JPS6198308A - Tightly collected fiber tape type optical cable - Google Patents

Abstract

PURPOSE:To prevent the induction of fiber distortion due to the disturbance of a tape position and to improve the reliability of the strength of the cable by coating optical fiber tapes tightly and unitedly with a cushioning material having a low Young's modulus and a protection layer having a Young's modulus higher than that of said cushioning material. CONSTITUTION:In an optical cable unit obtained by collecting optical fiber tapes each of which is formed by linearly aligning plural optical fiber cores and coating these cores collectively, the plural fiber tapes are laminated and tightly coated with layers while keeping the straightness of the tapes. For instance, four optical fiber tapes 4 are laminated and unitedly coated with a cushioning material 11 having a low Young's modulus and then coated with a protection layer 12. Thermosetting type silicone resin or ultraviolet setting resin (UV resin) can be applied to the cushioning material 11 and its Young's modulus is preferably about 0.1-1kg/mm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cable structure for improving the strength and reliability of an optical cable in which a plurality of optical fibers are coated in a tape-like manner and optical fiber tapes are assembled in a loose manner. be.

(Prior Art) FIG. 4(a) shows a cross section of an example of a conventional tip cable, and FIG. 4(b) shows an enlarged cross section of the optical fiber tape No. 411(a). In FIG. 4, 1 is an optical fiber, 2 is silicone for buffering, and 3 is a tape coating made of nylon or the like, forming a five-core optical fiber tape 4 as a whole. Four tapes are inserted into the tube 5 to form a unit 6. In the cable shown in FIG. 4(a), 10 units 6t are tied together around the tension member 7, and a presser winding 8 and a LAP jacket 9 are applied to make an optical cable with a total of 200 fibers. With this structure, the optical fiber tape 4 is loosely inserted into the tube 5.

It is known that it is more advantageous to insert the tape straight into the tube from the viewpoint of elongation strain of the optical fiber (Yose et al., "Study of subscriber high-density optical cable design method", Institute of Electronics and Communication Engineers). , Communication Method Study Group Materials, C3
81-151, January 19, 1982).

Therefore, in order to manufacture a unit 6tt of this type of cable, a method is adopted in which optical fiber tapes 4 are stacked and collected, a tube 6 is extruded thereon, and the tape is taken off as one piece and wound around a bobbin. However, with this method, when the tape is wound around the bobbin, the outer tape is longer and has extra length.

The amount of extra length εb inside the tube can be expressed by the following equation when the unit 6 is wound up to a radius R as shown in FIG.

εb-nt/R(1) where t is the thickness of the tape 4. n indicates the position of the fiber tape, n-2 for the outermost fiber and n-1 for the innermost fiber.

For example, the winding bobbin radius R-250, t-Lo, 45
If Tsuru is n-2, then εb-0,136%.

When assembling the unit 6, the wound unit is unrolled and the unit is straightened. This causes the outer tape to undulate within the tube by the extra length. Furthermore, since the unit 6 is twisted together, the undulating tape within the tube is bent into a spiral shape, resulting in a complex shape. In such a state, complex strains such as bending and twisting are applied to the tape. In other words, conventional optical cables have a serious drawback in that the strength of the fiber cannot be guaranteed due to complex distortions.

In order to investigate the complicated shape of the tape 4 and its negative shadow U within the tube of a conventional cable, an optical cable shown in FIG. 4 was manufactured. After extending this cable for 50 m and removing the jacket, the state of the tape inside the tube 5 was observed. The tube is cut every 50 cm and is divided into four colors: yellow, green, and red, and at the same time, a white line is attached to one end of each tape to identify the position.

At the time of manufacture, the inside of the tube is marked blue, yellow, and green from top to bottom, and the numbers indicate the number of strips from the blue tape, and the sign indicates + if the white line is in the same position as the white line of the blue tape. It can be seen that the blue tape has been replaced by a white stripe, and that the tape is twisted due to the reversal of sign. In order to measure the switching pitch of the tape 4, the relative position of the yellow tape was measured every 20 times, and the results are shown in FIG. From this result, it can be seen that the replacement pitch pe is about 50 or so. The strain that occurs in the fiber due to tape replacement can be modeled as a tape of width W being replaced with a pitch of pe, as shown in Figure 8.The equation of the curve representing the fiber in the tape can be calculated using a buckling model with both ends fixed. , y −w (cos(2
πx/p6) -1) (2). In this case, the radius of curvature ρ of the fiber is as follows. The maximum strain ε caused in the fiber by this bending. becomes . Here, df is the outer diameter of the fiber.

In the case of the experimental cable, W −1,6 mN, df
-0,12Fl, po-50, and εe-0,158% (5) is obtained from equation (4). Regarding twisting, twisting was observed in the tape after disassembly, and the results of measuring the rotation angle are shown in Figure 9. From this result, one period of twist pt z3 Q
Q: You can see that it's twisted just by fighting. Assuming that the tape is twisted spirally around the central fiber at a predetermined pitch, the resulting strain ε is expressed by the following equation.

d8 is the diameter of the fiber with silicone inside the tape.

n-2, ds-0, 8 fight, pt-3Q Q tim,
&ttL″f・51)ゝ6 ε, -0,008% (7) By taking the sum of equations (5) and (7), we can calculate the worst strain on the fiber due to the tape 8 in the tube. It can be seen that ε-0,1fl 6% (8) can work as follows.

Regarding the strain design of optical fiber cables, strain is applied through screening during fiber manufacturing, and the strength is guaranteed by using fibers that have passed through this screening. In this case, the screening strain is ε8, and the allowable strain that may act during use of the cable is ε. Then, in order to prevent the fiber from breaking for about 25 years, it is necessary to set εa/ε8:;q (9). (Y, Mitsunaga et, a/E
electron.

Lett, VOl, 17, A16, p, 5
67, 1981). 'Usually εs-0.5%, and in this case, 〒 and a; 0.167% (10).

For cable strain design, the tension at the time of installation should be 500 to 80.
Residual strain εi after applying 0 kg -0,03
%, strain due to temperature change εT”-0.05% (temperature 6
0°C), residual strain ε at the time of cable formation. -0,05%
, the uniform bending strain εB-0.08% is expected, and this total strain is 0.16%.

If the strain ε-0,166% [Equation (8)] due to tape replacement and twisting described above is added to this value, the total strain becomes 0.326%, and the allowable strain ε knee 0.1
It greatly exceeds 67% [Formula (No)]. In other words, it can be estimated that this cable does not have a lifespan of 25 years.

(Problems to be Solved by the Invention) As described above, in the conventional cable, the optical fiber tape 4 is inserted straight into the tube 5.
By going through the winding and straightening process after manufacturing,
Extra length of tape occurs. This effect causes the tape to be replaced or twisted, resulting in a serious disadvantage in that excessive strain is applied to the fiber.

(Means for Solving the Problems) In order to eliminate these drawbacks, the present invention integrally coats an optical fiber tape with a buffering low Young's modulus material and tightly gathers the optical fiber tape.

FIG. 1 is a cross-sectional view of an optical unit 10 showing one embodiment of the present invention, in which four optical fiber tapes 4 are laminated, which are integrally covered with a low Young's modulus buffer material 11, and further with a protective layer. This is a structure coated with 12. As described above, a structure in which the optical fiber tape is made straight and integrally coated is advantageous in terms of fiber distortion. The cushioning material 11 is made of thermosetting silicone or ultraviolet curable resin (UV resin).
etc. can be applied, and its Young's modulus is 0.1 to 1 kg/n
'112 or so is appropriate. If the value of Young's modulus is large, the shrinkage of the buffer material itself due to temperature changes will cause fiber micropends, leading to increased loss.

The retaining layer 12 is made of a material with a relatively large leg ratio in order to support external forces, especially lateral pressure. Young's modulus is approximately l
θ~200 kg7mm2 is suitable. Applicable plastics include thermoplastic nylon, urethane acrylate-based and epoxy-based UvM resins.

Furthermore, when connecting the optical fiber tapes, it is advantageous to take out the optical fiber tapes 4 one by one and use a known 5-fiber batch fusion splicer. It is desirable that the four optical fiber tapes can be removed separately with the tape coating 8 still attached. For this reason, it is suitable that the fiber tape 4 and the buffer material 11 have good releasability, but it is preferable that the Young's modulus of the buffer material 11 is smaller than the Young's modulus of the tape covering W3.

In order to make this purpose more clear, it is effective to apply a very thin layer of fluid liquid such as silicone oil to the surface of the tape after laminating the fiber tape during manufacturing, and to cover the buffer material 11 thereon.

FIG. 2 shows a 10G core unit 15 in which five optical units 10 shown in FIG. For the core material 13, W4 wire or the like can be used to improve strength.

For the presser winding 14, a combination of a plastic buffer string such as polypropylene yarn and tape is suitable in order to improve lateral pressure resistance. Using this 100 heart unit,
6J) A cross section of an embodiment of the present invention configuring an O-core optical cable is shown in FIG.

As a result of examining the characteristics of the structure shown in this example, no position holes were observed in the tape even after the optical units were twisted and assembled. As a result, distortion due to tape position holes [
Equation (8)] does not occur, and the strength reliability design conditions [Equation (1)
0) ) is found to be satisfied.

(Effects of the Invention) As explained above, in the tightly assembled fiber tape optical cable of the present invention, the optical fiber tape is tightly coated with a buffer material having a low Young's modulus and a protective layer having a higher Young's modulus. Unlike loose cables, which are inserted into the tube with a gap,
This has the advantage that the arrangement of the tapes within the tube is not disturbed.

As a result, 7-eye strain caused by placement holes is not induced, which has the great advantage of improving the strength and reliability of the cable.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of four optical fiber tapes constructed according to the present invention, FIG. 2 is a cross-sectional view of a 100-fiber unit made up of five optical fiber units constructed according to the present invention, and FIG. 6 by invention
4(a) is a sectional view of a conventional optical cable; FIG. 4(b) is a sectional view showing an example of a 00-core optical cable.
is an enlarged cross-sectional view of the optical fiber tape in Figure 4 (a), Figure 5 is a diagram explaining the difference in length of the 7-eyeper due to drum winding during cable manufacturing, Figure 6 (a) l (b) io) Extends conventional cable,
Figure 7 shows the results of disassembling and measuring the fiber position disturbance. Figure 7 shows the tape replacement pitch of a conventional cable.
Figure 8 is a diagram showing a model for calculating the fiber strain caused by tape replacement; Figure 9 is a diagram showing the results of measuring the pitch pt of tape twist in a conventional cable. 1... Optical fiber 2... Buffer layer 8... Tape coating 4... Optical fiber tape 5... Tube 6... Tube unit 7... Tension member

Claims (1)

[Scope of Claims] 1. An optical cable constituted by a unit composed of optical fiber tapes in which a plurality of optical fibers are arranged in a straight line and collectively coated, and the unit is composed of a plurality of laminated optical fiber tapes. A tightly assembled fiber tape type optical cable, characterized in that the optical cable is coated so as to be in contact with the optical fiber tape while remaining straight. 2. In an optical cable that is constructed by arranging a plurality of optical fibers in a straight line and collecting optical fiber tapes that are collectively coated to form a unit, the unit is composed of a plurality of stacked optical fiber tapes that are stacked in a straight line. Two layers of coating are applied so as to be in contact with the optical fiber tape, and the Young's modulus of the buffer material in contact with the optical fiber tape is the outer protective layer of the two layers and the optical fiber tape coating. A tightly assembled fiber tape type optical cable characterized by having a Young's modulus smaller than any of the materials. 3. The tightly assembled fiber tape type optical cable according to claim 1 or 2, characterized in that a thin oil layer is provided between the coating in contact with the optical fiber tape and the optical fiber tape.