JPH0315802A - Method for laying optical line and optical fiber cable used therefor - Google Patents

Abstract

PURPOSE:To branch the optical fiber cable without connecting optical fibers by integrating the optical fiber units corresponding to a required length and number of pieces including branch lines and simultaneously taking out the optical fiber units for the branch optical lines while laying the main optical line. CONSTITUTION:The optical fiber cable constituted by integrally housing the optical fiber units 5 of the length at which the main optical line can be formed from a start point to an end point and the optical fiber units 3, 4 of the length at which the branch optical lines can be formed from the start point via a branch point to the end point is used. The optical fiber cable is integrally led in from the start point up to the branch point. The leading in of the optical fiber cable is continued while the optical fiber cable is separated to the optical fiber units 5 for the main optical line and the optical fiber units 3, 4 for the branch optical lines at the branch point. The need for operations, such as connection of optical fibers, is eliminated at the branch point. The man-hours for operations are decreased and the attenuation of light signals occurring in the connection is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the structure of an optical fiber cable and its installation and branching method applied to an optical fiber cable installation route having branch points.

BACKGROUND OF THE INVENTION With the recent development of optical technology, large-scale optical systems using optical fiber cables have been realized. Optical fiber cable lines in such systems are usually formed including several branches, and the following methods have been proposed and implemented for laying optical fiber cable lines including branches. There is.

(1) A method of arranging the cables necessary to configure that section between each cable branch point, and connecting each branch point with the cable placed together with the main optical line, (2) Multiple optical fibers. After laying optical fiber cables equipped with units along the entire trunk route, only the optical fibers to be branched out at each branch point are taken out and connected to the branch cables, a method called "return branching." (4) Prepare optical fiber cables corresponding to the distance from the starting point to each terminal via each branch point, and connect them to each other using a common trunk route. How to install it, etc. These various installation methods are selected and implemented as appropriate depending on the installation mode of the optical fiber cable line, the installation environment, the application, and the like.

Problems to be Solved by the Invention However, the conventional optical fiber cable installation methods described above each have the following problems.

(1) In this method, the optical cable is connected to each branch point, that is, all the optical fibers in the optical cable are connected to each branch point. }, the connection loss accumulates as it goes toward the far end, and the most important feature of optical fiber, low loss, is not utilized. Moreover, this connection work itself is complicated and takes a long time, and is a major cause of increasing installation costs.

(2) In this method, at each branch point, although only the optical unit is required there, it is necessary to connect the branch cable and the optical fiber, and the connection work including the protection of the branch part is This is still a major factor in increasing installation costs.

Furthermore, since there is not enough extra length of optical fiber to be drawn out from the trunk route for splicing, a special fusion splicer is required for splicing the short extra length. Furthermore, the optical fibers remaining on the main route away from the branch point are not used and are wasted.

(3) The method of using a pre-branched optical fiber cable has practical problems, such as the outer diameter of the branch part of a pre-branched optical cable being thicker than that of a normal optical cable, and the difficulty of protecting the optical fiber at the branch part during installation. There are many problems, and the length of the branch cable portion of a prebranched optical fiber cable that can actually be used is limited to several meters.

(4) Although this method has no limitations on obstacles caused by optical fiber connections or on the possible line length, it is necessary to run as many cables through the same route as many times as necessary. Therefore, not only the cost of installing the cable increases, but also the time required for the installation work. Additionally, in routes where multiple cables are laid one on top of the other, space may be restricted due to the capacity of the conduit, and it may not be possible to lay the cables.

An object of the present invention is to provide a novel optical fiber cable installation method and a novel optical fiber cable for realizing the method, which was developed in view of the problems of the prior art as described above. .

According to the means for solving the problem, that is, according to the present invention, there is a main optical line that is continuous from a starting point to a terminal point, and the main optical line is arranged along the same route as the main optical line from the starting point to the branch point, and, A method of laying optical fiber lines formed by optical fiber units by a lead-in method, including branch optical lines arranged so as to follow unique routes from a branch point to each end point, the main optical fiber line An optical fiber unit long enough to form a path from a starting point to a terminal point and an optical fiber unit long enough to form a branched optical path from the starting point to the branching point to the terminal point are integrally accommodated. Using the optical fiber cables that have been installed, the optical fiber cables are drawn all together from the origin to the branch point, and at the branch point, the optical fiber cables are connected to an optical fiber unit for the main optical line and an optical fiber unit for the branch optical line. Provided is a method for laying an optical fiber line, which is characterized in that the optical fiber cable is continued to be drawn in while separating the optical fiber cable into two parts.

Further, as an optical fiber cable that can be advantageously used in the above-mentioned installation method according to the present invention, according to the present invention, a main optical line that is continuous from a starting point to a terminal point, and a continuous optical fiber line that is continuous from a starting point to a branch point of the main optical fiber line and a branch point of the main optical fiber line are provided. Laying optical fiber lines formed by optical fiber units using the pull-in method, including branch optical lines that are arranged along the same route and follow unique routes from the branch point to each end point. An optical fiber cable used in the process, comprising an optical fiber unit of a length that can form the main optical line from the starting point to the ending point, and an optical fiber unit that can form the branch optical path from the starting point to the ending point via the branch point. Provided is an optical fiber cable characterized in that it is constructed by integrally accommodating a length of optical fiber unit.

Function: The method of laying an optical fiber cable according to the present invention uses an optical fiber cable that is fabricated integrally with optical fiber units of the required length and number including each branch line, and after the branch point, the main optical line Its main feature is that the optical fiber unit for the branch optical line can be taken out at the same time while laying the optical fiber cable for the branch optical line.

The optical fiber cable used in this method includes optical fiber units for the main optical line and for the branch optical line, which are long enough to form each optical line from the start point to the end point without connection. When towing and laying this optical fiber cable, when the optical unit to be branched reaches the corresponding branch point, only that optical unit is taken out from the optical fiber cable, and while pulling the cable again, the branch At this point, an optical unit for a branch optical line housed in a cable is obtained. Note that if there are multiple branch points in the route, the work to take out the optical unit from within the cable is performed at each branch point.

By using such a laying method, at the same time as the laying of the main optical line is completed, optical units for the required length of the lead-in route are obtained at each branch point, and by laying them on the branch optical line, the optical line can be The installation of optical fiber cable throughout the area is completed.

According to the installation method according to the present invention, unlike the conventional installation methods (1) and (2), work such as connecting optical fibers at branch points is not required, so the work is easy. At the same time, there is no attenuation of the optical signal due to the connection.

Further, unlike the conventional laying method (3), there is no particular restriction on the length that can be used, and the branch line unit can be easily protected.

Furthermore, unlike the conventional installation method (4), there is no need to repeat the cable threading operation many times, and the number of man-hours and working time is extremely small.

In addition, when using the optical cable according to the present invention in the installation method according to the present invention, if the optical fiber unit is twisted in the longitudinal direction within the cable, at least the unit It is desirable that the cable structure is such that the twist is reversed every time a certain length is twisted in the part where the cable is taken out.

The configuration of the present invention will be explained in more detail below with reference to the drawings, but the following disclosure is merely one embodiment of the present invention and does not limit the technical scope of the present invention in any way.

Embodiment FIGS. 1(a) and 1(b) are diagrams illustrating the conceptual configuration of an optical fiber cable according to the present invention. That is, FIG. 1(a) is a diagram showing the configuration of an optical fiber line including a branch optical line to which the installation method according to the present invention can be applied. Moreover, FIG. 1(a) is a diagram explaining the structure of an optical fiber cable used for laying the optical fiber line shown in FIG. 1(a).

As shown in FIG. 1(a), this optical fiber line consists of a trunk optical line 1 laid from a starting point ○ and a branch point A.
Alternatively, branch lines 2 are laid down along unique routes from B to each terminal point a or b. Therefore, in order to lay such an optical fiber line, the first
As shown in Figure 3), if the lengths from the installation start point ○ to each of the nine branch points are h and h1, and the lengths of the respective lead-in routes are and l, then the optical units to be branched at each branch point Optical cables are prepared such that the lengths within the cables 3 and 4 correspond to A, +fa, and fe+zb, respectively.

When laying this cable, start pulling the optical cable from the starting point ○ of the optical path, and from the time the tip of the optical unit reaches the corresponding branch point, simultaneously pull the cable and connect the optical unit at each branch point. Take it out. Therefore, when the main optical line 1 has been laid, optical units with lengths corresponding to 12 and 1, respectively, can be obtained at each branch point.

Note that it is also possible to take out a plurality of optical units at the same branch point. In addition, the branched optical unit may be immediately installed on the lead-in route, but it may also be installed on the lead-in route after the main cable has been laid by first performing east-cutting or 8-character cutting at the branch point. good.

FIG. 2 is a diagram showing more specifically the configuration of an optical fiber cable that can be used in the installation method according to the present invention as described above. That is, in the installation method according to the present invention, it is necessary to take out the optical unit at the branch point while pulling and laying the cable, so the optical cable needs to have a structure that makes such work as easy as possible. .

As shown in FIG. 2, in this optical cable, each optical unit 10 serving as a unit of branching has a four-core optical fiber 6, and each fiber 6 has a grooved base plate having a tensile strength member 7 at the center. 8 and is covered with an outer cover 9. The optical unit 10 located at the center of the cable is a unit that is laid to the farthest end and does not need to be branched. Six strands are twisted together and a presser winding 13 is applied.

During installation, when the tip of the optical unit to be branched reaches a certain branch point, the optical unit can be easily taken out from inside the cable by cutting the presser winding. In addition, this optical fiber cable has a structure in which the twisting direction of the optical unit is reversed every fixed length, so that the optical unit can be easily taken out. Only the portion from which the optical unit is taken out may be twisted in alternating inversions, and the other portions may be twisted in one direction.

The cable may be wound loosely with string or tape, wrapped with string or the like at regular intervals, or wrapped with tape in layers. In addition, it is preferable that the part from which the optical unit is taken out at the branching point be immediately held down again with a string or tape to prevent the cable structure from collapsing, so that it does not interfere with the cable installation.

It is desirable that the structure of the optical fiber cable used in the method according to the present invention is such that it can be directly connected to a branch route and can sufficiently withstand the environment in which it is installed. Therefore, an ordinary optical cable having a tensile strength member and a jacket can also be used as an optical unit. Further, in some cases, the optical fiber itself may be regarded as an optical unit.

Furthermore, in FIG. 2, by inserting an intervening string 12 made of plastic or the like in a portion where an optical unit is not required in the longitudinal direction of the cable, the cable structure can be kept stable during cable manufacturing or installation. can. Also,
If the problem is that the number of optical units decreases toward the far end, and therefore the tensile strength of the cable decreases, by using a tensile strength body instead of the intervening string,
It is possible to reinforce the tensile strength of the cable.

Depending on the installation conditions and the number of optical units required, a tensile strength member or an intervening string may be used in place of the optical unit at the center of the cable. In that case, the optical unit installed to the farthest end may be It becomes either a twisted light unit.

FIG. 3 is a diagram showing another configuration example of an optical fiber cable that can also be advantageously used in the installation method according to the present invention.

In FIG. 3, the same members as those of the optical fiber cable shown in FIG. 2 are given the same reference numerals.

As shown in the figure, this optical fiber cable includes an optical fiber unit comprising a two-core optical fiber 6, a fibrous tensile strength member 7 disposed around it, and a jacket 9 surrounding these. One piece is housed in each groove of the grooved smoother 8, and the entire piece is wrapped with a presser winding l3. The grooved spacer 8 has six grooves, and therefore a maximum of six optical units can be accommodated within one cable cross section near the cable installation start point.

In Fig. 3, the grooved spacer has a tensile strength member at the center, but depending on the structure of each optical unit, installation conditions, etc., this may not be necessary, or conversely, the grooved spacer itself may have a tensile strength member. may be a tensile strength body.

Further, the groove formed in the spacer 8 is twisted so as to be reversed at regular intervals, similar to the optical unit on the outer peripheral side of the optical fiber cable shown in FIG.

In the grooved spacing type cable structure configured as described above, there is no need to insert an intervening string in a portion where an optical unit is not required in the longitudinal direction of the cable. Furthermore, since there is no fear that the optical unit will be untwisted when the optical unit is taken out, it is easy to press and wrap the optical unit again after the optical unit is taken out, and work efficiency is improved.

In addition, this cable structure allows the optical unit to be stored in the groove.
Because the cable is protected, the cable structure is more stable than a structure in which optical units are twisted directly, and it is suitable for harsher installation environments.

On the other hand, if the installation environment of the lead-in route is relatively good, the structure of the optical unit may be a normal optical single-core cord with a tensile strength member placed around the optical fiber core and an outer jacket. It can be applied even to cables that are not as resistant to installation environments as optical cables. In this case, depending on the installation environment of the trunk route, the cable structure shown in FIG. 3 may be further provided with a cable sheath as shown in the embodiment shown in FIG. N4 below.

FIG. 4 is a sectional view showing still another example of the structure of an optical fiber cable that can be used in the method according to the present invention.

In this embodiment, a tape-type optical fiber 15, which is constructed by arranging a plurality of optical fibers in parallel, is further provided with a plastic jacket 9.
A tape type optical cord 16 which has been subjected to the following steps is used as an optical unit, and a cable structure is constructed by a smoother 8 provided with a groove 14. Note that the spacer 8 includes a tensile strength member 7 at its center.

In this embodiment, it is possible to store a plurality of tape-type optical cords 16 in one groove 14, and in that case, tape-type optical cords corresponding to branch points at the far end starting from the installation start point are placed in the groove. It should be stored so that it is located on the bottom side of the

That is, since each tape-type optical cord 16 has a length according to the corresponding branch point, at each branch point, the tape-type optical cord 16 to be taken out is always located at the uppermost position in the groove. It turns out.

In the example shown in Fig. 4, two tape-type optical cords l6 can be accommodated in one groove 14, and therefore a maximum of 2 x 5 grooves = 10 tape-type optical cords can be accommodated within the cable cross section corresponding to the cable laying start point. It is. A thin polyethylene jacket 9 is applied to the spacer 8 that houses the tape-type optical cord 16. However, this can be easily removed at least in the part where the tape-type optical cord is taken out, and in this embodiment, this is achieved by embedding the tear string 17 in advance directly under the outer cover 9.

In this case, it is convenient to indicate in some way on the jacket the position on the cable at which branching should begin for each branching point.

Furthermore, depending on the installation method and environment, instead of applying an outer covering, it may be sufficient to simply wrap it with string or tape as shown in the embodiment shown in Figure 3. In this case, the tape-type optical cord can be taken out even more easily. Become.

The tape-type optical cord may have a structure in which a tensile strength member is provided between the built-in tape-type optical fiber and the cord jacket or inside the cord jacket.

A cable with this structure, which uses a tape-type optical cord as an optical unit, can be used in cases where the lead-in route corresponds to the wiring inside or around the equipment, or to indoor conduits or indoor wiring. It is desirable to apply it to places with relatively favorable environments.

That is, in such an installation environment, a single optical fiber cord as described in the explanation of the embodiment shown in FIG. 3 is often used, but if multiple optical fibers are required to be branched, , rather than branching multiple optical single-core cords at the same branch point,
It is only necessary to branch one tape-type optical cord containing the number of fibers that is the unit of branching, which simplifies the branching work, and the cable structure also has a high density of optical fibers (i.e., the same number of fibers has a small diameter). ) can be a cable.

Furthermore, depending on the installation environment of the lead-in route, it is possible to use only a tape-type optical fiber with the outer sheath removed instead of the tape-type optical cord, and in this case, it is possible to increase the number of optical fibers with the same cable outer diameter. On the other hand, it is possible to reduce the diameter of the cable with the same number of cores. In other words, if there is a restriction on the outer diameter of the trunk route cable and it is necessary to increase the density of optical fibers, a fourth optical fiber using only tape-type optical fibers may be used.
A cable structure similar to the diagram is valid.

For reference, FIG. 5 shows a graph comparing the tensile strength characteristics of a tape-type optical core and a tape-type optical cord. That is, FIG. 5 shows the results of a tensile test for a tape-type optical fiber of six single-mode optical fibers and a tape-type optical cord. The test shows the results of fixing both ends of a 2m long sample together and measuring the variation in optical output due to tension application using a light source with a wavelength of 1.3μm, as well as measuring the elongation strain of the optical fiber. .

As shown in FIG. 5, the tape type optical cord has less increase in optical loss for the same tension and has less elongation strain than the tape type optical core wire, so it is excellent in environmental resistance when installed. However, even with a tape-type optical fiber, if the tension is low, that is, in the example shown in Fig. 5, and the elongation strain of the optical fiber is defined as 0.5% or less, and the strain is 3 kg f or less, depending on the installation environment, It can be installed without any problems due to its characteristics.

The tape-type optical cord used in the test had a certain amount of tensile strength fiber inside, but if the installation conditions require a tensile strength higher than the characteristics shown in Figure 5, the tensile strength Va fiber This can be addressed by increasing . Of course, resistance to the installation environment cannot be determined by tensile properties alone; mechanical properties such as lateral pressure properties and bending properties must also be taken into account. In the comparison, the same thing can be said as in the case of the tensile properties mentioned above.

As mentioned above, as optical units and optical cables,
The installation method according to the present invention can be applied by designing a structure according to each installation environment and conditions.

Effects of the Invention As explained above, the method for laying an optical fiber line according to the present invention makes it possible to branch cables without connecting optical fibers even on routes that require connecting optical fibers at branch points. This is advantageous in terms of performance as a transmission line and overall construction cost. Further, since there is no unusable optical fiber remaining in the cable at the far end of the branch point as in the case of a rear branch, efficient use of optical fibers can be achieved.

The installation method according to the present invention uses an optical cable that has a structure that corresponds to the number of branch points in the installation route, the number of optical fibers to be branched, the spacing between branch points, the length of the lead-in route, the installation environment, etc. It can be widely used for laying optical fiber lines including branch lines, especially for wiring inside buildings or premises where the lead-in route length is not very long, for example, several tens of meters or less, and the number of branch points in the route is relatively large. It is effective when used to lay the optical fiber lines that make up the system.

[Brief explanation of the drawing]

1st r! 1I is a schematic diagram of a cable installation route and an optical cable corresponding thereto in the present invention. FIGS. 2 and 3 are diagrams showing different embodiments of the optical cable structure according to the present invention, each showing a portion in the longitudinal direction of the cable. FIG. 4 shows another embodiment of the optical cable structure according to the present invention, and is a sectional view at a certain position in the longitudinal direction of the cable. FIG. 5 is a graph showing the results of a tensile test comparing the tensile strength properties of a tape-type optical fiber and a tape-type optical cord. [Main reference numbers] 1. Main optical line, 2. Branch optical line, 3. Optical unit branched at branch point A, 4. Optical unit branched at branch point B, 5 ・ 6 ・8. 10. 11. 13. 15. 16. Optical unit passing through branch points A and B, optical fiber core, 7. Tensile strength member, grooved spacer, 9. Outer jacket, optical unit, optical unit branch. Starting point, l2...intervening string, presser winding,
14... air gap groove, tape type optical fiber, tape type optical cord, l7... tear string

Claims (4)

[Claims] (1) A main optical line that continues from the starting point to the terminal point, and a main optical line that is arranged along the same route as the main optical line from the starting point to the branch point, and a unique route from the branch point to each terminal point. A method of laying an optical fiber line formed by an optical fiber unit by a lead-in method, including a branch optical line arranged so as to trace the length of the main optical line from a starting point to a terminal point. An optical fiber cable configured by integrally accommodating an optical fiber unit and an optical fiber unit of a length that can form the branched optical line from the starting point to the ending point via the branching point, The optical fiber cable is pulled in all at once to the branch point, and at the branch point, the optical fiber cable is separated into an optical fiber unit for the main optical line and an optical fiber unit for the branch optical line, and the optical fiber cable is drawn in. A method of laying an optical line characterized by continuing. (2) A main optical line that continues from the starting point to the terminal point, and a main optical line that is arranged along the same route as the main optical line from the starting point to the branch point, and a unique route from the branch point to each terminal point. An optical fiber cable used when laying an optical fiber line formed by an optical fiber unit by a lead-in method, including a branch optical line arranged so as to trace the main optical line from the starting point to the ending point. It is characterized by being configured by integrally housing an optical fiber unit with a length that can be used to form up to 1000 yen, and an optical fiber unit with a length that can be used to form the branched optical line from the starting point to the ending point via the branching point. fiber optic cable. (3) The optical fiber cable according to claim 2, wherein the optical fiber units constituting one optical fiber cable are twisted while being reversed every predetermined length. fiber cable. (4) The optical fiber cable according to claim 2 or 3, characterized in that the optical fiber units are stacked and housed so that the optical fiber unit that is branched first is on the outside. fiber optic cable.