JPH03233505A - Pipe for laying optical fiber and method for laying optical fiber by using this pipe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a pipe for installing optical fibers that is useful in a forced air streamer construction method for optical fibers, and a method for quickly and efficiently installing optical fibers using the pipes. The present invention relates to a method for laying cables inside the building.

[Prior art] Optical communication using optical fiber as a transmission medium, transmission and processing of various information, measurement and various sensors using optical fiber, and applied technology in fields such as medical treatment and processing have been rapidly progressing. The scope of application of this technique is gradually expanding.

However, the current situation is that they have not yet been widely generalized, and are still in a transitional stage, with ample potential and a steady track record of success.

In other words, although the main line running through the archipelago has been tentatively completed,
Horizontal construction of local trunk lines is still insufficient, and the construction of subscriber lines is only at the stage of being put into practical use on a trial basis in urban centers.

However, it is clear that in the near future, optical networks will be widely constructed for communication and information management, and the day will come when subscribers will be able to use them freely, and by the year 2000 it will no longer be a dream. It is considered.

For this reason, in anticipation of the arrival of such an era, buildings that have been constructed in recent years are required to install optical fiber I/O in future buildings.
In many cases, optical fiber installation vias 1 are provided in advance to enable the construction of IH.

This pipe arrangement is done by using a metal cable wiring duct, or by attaching an optical fiber installation pipe to the main cable for power supply. When it becomes possible to use fiber, we will insert and install optical fiber into this pre-installed pipe to construct an optical transmission network. A pressurized air streamer construction method has been proposed as a means for inserting and arranging optical fibers.

Specifically, a plastic pipe such as polyethylene with a smooth inner surface and an inner diameter of about 6 mm and an outer diameter of about 81 IfI is installed in advance, and compressed air is sent from one end of such a pipe, and the air is carried by the air flow. The optical fiber is installed by inserting the streamer into the pipe.

[Problems to be Solved by the Invention] In the above-mentioned method of installing optical fibers using pressurized air, ideal installation can be performed quickly if the optical fiber unit flies over the center of the pipe on the airflow. be able to.

However, pipes are not always arranged in a straight line.
Usually there is a bend, and the optical fiber unit itself has a tendency to curl, so the optical fiber often comes into contact with the inner surface of the pipe and is pumped while being subjected to a large frictional force.

If this frictional force becomes excessive, it will take a lot of time to force-feed the optical fiber, and if the length of the optical fiber is long, it will be impossible to force-feed the optical fiber. That is, using the above-mentioned polyethylene pipe with a smooth inner surface, the length that an optical fiber can be installed by blowing air with compressed air is about 1 ks+ in the horizontal direction and about 100 m in the vertical direction. However, in reality, there are many cases where it is desirable to be able to install cables at longer lengths, and considering the tendency for structures such as buildings to become larger and taller, what will happen if the above is not enough? can also be considered.

In view of the above-mentioned circumstances, it is an object of the present invention to enable windsock installation using forced air while holding the optical fiber in the center of the pipe, thereby making it possible to greatly increase the length of the installation. At the same time, it is a new optical fiber installation method for the pressurized air streamer construction method that can speed up the installation work of inserting the optical fiber into the pipe by significantly reducing the occurrence of adhesive contact with the inner surface of the pipe. The present invention aims to provide a pipe and a method for installing an optical fiber using the pipe.

[Means for Solving the Problems] Firstly, the present invention provides a pipe having an internal space in which an optical fiber can be pumped by a pressure air streamer construction method, and a plurality of spiral grooves extending in a fixed direction are formed on the inner surface of the pipe. Second, air for pumping the optical fiber is forced into a pipe having such a spiral groove, and the air is given a rotational force in the spiral direction by the spiral groove formed on the inner surface of the pipe. The rotating pressurized air causes the optical fiber to be inserted into the pipe in a streamer manner.

[Effect] If a large number of spirals are formed in a certain direction on the inner surface of the pipe, will the air be spiralized when air is pumped? 11
A rotational force is generated by the wall surface, and the airflow moves through the pipe while rotating in a spiral manner. This rotation of the air causes a force to act on the optical fiber inserted into the streamer toward the center of the pipe, and the optical fiber is inserted while flying through the center of the pipe as desired, allowing for quick installation work. It can also enable installation over longer distances.

Furthermore, even if the optical fiber were to come into contact with the inner surface of the pipe, it would come into contact with the protrusion forming the groove, and the contact surface would become much smaller, thus avoiding the generation of excessive frictional force as in the conventional example. becomes possible.

[Example code] The present invention will be described below with reference to Examples.

FIG. 1 is a half-sectional explanatory diagram showing how an optical fiber unit 3 is inserted and installed in a pipe 1 according to the present invention by the forced air streamer construction method according to the present invention, and FIG. 2 is an end view thereof. .

A plurality of spiral grooves 2, 2 are formed in a certain direction on the inner surface of the pipe 1 according to the present invention, as shown in the figure, and the presence of the spiral fi 2.2 allows the air flow forced into the pipe 1 to be The air fluid generates a rotational flow in the direction of forming the spiral groove and travels inside the pipe 1 in a spiral manner, so that the air fluid becomes most active in the center of the pipe 1. As the air fluid flows through the pipe 1, an acting force acts on the air fluid so that it always gathers at the center of the pipe 1. Due to this phenomenon, the optical fiber unit 3 is strongly maintained in the center of the pipe, and the optical fiber unit 3 proceeds in the center where the flow is most active.

Regardless of whether the pitch of 2, 2 is large or small, a certain effect can be expected. If the pitch is large, the optical fiber unit 3 can be brought to the center of the pipe 1 by making the most of the force of the flow rate; if the pitch is small, the advancing force will be slowed down, but the force to maintain the optical fiber unit 3 in the center of the pipe 1 will be Become stronger.

The depth of the well 2 is not particularly specified, but it is necessary to have a certain depth. The width of the spring 2 needs to be smaller than the outer diameter of the optical fiber unit 3. This is because if the outer diameter is equal to or larger than the outer diameter of the optical fiber unit 3, there is a risk that the optical fiber unit 3 will enter the well 2.

There is no particular regulation regarding the groove spacing, but from the viewpoint that the larger the number of grooves, the greater the influence on the fluid, the narrower the groove spacing, the better.

The optical fiber installation pipe 1 configured as described above is
When constructing a building, etc., in anticipation of the future installation of optical fiber, it is installed in advance within the wiring tact within the building, or attached to the trunk cable, etc. laid within the duct. be done.

FIG. 3 is an explanatory cross-sectional view showing an example in which the pipe 1.1 according to the present invention is previously arranged at the stranding part of the building trunk cable 10 using a three-strand cable cable.

In this way, when configured as a composite pipe with the power cable 10, the pipe 1 will be twisted at the same pitch as the power cable, and if the optical fiber is fed under pressure as it is, the optical fiber will bend due to the twist It becomes difficult to move within 1.

Therefore, in this case, if a helix is attached in the same direction as the twisting direction of the pipe, the inertial force of the fluid on the inside of the pipe and the force that brings the optical fiber to the center will increase, so the pipe will not be twisted. It is thought that even if the optical fiber is in contact with the inner surface of the pipe, the probability of the optical fiber coming into contact with the inner surface of the pipe is reduced, and the optical fiber can be sent farther. If it is the same as a capeple, the flow of fluid in the pipe will be the same as the flow in a straight pipe, even though the pipe is twisted.

Therefore, it is believed that it is necessary to shift the helical pitch back and forth relative to the pitch of the power cable, thereby keeping the optical fiber centered and allowing it to fly farther.

On the other hand, if a pipe with a conventional configuration is installed, the inner diameter of the pipe will limit the outer diameter of the optical fiber unit that can be pumped into the pipe, making it difficult to install a thicker optical fiber unit. be.

However, according to the pipe according to the present invention, since the optical fiber to be pumped has a spiral groove, it is difficult for the optical fiber to come into contact with the inner surface of the pipe. This also has the great advantage of making it possible to respond flexibly to unpredictable future circumstances.

[Effects of the Invention] As described above, according to the pipe and installation method of the present invention, since a spiral flow in one direction is formed on the inner surface of the pipe 1, the pressurized air fluid progresses while swirling. However, the optical fiber unit is held at the center of the pipe, where the flow velocity is strongest, and can be laid quickly and efficiently even over long distances, and the outer diameter of the optical fiber unit to be laid can be quite wide. It can offer a number of advantages, including the ability to

[Brief explanation of drawings]

Fig. 1 is an explanatory half-sectional view showing how the method according to the present invention is carried out using the pipe according to the present invention, Fig. 2 is an explanatory view of the end thereof, and Fig. 3 is an explanatory view of the end face of the pipe according to the present invention. It is an explanatory cross-sectional view showing a state arranged in a twisted groove. 1: Pipe, 2: Spiral groove, 3: Optical fiber unit, 10: Electric cable. Hitachi Cable, Ltd.

Claims (2)

[Claims] (1) A pipe for installing optical fibers, which has an internal space in which optical fibers can be pumped by a forced air streamer method, and has a plurality of spiral grooves extending in a fixed direction on the inner surface of the pipe. (2) Air for pumping the optical fiber is pumped into the pipe according to claim 1, and a spiral groove formed in the inner surface of the pipe generates a force for rotating the air in the spiral direction, and the rotation progresses. An optical fiber installation method in which the optical fiber is inserted into a pipe using compressed air.