JPH04204407A - Optical fiber cable and slot rod - Google Patents

Abstract

PURPOSE:To obtain an optical fiber improved in transmission loss even in a state of being wound around a drum by setting a reverse twisted groove so that minimum connection virtual line connecting alternate reversal points of each reverse twisted groove forms a gentle helical shape. CONSTITUTION:The shape of the reverse twisted groove 2 is set so that the minimum connection virtual line 4 connecting alternate reversal points of each reverse twisted groove 2 along a surface of the slot rod 1 forms a gentle herical shape. As to one piece of reverse twisted groove 2 of the slot rod 1 and the optical fiber 3 inside it, their reversal point is sequentially rotated to either direction of right or left and the position is deviated. Therefore, when the optical fiber cable utilizing such a slot rod 1 is wound around a drum, etc., for a multiple number of times, the reverse tive twisted groove 2 (optical fiber 3) whose reversal point comes to the no.1 position in the outer periphery side is sequentially changed. Thus, even in a state of beings wound around the drum, the improved transmission loss of the optical fiber can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber cable and a slot rod used therein.

[Problems to be solved by conventional techniques and inventions] Generally,
In order to facilitate branching and connection work during optical fiber cable installation work, S-Z is installed on the surface of the slotted rod.
An optical fiber cable is used in which a plurality of reverse twist grooves are formed in the shape and optical fibers are housed in the grooves.

By the way, conventional optical fiber cables of this type have been constructed with an inverted twist angle of 180°, as shown in FIG. 1 (II). That is, FIG. 1(n) representatively shows a conventional slot rod 31 and one of the plurality of S-Z-shaped inverted twisted grooves 32 recessed in its surface. It shows. Since the optical fiber 33 is housed in the reverse twist groove 32, in the simplified drawing, the reverse twist groove 32 and the optical fiber 33 therein are shown as a single broken line. It is. As is clear from the figure, since the reverse twist angle is ±180°, the reverse twist position A3 of the reverse twist groove. B+, Ax
The imaginary line 34 connecting sequentially... becomes a straight line, and
It is parallel to the center line of Thronotokorad.

When an optical fiber cable using such a conventional slot rod is wound around a drum, the reversal point A1. B1
．． Ax... will be located only in a certain direction. For example, in FIG.
. . are eight, and if the reversal point A in Figure 1 (n) comes to the position numbered ■ on the outer circumference side, then the same reversal twist groove 3
2 (and the optical fiber 33 therein) other inversion point B,
, A, . . . also come to the position of the same number ■. When observing each optical fiber 33 and inverted twisted groove 32 in this way, the inverted locations are located at the same numbered positions in FIG.

In the case of S-Z type reverse twisting, since the twist angle changes within the reverse twist pitch P, if one optical fiber 33 shown in FIG. 1 (It) is observed, the slot rod 3
In which direction should 1 be curved - 1, that is, the inverted point A+
, B1. The amount of strain on the optical fiber 33 differs depending on whether At... is curved so that it comes to the number ■ in FIG. 4, or whether it is curved so that it comes to the numbers ■, ■, etc.
The stress applied to 3 is also different. Specifically, the amount of strain of the optical fiber 33 where the inversion points A, B, A, etc. are always at the numbers ■ to ■■ in Fig. 4 is compared with that of the other numbers ■ to ■. It has a large internal stress and has a negative effect on the transmission loss of the optical fiber.

Therefore, in the optical fiber cable using the conventional slot rod as described above, the strength and reliability of the optical fiber deteriorate when stored for a long time in a drum-wound state. On the other hand, the drum-wound state causes transmission loss degradation of the optical fiber. (Optical fiber transmission loss occurs even in a short period of time.) The purpose of the present invention is to make it possible to obtain good optical fiber transmission loss even in a drum-wound state, and to make it possible to obtain a good optical fiber transmission loss even in a drum-wound state. The point where the distortion state between is the same,
The amount of distortion is sufficiently smaller than that of the conventional method, and high reliability can be obtained even during long-term storage.

[Means to solve the problem]

In the optical fiber cable according to the present invention, in an optical fiber cable in which an optical fiber is housed in the reverse twist groove of a slot rod having at least one reverse twist groove, the reverse position of each of the above reverse twist grooves is The shape of the inverted twist groove was set so that the shortest connecting virtual line along the surface of the slot rod, which was tied one after another, drew a gentle spiral shape.

Further, the slot rod of the present invention has at least one
More than one inverted twist groove is recessed, and the shortest connecting imaginary line along the surface, which connects every inverted point of each inverted twist groove, draws a gentle spiral shape. The shape of the above-mentioned reverse twist groove was set.

[For production]

With regard to one inverted twisted groove of the slot rod and the optical fiber therein, the inverted point is sequentially rotated and shifted in one direction, either to the right or to the left. When an optical fiber cable using a rod is wrapped around a drum etc. many times, the number ■ on the outer circumference side in Figure 4
The reversal twist grooves (optical fibers) whose reversal points come at the positions of are sequentially alternated. In other words, when one inverted twisted groove (optical fiber) is observed, the positions of numbers ■■ in FIG. 4, where inverted locations appear one after another, change as they rotate in one direction.

Therefore, regarding multiple reverse twist grooves, number ■ in Figure 4
■...The probability that a reversal point will appear in the position is equalized, and the amount of strain and internal stress of all optical fibers become the same. Therefore, good optical fiber transmission loss can be obtained even in the drum-wound state. And the amount of distortion is much smaller than before,
High reliability can be obtained even after long-term storage.

[Example] The present invention will be explained below based on illustrated embodiments.

FIG. 2 shows a cross-sectional view of an example of the optical fiber cable 10. Reference numeral 1 is a slotted rod made of plastic, for example, and having eight reverse twisted grooves 2. As shown in FIGS. 2 and 3, a plurality of optical fibers 3 are housed in each inverted twist groove 2 of this slot rod. This optical fiber 3 is shown in the case where, for example, eight fibers are arranged in each reverse twist groove 2 as a two-core tape type optical fiber.

The slotted rod 1 has a tension member 5 in the center,
The outside of the slot rod 1 is covered with a presser winding 6 and a sheath 7.

Therefore, in FIG. 1(I), the slot rod l is shown in a simplified diagram, and in particular, only one of the plurality of reverse twisted grooves 2 is illustrated as a representative example, and S- Consider an imaginary line that connects the reversal points A, B, A, etc. of the reversal twist groove 2, which is recessed in a Z-shape so as to be reversed at a predetermined reversal twist pitch P. That is, the shortest connecting imaginary line 4 connecting the alternate reversal points A1 and A2 at the shortest distance along the surface 1a of the stator nod 1 is a gentle □, for example, 10 m to 1
The shape of the inverted twist groove 2 is determined so as to draw a □ spiral shape with a long twist pitch of 00 m.

Therefore, in the optical fiber cable 10 (see Fig. 2), the optical fibers 3...
Since the optical fiber 3 is accommodated, the shortest connecting imaginary line 4 connecting the S-Z reversal points every other way naturally draws a gentle spiral shape.

The reason why the twist pitch of this virtual line 4 is set to 10 m to 100 m is that if it is less than 10 m, it will be difficult to pull out the optical fiber 3 from the reverse twist groove 2 of the optical fiber cable 10 (during branching work etc.). If the distance exceeds 100 m, problems similar to those of the conventional system shown in FIG. 1(n) will arise. Preferably, the twist pitch of this virtual line 4 is 20 m to 50 m.

Although not shown in FIG. 1, the shortest connecting imaginary line connecting the next reversal point on the right side outside the drawing and the reversal point B1 also draws a spiral with the same twist pitch.

Next, a transmission loss comparison test was conducted between a product implementing the present invention and a conventional product.

(I) Implementation product of the present invention (see FIG. 1 (I)): As shown in FIGS. 2 and 3, the slot rod 1 has eight reverse twist grooves 2... Each dimension of 2 is groove bottom width C=2
m, groove width E-4, groove depth F=2.5-, and eight optical fibers 3 of two-core tape type are housed in each inverted twist groove 2. The width G of this tape-shaped optical fiber 3 was set to 0.7mm, and the thickness H was set to 0.4mm. Figure 1 (1
), the reverse twisting bin 1,000 P of the reverse twisting groove 2 is set to 230,
The reverse twist angle was set to ±150°. The outer diameter of the slot rod 1 is 16 mm, and the sheath 7 shown in Fig. 2 is
The outer diameter of is 21mmφ. The locus of the shortest connecting imaginary line 4 connecting every reversal point of the reversal twist groove 2 is set so as to draw a large helical state with a twist pinch of 35 m.

(II) Conventional product (see FIG. 1 (II)): The cross-sectional shape and dimensions of the optical fiber cable are the same as those of the product according to the present invention, and the optical fiber in the slot rod is also completely the same.

Then, as shown in Figure 1 (II), the reverse twist angle is set to ±1.
80'', the shape of the inverted twist groove was set so that the imaginary line 34 was a straight line and parallel to the center line of the optical fiber cable.

1,000P is 230m. Further, the outer diameter dimension and the sheath outer diameter are the same as those of the product according to the present invention.

The product according to the present invention and the conventional product each have a length of 1
000 m, the tram diameter was 11,000 a □, that is, in FIG. 4, the drum radius R was wound to 500 - □, and the transmission loss was measured for all optical fibers (128 cores).

The measurement results are shown in Tables 1 and 2. In addition, there are 16 optical fibers in each reverse twist groove, and the minimum 4i (MIN) and maximum value (MAX) of the optical transmission loss among them, as well as the average value (AVE) of the 16 fibers, are show.

(The following is a margin) If it exceeds 0.4 dB/-, it is judged as a defective product. From Tables 1 and 2, there are no defective products in the products according to the present invention, and the optical fibers in any of the reverse twist grooves exhibit a small, almost uniform transmission loss. On the other hand, in Table 2, the numbers ■ to ■ of the reverse twist grooves are shown in correspondence with Figure 4, and the drum winding has reverse twist points A, , B, , B, etc. on the outer circumferential side of the state. The transmission loss of the optical fiber in the corresponding reverse twist groove ■■■ was large, and the maximum number of defective fibers occurred (11 cores/16 cores).

It should be noted that the present invention is not limited to the illustrated embodiment and is of course free to change the design. For example, the optical fiber 3 may be a single core round shape, or a tape shape with three or more cores. It's good as well. Furthermore, the S-Z reversal twist angle can be freely selected as long as it is less than ±180°.

It is also preferable to assemble a plurality of optical fiber units shown in FIG. 2 into a cable. Further, it is also possible to form only one inverted twist groove 2 on one slot rod l.

[Effects of the Invention] With the above-described configuration, the present invention provides the following significant effects. That is, each inversion IW is wound around a drum or the like;
The amount of strain of the optical fibers 3... in 112... is made uniform, and the optical fibers 3... in any of the reverse twist grooves 2...
without giving excessive strain or internal stress.

Therefore, good optical fiber transmission loss can be obtained even in the drum-wound state.

Furthermore, since the state of distortion between the grooves is the same even in the drum-wound state, the amount of distortion is sufficiently smaller than in the past, and high reliability can be obtained even during long-term storage.

[Brief explanation of the drawing]

Fig. 1 is a simplified plan view for comparing and explaining the present invention and the conventional example, Fig. 2 is a cross-sectional view, Fig. 3 is a sectional view for explaining dimensional relationship, and Fig. 4 is an explanation of the operation of the present invention and the conventional example. FIG. ■...Slot rod', la...Surface, 2...
Reversed twist groove, 4...imaginary line, A1. At... Reversal point.

Claims (1)

[Claims] 1. In an optical fiber cable in which an optical fiber is housed in the reverse twist groove of a slot rod having at least one reverse twist groove, the reverse points of each of the above reverse twist grooves are aligned. Along the surface of the above slotted rod, tied with a skip,
An optical fiber cable characterized in that the shape of the inverted twist groove is set so that the shortest connecting virtual line draws a gentle spiral shape. 2. At least one or more inverted twist grooves are recessed on the surface, and the shortest connecting imaginary line along the surface, which connects the inverted points of each of the inverted twist grooves at every turn, forms a gentle spiral. A slotted rod characterized in that the shape of the above-mentioned inverted twist grooves is set so as to draw a shape.