collapsed by the applied tensile load, and an angle α corresponding to the collapse is obtained.
In a minute, a load is applied in the radial direction of the roll. Therefore, as the coating 34 is thicker and the outer diameter of the coating is larger, α decreases as shown in FIGS. 5 and 6 (from α _{1 in} FIG. 5 to FIG. 6).
Α ₂ is small). As described above, since the crushing rate (1−Cos α / 2) of the material of the coating 34 is reduced, the deterioration of the strength of the optical fiber is reduced.

The above test results show that the bending load on the screening roll, which was not a problem when the coating of the optical fiber was thick, was not negligible when the coating was thin. The screening test is originally performed to measure the tensile strength of the optical fiber, but when the coating of the optical fiber is thin, the bending load on the roll affects the measurement of the tensile strength.

From the above, simply by making the coating thicker, it is possible to conduct a screening test capable of measuring a mechanical strength close to the intrinsic mechanical strength of the optical fiber, but as described above, In order to obtain a high-density type optical fiber cable, it is required to reduce the diameter of the optical fiber, and conversely, the coating is required to be as thin as possible, so that the coating cannot be thickened. .

In order to satisfy the above contradictory demands, the present inventor has considered conducting a screening test in a state of an optical fiber ribbon, which is currently used as a means for reducing the diameter of an optical fiber. . In this case, when a screening test was performed while considering the shared load of the coating and determining a load proportional to the number of optical fibers 32, the results shown in FIG. 7 were obtained. As can be seen from FIG. 7, it was confirmed that the breaking characteristics of the optical fiber ribbon were the same as those obtained by increasing the outer diameter of the single-core coating.

Therefore, as described above, the present invention performs the screening test by setting the optical fiber 30 to be measured to the state of the optical fiber ribbon 38 as shown in FIG. To get the result. FIG. 8 shows that the optical fiber 30 to be measured is in contact with the screening roll, for example, the fixed roll 14 in the state of the optical fiber ribbon 38. For example, the outer diameter of the optical fiber 30 (the outer diameter of the coating)
Is 0.25 mm and the width of the optical fiber ribbon 38 is 1.
When the thickness is 1 mm and the thickness is 0.4 mm (see FIG. 3), the fixing roll 1 is removed from the optical fiber 32 of each optical fiber 30.
A coating thickness corresponding to dimensions up to 4 results in 0.075
mm, and thus, as in the case of a single core having a thick coating, the angle α corresponding to the collapse becomes smaller. For this reason, the bending load on the roll contact surface is further alleviated, and the amount of deformation (crushing rate) of the coating is reduced, and the screening test can be performed without being affected by the bending load.

[0017]

According to the present invention, as described above, since the screening test is performed by converting the optical fiber to be measured into a tape core, the screening operation can be performed in a state close to the true value even with a thin coating. Also, since a screening test is performed on a plurality of optical fibers in a single operation, there is a benefit that the operation efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of an optical fiber screening method.

FIG. 2 is a cross-sectional view of a single-core optical fiber for screening.

FIG. 3 is a cross-sectional view of an optical fiber ribbon when screening is performed by the method of the present invention.

FIG. 4 is a diagram showing a breaking characteristic with respect to a coating outer diameter when screening a single-core optical fiber.

FIG. 5 is a cross-sectional view of a portion where a single-core optical fiber having a thin coating contacts a screening roll.

FIG. 6 is a cross-sectional view of a portion where a single-core optical fiber having a thick coating contacts a screening roll.

FIG. 7 is a diagram showing a comparison result of breaking characteristics between a single-core optical fiber and an optical fiber tape;

FIG. 8 is a cross-sectional view of a portion where an optical fiber ribbon comes into contact with a screening roll according to the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Supply bobbin 14 Fixed roll 16 Movable roll 18 Fixed roll 20 Winding bobbin 22 Load 30 Optical fiber strand 32 Optical fiber 34 Coating 36 Tape material 38 Optical fiber tape core

Claims (1)

(57) [Claims] 1. An optical fiber, wherein a screening test is performed in a state of an optical fiber ribbon formed by arranging a plurality of optical fibers in parallel on a plane and covering the plurality of optical fibers at a time. Screening method.