JPH08240754A - Self-supporting type optical cable and dropping method - Google Patents

Abstract

PURPOSE: To provide a self-supporting type optical cable with which the efficient conduction of a dropping operation is possible and to provide a method for dropping using the self-supporting type optical cable. CONSTITUTION: A sheath 1 is supported by a supporting wire 5 and plural coated optical fibers 2 are housed in the sheath 1. The sheath 1 is provided with a slit 3 and apertures 4 at suitable intervals in its longitudinal direction. The dropping operation is executed by widening the apertures 4, selecting and taking out the coated optical fibers 2 to be dropped and cutting the fibers at the point apart from a station by a distance corresponding to the length of the dropping fibers necessary for dropping from the dropping point. The long-sized body is continuously drawn out of the slit up to the dropping point and the drawn out long-sized body is used as the dropping wire. This long-sized body is laid as it is up to a subscriber. As a result, the workability of the dropping is greatly improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable, and more particularly, to an optical cable that is imaginarily suspended in a subscriber optical line connecting a station and a subscriber, and a drop-down method for laying the optical cable to the subscriber. It is a thing.

[0002]

2. Description of the Related Art With the recent development of optical fiber networks, the installation of subscriber optical lines connecting stations with a large number of subscribers has been promoted. In the subscriber optical line, it is necessary to take out a part of the core wire from the imaginary suspended optical cable and drop it into the house of each subscriber. Since this withdrawal work is performed for each subscriber, this work efficiency becomes a problem.

As an example of the conventional pulling operation, the optical cable is cut at each pulling point and the required optical fiber core wire is pulled down. All other optical fiber cores were connected. As described above, cutting and connecting the optical cable at each pull-down point requires a large amount of work, which complicates the laying work, laying time, laying cost, and increasing line cost. Further, transmission loss occurs when connecting the optical fiber cores. There is a problem that the optical loss of the line increases because the number of connection points increases as the distance from the station increases.

In the subscriber optical line, in many cases, the optical cable is suspended in the air. Since transmission loss occurs in an optical fiber due to lateral pressure or the like, it is necessary to prevent lateral pressure from being applied during installation work and in the installed condition. Therefore, a self-supporting optical cable is used.

As a conventional self-supporting optical cable, for example, a messenger wire and a tubular body are integrally formed as described in Japanese Utility Model Laid-Open No. 59-90911.
It is known that an optical fiber cable is housed in a tubular body. In such a self-supporting optical cable, although a drain hole is provided, the entire circumference of the accommodated optical fiber cable is covered by the pipe body, so the pipe body is removed at each pulling point, It was necessary to take out the optical fiber cable. In addition, it was necessary to install a connection box at the portion where the pipe body was removed in order to protect the portion. Such work has led to complicated construction work, increased installation time, installation cost, and track cost.

The cable sheath with a suspension wire described in Japanese Patent Laid-Open No. 57-38507 has a plurality of cavities together with the suspension wire, and the cavity accommodates an optical cable. Further, the sheath is provided with a notch. By accommodating the optical cable in this cable sheath with suspension wire, the configuration is the same as that of the self-supporting optical cable, but this cable sheath with suspension wire is simply a bundle of multiple optical cables and can be pulled down to the subscriber. That is not considered.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a self-supporting optical cable capable of efficiently performing a pulling operation. It is also an object of the present invention to provide a withdrawal method using this self-supporting optical cable.

[0008]

According to a first aspect of the present invention, in a self-supporting optical cable, a tight slit extending in the longitudinal direction is provided and the slit is intermittently provided in the longitudinal direction as a part of the slit. An outer casing that accommodates a long body such as an optical cable or a tube body having an opening provided therein with an optical fiber core wire or a tensile strength body, and the long body that supports the outer jacket along its longitudinal direction. It is characterized in that it is constituted by a supporting member for suspending in an imaginary state.

According to a second aspect of the present invention, in the self-supporting optical cable according to the first aspect, the jacket is made of rubber,
It is characterized by being formed of plastic.

The invention according to claim 3 is the self-supporting optical cable according to claim 1 or 2, wherein the elongated body is fixed to the inner surface of the outer cover. .

According to a fourth aspect of the present invention, in the self-supporting optical cable according to the first or second aspect, the elongated body is fixed to the inner surface of the outer cover with a thermoplastic adhesive. It is what

According to a fifth aspect of the present invention, in the self-supporting optical cable according to the first or second aspect, the inner surface of the outer cover is provided with a protrusion that fits with the elongated body, and the elongated body is provided. The body is fitted to the protrusion and fixed to the inner surface of the outer cover.

According to a sixth aspect of the present invention, in the self-supporting optical cable according to any one of the first to fifth aspects, the elongated body is accommodated in the jacket with slack with respect to the support line. It is characterized by being.

According to a seventh aspect of the present invention, a part of the optical fiber core wires is selected from the optical cables suspended imaginarily, and the optical fiber core wires or the optical cable including the optical fiber core wires is used by the subscriber. The self-supporting optical cable according to any one of claims 1 to 7 is used as the above-mentioned optical cable suspended in an aerial manner in the pulling-down method of laying up to 1 in the vicinity of the subscriber in the installation route of the optical cable. A point is set as a withdrawal point, and an elongated body to be withdrawn at a point separated from the station by a distance corresponding to the length of the withdrawal line necessary for withdrawal from the withdrawal point is cut continuously from the slit to the withdrawal point. It is characterized in that the body is pulled out, and the elongated body pulled out is used as a pull-down line to pull down to the subscriber.

The invention according to claim 8 is the drawing-down method according to claim 7, characterized in that the drawing-down line is fixed to the jacket on the left side or the right side of the slit at the drawing-down point. .

According to a ninth aspect of the present invention, in the pulling-down method according to the seventh or eighth aspect, the pulling-down line is pulled down from the opening provided in the outer cover.

According to a tenth aspect of the present invention, in the withdrawal method according to the seventh aspect, a notch connected to the slit provided in the outer cover is formed, and the withdrawal line is extended to the subscriber through the notch. It is characterized by withdrawing.

[0018]

According to the first aspect of the present invention, the outer cover is provided with the closely-attached slit and the opening portion intermittently as a part of the slit. The slit can be opened by putting a finger on the opening, and the work of taking out, cutting, and pulling out the long body to be dropped can be easily performed without removing the outer cover. Further, by pulling out the long body taken out, the long body can be taken out continuously from the slit, and the long body taken out can be used as it is as a drop line. In such a pulling operation, cutting of the entire self-supporting optical cable at the pulling point as in the past,
There is no need to perform connection work, and the laying work can be greatly simplified, and laying time, laying cost, and line cost can be reduced. Moreover, since the number of connection points can be reduced, transmission loss can be reduced. The opening can be provided below the jacket, in which case water can be prevented from collecting in the jacket. The outer cover can be made of rubber or plastic, as in the second aspect of the invention.

According to the third aspect of the invention, the elongated body is fixedly housed in the inner surface of the outer cover. This allows
It becomes easier to select the optical cable to be pulled down, and it is possible to prevent the pulled-down lines from being entangled with each other.

As a fixing method, for example, a thermoplastic adhesive can be used as in the invention described in claim 4. Thereby, for example, when the outer cover is manufactured by extrusion, the heat can be used to fix the outer cover, which simplifies the processing and reduces the cost. Further, as in the invention described in claim 5, it is possible to fix the elongated body to the inner surface of the outer cover by providing a fitting projection on the inner surface of the outer cover. In this case, since it can be fixed to the inner surface of the outer cover without being constrained in the longitudinal direction, it can be fixed so as not to be a resistance when pulling out. Further, even if the self-supporting optical cable is suspended in an imaginary state and extends, the fixed position is merely displaced in the longitudinal direction, so that the fixed state is maintained without receiving a pulling force.

According to the sixth aspect of the present invention, the long body can be easily taken out at the pulling-down point by slackly accommodating the long body in the outer cover. Moreover, even if the self-supporting optical cable is suspended in the air and is stretched or strained, the elongated body accommodated in the outer cover is not stretched or strained, and thus reliability is not impaired.

According to the invention of claim 7, claim 1
The self-supporting optical cable described in any one of 1 to 6 is used, and for example, a series of several spans are set up. In the laying route of the installed self-supporting optical cable, one point near the subscriber is used as the withdrawal point, and the length of withdrawal from the station by a distance corresponding to the length of the withdrawal line required for the withdrawal from that point Cut the scale. Then, the elongated body is continuously drawn from the slit from the cut end to the withdrawal point, and the drawn elongated body is used as a withdrawal line to be withdrawn to the subscriber. By using such a drop-down method, it is not necessary to disconnect and connect the entire self-supporting optical cable at the pull-down point in the section where a series of lines are crossed, and the pull-down line at the pull-down point is required. Connection work with can also be omitted. As a result, the workability of withdrawal can be significantly improved, the installation work can be greatly simplified, and the installation time, installation cost, and line cost can be reduced.

At the draw-down point, if the draw-down line is fixed to the casing on the left side or the right side of the slit as in the invention described in claim 8, it is necessary to pull out the draw-down line so as to pass through the draw-down point later. If it happens,
You can draw out the necessary drop line. Further, when the pull-down line is pulled out from the pull-down point, the pull-down line can be pulled out from the opening provided in the outer cover, so that the pull-down line can be taken out without applying lateral pressure, and the reliability is not impaired.

Further, at the point of withdrawal, claim 10
As in the invention described in (1), if the notch connected to the slit is put in the jacket and the drop line is drawn down to the subscriber through the notch, the slit part can be made to have no drop line. Therefore, even if it is necessary to draw the drop line so that it will pass the drop point later, the already drawn drop line does not get in the way.

[0025]

1 is a perspective view showing an embodiment of a self-supporting optical cable of the present invention, and FIG. 2 is a sectional view of the same. In the figure, 1 is a jacket, 2 is an optical fiber core wire, 3 is a slit, 4
Is an opening, and 5 is a support line.

The jacket 1 has a plurality of optical fiber core wires 2 inside.
Alternatively, an optical cable, a tubular body, etc. can be accommodated. The outer cover 1 can be formed of, for example, rubber or plastic. Of course, it is also possible to use other materials. The outer cover 1 has a slit 3 in the longitudinal direction.
Is provided. The slit 3 is for taking out the optical fiber core wire 2 and the like housed in the jacket 1. FIG. 2A shows the aa ′ cross section of the self-supporting optical cable including the slit 3. Thus, the slits 3 are in close contact with each other in a normal state.

Further, the outer cover 1 is provided with openings 4 at appropriate intervals. FIG. 2B shows a bb ′ cross section of the self-supporting optical cable including the opening 4. This opening 4 constitutes a part of the slit 3 and is shown in FIG.
As shown in FIG. 3, the slit 4 does not come into close contact with the opening 4 and has a void. As shown in FIGS. 1 and 2, the slit 3 and the opening 4 are provided in the lower portion of the jacket 1, and have a function of discharging water accumulated in the jacket 1 from the gap of the opening 4. In addition, at the time of withdrawal, a nail, a finger, a tool, or the like is hooked on the opening 4 to widen the opening and cover the outer cover 1
It is possible to take out the optical fiber core wire 2 and the like from the inside.

The support wire 5 is arranged along the outer cover 1. The jacket 2 is supported by the support wire 5. When the self-supporting optical cable is laid, the supporting wire 5 is pulled by a predetermined tension and locked to, for example, a power pole.

FIG. 3 is a sectional view of an example of the optical cable housed in the outer cover. In the figure, 11 is an optical cable, 12 is an optical fiber core wire, 13 is a steel core, and 14 is a jacket. In addition to the above-mentioned optical fiber core wire 2, the optical cable 11 as shown in FIG. 3 can be housed in the jacket 1. FIG.
The optical cable 11 shown in (1) has steel cores 13 arranged on both sides of an optical fiber core wire 12 and is integrated by a jacket 14. As a specific example, for example, a nylon-coated core wire having a diameter of 0.9 mm can be used as the optical fiber core wire 12, and PVC or the like can be used as the jacket. As a whole, an optical cable having a width of about 7 mm and a thickness of about 4 mm can be used. Of course, an optical cable having another shape such as a substantially circular shape may be housed in the jacket 1.

Furthermore, a tube body made of, for example, plastic or the like can be housed in the outer cover 1. After laying the self-supporting optical cable, an optical fiber core wire can be inserted into the tube body, for example, by pressure feeding with gas. Of course, it is also possible to accommodate electric wires and the like in the jacket 1, and it is also possible to accommodate them by mixing them.

The optical fiber core wire 2, the optical cable 11, the tube body, and the like housed in the jacket 1 are housed with slack with respect to the support wire 5. As a result, even if tension is applied to the support wire 5 and the jacket 1, no tension is applied to the contained optical fiber core wire 2, the optical cable 11, the tube body, etc., and good transmission conditions are maintained. You can Further, the work of taking out the optical fiber core wire 2, the optical cable 11, the tube body and the like from the inside of the jacket 1 can be easily performed.

FIG. 4 is a sectional view showing another embodiment of the self-supporting optical cable of the present invention. In the figure, the same parts as those in FIG. Reference numeral 21 is a fitting projection. In the second embodiment, the optical fiber core wire 2
An example of fixing the to the inner surface of the jacket 1 is shown.

In FIG. 4A, the optical fiber core wire 2 is fixed to the inner surface of the jacket 1 with an adhesive. Various kinds of adhesives can be used, and as one of them, for example, a thermoplastic adhesive can be used. Jacket 1
For example, it can be formed by extrusion molding, but when a thermoplastic adhesive is used, the bonding can be performed using the heat when forming the jacket 1.

In FIG. 4B, a fitting projection 21 is provided on the inner surface of the outer cover 1. The optical fiber core wire 2 accommodated inside the jacket 1 is fitted and fixed to the fitting projection 21.

FIG. 4C also shows an example in which the fitting projection 21 is similarly provided. Here, the optical cable 11 shown in FIG. 3 is fitted to the fitting projection 21. Optical cable 11
Has a recess formed in the center thereof, and the fitting projection 21 can be fitted into this recess to lock the optical cable 11.

As shown in FIGS. 4A to 4C, when the optical fiber core wire 2, the optical cable 11, the tube body, etc. are fixed to the inner surface of the jacket 1, each optical fiber core wire 2 and the optical cable 1 are fixed.
1. It becomes easy to identify the tube and the like, and it becomes easy to select the optical fiber core wire 2 and the like to be pulled down during the pulling operation. Further, since the optical fiber core wire 2 and the like can be housed in the outer cover 1 in an orderly manner, problems such as being entangled inside do not occur. Further, as shown in FIGS. 4B and 4C, in the structure in which the fitting protrusion 21 is provided, the fitting protrusion 21 may be arranged apart from each other, and the gripping force is weaker than that of the adhesive, so that the fitting protrusion 21 is pulled down. Sometimes, when pulling out the optical fiber core wire 2 or the like, it is not necessary to give such a resistance.

FIG. 5 is an illustration of an embodiment of the withdrawal method of the present invention. 31 is a self-supporting optical cable, 32
Is a telephone pole, 33 is a subscriber's house, and 34 is a notch. The self-supporting optical cable 31 is the self-supporting optical cable of the present invention as shown in the above-mentioned first to third embodiments. Here, the self-supporting optical cable 31 is suspended by using a utility pole 32 or the like. At this time, the self-supporting optical cable 31 can be set over several spans in series. Now, consider a case where the optical fiber core wire or the optical cable housed in the self-supporting optical cable 31 is dropped from the drop point to the subscriber's home 33. At this time,
The length of the cable required for withdrawal from the withdrawal point to the subscriber's home 33 is x.

First, as shown in FIG. 5 (A), a cutting point is set at a position downstream of the drop point, that is, on the side opposite to the exchange, by the length x of the cable required for the drop, and this cut point is set. Cut the optical fiber core, optical cable, tube, etc. At this time, a nail, a finger, a tool, or the like may be hooked on the opening 4 at the cutting point, the opening may be widened, and the optical fiber core wire, the optical cable, or the tube body to be pulled out from the inside of the jacket 1 may be taken out. As shown in FIG. 4, when a self-supporting optical cable in which an optical fiber core wire, an optical cable, and a tube body are fixed to the inner surface of the jacket 1, an optical fiber core wire, an optical cable, which should be pulled down,
It is easy to identify the pipes, etc., and selection becomes easy.

Then, as shown in FIG. 5B, the slit 3 is expanded by pulling down the optical fiber core wire or the optical cable, the tube body, etc., which is cut at the cutting point and which is to be pulled down, and the optical fiber core to be pulled down. The wire, the optical cable, the tube, or the like is continuously drawn out from between the slits 3. At this time, when a self-supporting optical cable in which an optical fiber core wire, an optical cable, a tube body or the like is fixed to the inner surface of the jacket 1 as shown in FIG. The body or the like does not get entangled inside the outer cover 1.

The optical fiber core wire, the optical cable, the tube body, etc., which have been pulled out to the pull-down point in this way, have a length x or more necessary for the pull-down, and as shown in FIG. It is sufficient to lay a line up to the subscriber's house 33 as a drop line and connect it to the indoor line.

At the draw-down point, a slit 34 is made from the slit 3. Then, as shown in FIG. 5C, the extracted optical fiber core wire or optical cable,
The pipe or the like is retracted into the notch 34 and fixed. In this way, the drop line is drawn to the subscriber's home 33 through the notch 34. This completes the withdrawal work to the subscriber's home 33.

As described above, by retracting the drop line by using the notch 34, it is possible to make the state in which there is no drop line in the slit 3, and even when the drop line that passes the pull point is drawn later,
The already drawn out line does not get in the way.
In addition, you do not have to perform the troublesome work of cutting all optical fiber cores, optical cables, etc. at the pull-down point as in the past and then connect them, just cut the necessary ones at the cut points and pull out from the slit. Therefore, the withdrawal work can be greatly simplified. In addition, since there are few connection points, the transmission loss due to withdrawal can be minimized. Furthermore, since the cut-out line allows the pull-out line to be taken out so that lateral pressure is not applied to the drop-down line, stable performance can be maintained.

When the opening 4 has a certain size, the pull-down point is set at the position where the opening 4 exists, and the pull-down line is fixed to the left or right jacket 1 of the opening 4, It may be withdrawn. In this case, when pulling out a drop line that passes through the drop point later, the pull line may be passed to the right or left of the draw line already drawn in the opening 4. Moreover, since the opening 4 is not in close contact like the slit 3, the drop line is not subjected to lateral pressure, and stable performance can be maintained. Of course, it may be withdrawn in the middle of the slit 3. In this case, if the outer cover 1 is fixed on the right side or the left side, the slit 3 can be utilized as it is. However, it is conceivable that a later pulling line that passes through the pulling point may require a larger pulling force than when it passes by the already drawn pulling line.
Also, since the slit 3 is in close contact in a normal state,
If left as it is, side pressure will be applied to the drop line. Therefore, it is necessary to take measures to prevent lateral pressure.

[0044]

As is apparent from the above description, according to the self-supporting optical cable of the present invention, since it has the slit and the opening which is a part of the slit, the work of removing the outer cover is not required. It is possible to easily perform operations such as taking out, cutting, and pulling out an elongated body such as an optical cable or a tubular body having the optical fiber core wire or the strength member housed therein. Particularly in the pulling out work, the optical fiber core wire or the optical cable, the tube body, etc. to be pulled out can be continuously taken out from the slit, and the work is very simple. In addition, it is not necessary to disconnect and connect the entire self-supporting optical cable at the pull-down point as in the past.
The laying work can be greatly simplified, and the laying time, laying cost, and line cost can be reduced. Furthermore, since the number of connection points can be reduced, transmission loss can be reduced. It is desirable that the outer cover be formed of rubber or plastic that can be obtained at a low cost and in a stable shape by extrusion.

Further, the long body may be fixed to the inner surface of the jacket, which facilitates selection of the optical cable to be pulled down and prevents the pull-down lines pulled out at the pull-down point from being entangled with each other. be able to. As a fixing method, for example, a thermoplastic adhesive can be used. Thereby, for example, when the outer cover is formed by extrusion, the heat can be used to fix the outer cover, which simplifies the processing and reduces the cost. Further, a fitting projection may be provided on the inner surface of the outer cover to fix the optical cable or the elongated body to the inner surface of the outer cover. In this case, since it can be fixed to the inner surface of the outer cover without being constrained in the longitudinal direction, it can be fixed so as not to be a resistance when pulling out.

Furthermore, by storing the long body in the outer cover with slack, the long body can be easily taken out at the pulling-down point.

When the self-supporting optical cable of the present invention as described above is used, the pulling operation is performed by pulling a long body at a point separated from the station by a distance corresponding to the length of the pulling line required for the pulling from the pulling point. Disconnect the
The elongated body may be continuously drawn out from the slit to the withdrawal point, and the drawn out elongated body may be used as a draw-down line to be drawn down to the subscriber. Therefore, the drop line can be obtained by simply pulling the optical fiber core wire or the like from the cutting point to the drop point after the cutting work, and it is not necessary to connect the optical fiber core wire at the drop point. As a result, the workability of the withdrawal can be greatly improved, the installation work can be greatly simplified, and the installation time, installation cost, and line cost can be reduced.

At the draw-down point, if the draw-down line is fixed to the jacket on the left side or the right side of the slit, the necessary draw-down line can be drawn out when it becomes necessary to draw the draw-down line so as to pass through the draw-down point later. be able to. Further, when the drop line is pulled out from the drop point, by pulling it down through the opening provided in the outer cover, the drop line can be taken out without applying lateral pressure, and the reliability is not impaired.

If a notch connected from the slit is inserted in the jacket at the drop point and the drop line is drawn to the subscriber through the notch,
Since there is no drop line in the slit part, even if it is necessary to pull out the drop line so as to pass the pull point later, the already drawn pull line does not get in the way, etc. Has the effect of.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a self-supporting optical cable of the present invention.

FIG. 2 is a sectional view showing an embodiment of the self-supporting optical cable of the present invention.

FIG. 3 is a cross-sectional view of an example of an optical cable housed in a jacket.

FIG. 4 is a sectional view showing another embodiment of the self-supporting optical cable of the present invention.

FIG. 5 is an explanatory diagram of an embodiment of the withdrawal method of the present invention.

[Explanation of symbols]

1 ... Jacket, 2 ... Optical fiber core wire, 3 ... Slit, 4 ... Opening part, 5 ... Support wire, 11 ... Optical cable, 12 ... Optical fiber core wire, 13 ... Steel core, 14 ... Jacket, 21 ... Fitting Combined projection,
31 ... Self-supporting optical cable, 32 ... Utility pole, 33 ... Subscriber house, 34 ... Notch.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shigeru Tanaka 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Kazuo Hokari 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corp. (72) Inventor Osamu Kawada 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corp.

Claims (10)

[Claims] 1. An optical cable in which a tight slit extending in the lengthwise direction is provided and an opening is intermittently provided in the longitudinal direction as a part of the slit, and an optical fiber core wire or a tensile strength member is incorporated therein, or A self-characterized body comprising: an outer casing for accommodating a long body such as a tubular body; and a support member for supporting the outer casing along its longitudinal direction and suspending the long body in an imaginary manner. Supported optical cable. 2. The self-supporting optical cable according to claim 1, wherein the outer cover is made of rubber or plastic. 3. The self-supporting optical cable according to claim 1, wherein the elongated body is fixed to an inner surface of the outer cover. 4. The self-supporting optical cable according to claim 1, wherein the elongated body is fixed to the inner surface of the outer cover with a thermoplastic adhesive. 5. A protrusion for fitting with the elongated body is provided on an inner surface of the outer cover, and the elongated body is fitted with the protrusion to be fixed to an inner surface of the outer cover. Claim 1
Alternatively, the self-supporting optical cable described in 2. 6. The self-supporting optical cable according to claim 1, wherein the elongated body is accommodated in the jacket with slack with respect to the support wire. 7. A withdrawal method for selecting a part of optical fiber core wires from an optical cable suspended imaginarily and laying the optical fiber core wires or an optical cable including the optical fiber core wires to a subscriber. The self-supporting optical cable according to any one of claims 1 to 7 is used as the optical cable suspended in the air, and one point near the subscriber is set as a withdrawal point in the installation route of the optical cable,
From the withdrawal point, the long body to be withdrawn at a point separated from the station by a distance corresponding to the length of the withdrawal line necessary for withdrawing was cut, and the long body was continuously drawn from the slit to the withdrawal point and pulled out. A withdrawal method comprising using a long body as a withdrawal line to withdraw to the subscriber. 8. The pulling-down method according to claim 7, wherein the pulling-down line is fixed to the casing on the left side or the right side of the slit at a pulling-down point. 9. The drawing-down method according to claim 7, wherein the drawing-down line is drawn down from the opening provided in the outer cover. 10. The withdrawal method according to claim 7, wherein a notch connected to the slit provided in the outer cover is made, and the withdrawal line is withdrawn to the subscriber through the notch.