JP2942270B2 - Water immersion sensor and water immersion detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a waterlogging sensor and a waterlogging detection method using an optical transmission body.

<Prior art> A conventional immersion sensor using an optical transmission body such as an optical cable or an optical fiber cord is installed at a connection point between them.
Water intrusion has been detected by bending a part of an optical fiber in an optical cable or an optical fiber cord or applying a side pressure to increase optical loss.

For example, in a water immersion sensor disclosed in Japanese Patent Application Laid-Open No. 62-52433, an optical fiber is inserted into a case body containing a water-absorbing agent that expands by absorbing water, and an uneven plate sandwiching the optical fiber is further inserted into the case body. It is provided. For this reason, if the water-absorbing agent expands during water immersion, the optical fiber is pinched by the uneven plate and deformed into a waveform, and it was possible to detect the water immersion by measuring the increased optical loss.

<Problem to be Solved by the Invention> A conventional immersion sensor is to apply an optical loss by adding a bend or the like to an optical fiber housed in an optical cable or the like laid in advance at the time of inundation. The optical loss α per unit length in the optical fiber is given by the following equation (1)
Indicated by

However, this is the case where a single mode fiber is used, where R is a bending radius and A and B are constants.

However, even if the optical fiber is manufactured within the same standard, the above constants A and B are not the same, and therefore, even if the optical fiber is bent with the same bending radius R, the optical loss is greatly different. there were. On the other hand, since there are optical fibers having small optical loss even when bent at the same bending radius R, the bending radius R is set to be constant in order to be able to detect inundation with all optical fibers within the standard. Need to be relatively small.

Therefore, if water is inundated in a plurality of places, an optical loss may be given to the optical fiber more than necessary, and the dynamic range of the optical pulse tester may be deviated, so that there is a disadvantage that the backward detection cannot be performed.

The present invention has been made in view of the above prior art, and has as its object to provide a waterlogging sensor and a waterlogging detection method in which an increase in optical loss during waterlogging is stable.

<Means for Solving the Problems> The configuration of the immersion sensor of the present invention that achieves the above object includes an optical transmission body that causes optical loss when stress is applied,
In a waterlogging sensor comprising an optical loss applying member for applying a constant stress to the optical transmission body during flooding, when the optical transmission body is preliminarily measured for optical loss against stress as the optical transmission body,
It is characterized in that a plurality of optical transmitters having an optical loss falling within a range of about 0.05 dB are arranged and used in series. In addition, the configuration according to the immersion detection method of the present invention that achieves the above object includes an optical transmission body that causes optical loss when stress is applied, and an optical loss applying member that applies a constant stress to the optical transmission body when the optical transmission body is immersed in water. In the waterlogging detection method using a waterlogging sensor consisting of: Optical transmitters are arranged in series and used.
An optical pulse tester is connected to the optical transmitter via another optical transmitter, and an optical loss is measured.

<Operation> When a certain stress is applied from the optical loss applying member to the optical transmission body in which the range of the optical loss is defined with respect to the stress at the time of immersion in water, the optical loss is stably generated within the above range.

<Embodiment> Hereinafter, the present invention will be specifically described based on an embodiment shown in the drawings.

FIG. 1 shows an embodiment of the present invention. In the embodiment shown in the figure, an optical fiber is used as an optical transmission body. That is, the immersion sensor 1 according to the present embodiment includes an optical fiber 2 having an optical loss range defined for stress such as bending and pressure, as described later, and bending the optical fiber 2 with a predetermined radius of curvature. And an optical loss imparting member 3 to be added. As the optical loss applying member 3, for example, a wonder yarn (registered trademark of Kao Corporation) is inserted into a plastic pipe as a water-absorbing shrinkable string, and one end thereof is fixed to one end of the pipe, while the wonder yarn is fixed. Is vertically hooked to the optical fiber 2. Therefore, when the wonder yarn absorbs water and contracts, the optical fiber 2 is bent so as to be drawn into the pipe.

Further, both ends of the optical fiber 2 are connected to an optical fiber 6 drawn out of an optical cable 5 via a fusion portion 4, and this optical cable is connected to an optical pulse tester, a power meter and the like (not shown). If an optical pulse tester is used, a loss increase of about 0.2 dB can be sufficiently detected.However, with a commercially available optical fiber that satisfies ordinary standards,
It causes further loss. For example, as a single mode fiber for the 1.3 μm band, from among commercially available products within the standard of MFD of 9.2 to 10.8 μm and effective cutoff of 1.150 to 1.290 μm
Fifty samples were randomly extracted, and the increase in loss during water immersion was measured by the optical loss imparting member 3. As shown in FIG. 2, the loss increased over a wide range. Therefore, if the standard is used, the loss is expected to increase further.

However, since the immersion sensor 1 of the present embodiment uses the optical fiber 2 which causes an increase of 0.45 to 0.50 dB when immersed in water, for example, FIG. It can be seen that the distribution of loss is very stable as shown in FIG. That is, the optical loss imparting member 3
By simply bending the optical fiber 2 with a constant radius of curvature, the range in which optical loss occurs is not fixed. However, if the optical fiber 2 is selected according to its characteristics and used in a water immersion sensor, the range of optical loss can be arbitrarily determined. Can be set to

Next, another embodiment of the method of using the immersion sensor of the present invention will be described with reference to FIG. As shown in the figure, 10
The 00m optical fiber is cut into 300m, 300m, and 400m to form optical fibers 7, 8, and 9, with a water sensor 1 having an optical fiber length of 1m interposed therebetween. Spliced. A 1.55 μm laser diode 13 is connected to one end of the optical fiber 6 via a V-groove 11 and a pigtail 12, and a power meter 16 is connected to the immersion sensor 1 connected to the optical fiber 9 via a V-groove 14 and a pigtail 15. Connected. When such equipment was immersed in order from one side and the optical loss was measured during that time, the increase in optical loss was 0.47 dB, 0.51 dB,
The stable optical loss increase was 0.49 dB.

<Effect of the Invention> As described above in detail based on the embodiment, the waterlogging sensor and the waterlogging detection method of the present invention measure the optical loss with respect to the stress as an optical transmission body in advance and set Since a plurality of optical transmitters having an optical loss that falls within a range of about a decibel variation are used in series,
A stable increase in optical loss is obtained at the time of flooding, and this is effective when a plurality of flood sensors are optically installed on a series of optical transmission bodies.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a waterlogging sensor according to an embodiment of the present invention, and FIG. 2 is a diagram showing an increase in optical loss when waterlogging is detected by using 50 extracted single-mode fibers. FIG. 3 is a histogram of an increase in optical loss when water intrusion is repeatedly detected using an optical fiber that causes a predetermined optical loss, and FIG. 4 is a method of water intrusion detection using the water intrusion sensor of the present invention. It is explanatory drawing which shows an Example. In the drawing, 1 is an immersion sensor, 2, 6, 7, 8, 9 are optical fibers, 3 is an optical loss imparting member, 4, 10 is a fused portion, 5 is an optical cable, 11, 14 is a V groove, 12 , 15 is a pigtail, 13 is a laser diode, and 16 is a power meter.

Continuing from the front page (72) Inventor Hirotsuru Matsumoto 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Naohiro Tsuchiya 1-16-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone (56) References JP-A-62-266333 (JP, A) JP-A-62-240833 (JP, A) JP-A-62-52433 (JP, A) JP-A-62-28634 (JP, A A)

Claims (2)

(57) [Claims] An immersion sensor comprising: an optical transmission member that generates optical loss when stress is applied; and an optical loss applying member that applies a constant stress to the optical transmission member when immersed in water. A water immersion sensor characterized in that a plurality of optical transmission bodies having an optical loss such that the optical loss is measured in advance and falls within a range of about 0.05 dB at the time of immersion are used in series. 2. A waterlogging detection method using a waterlogging sensor comprising an optical transmission member that generates an optical loss when stress is applied and an optical loss applying member that applies a constant stress to the optical transmission member when the optical transmission member is flooded. A plurality of optical transmission bodies having an optical loss such that the optical loss with respect to the stress is measured in advance as the optical transmission body and falls within a range of about 0.05 dB at the time of flooding are used in series, and further, An inundation detection method, comprising: connecting an optical pulse tester to the optical transmitter via another optical transmitter, and measuring an optical loss.