JPH06100528B2 - Optical fiber infiltration detection line and infiltration detection type optical fiber cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is capable of detecting a flooded state and a flooded portion over a long span, and is not affected by electromagnetic interference. Optical fiber Flood sensing line and flood sensing optical fiber It is about cables.

(Prior Art) Conventional sensors used for water immersion detection include (1) a sensor that electrically detects using a humidity sensor, and (2) a sensor that electrically detects using a water alarm line. FIG. 8 shows a conventional example of the above (1), 1 is a humidity sensor, 2 is a transmitter,
Reference numeral 3 is a signal line, and 4 is a receiving unit. In this case, the humidity at a specific location is converted into an electric signal to detect the flooded state. However, in order to monitor multiple locations, multiple humidity sensors and multiple transmitters are required, which increases the complexity and cost of the device. There was a flaw. In addition, the continuous inundation monitoring was extremely difficult in practice.

FIG. 9 shows the conventional water immersion alarm line of (2), 5 is an insulator, and 6 is a conductor.

FIG. 10 shows an example of use of the above (2), 7 is an inundation warning line,
Reference numeral 8 is a pulse tester. As shown in FIG. 9, the inundation alarm line is a balanced pair in which the conductor is partially exposed, and this is laid at the measured point. If water enters the installation area,
Since the line resistance of the inundation alarm line decreases, the inundation can be detected by measuring the line resistance value. Further, since the characteristic impedance changes at the flooded portion, it is also possible to measure the flooded portion from the reflection of the electric pulse due to the mismatch of the characteristic impedance using a pulse tester.
In this case, since the electric pulse is used, the transmission loss of the cable made of a conductor becomes large in a long span, which makes it difficult to perform high-precision monitoring. Further, since the conventional examples (1) and (2) both use an electric signal, they have a drawback that they are susceptible to electromagnetic interference.

Further, conventionally, another inundation warning wire used for a communication line has a single structure in which a central conductor is partially exposed from an insulating coating, and this infiltration warning wire is made of a metal tape coated on a cable core. A cable for communication with a flood alarm wire was manufactured by putting the cable on the inside and coating the cable on the outside of the metal tape.

However, research on a non-metal type optical fiber cable that is completely free from electromagnetic interference has been advanced in recent years, and such a cable has a drawback that the conventional flooding alarm line using metal cannot be applied. The maximum distance measured by the pulse tester is about 15 km for the metal flood alarm line.
In this case, the measurement accuracy of water intrusion detection is several 100 m, and there is a drawback that it is not suitable for a cable capable of long-distance relay transmission over 20 km such as an optical fiber.

(Problems to be Solved by the Invention) To provide a water detection line and a water detection type optical fiber cable that can perform high-precision water monitoring over a long span and that is not affected by electromagnetic interference. is there.

The present invention detects the water-immersed state at a specific location by increasing the bending loss of the brazing optical fiber core due to the swelling action of the water-absorbing material.
FIG. 1 is an embodiment diagram of an optical fiber immersion detection line of the present invention, in which (a) and (c) show a cross section perpendicular to the optical fiber core axis, and (b) shows AA of (a). ′ Shows a cross section, and (d) shows a cross section at BB ′ of (c). In FIG. 1, 9 is a water absorbing material, 10 is an optical fiber core wire, 11
Is a corrugated member, and 12 is a holding member. The optical fiber core is
The one that is easily affected by the bending loss is preferable, and for example, the one in which a single mode fiber having a low refractive index difference is coated with a flexible material is suitable. As the water-absorbing material, a starch-based material, a cellulose-based material or the like having a large water-absorption swelling effect and a gelling effect is suitable. The corrugated member and the pressing member are preferably made of a plastic material that absorbs little water, and (a) shows a tape-shaped structure in which the corrugated member 11 also serves as a holding member for the water-absorbing material. In (c), the corrugated member (core with groove) 11 is processed into a cylindrical shape (or a cylindrical shape), and the optical fiber core wire 10 is housed in a groove (having irregularities at the bottom) provided in the outer peripheral portion thereof. It has a columnar (or cylindrical) structure in which a water absorbing material 9 and a pressing member 12 are wound around in this order. In both of the structures (a) and (c), it is necessary for water to permeate well into the water absorbing material, and it is preferable to provide an appropriate slit as shown in (a) and (d), for example.

FIG. 2 shows an example of use of the water immersion detection device according to the present invention, in which 13 is an optical fiber water immersion detection line and 14 is an optical pulse tester.

FIG. 3 shows the behavior of the optical fiber core wire when the optical fiber immersion detection wire of the present invention is inundated. 9 to 11 are the same as in FIG. The optical fiber core wire is bent with a radius of curvature R by the action of the swelling pressure of the water absorbing material and the wavy tape. FIG. 4 shows the relationship between the bending radius and the optical loss when the optical fiber core wire is uniformly bent. Λ is the wavelength, Δ is the relative refractive index difference of the optical fiber, and a is the core radius of the optical fiber. . When bending is applied to the optical fiber core, the loss sharply increases as the bending radius decreases.

Therefore, by appropriately selecting the uneven shape of the wavy member having unevenness on the bottom, when the water-absorbing material swells during water absorption, it is possible to give the optical fiber core an appropriate radius of curvature, As the radius of curvature becomes smaller, the loss of the optical fiber core wire increases, and it is possible to detect the waterlogged portion by observing the waveform of the optical pulse tester.

In addition, in the measurement using the optical pulse tester, from FIG. 4, in the single mode fiber, when the long wavelength band (λ = 1.3 μm) apart from the cutoff wavelength is used, the short wavelength band (λ = It can be seen that the bending loss can be detected with higher sensitivity than the use of 0.85 μm). In addition, since the optical pulse tester can detect loss changes of 0.1 dB or more with high accuracy, the radius of curvature of the optical fiber core is set to 30 mm as shown in Fig. 4.
If it is less than mm (λ = 1.3 μm), the optical loss will be 0.1 dB or more, and the flooded part can be detected sufficiently accurately.

FIGS. 5, 6 and 7 show an embodiment of the water detection type optical fiber cable of the present invention, 9 is a water absorbing material (water absorbing tape), 10 is an optical fiber core wire, 11 is a corrugated member (corrugated tape) ), 15 is a cable jacket, 16 is a cable core, and 17 is a grooved plastic core.

FIG. 5 shows an embodiment in which an optical fiber water immersion detection line (water infiltration warning line) is vertically attached to a cable core, which is effective for water infiltration detection of a water infiltration warning line fabric.

FIG. 6 shows a corrugated member (corrugated tape) 11 and an optical fiber core wire 10.
Shows an example in which is wound around the cable core 16 in a spiral shape, and is wound with a water absorbing material (water absorbing tape) 9 thereon,
With this structure, it is possible to detect which position of the jacket 15 is submerged.

FIG. 7 (a) shows an embodiment in which a grooved plastic cable core 17 is used, in which the groove bottom is provided with irregularities and the outer side is wound with a water absorbing tape or yarn.

FIG. 7 (b) is an enlarged perspective view of the grooved plastic core of FIG. 7 (a).

(Effects of the Invention) As described above, the optical fiber immersion detection line of the present invention utilizes the increase in optical loss due to the bending of the optical fiber core wire, so that it does not suffer from electromagnetic interference and the optical pulse tester is used. By using it, there is an advantage that high precision inundation monitoring in a long distance section is possible.

Further, the water detection type optical fiber cable of the present invention also has the same advantage, and the optical fiber cable can be made non-metallic.

[Brief description of drawings]

FIG. 1 shows an embodiment of an optical fiber water immersion detection line of the present invention. (A) and (c) are cross-sectional views perpendicular to the optical fiber core axis, and (b) is a cross section taken along line AA 'of (a). Figure, (d)
Is a cross-sectional view taken along the line BB ′ of (c), FIG. 2 is a block diagram of a water immersion monitoring device using the optical fiber water immersion detection line of the present invention, and FIG. 3 is an optical fiber water immersion detection line of the present invention. FIG. 4 is a diagram showing the behavior of the optical fiber core wire at this time, FIG. 4 is a diagram showing the relationship between the bending radius and the optical loss in the optical fiber core wire, and FIGS. 5, 6, and 7 are the inundation detection type of the present invention. An embodiment of an optical fiber cable is shown, and FIG. 5, FIG. 6 and FIG. 7 (a) are cross-sectional views perpendicular to the longitudinal direction of the cable, and FIG. 7 (b) is a grooved member of FIG. 7 (a). Fig. 8 is an enlarged perspective view of the plastic cable core, Fig. 8 is a configuration diagram of a conventional inundation monitoring device when a humidity sensor is used, Fig. 9 is a perspective view showing the structure of a conventional inundation alarm line, and Fig. 10 is an inundation alarm. It is a block diagram of the conventional infiltration monitoring apparatus which used the line. 1 ... Humidity sensor, 2 ... Transmission part 3 ... Signal line, 4 ... Reception part 5 ... Insulator, 6 ... Conductor 7 ... Water intrusion alarm line, 8 ... Pulse tester 9 ... Water absorbing material , 10 ...... Optical fiber core wire 11 ...... Wavy member, 12 ...... Presser member 13 ...... Optical fiber immersion detection wire 14 ...... Optical pulse tester, 15 ...... Cable jacket 16 ...... Cable core 17 ...... Groove With plastic cable core

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location G02B 6/00 (72) Inventor Naoshi Uesugi 162 Shirahone, Shirokata, Tokai-mura, Naka-gun, Ibaraki Prefecture Nippon Telegraph and Telephone Corporation, Ibaraki Research Institute of Telecommunications (56) Reference JP 57-128304 (JP, A) JP 60-117122 (JP, A) JP 57-114947 (JP, U) JP Kai 60-181648 (JP, U)

Claims (4)

[Claims] 1. A pressing member, a water absorbing material that swells by a water absorbing action, an optical fiber core wire, and a corrugated member having irregularities on the surface in contact with the optical fiber core wire are arranged in contact in this order, and the pressing member is An optical fiber immersion detection line, characterized in that it is formed integrally with the corrugated member or is formed separately from the corrugated member, and that the pressing member has a hole for exposing the water absorbing material. 2. An optical fiber infiltration detection line in which a water absorbing material swelling by a water absorbing action, an optical fiber core wire, and a corrugated member having irregularities on a surface in contact with the optical fiber core wire are arranged in contact in this order, A water immersion detection type optical fiber cable, which is installed on the outer periphery of a cable core in the longitudinal direction, and a jacket is provided on the outside of the cable core and the optical fiber water immersion detection line. 3. The water absorbing material is uniformly distributed on the outer periphery of the cable core.
The water detection type optical fiber cable described in the item. 4. The water detection type optical fiber cable according to claim 2, wherein the corrugated member is shared with the bottom of the groove of the grooved cable core.