JPH0972794A - Optical fiber temperature sensor and temperature monitoring system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber temperature sensor which can be installed without requiring a large-scale laying construction and can detect the abnormality in the temperature at a specific point along an optical fiber with a single detection optical fiber using an inexpensive signal processing device and an optical fiber temperature monitoring system using it. SOLUTION: A light signal is transmitted through an optical fiber temperature sensor 10 where a temperature sensor 14 including a shape memory alloy wire 16 for bending an optical fiber 12 in the longitudinal direction for measuring the transmission loss of the light signal is fixed at a specific temperature of a position in the longitudinal direction of the optical fiber 12, thus detecting the temperature of a part where the temperature sensor 14 is fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber temperature sensor for detecting an abnormal temperature rise due to a fire or a plant failure, and a temperature monitoring system using the same, more specifically, for example, a building, an underground mall, The present invention relates to a multi-point type optical fiber temperature sensor applied to remote and wide area temperature monitoring in tunnels, various plants and the like, and a temperature monitoring system using the same.

[0002]

2. Description of the Related Art A multi-point temperature monitoring system 80 as shown in FIG. 8 is known as a representative of conventional multi-point temperature monitoring systems. This multi-point temperature monitoring system 80
Is a system in which a large number of thermocouples 81a, 81b, 81c are used as temperature detecting elements and are arranged. The multipoint temperature monitoring system 80 shown in FIG. 8 includes thermocouples 81a, 81b,
81c is a subsystem A, and is composed of a plurality of subsystems such as subsystem B and subsystem C. Subsystem A is configured as described below. Since the subsystem B and the subsystem C are the same as the subsystem A, detailed description thereof will be omitted.

In FIG. 8, 82a, 82b, 82c
Is a converter that converts thermoelectromotive force of the thermocouple into a predetermined electric signal. Reference numerals 83a, 83b, and 83c are signal transmission lines. Reference numeral 84 is a device that multiplexes and transmits signals from the respective converters. Reference numeral 85 is a transmission path for multiplexed signals. Reference numeral 86 denotes a main signal processing device that performs a function of extracting each signal from the multiplexed signal, a display, and the like. The multipoint temperature monitoring system 80 using the thermocouple as the detection element has the following disadvantages. As the number of monitoring points increases, the number of converters 82a, 82b, 82c, the multiplex transmission device 84, and the transmission line 85 also increase, and a large-scale installation work of the equipment installation line is involved, so the equipment and installation work become expensive. . Also, thermocouples 81a, 81b, 81
When it is necessary to change the installation location of the sensing element consisting of c, not only the thermocouples 81a, 81b and 81c but also the converter 82a,
Relocation of 82b, 82c and multiplexer 84 is also unavoidable. The converters 82a, 82b, 82c and the multiplexer 84 are electronic circuits, require a proper installation environment, and are not necessarily flexible in the installation location.

As a means of compensating for the above disadvantages, a temperature monitoring system using an optical fiber temperature sensor has been proposed. An optical fiber Raman temperature sensor is well known as an optical fiber temperature sensor of this temperature monitoring system. The detection principle of the optical fiber temperature sensor is as follows. When light propagates in the optical fiber, light having a wavelength different from that of the incident light is generated due to a scattering phenomenon called Raman effect in the optical fiber. The scattered light having a shorter wavelength than the incident light is called anti-Stokes light, and the scattered light having a longer wavelength is called Stokes light. The intensity of this Raman scattered light depends on the temperature of the optical fiber. Therefore, conversely, by measuring the intensity of Raman scattered light, the temperature of the optical fiber, that is, the temperature of the environment in which the optical fiber is placed can be known.

When pulsed light is incident on the optical fiber of a temperature sensor using this principle, the pulsed light propagates through the optical fiber and is Raman scattered. Part of the generated anti-Stokes light and Stokes light returns to the incident end of the optical fiber. By measuring the time from the incidence of a light pulse until the Raman scattered light returns and the intensity of the Raman scattered light, the location where Raman scattering occurs and the temperature at that location can be known.

Since the incident pulsed light is Raman-scattered at every part of the fiber, the temperature of any part along the fiber can be known. FIG. 9 shows a basic configuration of a temperature monitoring system 90 using an optical fiber temperature sensor. Reference numeral 91 is an optical fiber as a temperature detecting element, 92 is a pulse light source, and 93 is a drive circuit thereof. An optical multiplexer / demultiplexer 94 discriminates the function of allowing the light from the pulse light source 92 to enter the optical fiber 91 and the Raman scattered light returned from the optical fiber 91, and guides them to the optical receivers 95a and 95b. Reference numeral 96 denotes a main signal processing device, which amplifies and averages the electric signal obtained by photoelectric conversion by the optical receivers 95a and 95b, outputs the electric signal after converting it into temperature, and controls the drive circuit 93. It is a circuit having a function of performing. Reference numeral 97 is a reference optical fiber for knowing the intensity of Raman scattered light at a reference temperature when the temperature is converted.

[0007]

The optical fiber temperature monitoring system 90 utilizing the above-mentioned principle of Raman scattered light can measure the temperature at any position along the optical fiber 91 with one detection optical fiber 91. , It has advantages such as no large-scale installation work, but has the following disadvantages. Since the magnitude of Raman scattered light is extremely weak, a pulsed light source 92 having a large output is required. For example, when using an LD light source, a drive circuit 93 that generates a large drive current in a pulse shape is required.

Further, the photo-receivers 95a and 95b with high conversion efficiency for converting a weak optical signal into an electric signal, a high performance amplifier for amplifying a weak electric signal, and a noise signal are simultaneously amplified together with the signal, so that noise There is a need for a main signal processing device 96 that performs an advanced signal processing and is provided with an averaging processing circuit for extracting a signal from the like. Therefore, not only the complicated configuration as shown in FIG. 9 but also an expensive measurement system is usually provided. In addition, since advanced signal processing is performed, adjustments and maintenance related to measurement are troublesome.

The present invention solves the above-mentioned problems and can be installed without a large-scale installation work, and a single detection optical fiber can be used to inexpensively detect an abnormal temperature at a predetermined position along the optical fiber. An object of the present invention is to provide an optical fiber temperature sensor that can be detected by a signal processing device and an optical fiber temperature monitoring system using the same.

[0010]

The present invention has the following means in order to solve the above problems.

The optical fiber temperature sensor according to claim 1 of the present invention is a temperature detecting member including a shape memory alloy wire which bends in the longitudinal direction of the optical fiber at a prescribed temperature at a prescribed position in the longitudinal direction of the optical fiber. Is fixed.

In an optical fiber temperature sensor according to a second aspect of the present invention, the temperature detecting member is a tape-shaped member in which a pressure-sensitive adhesive is applied to at least one surface of a plastic resin material containing a shape memory alloy wire. It is characterized by

According to a third aspect of the present invention, in a temperature monitoring system, a temperature detecting member including a shape memory alloy wire which bends in a longitudinal direction of an optical fiber at a predetermined temperature at a predetermined temperature is provided. An optical signal is transmitted to a fixed optical fiber temperature sensor, the transmission loss of the optical signal is measured, and the temperature of the portion where the temperature detecting member is fixed is detected.

In the temperature monitoring system according to the fourth aspect of the present invention, it is an OTDR device that measures the transmission loss.

The optical fiber temperature sensor and the temperature monitoring system using the same according to the present invention are such that the shape memory alloy wire of the temperature detecting member recovers its shape at a predetermined temperature to give a bend in the longitudinal direction of the optical fiber. is there. The optical fiber bent by the temperature detecting member causes optical transmission loss at that portion.
This state is measured by measuring the optical transmission loss of the optical fiber in the longitudinal direction, for example, a standard OTDR that has been conventionally used.
The temperature is detected by an (Optical Time Domein Reflection) device to detect an abnormality in the temperature of the portion to which the temperature detecting member is fixed.

The optical fiber temperature sensor and the temperature monitoring system using the optical fiber temperature sensor can easily monitor the temperature at a plurality of locations by only laying one optical fiber, and therefore it is easy to perform without large-scale laying work. Can be installed in Moreover, since the optical transmission loss of the bent optical fiber is measured, it is possible to perform temperature monitoring without using an advanced device such as an optical fiber Raman temperature sensor that performs advanced signal processing. Maintenance is also easy. further,
By changing the temperature detecting member to a tape-like one side with an adhesive applied, it is possible to easily change the temperature detecting member by peeling off the adhesive tape-shaped temperature detecting member, for example, when changing the temperature detecting portion. it can.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to embodiments. (Embodiment 1) FIG. 1 shows an embodiment of an optical fiber temperature sensor of the present invention. In an optical fiber temperature sensor 10, a temperature detecting member 14 is fixed at a predetermined position of an optical fiber wire 12. It was done. Optical fiber strand 12
Is an ordinary optical fiber having, for example, NA = 0.2, a core diameter of 50 μm, a fiber diameter of 125 μm, and a UV urethane coating outer diameter of 250 μm.

As shown in FIG. 2, the temperature detecting member 14 has a shape memory alloy wire 16 enclosed in a vinyl resin 18 and is formed in a tape shape by applying an adhesive 20 on one surface thereof. Is. The shape memory alloy wire 16 is, for example, a linear Ti Ni alloy wire having a diameter of 0.2 mm and a length of 20 mm which is subjected to a memory treatment so as to be bent at about 100 ° C. at about 90 degrees. The temperature detecting member 14 is the optical fiber element wire 1.
The optical fiber temperature sensor 10 is formed by bonding the two on both sides. The optical fiber temperature sensor 10 is used to configure a temperature monitoring system 30 as shown in FIG. The temperature monitoring system 30 includes an optical fiber temperature sensor 1
The OTDR device 32 is arranged at one end of 0,
The optical transmission loss of the optical fiber temperature sensor 10 is monitored.

Regarding this temperature monitoring system 30, the OT
The third temperature detection member 14 on the side of the DR device 32 is installed in a heating box (not shown), and the optical fiber temperature sensor 10 is used by the OTDR device 32 while increasing the temperature from room temperature to 120 ° C.
When the optical transmission loss is monitored, the temperature detection member 14 is bent and deformed at about 100 ° C., and the optical fiber element wire 12 is bent accordingly, and the third temperature detection member 14 on the OTDR device 32 side is generated. It was detected that a transmission loss occurred.

(Embodiment 2) FIG. 4 shows another example of the embodiment of the optical fiber temperature sensor of the present invention. A feature of the optical fiber temperature sensor 40 of the present embodiment is that the temperature detecting member 42 is fixed to the optical fiber core wire 44 in a flat tape shape. Optical fiber core 4
4 has NA = 0.2, core diameter 50 μm, fiber diameter 12
5 μm, a silicone primary coat and a nylon secondary coat (finished outer diameter 0.9 mm) were applied.
The temperature detection member 42 is a shape memory alloy wire 46 enclosed in a vinyl resin 48, and the adhesive 20 is provided on one surface thereof.
Is applied to form a tape.

The shape memory alloy wire 46 is, for example, about 100.degree.
0.5m in diameter that has been memorized so that it bends sinusoidally
It is a linear Ti Ni alloy wire having a length of m and a length of 100 mm.
The temperature detecting member 42 is attached to the optical fiber core wire 44 together with the vinyl tape 50 to form the optical fiber temperature sensor 40. In FIG. 4, reference numeral 52 is an adhesive applied to the vinyl tape 50. A temperature monitoring system 60 is configured using the optical fiber temperature sensor 40 as shown in FIG.

Regarding this temperature monitoring system 60, the OT
The third temperature detecting member 42 on the side of the DR device 32 is installed in a heating box (not shown), and the optical fiber temperature sensor 40 is used by the OTDR device 32 while increasing the temperature from room temperature to 120 ° C.
When the optical transmission loss of the OTDR device 32 is monitored, the temperature detecting member 42 is bent and deformed into a sine wave at about 100 ° C., and the optical fiber core 44 is bent accordingly.
It was detected that a transmission loss occurred in the third temperature detection member 42 on the side.

(Other Embodiments) FIG. 6 shows another example of the embodiment of the optical fiber temperature sensor of the present invention. Optical fiber temperature sensor 70 of the present embodiment
The feature is that the temperature detection member 72 is a half sleeve with an adhesive 74. As in the case of the first embodiment, a detailed description will be given with the inclusion of the shape memory alloy wire 76, which has been subjected to the memory treatment so as to be bent into a predetermined shape at a predetermined temperature, in the temperature detection member 72 in the form of a half sleeve. Omit it.

The optical fiber temperature sensor 70A of FIG. 7 shows another example. The feature of the optical fiber temperature sensor 70A of the present embodiment is that the temperature detecting member 72A is a split sleeve with an adhesive 74. As in the first embodiment, a detailed description is omitted because the shape-memory alloy wire 76, which has been subjected to a memory treatment so as to be bent into a predetermined shape at a predetermined temperature, is included in the split sleeve-shaped temperature detection member 72A. To do. Of course, the optical fiber temperature sensors 70 and 70A can be used as a temperature monitoring system as in the first embodiment. Incidentally, the optical fiber temperature sensor is not limited to the above-mentioned shape, and in short, if the shape-memory alloy wire that has been subjected to the memory processing so as to bend at a predetermined temperature into a predetermined shape is included in the temperature detecting member. It's good.

[0025]

As described above, the optical fiber temperature sensor of the present invention and the temperature monitoring system using the same can greatly monitor the temperature at a plurality of locations by laying one optical fiber. It can be easily installed without large-scale installation work. Moreover, since the optical transmission loss of the bent optical fiber is measured, it is possible to perform temperature monitoring without using an advanced device such as an optical fiber Raman temperature sensor that performs advanced signal processing. Maintenance is also easy. Further, by making the temperature detecting member into a tape shape with one surface coated with an adhesive, for example, when changing the temperature detecting portion, the temperature detecting member in the form of an adhesive tape is peeled off and easily changed. be able to.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of an embodiment of an optical fiber temperature sensor of the present invention.

FIG. 2 is a perspective view showing an example of a temperature detecting member used in the optical fiber temperature sensor of FIG.

FIG. 3 is an explanatory diagram showing an example of an embodiment of a temperature monitoring system using the optical fiber temperature sensor of FIG.

FIG. 4 is a perspective view showing another example of the embodiment of the optical fiber temperature sensor of the present invention.

5 is an explanatory diagram showing another example of the embodiment of the temperature monitoring system using the optical fiber temperature sensor of FIG.

FIG. 6 is a perspective view showing another example of the embodiment of the optical fiber temperature sensor of the present invention.

FIG. 7 is a perspective view showing still another example of the embodiment of the optical fiber temperature sensor of the present invention.

FIG. 8 is an explanatory diagram showing a conventional temperature monitoring system using a thermocouple.

FIG. 9 is an explanatory diagram showing a conventional temperature monitoring system using an optical fiber temperature sensor.

[Explanation of symbols]

 10 Optical Fiber Temperature Sensor 12 Optical Fiber Element Wire 14 Temperature Detection Member 16 Shape Memory Alloy Wire 18 Plastic Resin 20 Adhesive 30 Temperature Monitoring System 32 OTDR Device

Claims (4)

[Claims] 1. An optical fiber, wherein a temperature detecting member containing a shape memory alloy wire that bends in the longitudinal direction of the optical fiber at a predetermined temperature is fixed at a predetermined position in the longitudinal direction of the optical fiber. Temperature sensor. 2. The light according to claim 1, wherein the temperature detecting member is a tape-shaped member in which a pressure-sensitive adhesive is applied to at least one surface of a plastic resin material containing a shape memory alloy wire. Fiber temperature sensor. 3. An optical signal to an optical fiber temperature sensor to which a temperature detecting member containing a shape memory alloy wire that bends in the longitudinal direction of the optical fiber at a predetermined temperature is fixed at a predetermined position in the longitudinal direction of the optical fiber. The temperature monitoring system is characterized in that the temperature of a portion to which the temperature detecting member is fixed is detected by transmitting the optical signal and measuring the transmission loss of the optical signal. 4. The temperature monitoring system according to claim 3, wherein it is an OTDR device that measures the transmission loss.