JP2835298B2 - Fiber optic cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber cable in which a tape-shaped optical fiber core is accommodated in a groove of a grooved spacer having an SZ spiral groove whose spiral direction is periodically reversed on the outer periphery. Things.

[0002]

2. Description of the Related Art An optical fiber cable in which an SZ spiral groove is formed on the outer periphery and an optical fiber core wire is housed in the groove is used for connection and terminal processing.
There is an advantage that it is easy to take out the optical fiber from the groove. This type of cable uses a tape-shaped optical fiber core as the optical fiber core.Conventionally, multiple tape-shaped optical fiber cores are stacked in the depth direction of the groove and stored in the groove. (Japanese Unexamined Patent Publication No. 2-83)
No. 507) and a device laminated in the width direction of the groove and housed in the groove (Japanese Patent Application Laid-Open No. 4-55803) are known.

[0003]

A tape-shaped optical fiber core is formed by arranging a plurality of optical fibers in parallel on the same plane and applying a common coating to form a tape. For this reason, each optical fiber bends uniformly in the direction of bending the tape surface, and almost no increase in transmission loss occurs,
When bending in the direction of bending the tape side edge (edgewise bending) in the tape surface, distortion occurs in the compression direction in the optical fiber on the inner side of the bend, and the optical fiber on the outer side of the bend in the tape. Causes strain in the tensile direction, causing a large increase in transmission loss.

In a conventional optical fiber cable, a plurality of tape-shaped optical fiber cores are housed in an SZ spiral groove of a grooved spacer in a state of being laminated in a certain direction with respect to the direction of the groove. Therefore, there is a portion where each tape-shaped optical fiber is necessarily bent in the direction of bending the side edge of the tape. For example, in a cable in which a plurality of tape-shaped optical fiber cores are stacked in the depth direction of the groove, each tape-shaped optical fiber core mainly has a tape side edge at a reversal part of the groove (a part where the spiral direction is reversed). Subject to bending in the direction of bending. In a cable in which a plurality of tape-shaped optical fibers are laminated in the width direction of the groove, the tape side edge is mainly located at an intermediate portion between the inverted portions of the groove (between one inverted portion and the next inverted portion). Is subjected to bending in the direction of bending.

As described above, the optical fiber cable of the type in which the grooved spacer having the SZ spiral groove is used and the tape-shaped optical fiber is accommodated in the groove is inevitably impossible with the tape-shaped optical fiber. Bending stress is applied,
In addition to the increase in transmission loss of the optical fiber, there is also a problem in terms of long-term reliability, and it has been said that practical use is difficult.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical fiber cable of a type in which a tape-shaped optical fiber core is accommodated in an SZ groove of a grooved spacer, and the transmission loss of the optical fiber is sufficiently reduced. To provide a cable structure that can be used.

[0007]

In order to achieve this object, the present invention provides a grooved spacer having an SZ helical groove whose helical direction is periodically reversed on the outer periphery, and a grooved spacer having the groove formed therein. In the optical fiber cable provided with the accommodated tape-shaped optical fiber core wire, the reversal angle of the groove of the grooved spacer (the rotation angle in the circumferential direction of the grooved spacer from one reversal part of the groove to the next reversal part) θ Is greater than 180 °, and the tape-shaped optical fiber core is oriented such that the tape surface faces the groove bottom at the center between the inverted parts of the groove (the central part between one inverted part of the groove and the next inverted part). In the reverse part of the groove, assuming that the tape face was stored in the groove with the tape surface facing the groove bottom, with the tape side edge located inside the bend of the groove of the reverse part facing the groove bottom, Housed in a groove. (Claim 1).

Further, in the present invention, when a plurality of tape-shaped optical fiber cores are accommodated in one groove, the plurality of tape-shaped optical fiber cores are provided at the center of the groove between the inverted portions. Are stacked in the depth direction of the groove, and are stacked in the width direction of the groove at the inversion portion of the groove (claim 2).

In the present invention, the cross-sectional dimension of the groove is preferably set to a size such that the circumscribed circle of the cross-section of the laminated body of the tape-shaped optical fiber cores fits in the groove.

In the present invention, the width of the optical fiber ribbon accommodated in the groove is W, the thickness is T, and the number of laminated optical fibers is N.
In this case, it is preferable that the cross-sectional dimension of the groove of the grooved spacer is set so that the inscribed circle diameter E and the depth D of the groove satisfy the following formulas.

[0011]

[Equation 2] D ≧ E ≧ ｛W ² + (NT) ² ｝ ^1/2

The direction of the groove of the grooved spacer (the direction of the opening)
Is constantly changing in the longitudinal direction of the grooved spacer. In the cable of the present invention, the direction of the tape-shaped optical fiber core with respect to the direction of the groove changes in the groove. In other words, the tape-shaped optical fiber core wire has the tape surface facing the groove bottom at the center between the inverted portions of the groove, but at the inverted portion of the groove, when the tape is stored in the groove with the tape surface facing the groove bottom. The orientation in the groove changes such that the side edge of the tape that is on the inside of the bend faces the groove bottom (the tape stands in the groove).

When the orientation in the groove is changed in this way, the tape-shaped optical fiber core is bent mainly in the direction in which the tape surface is curved, even at the center between the inverted portions of the groove or at the inverted portion of the groove. And bending in the direction of bending the side edge of the tape is hardly added. Also, the twist applied to the tape-shaped optical fiber core is reduced. For this reason, the increase in the transmission loss of the optical fiber in the optical fiber ribbon is extremely small.

The reason why the inversion angle of the groove is set to be larger than 180 ° is that the tape-shaped optical fiber core is turned from the state where the tape surface is directed to the groove bottom at the center between the inversion parts of the groove and at the inversion part of the groove. Until the side edge of the tape is directed to the bottom of the groove, a rotation angle of at least 90 ° is required in order to change the direction without difficulty, and the reversal angle of the groove needs to be greater than 180 °. It is.

If the reversal angle of the groove is more than 360 °, the ease of taking out the optical fiber ribbon from the groove is impaired. Considering the ease of taking out the optical fiber ribbon from the groove, the reversal angle of the groove is 360 ° or less. Therefore, the reversal angle of the groove is usually selected within a range of more than 180 ° and 360 ° or less. The preferred range of the groove reversal angle is 2
10 ° to 330 °, more preferably 270 ° to 3 °
00 °.

Further, the cross-sectional dimension of the groove is set to a size such that the circumscribed circle of the cross-section of the laminated body of the tape-shaped optical fiber cores fits in the groove, or the inscribed circle diameter E and the depth D of the groove are expressed by Equation (2). By setting as in the formula, the laminated body of the tape-shaped optical fibers can be easily turned in the groove. This also facilitates dispersion of internal stresses generated when the tape-shaped optical fiber core is bent or twisted. Therefore, setting the dimensions of the groove as described above is also effective in suppressing an increase in the transmission loss of the optical fiber.

Further, the width / thickness of the tape-shaped optical fiber core increases as the number of optical fibers increases, and the adverse effect of bending in the direction of bending the side edge of the tape increases. This is particularly effective when a tape-shaped optical fiber core having four or more cores having a relatively large diameter is used.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 and 2 are explanatory diagrams showing a basic configuration of an optical fiber cable according to the present invention. FIG. 1A schematically shows a cross section of the grooved spacer 11, and FIG. 1B schematically shows a side surface of the grooved spacer 11. Reference numeral 13 'denotes a locus of an SZ spiral groove formed on the outer periphery of the grooved spacer 11. FIGS. 2 (a) to 2 (k) correspond to FIG.
It is sectional drawing in the aa line-kk line of (B).

Reference numeral 11 denotes a grooved spacer, 13 denotes an SZ spiral groove formed on the outer periphery thereof, and 15 denotes a tape-shaped optical fiber core housed in the groove 13. In this example, 3
The tape-shaped optical fiber cores 15 are stored in a stacked state. One by one of three tape-shaped optical fiber core wires 15;
In order to identify the direction, a circle mark and a cross mark are put on one side of the two outer tape-shaped optical fibers 15.

As shown in FIG. 1B, the groove 13 is formed on the outer periphery of the grooved spacer 11 so that the spiral direction is periodically inverted. Reference numeral 17 denotes a reversal portion in the spiral direction of the groove, 19 denotes a central portion between the reversal portions of the groove (a central portion between one reversal portion 17 of the groove and the next reversal portion 17), and P denotes a reversal pitch of the groove (1). Center axis distance of the grooved spacer from one inversion portion 17 to the next inversion portion 17). In FIG. 1A, θ is the reversal angle of the groove (the rotation angle in the circumferential direction of the grooved spacer from one reversal part 17 of the groove to the next reversal part 17). In this example, θ = 300 °. In FIG. 2, only one inversion pitch from (a) to (k) is shown, but at the next one inversion pitch, the state is reversed from (k) to (a), and this is repeated thereafter. Will be.

In the central portion 19 between the inverted portions of the groove 13, FIG.
As shown in the figure, the tape-shaped optical fiber core wire 15 is housed in the groove 13 with the tape surface facing the groove bottom, and the inverted portion of the groove 13
At 17, as shown in FIGS. 2 (a) and 2 (k), the tape-shaped optical fiber core 15 is inserted into the groove 13 with the tape side edge directed toward the groove bottom (with the tape standing in the groove). It is stored.
However, in FIGS. 2A and 2K, the direction of the tape-shaped optical fiber core 15 with respect to the direction of the groove 13 is opposite. That is, in FIG. 2 (a), the side edge of the tape-shaped optical fiber core wire 15 opposite to the mark “・” and “x” faces the groove bottom, but in FIG. The side edge on the mark side faces the groove bottom. In this state, when assuming that the tape-shaped optical fiber core wire 15 is stored in the groove with the tape surface facing the groove bottom in any of the inverted portions, the tape-shaped optical fiber core 15 is located on the inside of the bend of the groove of the inverted portion. Is arranged so that the tape side edge faces the groove bottom.

The "inside of the bend of the groove of the reversing portion" is the portion 17a in FIG. FIG. 3 shows a side surface of the grooved spacer 11 having one SZ spiral groove 13. 17 is groove 13
17a is the inside of the bend of the groove of the reversing part 17, 17b is the outside of the bend of the groove of the reversing part 17, and 19 is the center between the reversing parts.

The tape-shaped optical fiber core wire 15 housed in the groove 13 as described above is connected to the inverted portion 17 at the central portion 19 between the inverted portions.
However, it can be bent mainly in the direction of bending the tape surface. Therefore, this state is the state where the bending of the tape-shaped optical fiber core 15 in the direction of bending the side edge of the tape is the least.

Further, in such a storing method, the twist applied to the tape-shaped optical fiber core 15 is reduced. FIG.
At first glance, (a) to (k), it seems that the laminated body of the tape-shaped optical fiber cores 15 is rotated and twisted in the groove 13, but actually, (a) to (d) In the section and the section from (h) to (k), only the direction of the groove 13 changes, and the direction of the tape-shaped optical fiber core 15 hardly changes.

This means that the optical fiber core 15 is hardly twisted in the above section. The torsion is applied to the tape-shaped optical fiber core 15 mainly in the section from FIG. 2D to FIG. 2H (about 120 ° out of 300 ° inversion angle). In a conventional cable, a twist is applied to the tape-shaped optical fiber core wire at any position between one inverted portion and the next inverted portion. In contrast, the cable of the present invention has a tape-shaped optical fiber core. The twist applied to the line is significantly reduced (about 180 ° less at one reversal pitch).

Next, the reversal angle θ of the groove of the grooved spacer will be described. The direction of the groove 13 is changed from the state shown in FIG. 2A in which the tape-shaped optical fiber core 15 is directed to the groove bottom to the state shown in FIG. 2D in which the tape surface is directed to the groove bottom. 90 °
Need to rotate at a larger angle. Similarly, from the state of (h) to the state of (k), the direction of the groove 13 is 90 degrees.
Must rotate at an angle greater than °. In other words,
In order to obtain a state in which the tape-shaped optical fiber 15 is oriented such that the tape side edge is directed to the groove bottom at the inverted portion of the groove and the tape surface is directed to the groove bottom at the center between the inverted portions of the groove, Each of the grooves needs to rotate at an angle of at least 90 ° in the circumferential direction of the grooved spacer.

Therefore, the reversal angle θ of the groove 13 of the grooved spacer 11 needs to be larger than 180 °. The upper limit of the inversion angle θ of the groove 13 is desirably 360 ° or less as described above. Therefore, the groove reversal angle θ is usually 180 ° <θ ≦ 3
It is set to an appropriate value within the range of 60 °.

The relationship between the direction of the groove 13 and the direction of the tape-shaped optical fiber 15 shown in FIGS. 2A to 2K is an ideal state. Actually, the tape-shaped optical fiber core 15 is a groove 13
Since it is free inside, the direction changes to the most stable state in the groove 13 due to its own elasticity, rigidity, bending force at the inversion portion, or the like. 4A to 4K show specific examples. 4 (a) to 4 (k) respectively show aa in FIG. 1 (B).
It is sectional drawing in the line-kk line.

In the central portion 19 between the inverted portions of the groove 13, the tape-shaped optical fiber core wire 15 is housed in the groove 13 with the tape surface facing the groove bottom as shown in FIG. This is the same as in FIG. In the example of FIG. 4, the direction of the groove 13 is changed from (f).
When rotated by 90 °, that is, in (c) and (i), the tape-shaped optical fiber core wire 15 becomes almost upright in the groove 13,
Further, at the reversal portion 17 of the groove 13, the tape-shaped optical fiber core wire 15 is inclined from the upright state toward the inside of the bend of the groove of the reversal portion 17, as shown in FIGS. In the present invention, "the tape-shaped optical fiber core wire is housed in the groove with the tape side edge facing the groove bottom at the inverted portion of the groove" is shown in FIG.
(A) and (k).

In FIG. 2 and FIG. 4, the whole or a part of the side edge of the laminated body of the tape-shaped optical fiber cores 15 is in contact with the groove bottom at the reversal part of the groove 13; Depending on the tension applied to the tape or the magnitude of the reversal angle of the SZ spiral groove, the side edge of the laminate of the tape-shaped optical fiber core wires may float from the groove bottom without contacting the groove bottom. 5A and 5B show specific examples. FIG. 5A is a view showing a state in which the side edge of the laminated body of the tape-shaped optical fiber core wires 15 in FIG. FIG. 5B is a view showing a state where the side edge of the laminated body of the tape-shaped optical fiber core wires 15 in FIG. 4A is lifted from the groove bottom. 17a indicates the inside of the bend of the inverted portion as described above, and 17b indicates the outside of the bend of the inverted portion. In the present invention, "a tape-shaped optical fiber core wire is housed in a groove with its side edge facing the groove bottom at the inverted portion of the groove" means a tape-shaped optical fiber as shown in FIGS. 5 (A) and 5 (B). This includes the state where the optical fiber core wire 15 is floating from the groove bottom.

The laminated body of the tape-shaped optical fibers accommodated in the SZ spiral groove has a completely laminated state (the tape-shaped optical fibers are not restrained). There may be a case where the side edges are slightly shifted from each other (a state where the side edges are not shifted from each other) (a state where the side edges of each tape-shaped optical fiber core wire are shifted from each other). FIG. 6 (A)
And (B) show specific examples thereof. FIG. 6A shows a state in which the laminated state of the tape-shaped optical fiber cores 15 is slightly shifted when the laminated body of the tape-shaped optical fiber cores 15 is in contact with the groove bottom, and FIG. B) shows a state in which the laminated state of the tape-shaped optical fiber cores 15 is slightly shifted when the laminated body of the tape-shaped optical fiber cores 15 is floating from the groove bottom. In the present invention, "a tape-shaped optical fiber core wire is housed in a groove with its side edge facing the groove bottom at the inverted portion of the groove" means a tape-shaped optical fiber as shown in FIGS. 6 (A) and 6 (B). This includes a state where the lamination state of the laminated body of the optical fiber core wires 15 is slightly shifted.

Next, the dimensions of the groove of the grooved spacer will be described. In order to obtain a state where the tape surface is directed to the groove bottom and a state where the tape side edge is directed to the groove bottom in the groove of the grooved spacer, the tape-shaped optical fiber core must be Without breaking the laminated state in the groove in the groove,
It is preferable that the direction can be relatively changed.
On the other hand, it is extremely difficult to change the size of the groove in the longitudinal direction in manufacturing the grooved spacer. Therefore, assuming that the size of the groove is constant over the entire length, the size of the groove of the grooved spacer may be determined as follows. That is, as shown in FIG. 7, when the width of the tape-shaped optical fiber core 15 is W, the thickness is T, and the number of laminated layers is N, the groove 13 of the grooved spacer 11 is formed.
Are set so as to satisfy the following equations, respectively.

[0033]

[Equation 3] D ≧ E ≧ ｛W ² + (NT) ² ｝ ^1/2

In this manner, the inscribed circle diameter E of the groove 13 is obtained from the length L of the diagonal line of the laminated body of the tape-shaped optical fiber cores 15.
And the depth D is increased, so that the laminated body of the tape-shaped optical fiber cores 15 in the groove 13 can relatively change direction without disturbing the laminated state and generating unreasonable stress. It is possible.

When the grooved spacer is manufactured by extrusion molding, both side walls of the groove may be inclined toward the inside of the bend of the inverted portion at and near the inverted portion of the groove. When the inclination of the groove occurs near the groove, the inscribed circle diameter E and the depth D of the groove may be set so as to satisfy Expression 3 at a portion other than the inverted portion of the groove and the vicinity thereof. Although FIG. 7 shows a case of a rectangular groove, the same can be said for a trapezoidal groove.

FIGS. 8A and 8B show an embodiment of the optical fiber cable according to the present invention. (A) is a cross-sectional view (corresponding to a cross section taken along line ff in FIG. 1) of a center portion between the inverted portions of the groove 13,
(B) is a cross-sectional view (corresponding to the cross section taken along the line aa or the line kk in FIG. 1) of the inverted portion of the groove 13. Grooved spacer 11
Is an extruded product of polyethylene having a tension member 21 of a steel stranded wire at the center. The outer diameter of the grooved spacer 11 is 15.8 mm, and the groove bottom diameter is 10 mm. The cross-sectional dimensions of the groove 13 are such that the groove bottom width is 1.3 mm, the groove top width is 4.5 mm, and the groove depth is 2.3 mm. The inversion angle θ of the groove 13 is about 300 °, and the inversion pitch P is about 240
mm.

Eight grooves 13 are formed in the grooved spacer 11, and one of the grooves 13 accommodates a laminated body of four tape-shaped optical fiber cores 15, one of which is adjacent to the other. The groove 13 accommodated therein a laminated body of two tape-shaped optical fibers 15. The laminated body of the tape-shaped optical fiber cores 15 has the tape surface facing the groove bottom as shown in FIG. 8A at the center between the inverted portions of the groove 13, and as shown in FIG. 8B at the inverted portion. The tape was housed in the groove 13 so that the side edge of the tape faced the groove bottom. Each of the tape-shaped optical fibers 15 was kept in the groove 13 so that no tension was applied. In addition, 23 is a holding roll, and 25 is a sheath.

Each tape-shaped optical fiber core 15 is shown in FIG.
As shown in the figure, a common coating 29 is applied to four optical fibers 27 arranged in parallel. The cross-sectional dimensions are 1.1 mm in width and thickness.
0.4 mm. FIG. 9 (D) shows a cross-sectional dimension of a laminated body of four tape-shaped optical fiber core wires 15, and FIG. 9 (B) shows a cross-sectional dimension of a laminated body of two tape-shaped optical fiber core wires 15.
It is as follows.

The above-mentioned optical fiber cable was made as a prototype, and the tape-shaped optical fiber core wire was housed in the groove of the grooved spacer, and the presser winding 23 was wound, and the tape 25 was formed. The transmission loss of the optical fiber 15 was measured. The measurement wavelength λ is 1.55 μm. Table 1 shows the results.

[0040]

[Table 1]

Since the target value of the transmission loss was 0.25 dB / km or less on average, it was confirmed that this cable had sufficient performance.

Also, depending on the manufacturing conditions, FIG.
As shown in (B), the laminate of the tape-shaped optical fibers 15 may float from the groove bottom at the reversal part of the groove 13, but also in this case, the transmission loss becomes 0.25 dB / km or less. It was confirmed that it had sufficient performance. Note that FIG.
(A) is a cross-sectional view (corresponding to a cross section taken along the line ff in FIG. 1) of the groove 13 at the center between the inverted portions, and (B) is a cross-sectional view (aa line or k in FIG. 1) of the inverted portion of the groove 13. −corresponding to the k-line section).

FIGS. 11A to 11C show another embodiment of the optical fiber cable according to the present invention. 1A is a cross-sectional view (corresponding to a cross section taken along the line aa in FIG. 1) of the groove 13 at one inversion portion, and FIG. 1B is a cross-sectional view at the center between the inversion portions of the groove 13 (line ff in FIG. 1). (C) is a cross-sectional view (corresponding to a cross section taken along the line kk in FIG. 1) of the other inverted portion of the groove 13. The grooved spacer 11 is an extruded product of polyethylene, and has a tension member 21 made of a single steel wire at the center. Outer diameter of grooved spacer 11 is 10.8 mm, groove bottom diameter is 8.0 mm
It is. The cross-sectional dimensions of groove 13 are groove width 2.0 mm and groove depth 1.4
mm. The inversion angle θ of the groove 13 is about 290 °, and the inversion pitch P is about 250 mm.

Five grooves 13 are formed in the grooved spacer 11, and one tape-shaped optical fiber core 15 is formed in the first groove 13.
In the second groove 13, a laminated body of two tape-shaped optical fiber cores 15 is inserted. In the third groove 13, a laminated body of three tape-shaped optical fiber cores 15 is inserted. The numbered groove 13 accommodated therein a laminated body of two tape-shaped optical fibers 15. The tape-shaped optical fiber core wire 15 and the laminate thereof are arranged such that the tape surface faces the groove bottom as shown in FIG. 11B at the center between the inverted portions of the groove 13 and FIG. ), The tape was housed in the groove 13 such that the side edge of the tape faced the groove bottom. Each of the tape-shaped optical fibers 15 was kept in the groove 13 so that no tension was applied. In addition, 23 is a holding roll, and 25 is a sheath.

Each tape-shaped optical fiber core 15 is shown in FIG.
As shown in FIG. 7, a common coating 29 is applied to four optical fibers 27, and the cross-sectional dimensions thereof are 1.1 mm in width and 0.4 mm in thickness. The cross-sectional dimension of the laminated body of the two tape-shaped optical fiber cores 15 is as shown in FIG. 9B, and the cross-sectional dimension of the laminated body of the three tape-shaped optical fiber cores 15 is shown in FIG. It is as follows.

The optical fiber cable as described above was prototyped, and the tape-shaped optical fiber core wire was stored in the groove of the grooved spacer, and the holding tape 23 was wound, and the tape-shaped optical fiber cable was provided with the sheath 25. The transmission loss of the optical fiber 15 was measured. The measurement wavelength λ is 1.55 μm. Table 2 shows the results.

[0047]

[Table 2]

Since the target value of the transmission loss was 0.25 dB / km or less on average, it was confirmed that this cable had sufficient performance.

Further, depending on the manufacturing conditions, FIG.
As shown in (C), the laminated body of the tape-shaped optical fiber cores 15 may be in a state of being floated from the groove bottom at the reversal part of the groove 13, but also in this case, the transmission loss is 0.25 dB / km or less. And it was confirmed that it had sufficient performance. FIG. 1
2A is a cross-sectional view (corresponding to a cross section taken along line aa in FIG. 1) of one inversion portion of the groove 13, and FIG. 2B is a cross-sectional view of a center portion between the inversion portions of the groove 13 (ff in FIG. 1). (Corresponds to the line section), (C)
Is a cross-sectional view (corresponding to a cross section taken along the line kk in FIG. 1) of the other inversion portion of the groove 13.

FIGS. 13A and 13B show still another embodiment of the present invention. (A) is a cross-sectional view (corresponding to a cross section taken along the line ff in FIG. 1) of the groove 13 at the center between the inverted portions, and (B) is a cross-sectional view (aa line or k in FIG. 1) of the inverted portion of the groove 13. −corresponding to the k-line section). In this embodiment, a laminated body of a plurality of tape-shaped optical fiber cores 15 is provided with a grooved spacer 11 in a state in which a cushioning protective tape 31 made of foamed plastic or the like is arranged along a surface on which the side edges of the tape are arranged. In the groove 13. By doing so, the side edge of the tape-shaped optical fiber core 15 is not directly pressed against the groove bottom or the groove wall, which is effective for suppressing an increase in transmission loss.

FIG. 14 shows still another embodiment of the present invention. In this embodiment, the grooved spacer 11 is individually grooved.
This is an example in which a plurality of segment-shaped groove members 33 having 13 are twisted around the tension member 21 by SZ twist. The other configuration is the same as that of the embodiment of FIG. 11, and therefore the same portions are denoted by the same reference numerals and description thereof will be omitted.

In the above embodiment, a grooved spacer having a plurality of grooves is used. However, the number of grooves in the grooved spacer used in the present invention is not limited. And as shown in FIG. 3, it may have only one groove.

In the above embodiment, the case where a tape-shaped optical fiber having a thickness of 0.4 mm is used has been described. However, in the present invention, a tape-shaped optical fiber having a different thickness can be used. . For example, with 4 cores, 0.25-0.27mm thick,
Uses a 1.1 mm wide tape-like optical fiber core (this is a tape-like optical fiber with a thickness almost the same as the outer diameter of the optical fiber because the outer diameter of the optical fiber is 0.25 mm) Then, assuming that a laminated body of five tape-shaped optical fiber cores is accommodated in one groove, the groove width is 1.6 mm and the groove depth is 1.6.
mm, the outer diameter of the grooved spacer having five grooves can be about 11 mm. As a result, it has been found that the storage density of the tape-shaped optical fiber cores can be increased, and the arrangement of the tape-shaped optical fiber cores due to the external force at the cable cut end can be prevented. In addition, the transmission loss of a tape-shaped optical fiber cable with a cable of this size is
0.21dB / km on average, minimum 0.
19dB / km, maximum 0.25dB / km, average was 0.20dB / km, minimum 0.19dB / km, maximum 0.24dB / km at the stage of "sheathing".

FIGS. 15A to 15C show still another embodiment of the optical fiber cable according to the present invention. (A) is a groove
13 is a cross-sectional view (corresponding to a cross section taken along the line aa in FIG. 1) of one of the inverted portions, FIG. 13B is a cross-sectional view (corresponding to a cross section taken along the line ff in FIG. (C) is a cross-sectional view of the other inverted portion of the groove 13 (corresponding to a cross section taken along line kk in FIG. 1).
It is. In this cable, among a plurality of SZ spiral grooves 13 formed in a grooved spacer 11, a tape-shaped optical fiber core wire 15 is housed in some of the grooves, and a single-core optical fiber is The fiber core 35 is housed and filled with jelly 37.

The grooved spacer 11 is an extruded product of polyethylene, and has a tension member 21 at the center. The outer diameter of the grooved spacer 11 is 15.6 mm. The cross-sectional dimensions of the groove 13 are as follows: groove numbers 1, 4, 5, and 6 where the groove bottom width and the groove top width are equal have a groove width of 2.4 mm and a groove depth of 3.4 mm. Groove numbers 2 and 3 have a large groove bottom width of 2.0m
m, groove top width 4.3 mm, groove depth 3.4 mm. The inversion angle θ of the groove 13 is about 280 °, and the inversion pitch P is about 250 mm.

Three tape-shaped optical fiber cores 15 were stacked and stored in the grooves 13 of the groove numbers 1 and 4. No. 2 and No. 3 grooves
13 contains four single-core optical fiber cores 35 and is filled with jelly 37. The tape-shaped optical fiber core 15 has a groove
At the center between the reversing portions 13, the tape side faces the groove bottom as shown in FIG. 15B, and at the reversing portion, the tape side edges are inclined as shown in FIGS. Facing the groove
Stored in 13. Each of the tape-shaped optical fibers 15 was kept in the groove 13 so that no tension was applied. Note that
Reference numeral 23 denotes a holding roll, and reference numeral 25 denotes a sheath.

Each of the optical fibers 15 is shown in FIG.
As shown in FIG. 1, a common coating 29 is applied to four optical fibers 27, and the cross-sectional dimensions thereof are 1.1 mm in width and 0.4 mm in thickness.
FIG. 9C shows the cross-sectional dimensions of the laminate of the three tape-shaped optical fibers 15. The single-core optical fiber 35 is a nylon-coated core having an outer diameter of 0.9 mm.

The optical fiber cable as described above is manufactured as a trial, and the tape-shaped optical fiber core 15 and the single-core optical fiber core 35 are housed in the groove of the grooved spacer 11 and the holding coil 23 is wound. At the stage where 25 was performed, the transmission loss of each optical fiber core was measured. The measurement wavelength λ is 1.55 μm. As a result, the transmission loss of the tape-shaped optical fiber cable is
0.22dB / km on average, minimum 0.
The average was 0.23 dB / km, the minimum was 0.21 dB / km, and the maximum was 0.24 dB / km when the sheath was applied. In addition, the transmission loss of a single-core optical fiber cable is 0.21 dB / km on average and 0.20 dB / k minimum at the “stage when the holding coil is wound”.
m, maximum 0.21dB / km, average 0.2 at "stage with sheath"
It was 2 dB / km, minimum 0.21 dB / km, maximum 0.23 dB / km.
Therefore, it was confirmed that this cable also had sufficient performance.

In general, when a single-core optical fiber core is housed in an SZ spiral groove, it becomes unstable in a laid state due to the characteristics of the groove. By filling jelly only in the groove in which is stored, the single-core optical fiber can be semi-fixed, and an optical fiber cable having stable characteristics can be obtained.

FIGS. 16A to 16C show still another embodiment of the optical fiber cable according to the present invention. (A) is a groove
13 is a cross-sectional view (corresponding to a cross section taken along the line aa in FIG. 1) of one of the inverted portions, FIG. 13B is a cross-sectional view (corresponding to a cross section taken along the line ff in FIG. (C) is a cross-sectional view of the other inverted portion of the groove 13 (corresponding to a cross section taken along line kk in FIG. 1).
It is. The cable has a plurality of SZ spiral grooves 13 formed in a grooved spacer 11 and tape-shaped optical fiber cores 15.
And filled with Jerry 37.
This cable structure has an effect that the water running property in the cable is sufficiently suppressed by the jelly.

FIGS. 17 and 18 show still another embodiment of the optical fiber cable according to the present invention. FIG. 17 (A)
Is a cross-sectional view (corresponding to a cross section taken along the line aa in FIG. 1) of one inversion portion of the groove 13, and FIG. Equivalent). Although a cross-sectional view of the other inverted portion of the groove 13 is omitted, it is left-right symmetric with respect to FIG. Also, the holding roll and the sheath are not shown.

In this embodiment, the groove 13 has a trapezoidal cross section, and ten 8-core tape-shaped optical fiber cores 15 are stacked and housed in the trapezoid. 8-core optical fiber ribbon
The cross-sectional dimensions of 15 are 2.2 mm in width and 0.27 mm in thickness.
The cross-sectional dimension of the stacked body is 2.7 mm in thickness and 3.48 mm in diagonal length. On the other hand, the groove 13 of the grooved spacer 11 is a trapezoidal groove, and its cross-sectional dimensions are, for example, a groove bottom width of 3.2 mm, a groove top width of 5.2 mm, and a groove depth of 4.5 mm. This dimension has a groove bottom width (3.2 mm) smaller than the diagonal length (3.48 mm) of the laminate, but is large enough to accommodate the circumcircle M of the cross section of the laminate of the tape-shaped optical fiber cores 15. The body can turn freely in the groove 13.

Therefore, no excessive stress is applied to the tape-shaped optical fiber core 15, as in the embodiments shown in FIGS. 8, 10, 11 and the like. The transmission loss of the tape-shaped optical fiber cable with a cable of this size is 0.21 dB / km on average, 0.19 dB / km minimum, and 0.24 dB maximum at the "stage when the holding coil is wound".
km, 0.21 dB / km on average at the “sheathed stage”, min.
It was 19 dB / km and the maximum was 0.25 dB / km.

In the case of a trapezoidal groove, as in this embodiment, the cross-sectional dimension of the groove 15 is such that the circumscribed circle M of the cross-section of the laminated body of the tape-shaped optical fiber cores 15 can be accommodated, and the width of the groove bottom is set to the tape-shaped If the width is larger than the fiber core wire 15 and smaller than the length of the diagonal line of the laminate, the groove size can be made relatively small, so that a large number of grooves 13 are formed on the outer periphery of the grooved spacer 11 as shown in FIG. It is effective in constructing a high-density cable.

[0065]

As described above, according to the present invention, an optical fiber having a tape-shaped optical fiber core wire housed in a groove of a grooved spacer having an SZ helical groove whose helical direction is periodically reversed on the outer periphery. In the fiber cable, since the torsion applied to the tape-shaped optical fiber and the bending mainly in the direction of bending the side edge of the tape can be reduced, the transmission loss of the tape-shaped optical fiber can be suppressed sufficiently. Therefore, the present invention greatly contributes to the practical use of this type of cable.

[Brief description of the drawings]

FIG. 1A is a schematic diagram illustrating a cross section, and FIG. 1B is a schematic diagram illustrating a side surface, for describing an optical fiber cable according to the present invention.

2 (a) to 2 (k) each show an example of the relationship between the direction of a groove and the direction of an optical fiber ribbon. FIG.
Sectional drawing in the aa line-kk line of FIG.

FIG. 3 is a side view showing an example of a grooved spacer used in the present invention.

FIGS. 4A to 4K show other examples of the relationship between the direction of the groove and the direction of the optical fiber ribbon, and are cross-sectional views taken along lines aa to kk in FIG. FIG.

FIGS. 5A and 5B are cross-sectional views each showing a state in which a laminated body of tape-shaped optical fibers is floating from a groove bottom at an inverted portion of the groove.

FIGS. 6A and 6B are cross-sectional views each showing a state in which the lamination state of the tape-shaped optical fibers in the grooves is slightly shifted;

FIG. 7 is a cross-sectional view showing the relationship between the dimension of the tape-shaped optical fiber core wire and the dimension of the groove of the grooved spacer in the optical fiber cable according to the present invention.

FIG. 8A is a cross-sectional view of the optical fiber cable according to one embodiment of the present invention, which is taken at a central portion between the inverted portions of the groove;
(B) is a cross-sectional view of the inversion of the groove.

FIGS. 9A to 9D are cross-sectional views each showing a laminated state of tape-shaped optical fibers.

FIG. 10A is a cross-sectional view of an optical fiber cable according to another embodiment of the present invention, showing a central portion between the inverted portions of the groove;
(B) is a cross-sectional view of the inversion portion of the groove.

11 (A) and (C) are cross-sectional views of the optical fiber cable according to still another embodiment of the present invention at the inverted portion of the groove, and FIG. 11 (B) is a cross-sectional view at the center between the inverted portions of the groove.

12 (A) and 12 (C) are cross-sectional views of the optical fiber cable according to still another embodiment of the present invention at the inverted portion of the groove, and FIG. 12 (B) is a cross-sectional view at the center between the inverted portions of the groove.

13A is a cross-sectional view of an optical fiber cable according to still another embodiment of the present invention, in which FIG.

FIG. 14 is a cross-sectional view of an optical fiber cable according to still another embodiment of the present invention at a central portion between inverted portions of a groove.

FIGS. 15A and 15C are cross-sectional views of an optical fiber cable according to still another embodiment of the present invention, in which a cross-section is taken at an inverted portion of a groove, and FIG.

FIGS. 16A and 16C are cross-sectional views of the optical fiber cable according to still another embodiment of the present invention, in which (A) and (C) are cross-sectional views at the inverted portion of the groove, and FIG.

FIG. 17A is a cross-sectional view of an optical fiber cable according to still another embodiment of the present invention, in which the groove is the inverted portion;
(B) is a cross-sectional view of a central portion between the inverted portions of the groove.

18 is an enlarged cross-sectional view showing the relationship between the dimensions of the optical fiber ribbon and the groove dimensions in the cable of FIG. 17;

[Explanation of symbols]

 11: grooved spacer 13: SZ spiral groove 13 ': track of groove 13 15: tape-shaped optical fiber core wire 17: inverted portion of groove 13 19: central portion between inverted portions of groove 13 27: optical fiber 29: Common coating

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuo Hokari, Inventor 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Shigekazu Hayami 1-1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (58) Fields surveyed (Int.Cl. ⁶ , DB name) G02B 6/44 366

Claims (5)

(57) [Claims] 1. An SZ in which the helical direction is periodically inverted on the outer periphery.
In an optical fiber cable including a grooved spacer having a spiral groove and a tape-shaped optical fiber core wire housed in the groove of the grooved spacer, the reversal angle of the groove of the grooved spacer (1 of the groove) Rotation angle in the circumferential direction of the grooved spacer from one reversing part to the next reversing part)
θ is greater than 180 °, and the tape-shaped optical fiber core is oriented with the tape face toward the groove bottom at the center between the inverted parts of the groove (the central part between one inverted part of the groove and the next inverted part). In the state, in the state where the tape side is located inside the bend of the groove of the reversing part, with the tape side edge facing the groove bottom, assuming that the tape face is directed to the groove bottom and stored in the groove at the reversal part of the groove An optical fiber cable, which is housed in a groove. 2. The optical fiber cable according to claim 1, wherein a plurality of tape-shaped optical fiber cores housed in the same groove are laminated in the depth direction of the groove at the center between the inverted portions of the groove. In addition, the inversion portion of the groove is stacked in the width direction of the groove. 3. The optical fiber cable according to claim 1, wherein the cross-sectional dimension of the groove of the grooved spacer is such that the circumscribed circle of the cross-section of the laminated body of the tape-shaped optical fiber core wires fits in the groove. It is characterized by becoming. 4. The optical fiber cable according to claim 1, wherein the width of the tape-shaped optical fiber core is W, the thickness is T, and the number of laminated fibers is N, wherein The tangent diameter E and the depth D of the groove each satisfy the following expression. [Equation 1] D ≧ E ≧ ｛W ² + (NT) ² ｝ ^1/2 5. The optical fiber cable according to claim 1, wherein the tape-shaped optical fiber core is a cable.
Features having an optical fiber with more than the core.