JP6459833B2 - Fiber optic cable - Google Patents

Description

  The present invention relates to an optical fiber cable, and more particularly, to an optical fiber cable including a slot rod formed with a plurality of grooves for accommodating a plurality of optical fiber ribbons.

  A type including a slot rod (also referred to as a spacer) in which a plurality of grooves are formed is distributed in the optical fiber cable. Each groove can accommodate an optical fiber tape core (hereinafter referred to as a tape core) in which a plurality of optical fibers are arranged in parallel. A tension member is embedded in the center of the slot rod, while the outside of the slot rod is wound with, for example, a press-wound tape and further covered with a cable jacket (also referred to as a sheath).

  When the accommodated tape core wire receives pressure from the side wall of the groove, microbend loss or macro bend loss occurs, and the transmission characteristics of the optical fiber core wire deteriorate. In order to avoid this, for example, Patent Document 1 discloses a technique for freely rotating a tape core wire in a groove.

JP 2014-211151 A

By the way, when the optical fiber cable is bent in an arc shape, the tension member becomes the bending center, tensile stress is generated outside the tension member, and compressive stress is generated inside the tension member. Causes compression distortion. If this tape core wire can be moved in the longitudinal direction of the cable so as to cancel the compressive strain, a slight transmission loss is sufficient.
However, when the tape core is mounted in the groove at a high density, it becomes difficult to move the tape core in the longitudinal direction of the cable, and the part that cannot withstand the compressive strain jumps out of the groove. Bendros may occur. Therefore, it is desired to suppress the occurrence of macrobend loss even if the tape core wire is mounted in the groove of the slot rod at a high density.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical fiber cable that can suppress the occurrence of macrobend loss even when a tape core wire is mounted in a groove at a high density. And

Optical fiber cable according to one embodiment of the present invention, a plurality of optical fibers and an optical unit ribbons were collected plurality arranged in parallel, plural rows have a groove you accommodating a plurality of optical units An optical fiber cable comprising a slot rod, a tension member to which tension is applied, and a cable jacket covering the outside of the slot rod, wherein a plurality of the optical units are housed in each of the plurality of grooves. Each of the optical units is pre-twisted into a circular cross-sectional shape and stored in the groove, and the optical unit occupancy calculated from the cross-sectional area of the optical unit with respect to the cross-sectional area of the groove is The twist pitch of the optical unit is shorter than the twist pitch of the groove.

  According to the above, even if the tape core wire is mounted in the groove at a high density, the occurrence of macrobend loss can be suppressed.

It is a figure which shows an example of the optical fiber cable by 1st Embodiment of this invention. It is sectional drawing which shows an example of an optical fiber cable. It is a figure which shows an example of the structure of an intermittent tape core wire. It is a figure for demonstrating the state which bent the optical fiber cable in circular arc shape. It is a figure for demonstrating the slot rod by other embodiment.

[Description of Embodiment of the Present Invention]
First, the contents of the embodiment of the present invention will be listed and described.
Optical fiber cable according to one embodiment of the present invention, the groove you housing (1) and the optical unit ribbons were collected plurality of arranging the plurality of optical fibers in parallel, a plurality of light units and plural rows slots rods having a tension member tension is loaded, an optical fiber cable with the cable jacket capital covering the outside of the slot rod, wherein the light unit each of the grooves of said plural rows Before being housed in a plurality of pieces, each of which is pre-twisted into a round cross-sectional shape and housed in the groove, and is calculated from the cross-sectional area of the optical unit with respect to the cross-sectional area of the groove. The occupation ratio is 25% or more and 60% or less, and the twist pitch of the optical unit is shorter than the twist pitch of the groove. By storing the pre-twisted optical unit in the groove of the slot rod, the occurrence of macrobend loss can be suppressed even if the tape core wire is mounted in the groove at a high density. Specifically, if the occupancy is 60% or less in a state where the optical unit is twisted, even if the cable is bent in an arc shape, the compressive strain is dispersed without concentrating on some optical fiber core wires. Generation of macrobendros can be suppressed and cable bending characteristics can be improved. Further, if the occupancy ratio in the twisted optical unit is 25% or more, the density can be increased. As a result, the transmission loss of the optical fiber core can be kept small even if the tape core is mounted in the groove at a high density. In addition, since the compressive strain is dispersed as compared with the case where the twist pitch of the optical unit is equal to or longer than the twist pitch of the grooves, the cable bending characteristics can be easily improved.

(2) As for the said tape core wire, the connection part and the non-connection part are intermittently formed in the longitudinal direction between the said adjacent optical fiber core wires. If the optical unit is composed of intermittent tape cores, the intermittent tape cores are more flexible than general tape cores, so that the occupation ratio can be increased. (3) before Kimizo is than SZ locus and the short period of the short period is constructed by combining the SZ locus long period. The cable is wound around the body of a take-up drum (not shown) with a relatively high tension in order to prevent the coil from collapsing, and the tension applied to the upper-layer cable becomes the side pressure of the lower-layer cable. Therefore, if the groove is configured as a composite type of SZ on SZ, the period becomes random (not constant), so the side pressure generated in the tape core wire during drum winding can be randomized, which also improves the side pressure characteristics. Contribute.

[Details of the embodiment of the present invention]
Hereinafter, preferred embodiments of an optical fiber cable according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a view showing an example of an optical fiber cable according to the first embodiment of the present invention, FIG. 2 is a cross-sectional view showing an example of an optical fiber cable, and FIG. 3 is an example of the structure of an intermittent tape core wire. FIG.

  The optical fiber cable 1 shown in FIGS. 1 and 2 is an SZ twisted tape slot type cable, and is an optical unit 17, a slot rod 20, and a presser winding wound around the slot rod 20 in vertical or horizontal winding. A tape 30 and a cable jacket 31 that covers the outside of the press-wound tape 30 are provided. FIG. 1 is a schematic diagram when the intermediate branch is made. The cable jacket 31 and the holding tape 30 shown in FIG. 2 are partially removed, and the slot rod 20 and the optical unit hanging from the slot rod 20 are shown. 17 is visible. Moreover, the twist pitch P of the slot groove | channel 22 is comprised by the inversion part, the S twist part, the inversion part, the Z twist part, and the inversion part.

As shown in FIG. 2, the slot rod 20 has a tension member 21 embedded in the center thereof. The tension member 21 is made of a wire having a resistance to tension and compression, for example, a steel wire or FRP (Fiber Reinforced Plastics).
A plurality of (for example, five) SZ-shaped slot grooves 22 are formed on the outer peripheral surface of the slot rod 20 along the longitudinal direction of the cable. The slot groove 22 corresponds to the groove of the present invention.

  The optical unit 17 includes, for example, six 12-fiber intermittent tape cores 10 stacked to form 72 cores, and is further twisted in a spiral in one direction and bundled with a bundle member for identification (not shown). The optical unit may be twisted together in an SZ shape such as a spiral shape that is periodically reversed, in addition to a structure twisted in a spiral shape in one direction.

  The intermittent tape core wire is formed by arranging a plurality of optical fiber core wires in parallel and intermittently connecting adjacent optical fiber core wires by a connecting portion and a non-connecting portion. Specifically, FIG. 3 (A) shows a state in which the intermittent tape core wires are opened in the arrangement direction, and FIG. 3 (B) shows a cross-sectional view taken along line BB in FIG. 3 (A). The illustrated intermittent tape core wire 10 is configured by intermittently connecting 12 core tape wires every two fibers.

  As shown in FIG. 3B, a tape coating 14 made of an ultraviolet curable resin or the like is provided around each optical fiber core wire 11, for example, the core wires in which two cores are integrated are not connected to the connecting portion 12. The parts 13 are intermittently connected. In the connecting portion 12, the adjacent tape coatings 14 are continuous, and in the non-connecting portion 13, the adjacent tape coatings 14 are separated without being connected.

  The optical fiber core accommodated in the intermittent tape core wire is further coated with a colored coating on the outside of what is called an optical fiber strand obtained by coating a glass fiber having a standard outer diameter of 125 μm with a coating outer diameter of about 250 μm. Therefore, the number of optical fiber core wires accommodated is arbitrary. In addition, an intermittent tape core wire does not need to provide a connection part and a non-connection part for every 2 cores, for example, may connect intermittently with a connection part and a non-connection part for every 1 core.

Each slot groove 22 described in FIG. 2 accommodates, for example, four bundles of optical units 17 (72 cores) in a state of being twisted in a spiral in one direction, for example, and includes five slot grooves 22. The optical fiber cable 1 constitutes a 1440-core cable. The twisting of the optical unit and the storing in the slot can be performed in the same process.
The slot rod 20 is wound with a press-wound tape 30 so that the optical unit 17 does not jump out, and is collected into a round shape, for example.

As the press-wrapping tape 30, for example, a non-woven fabric formed in a tape shape, a laminate of a base material such as polyethylene terephthalate (PET) and the non-woven fabric, or the like is used. In addition, you may provide a water absorbing agent (for example, water absorption powder) to the press-wound tape. If the holding tape functions as a water absorbing layer, it is possible to stop water on the intermittent tape core.
The outer side of the press-wound tape 30 is covered with a cable jacket 31 made of, for example, PE (polyethylene), PVC (polyvinyl chloride), or the like, and is formed in a round shape, for example.

FIG. 4 is a diagram for explaining a state where the optical fiber cable is bent in an arc shape.
When the optical fiber cable is bent in an arc shape, the tension member becomes the bending center, tensile stress is generated outside the tension member, and compressive stress as shown by the arrow in FIG. A compressive strain is generated in the tape core located at the position. If this tape core wire can be moved in the longitudinal direction of the cable so as to cancel the compressive strain, a slight transmission loss is sufficient.

However, when the tape core wire is mounted in the slot groove at a high density, it becomes difficult to move the tape core wire in the cable longitudinal direction, and the portion that cannot withstand the compressive strain jumps out of the slot groove. In some cases, macrobendros may occur.
Therefore, in the present embodiment, the optical unit 17 previously twisted in, for example, a unidirectional spiral described in FIG. 2 is accommodated in the slot groove 22 so that the tape core wire can be mounted in the slot groove with high density. The occurrence of macrobendros is controlled.

  More specifically, the occupation ratio calculated from the cross-sectional area of the optical unit 17 with respect to the cross-sectional area of the slot groove 22 described in FIG. 2 (that is, the total cross-sectional area of the tape core wire / the cross-sectional area of the slot groove) is 25% or more and 60% or less. It is said. Note that the total cross-sectional area of the tape core wire includes the cross-sectional areas of the tape coating 14 and the tape 15 described in FIG. Further, as the number of the optical units 17 increases, the cross-sectional area increases.

Then, the twist pitch of the optical unit 17 is set to 500 mm, the twist pitch P of the slot groove 22 is set to 700 mm, and the occupation ratio is set to 50%, and the optical fiber cable 1 is bent so as to form an arc of φ500 mm. Transmission loss was measured.
When a conventional optical fiber cable (with an untwisted tape core wire housed in a slot groove) is bent into an arc shape, the transmission loss (wavelength 1550 nm) is 1 dB / km or more. When the optical fiber cable 1 (with the twisted optical unit 17 housed in the slot groove 22) was bent into an arc shape, the transmission loss was 0.1 dB / km or less.

  Further, when the experiment was performed while changing the occupancy rate, transmission loss could not be suppressed when the occupancy rate exceeded 60% with twisted optical units. This is considered to be because the macrobendros increased because the part that could not withstand the compressive strain popped out. Therefore, it can be seen that if the occupation ratio is 60% or less, the cable bending characteristics can be improved even if the tape core wires are mounted in the slot grooves at a high density.

  On the other hand, when the occupation ratio of the twisted optical unit is less than 25%, it is not possible to increase the density.

Further, by twisting the optical units, the above-mentioned occupancy can be realized even if a general tape core is used, but if it is constituted by an intermittent tape core, it has flexibility, so it is easier to increase the density. be able to.
Furthermore, if the twist pitch of the optical unit is made shorter than the twist pitch of the slot groove, the compressive strain is more easily dispersed than if the twist pitch of the slot groove is equal to or longer than that of the slot groove. Become easier.

FIG. 5 is a view for explaining a slot rod according to another embodiment.
In the above-described embodiment, the slot groove is configured by one type of twist pitch, but is configured by combining an SZ locus made of a short cycle, for example, a sine curve, and an SZ locus made of, for example, a sine curve having a longer period than the short cycle. (Composite SZ type; also referred to as SZ on SZ).
Specifically, in FIG. 5, the short period pitch P is set to 700 mm, and the long period pitch P ′ is set to about 9100 mm. The cable is wound around the body of a take-up drum (not shown) with a relatively high tension in order to prevent the cable from collapsing, and the tension applied to the upper cable becomes the side pressure of the lower cable. Therefore, if the slot groove is configured as a composite SZ type, the cycle becomes random (not constant), so the side pressure generated in the intermittent tape core wire during drum winding can be randomized, which also contributes to the improvement of the side pressure characteristics. To do.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber cable, 10 ... Intermittent tape core wire, 11 ... Optical fiber core wire, 12 ... Connection part, 13 ... Non-connection part, 14 ... Tape coating | cover, 17 ... Optical unit, 20 ... Slot rod, 21 ... Tension member , 22 ... slot groove, 23 ... slot rib, 30 ... holding tape, 31 ... cable jacket.

Claims (3)

An optical unit ribbons were collected plurality of arranging the plurality of optical fibers in parallel, a slot rod having plural rows of grooves you accommodating a plurality of optical units, a tension member tension is loaded And an optical fiber cable comprising a cable jacket covering the outside of the slot rod,
Before the optical unit is housed in each of the plurality of grooves , each of the optical units is pre-twisted into a circular cross-sectional shape and stored in the groove, and the optical unit with respect to the cross-sectional area of the groove The occupancy of the optical unit calculated from the cross-sectional area is 25% or more and 60% or less,
An optical fiber cable, wherein a twist pitch of the optical unit is shorter than a twist pitch of the groove.   2. The optical fiber cable according to claim 1, wherein the tape core wire has a connection portion and a non-connection portion formed intermittently in a longitudinal direction between the adjacent optical fiber core wires.   The optical fiber cable according to claim 1 or 2, wherein the groove is configured by combining a short-period SZ locus and an SZ locus having a longer period than the short period.

Images