JPH06118287A - Pipe, transmission cable using it, and its diagnostic method - Google Patents

Abstract

PURPOSE:To feed a laser beam to detecting fibers after pipe cables are installed, measure the reflected light, and diagnose the state of the cables by inserting transmission lines into the pipes, and burying the detecting optical fibers in the pipes over the whole length. CONSTITUTION:A transmission cable is arranged with a tensile strength wire 1 at the center and six pipes 2, 2... around it, they are covered with a plastic sheath 4, detecting optical fibers 3 are spirally buried against the longitudinal axis of the pipes 2, 2... at the thick internal sections of the pipes 2, 2..., and transmission lines 5 are inserted into the pipes 2, 2.... A laser beam 11 is fed to the detecting fibers 3 after the pipe cables are installed, the reflected light 13 is measured, and the state of the cables can be diagnosed (when external pressure is locally applied to a cable or the cable is bent at the curvature smaller than the specified one, the light reception level of the reflected light of the detecting fiber 3 at this portion is decreased, for example).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe, a transmission cable formed by inserting a transmission line into the pipe, and a diagnostic method thereof.

[0002]

2. Description of the Related Art As one means for forming and laying a transmission cable, a pipe cable in which pipes 2 are assembled is previously laid as described in Japanese Patent Laid-Open No. 59-10460, and is transmitted to this pipe. There is a method of inserting the line 5 with compressed air (FIG. 4) and realizing a network that meets demand. Here, the transmission line 5 may be an optical fiber, a metal electric wire, or a combination thereof. This method does not damage the transmission line because no external force is applied to it during installation. It is easy to change and add routes after laying, and the cost can be reduced.

[0003]

Although the prior art has the above-mentioned characteristics, the pipe is deformed at the time of laying the pipe cable or thereafter, and the transmission line cannot be passed,
In some cases, it was re-installed again. However, there is no established method for inspecting the deformation of the pipe when the pipe cable is laid, and there is a problem that the wiring is hindered. Therefore, it is an object of the present invention to provide a pipe, a transmission cable using the pipe, and a diagnostic method for the pipe, which solve the above problems.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a plastic pipe having a predetermined wall thickness, which is spiral or axial with respect to the axis of the pipe on its inner surface, outer surface or inside the wall thickness. It is a pipe in which a detection fiber is arranged. The present invention also provides a cable in which a transmission line is inserted inside a pipe, wherein the pipe has a sensing fiber on its inner surface, outer surface, or inside the wall thickness that is spiral or along the axis of the pipe. Is provided, and in particular, the transmission line is a transmission cable including an optical transmission fiber.

Further, according to the present invention, laser light is incident on a detection fiber provided on the inner surface, outer surface or inside of the wall of the pipe of the transmission cable formed by inserting the transmission line inside the pipe. A diagnostic method for a transmission cable, which measures the reflected light and detects the state of the pipe from the change in the reflected light.

[0007]

In the transmission cable of the present invention having the above-mentioned structure, the transmission line is inserted inside the pipe, and the optical fiber for detection is embedded over the entire length of the pipe. Therefore, by sending a laser beam to the detection fiber after laying the pipe cable and measuring the reflected light (for example, when external pressure is locally applied to the cable or the cable is bent with a curvature smaller than the specified value, the detection fiber of that part is detected). Can diagnose the condition of the cable (since the received light level of the reflected light is reduced due to the increased light leakage). Further, the pipe of the present invention is characterized in that even a general pipe such as a water pipe can be detected in a similar manner after being laid.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a transmission cable of the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. FIG. 1 is a sectional view showing the structure of this embodiment. The transmission cable has a tensile strength wire 1 in the center and six pipes 2, 2 ... Arranged around it, and these are covered with a plastic sheath 4. Inside the wall thickness of the pipes 2, 2. The optical fiber 3 for detection is embedded in a spiral shape with respect to the longitudinal axis of the pipe, and the transmission line 5 is inserted inside the pipe. The tensile strength wire 1 has a steel wire coated with polyethylene (hereinafter abbreviated as PE). The pipes 2, 2 ... Are made of a material having a density of 0.92 gr / cc and a low density PE of MI (melt index) of 0.25 gr / 10 min. Finished to an outer diameter of 8 mm.

This pipe is formed by extruding a thin-walled pipe once, and a detection fiber 3 is provided around the pipe at a pitch of 100 mm.
Main winding was carried out, and PE was again extrusion-coated thereon. If the cable is laid with a relatively large radius of curvature, the sensing fiber can be embedded along the axis of the pipe, which is more sensitive than the spiral case and the fiber can be shorter. If necessary, a plurality of detection fibers may be embedded, and the detection fibers may be formed by adhering to the inner and outer surfaces of the pipe. The transmission line 5 to be inserted has a diameter of 125 m.
UV curing resin is applied on the glass fiber of m,
Seven pieces of this were twisted and a foamed PE layer was coated thereon to form an optical fiber unit having an outer diameter of 2 mm.

FIG. 2 is an explanatory diagram relating to the diagnostic method of this embodiment. The laser light 11 is incident on the detection fiber 3 through a lens (not shown) and a dummy fiber through the half mirror 14 and reflected from the unit length of this fiber 1
3 goes through Half Mira 14 and Optical Time Domain Reflec
Enter the t meter (hereinafter abbreviated as OTDR). OTD
In R, the horizontal axis represents the length direction of the detection fiber, and the vertical axis represents the light reception level reflected from each point of the fiber. In FIG. 3, when the detection fiber is buried in a normal state, the reception level becomes an inclined straight line as shown by 21, but when the pipe undergoes deformation such as buckling in the middle, incident light remarkably occurs at that portion. Light leakage occurs, and the light receiving level sharply decreases as indicated by 22. In this way, the laser light is made incident on the detection fiber 3 arranged in the pipe 2, and the reflected light from this fiber is measured.
The position of the deformation can be diagnosed.

The pipe cable shown in FIG.
m, wound on a drum with a barrel diameter of 1.5 m, and measured the light receiving level of the detection fibers 3 of the pipes 2, 2 ... By the method shown in FIG. It was shown and judged to be normal. So 2
5kg / cm optical fiber unit for the pipe of the book
Compressed with ² compressed air. The time required was 3.5 minutes or less. Then, the pipe cable was pulled out from the drum, the portion at 20 m was bent once into a circle having a diameter of 40 cm, and the reflected light of each pipe was measured.
A slight decrease was observed at 0 m. When the optical fiber unit was inserted through the two pipes in this state, they were completed within 4.5 minutes. Furthermore, when the reflected light was measured by reducing the diameter of the circle to 20 cm, a clear step appeared at the light receiving level of each pipe of 20 m. In this state, when the optical fiber unit was inserted into the remaining two pipes, it clogged at 20 m.

[0012]

According to the transmission cable of the present invention, a transmission line is inserted inside a pipe, and an optical fiber for detection is embedded in the pipe over its entire length. Therefore, after laying the pipe cable, send laser light to the detection fiber and measure the reflected light,
The condition of the cable can be diagnosed. Further, the pipe of the present invention has the same effect on a general pipe such as a water pipe.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of this embodiment.

FIG. 2 is an explanatory diagram related to a diagnosis method of the present embodiment.

FIG. 3 is a diagram showing a display of OTDR.

FIG. 4 is a cross-sectional view showing a conventional cable configuration.

[Explanation of symbols]

 1: Strength line 2: Pipe 3: Detection fiber 4: Sheath 5: Transmission line 11: Laser light 12: Incident light 13: Reflected light 14: Half mirror 15: OTDR

Claims (4)

[Claims] 1. A plastic pipe having a predetermined wall thickness, wherein a sensing fiber is arranged on the inner surface, outer surface or inside the wall of the pipe in a spiral shape or along the axis with respect to the axis of the pipe. A pipe characterized by that. 2. A cable in which a transmission line is inserted inside a pipe, wherein the pipe has a sensing fiber on its inner surface, outer surface, or inside the wall thickness, which is spiral or along the axis of the pipe. A transmission cable that is provided. 3. The transmission cable according to claim 2, wherein the transmission line includes an optical transmission fiber. 4. A laser beam is incident on a detection fiber provided on an inner surface, an outer surface or inside the wall of the pipe of a transmission cable formed by inserting a transmission line inside the pipe, and the reflection thereof is reflected. A method for diagnosing a transmission cable, which comprises measuring light and detecting a state of the pipe from a change in reflected light.