JPH0560956A - Optical fiber cable - Google Patents

Abstract

PURPOSE:To surely protect optical fibers against high temps. and long-term fires by packing ceramic powder which is sintered and calcined when a prescribed temp. is attained into the gap between the inner protective pipe and outer protective pipe of an optical fiber unit. CONSTITUTION:The optical fiber unit 7 coated with an upper winding tape 8 consisting of a flame-retardant resin consists of the optical fibers 4, etc., and is inserted into the inner protective pipe 9 consisting of a stainless steel, by which the optical fiber unit is protected against the external force, etc. The inner protective pipe 9 is freely inserted into the outer protective pipe 12 consisting of an outer flame-retardant resin pipe 11 and an inner stainless steel pipe 10 and is coated with the outer protective pipe 12. Further, the ceramic powder 13 is packed into the gap between the inner protective pipe 9 and the outer protective pipe 12. The ceramic powder 13 shuts off the heat when the outer peripheral temp. rises high. The ceramic powder 13 is successively sintered or calcined from its outer side and is cured when the powder 13 is heated to the prescribed temp. or above.

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 constructed by inserting an optical fiber unit having a plurality of optical fibers into an inner protective tube and loosely inserting the inner protective tube into an outer protective tube.

[0002]

2. Description of the Related Art Conventionally, this type of optical fiber cable has been used as a communication line or a communication control cable in, for example, an intelligent building. And communication or control is secured even in the case of abnormally high temperature such as fire,
Optical fiber cables have been given a heat-resistant function so that damage can be minimized.

This conventional optical fiber cable having a heat-resistant function is constructed as shown in FIG. That is, the optical fiber unit 2 including the plurality of optical fibers 23, the spacer 24, and the tension member 25.
6 is wound and covered with an upper winding tape 27 made of synthetic resin, and a buffer layer 28 made of synthetic resin is fitted on the outer surface of the upper winding tape 27, and the inner side formed by the buffer layer 28 and the upper winding tape 27. A protective tube 29 is loosely inserted in an outer protective tube 32 composed of an aluminum tube 30 and a synthetic resin sheath 31.

[0004]

As described above, in the above-mentioned conventional optical fiber cable, the inner protective tube 29 and the outer protective tube 32 are made of synthetic resin and aluminum, respectively. Most are vinyl. Therefore, even if a void is formed between the inner and outer protection tubes 29, 32, it cannot be said that the tube is strong against heat.
Therefore, in a fire of a relatively short time within 20 to 30 minutes, the optical cable exhibits a certain degree of heat resistance, but has a high combustion temperature, such as a fire in a skyscraper or an oil plant, In the case of a long fire, such as hours or days, it is absolutely impossible to protect the optical fiber. In the case of such a high temperature or a fire for a long time, the heat may cause the synthetic resin part to burn or melt down, and in some cases the aluminum part may burn down, causing the fiber optic cable to break or break. There was probably a risk of

Further, in the conventional optical cable, even if it has a heat-resistant function, the main component of the heat-resistant function is a material weak to heat such as synthetic resin or aluminum. Therefore, even if the escape of the cable is avoided, the synthetic resin, aluminum, etc. are altered or deformed, so that the wall cannot support the shape of the cable itself due to the disappearance or burning of the wall or floor supporting the cable, In some cases, it may bend or bend beyond the allowable limit. In such a case, mechanical pressure is applied to the optical fiber, the transmission signal is significantly attenuated, and the above-mentioned communication and control functions are impaired.

An object of the present invention is to provide an optical fiber cable capable of reliably protecting the optical fiber and operating the communication system without any trouble even when a high temperature or a fire for a long time occurs.

[0007]

In order to achieve the above object, the present invention inserts an optical fiber unit in which a plurality of optical fibers are arranged side by side into an inner protective tube and coats the optical fiber unit with the inner protective tube. Means of loosely inserting the inner protective tube into the outer protective tube, covering the inner protective tube with the outer protective tube, and further filling the void between the inner protective tube and the outer protective tube with ceramic powder that is sintered at a predetermined temperature. Is taking.

[0008]

In the present invention, the heat of fire is blocked by the ceramic powder and is hardly transmitted to the optical fiber portion. Then, when the ceramic powder is heated to a predetermined temperature or higher, the powder is sintered or fired and hardened.

[0009]

[First Embodiment] A first embodiment of the present invention will be described below with reference to FIGS. The optical fiber 4 is an optical fiber strand 1 and a coating layer 2 located on the outer periphery thereof.
The buffer layer 3 is formed on the outer periphery of the buffer layer 3.
In this embodiment, there are two optical fibers 4, which are arranged in parallel to each other, and two spacers 5 made of a soft-flammable resin are arranged in parallel between both optical fibers 4.
Further, a tension member 6 made of a piano wire is stretched at the center of the area where the optical fiber 4 and the spacer 5 are juxtaposed. The optical fiber 4, the spacer 5, the tension member 6 and the like constitute an optical fiber unit 7.

The optical fiber unit 7 is covered with an upper winding tape 8 made of soft-flammable resin. The optical fiber unit 7 covered with the upper tape 8 is inserted into an inner protective tube 9 made of stainless steel, and is covered with the inner protective tube 9 to be protected from external force.

The inner protective tube 9 is loosely inserted into an outer protective tube 12 composed of an inner stainless steel tube 10 and an outer non-twisting resin tube 11, and is covered with the protective tube 12. .. Furthermore, the inner protective tube 9 and the outer protective tube 12
A ceramic powder 13 is filled in the space between and. This ceramic powder 13 has a particle size of 1-10.
It is made of ceramics having a low thermal conductivity, such as alumina, zirconia, and talc. The ceramic powder 13 is in a green state before firing or sintering.

When the ambient temperature of the optical fiber cable laying place of this embodiment becomes high due to a fire or the like and the outer peripheral temperature of the optical fiber cable becomes high, the ceramic powder 13 blocks this heat and the heat is removed. Almost no information is transmitted to the optical fiber unit 7. Therefore,
The optical fiber 4 can be protected from high heat and there is no hindrance to signal transmission.

When the ceramic powder 13 is heated to a predetermined temperature or higher due to a high temperature of fire or continuous fire for a long time, the powder 10 is sequentially sintered from the outside as shown in FIG. Alternatively, it is baked and cured. That is,
The heat of the fire is used to harden the ceramic powder 13 and dramatically increase the mechanical strength. Therefore, even if the walls that support the optical cable disappear or burn out,
Alternatively, in some cases, even if the resin tube 11 or the stainless steel tube 10 of the outer protective tube 12 is melted down, the optical fiber cable keeps its shape. Therefore, the transmission signal is not attenuated by the mechanical pressure applied to the optical fiber 4. Therefore, the communication function and the control function can be maintained even for a long time or a high temperature fire.

As described above, this optical fiber cable exhibits extremely high heat resistance in a fire or the like. Further, as described above, since the ceramic powder 10 effectively has a heat-resistant function, it is not necessary to provide a thick heat-resistant layer around the optical fiber unit 7, and the entire optical fiber cable can be made small in diameter and easy to handle. it can.

When laying an optical fiber cable, it is necessary to bend the cable,
In this case, since the ceramic powder 13 has an extremely small particle diameter, there is no problem in the followability with respect to the shape change, and it goes without saying that the powder 13 does not hinder the bending process.

[0016]

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. In this second embodiment,
A plurality of pressure-releasing pipes 14 are embedded inside the ceramic powder 13 so as to extend in the same direction as the optical fiber unit 7, and their ends are opened to the outside of the cable at appropriate positions. Each of the pressure releasing pipes 14 bends a flat plate along the width direction as shown in FIG.
It is configured by abutting the edges in the width direction.

Therefore, when the ceramic powder 13 is sintered or fired, the gas generated from the binder impregnated in the ceramic powder 13 is introduced into the pipe 14 from the butt portion 14a of the pressure release pipe 14. , Is discharged to the outside through the pipe 14.

Therefore, the temperature rise inside the optical fiber cable including the ceramic powder 13 can be suppressed, and the internal pressure increase of the optical fiber cable due to gas can be suppressed to prevent the cable from bursting and the optical fiber 4
It is possible to prevent a large internal pressure from being applied to.

[0019]

As described in detail above, the present invention has the effect of effectively protecting the optical fiber from the high heat when a fire or the like occurs.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an optical fiber cable showing a first embodiment embodying the present invention.

FIG. 2 is a perspective view of an end portion of an optical fiber cable.

FIG. 3 is a cross-sectional view showing an operating state of the optical fiber cable at the time of fire.

FIG. 4 is a cross sectional view of an optical fiber cable showing a second embodiment of the present invention.

FIG. 5 is an enlarged cross-sectional view of the vicinity of a pressure relief pipe of a second embodiment.

FIG. 6 is a cross-sectional view of a conventional optical fiber cable.

[Explanation of symbols]

1 optical fiber strand, 4 optical fiber, 9 inner protective tube, 12 outer protective tube, 13 ceramic powder.

Claims (1)

[Claims] 1. An optical fiber unit in which a plurality of optical fibers are arranged in parallel is inserted into an inner protective tube to cover the optical fiber unit with an inner protective tube, and an inner protective tube is loosely inserted into an outer protective tube to form an outer protective tube. An optical fiber cable characterized by covering an inner protective tube, and further filling a space between the inner protective tube and the outer protective tube with a ceramic powder that is sintered or fired at a predetermined temperature.