JPH07234166A - Optical fiber temperature monitoring device - Google Patents

Abstract

PURPOSE:To provide an optical fiber temperature monitoring device that detects temperature at two or more points and determines the temperature detecting positions by detecting with an optical pulse tester the positions, bent by more than the specified degrees by deforming the shape memory alloy at a temperature set point, on optical fibers in a combination of a shape memory alloy and optical fibers. CONSTITUTION:An optical fiber temperature monitoring device comprises an optical fiber temperature detecting device made of an optical fiber 1 coated with shape memory alloys 3a, 3b to form optical fiber sensors 5, 5b, 5x, means of holding the optical fiber 1, and means 6, which is connected to the optical fiber temperature detecting device. The means 6 transmits and receives optical pulses, and does arithmetic on, displays, and stores optical pulses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a shape memory alloy and an optical fiber in combination to pass through the optical fiber by a method in which the shape change of the shape memory alloy at a set temperature is utilized to bend the optical fiber beyond a specified curvature. Optical fiber temperature monitoring device that detects the temperature change and its position by a method that changes the attenuation of the reflected light and reflects the change of the attenuation of the return light and the position of its occurrence using an optical pulse tester. Regarding

BACKGROUND OF THE INVENTION An optical fiber gives a loss to light propagating through it when it is bent to a certain degree or more. The occurrence of the loss due to this bending will be described. As shown in FIG. 3, the optical fiber 1 has a structure in which the periphery of the central core 2 is covered with the cladding 10. Then, the light propagates in the core while being repeatedly reflected. In order for light to undergo total internal reflection on the inner peripheral surface, it is necessary that the incident angle α, which indicates the inclination angle with respect to the normal line, be equal to or greater than the critical angle αc determined by physical properties such as the refractive index of the core. When the incident angle α is less than the critical angle αc (α <αc), the light is not totally reflected and a part of the light is incident on the clad and leaks from the core to the outside to increase the propagation loss. Therefore, as shown in FIG. 3, when the optical fiber is bent beyond the specified curvature, the propagation loss sharply increases at the bending point and the reflected light from the point beyond that point also rapidly attenuates. The present application utilizes the characteristics of this optical fiber.

[0003]

2. Description of the Related Art A conventional temperature monitoring device uses a conventional method as a temperature sensor because it uses a resistor whose resistance value changes with temperature or a device such as a bimetal which opens and closes an electrical contact with temperature. When performing temperature monitoring, it was necessary to wire one detection circuit to one temperature sensor.

[0004]

Therefore, if it is attempted to simultaneously monitor the temperature of a large number of points by the conventional method, a pair of detection circuits are provided for each temperature sensor, so that the number of points to be monitored increases. The wiring for the detection circuit was so complicated and enormous. Further, unless the installation location of the detection sensor and the detection circuit corresponding thereto are surely identified, it is not possible to know at which position the temperature is detected. The present invention has been made to solve such a problem, and an object of the present invention is to provide a temperature monitoring device capable of simultaneously monitoring different temperatures at a large number of points with one optical fiber.

[0005]

In order to solve the above-mentioned problems, in the optical fiber temperature monitoring apparatus of the present invention, a part of the optical fiber is covered with a shape memory alloy, and the shape memory alloy has a predetermined temperature. By deforming into a shape, the optical fiber in that part is given a bend of a specified curvature or more,
An optical fiber temperature sensor is formed at an arbitrary position of the optical fiber, an optical pulse is transmitted from one end of the optical fiber, the intensity of return light propagated in the optical fiber and reflected from the optical fiber temperature sensor, and The position where the returning light is generated is measured from the arrival time at the sending point, and compared with the measured value at the same position measured and stored in the previous measurement, and the change is automatically detected. It is equipped with an optical pulse tester that detects the course of the temperature change and the position where the temperature change occurs.

The specific structure of the temperature sensor for realizing this is the structure shown in FIG. 2, which is composed of a fixed frame 9, a shape memory alloy member 3, a front protective plate 8 and a rear protective plate 7. The shape memory alloy member is provided with a groove 15 capable of accommodating an optical fiber therein, and an arbitrary part of the optical fiber is accommodated along the groove so that the optical fiber in the groove is deformed by the deformation of the shape memory alloy member. Is also deformed and bent to form an optical fiber temperature sensor. Further, the deformation action of the shape memory alloy member is configured to press the member from both sides. Then, it is guided by the front / rear surface protection plate and is protected so that the internal optical fiber does not protrude due to the deformation of the member. Fixed frame 9
Holds the both ends of the shape memory alloy member in a deformable manner so as to ensure the shape change of the member, and acts so as not to exert the influence of the shape change on the optical fiber outside the fixed frame. In addition, the thickness of the fixed frame is slightly larger than that of the shape memory alloy member, and the shape memory alloy member can be freely shaped as the temperature changes in the internal space covered by the front and rear protective plates. You can change.

[0007]

The principle of the optical fiber temperature sensor used in the optical fiber temperature monitoring device will be described. The optical fiber temperature sensor 5 has the structure shown in FIGS. 1 and 2, and is an optical fiber covered with a shape memory alloy 3 that changes its shape at a set temperature T ° C. The shape memory alloy holds the internal optical fiber with a gentle curvature as shown in the shape memory alloy 3a in FIG. 1 until the temperature reaches T ° C.
When the temperature reaches ℃, the shape is deformed as shown in the shape memory alloy 3b of FIG. 1 and the optical fiber 1 inside is bent to a specified curvature or more.

The optical fiber temperature sensor bends the optical fiber at the set temperature until it reaches the critical angle αc, and attenuates the reflected light in that state. Therefore, as shown in FIG. 3, when the optical fiber is bent beyond the specified curvature, the propagation loss rapidly increases at the bending point, and the reflected light from that point further abruptly attenuates.

An optical pulse is applied from the tip of the optical fiber to which the optical pulse tester 6 is connected to the optical fiber temperature sensor that has reached the set temperature and is bent over the specified curvature. Although this optical pulse propagates in the optical fiber 1, it senses a temperature at a set temperature and is greatly attenuated at the position of the optical fiber temperature sensor 5 which is bent beyond a specified curvature.

The optical pulse propagates while generating reflected light due to backscattering at each point of the optical fiber, but the reflected light after passing through the above-mentioned attenuation point is greatly attenuated. Therefore, if the optical pulse tester 6 sends an optical pulse and observes the reflected light, the optical pulse tester bends due to a temperature difference from the time difference from the application time of the optical pulse to the time when the reflected light is greatly attenuated. The optical fiber length up to can be calculated. Therefore, the position of the optical fiber whose temperature has changed can be specified.

Further, a shape memory alloy (3, 13) which is temperature-sensitive to a plurality of set temperatures in one optical fiber temperature sensor.
By providing a plurality of stages, it is possible to perform temperature detection in a plurality of stages. In this case, it is also possible to use one shape memory alloy that gradually senses a plurality of temperatures (FIG. 7).

[0012]

【Example】

[Embodiment 1] Next, an outline of the temperature detecting method of the present application using the optical fiber temperature sensor 5 and the optical pulse tester 6 will be described. An optical pulse tester 6 applies an optical pulse from the tip of the optical fiber to which the sensor is connected to the optical fiber temperature sensor that has reached a set temperature and is bent over a specified curvature. Although this optical pulse propagates in the optical fiber 1, it is temperature-sensitive at the set temperature and is greatly attenuated at the position of the optical fiber temperature sensor 5 which is bent beyond a specified curvature. Further, the optical pulse propagates while generating reflected light due to backscattering at each point of the optical fiber, but the reflected light after passing through the attenuation point is greatly attenuated.

Therefore, if the optical pulse is sent by the optical pulse tester 6 and the reflected light is observed, the temperature is sensitive and bent from the time difference from the application time of the optical pulse to the time when the reflected light is greatly attenuated. Since the optical fiber length up to the optical fiber temperature sensor can be calculated, the position of the optical fiber temperature sensor that has detected the temperature can be specified. In the optical fiber temperature sensor, the reflected light of the transmitted pulse is the optical pulse tester 6
You can connect as many as you want to a single optical fiber as long as it can be observed. Further, by using shape memory alloys that react at different set temperatures, it is possible to manufacture optical fiber temperature sensors that detect different temperatures.

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view showing a schematic configuration of an optical fiber temperature monitoring device of an embodiment, in which an optical pulse tester 6 is connected to optical fiber temperature sensors 5, 5b, ..., 5x via an optical connector 4 and an optical fiber 1. Has been done. First, the optical pulse tester 6 is constructed, for example, as shown in FIG. That is, the optical pulse output from the optical pulse generation circuit 6a composed of a laser light source device or the like at a constant cycle is supplied to the external optical fiber 1 via the optical pulse transmission section 6b and the transmission / reception coupling section 6c. On the other hand, the light input from the optical fiber 1 into the device through the transmission / reception coupling unit 6c is converted into an electric signal by the optical pulse reception unit 6d and input to the signal processing unit 6e.

The signal processing unit 6e displays the transmission signal and the reception signal on the CRT display unit 6f, converts each signal into digital data and transmits it to the arithmetic processing unit 6g. The arithmetic processing unit 6g executes various arithmetic processes such as the optical fiber length, displays the arithmetic result on the CRT display unit 6f, and stores it in the storage unit 6h. The timing circuit 6i measures the transmission / reception timing difference of the optical pulse. Next, the operation of combining the optical pulse tester thus configured with the optical fiber temperature sensor 5 will be described.

FIG. 5 is a table of signals displayed on the CRT display section 6f when one of the optical fiber temperature sensors (5x in FIG. 1) set in the middle of the optical fiber is temperature-sensitive and bends beyond the specified curvature. It is an example. The operator operates the operation panel to take the generation cycle of the optical pulse in the optical pulse generation circuit 6f to reciprocate the entire length of the optical fiber 1 where the optical signal is extended to install the optical fiber temperature sensor. Adjust to a constant cycle longer than the time. Then, the optical pulse 71 output from the optical pulse tester 6 is applied to the optical fiber 1 via the optical connector at the input end. For example, time to
When the optical pulse 71 is transmitted at, the optical pulse 71 propagates through the connected optical connector 4 through the optical fiber 1 and the optical fiber temperature sensors 5, 5b, ... 5x. Then, the backscattered light 72 from each part of the propagation path of the optical pulse 71 is incident on the optical pulse tester 6 while the optical pulse 71 propagates through these parts.

The optical pulse tester 6 sends out an optical pulse 71 at time t 0 and at the same time receives the backscattered light of the optical pulse 71 by the transmission / reception coupling section 6c and the optical pulse receiving section 6d and measures the optical intensity thereof. C is processed by the signal processing unit 6e.
The display section 6f composed of an RT display or the like provides a display as shown in FIG. In FIG. 5, the horizontal axis represents the elapsed time t, or the length of the optical fiber, that is, the distance d, and the vertical axis represents the intensity of backscattered light. The elapsed time t is obtained from the timing circuit 6i. Further, in the optical pulse 71 propagating in the optical fiber, even if the above-mentioned incident angle α is the critical angle α,
A certain amount is attenuated even if it is equal to or more than c. Therefore, the light intensity of the backscattered light 72 received by the optical pulse tester 6 is attenuated as the optical pulse 71 moves far from the input end.

Since the optical pulse tester 6 operates in this way, in the CRT display shown in FIG. 5, the optical pulse 71 propagates in the optical fiber, and the temperature of the optical pulse 71 is sensed on the way and the optical fiber temperature is bent beyond the specified curvature. When reaching the sensor 5x, the optical pulse 71 is rapidly attenuated while passing through the inflection point D.
As a result, the backscattered light 71 of the optical pulse immediately after passing through the inflection point is incident on the optical pulse tester at time tn,
The intensity of the received light drops sharply. By observing this decrease in strength on the CRT display section 6f, the temperature at the installation position can be detected. When passing through an optical fiber temperature sensor having no temperature-sensitive bending, abrupt attenuation of light intensity does not occur. In FIG. 5, tm indicates that the temperature is not sensed, and tn indicates that the temperature is sensed. Further, since the optical pulse 71 is Fresnel-reflected at the tip of the optical fiber and bounces back, a pulse waveform showing strong Fresnel reflection is generated at the time of points A and B corresponding to the input end and the tip.

Next, the distance to the temperature-bent optical fiber temperature sensor 5x is calculated by calculating the time (tn-t) from the transmission time t o of the optical pulse to the time tn at which the light intensity sharply decreases.
o) multiplied by the propagation velocity of the light in the fiber (known),
Since it is a round trip, it is calculated by halving this. Further, the distance to the tip of the optical fiber (or the cutting point in case of an accident) is the time (too) from the transmission time to until the time too when the optical fiber tip returns after being Fresnel-reflected.
It is calculated by multiplying -to) by the propagation velocity of light and halving it. This calculation is performed by the calculation processing unit 6g.

Further, the optical fiber temperature sensors 5, 5b, ...
In order to know the installation location of how much 5x is installed from the input end of the optical fiber, when connecting the optical fiber temperature sensor to the optical fiber, connect each to the optical fiber in a temperature-sensitive state. Just do it. Then, if the optical pulse tester 6 sends an optical pulse 71 from the start end of the optical fiber, the optical fiber temperature sensor 5 portion becomes a large signal attenuation point, and a pulse waveform indicating Fresnel reflection is returned from that portion. Therefore, it is possible to calculate the distance to the optical fiber temperature sensor, obtain the installation distance, and record it in advance.

Further, the sending time to, the time tn at which the light intensity sharply decreases, the time too at which a strong pulse waveform is generated,
The distance from the tip of the optical fiber to the optical pulse tester 6 calculated using these times is stored in the storage unit 6h and CR after the arithmetic processing in the arithmetic processing unit 6g.
It is displayed on the T display portion 6f. Further, the storage unit 6h stores specifications and information about the detected temperature of each optical fiber temperature sensor 5 and a specific installation location corresponding to the distance on the optical fiber. Can be displayed on the CRT display section 6f as required. Also,
CR which temperature sensor at which installation location is sensitive
It can also be displayed on the T display portion 6f. Note that these specifications are held in the storage unit 6h at least until the calculation of the specifications is completed or the calculation specifications and information are updated by the next monitoring.

Further, when a break occurs in the optical fiber temperature sensor, the optical connector or the optical fiber during the operation of the apparatus, the Fresnel reflection mentioned above occurs from this break point so that the failure position can be found and the optical pulse test can be conducted. It is possible to recover one after another from a place near the container 6.

[Embodiment 2] In the optical fiber temperature sensor, as shown in FIGS. 2A to 2H, the protective plate is removed and the optical fiber is housed in the groove of the shape memory alloy member.
Since the protective plate is closed, the sensor can be installed afterwards at any position of the optical fiber without cutting the optical fiber. Further, the front protective plate 8 and the rear protective plate 7 are provided with small holes on the entire surface to improve heat transfer from the outside, and the shape memory alloy member is sandwiched between the front and rear protective plates. Has been done. Until the temperature of the shape memory alloy member reaches the shape memory temperature T ° C,
The internal optical fiber is held with a gentle curvature, but when the temperature reaches T ° C., the internal optical fiber 1 is bent so as to have a prescribed curvature (critical angle) or more. The protective plate may be formed in a net shape instead of the small holes formed in the protective plate.

The optical fiber temperature sensor used in the optical fiber temperature monitoring device will be described. By accommodating an arbitrary part of the optical fiber along the groove (FIG. 2 (f)) and deforming the shape memory alloy member, the optical fiber in the groove is also deformed and bent to form an optical fiber temperature sensor. Further, since the deformation action of the shape memory alloy member is configured to press the member from both sides by the protective plates (7, 8),
The inner optical fiber is protected from being protruded by the deformation of the member induced by the both protective plates. The fixed frame 9 holds the both ends of the shape memory alloy member in a deformable manner so that the shape change of the shape memory alloy member can be surely performed, and acts so as not to give an influence of the shape change to the optical fiber outside the fixed frame. . The thickness of the fixed frame is slightly larger than that of the shape memory alloy member, so that the shape memory alloy part can freely change its shape in the internal space covered by the front and rear protective plates. Has become.

The front protection plate and the rear protection plate are as described above.
Small holes are formed on the entire surface in order to improve the transfer of heat from the outside, and the shape memory alloy member is sandwiched between the front and rear protective plates (7 and 8 in FIG. 1). The shape memory alloy member holds the internal optical fiber with a gentle curvature as shown in the temperature sensor 3a in FIG. 1 until the temperature reaches the shape memory temperature T ° C. However, if the temperature reaches T ° C. The shape is deformed as shown by the temperature sensor 3b of No. 1, that is, the internal optical fiber 1 is bent so as to have a specified curvature (critical angle) or more. Specifically, the temperature sensor 5 provided at a desired position of the optical fiber has a shape memory alloy 3 with a groove for accommodating the optical fiber along the groove therein.
A fixing frame 9 for fixing both ends of the shape memory alloy in the longitudinal direction in a deformable manner, a rear surface protection plate 7 and a front surface protection plate 8 for protecting the side surfaces of the shape memory alloy, and the both protection plates (7,
8), the shape memory alloy is freely guided in the planes of both protective plates so that the shape memory alloy can be deformed, and the shape memory alloy is in a steady temperature state. A second bending state 3b which is a temperature state, and the second state maintains the angle at which the optical fiber is bent to be equal to or more than the specified curvature, and the optical fiber is bent in the first and second bending states. It is characterized in that the length before and after bending of the fiber 1 is set to be kept the same.

[Third Embodiment] Further, a shape memory alloy (3, 1) that senses a plurality of preset temperatures in one temperature sensor is used.
A plurality of 3) are provided to detect the temperature in a plurality of stages. In this case, the temperature is sensed stepwise at a plurality of temperatures, and the change state can be detected from the optical pulse tester 6 (FIG. 7).

That is, a means for comparing changes in the amount of attenuation is provided in the arithmetic processing unit 6g so as to compare and detect temperatures that change stepwise. A plurality of shape memory alloys that change above a certain temperature are arranged in series and arranged so that the attenuation amounts at these set temperatures are added. Alternatively, a composite shape memory alloy that is temperature sensitive at each of a plurality of temperatures is installed. In this way, if the attenuation amount is configured to increase as the temperature gradually rises, the attenuation amount and the temperature stored in the memory of the optical pulse tester 6 can be changed when the temperature change changes stepwise. When the amount of attenuation above a certain amount is detected, it is judged that the temperature is further changed and recorded (in this case, the temperature sources may be at substantially the same optical fiber position).

Further, if a plurality of known optical fiber temperature sensors 3 and 13 having different preset temperatures are installed at a distance of the optical fibers, the distances of the optical fibers measured by the optical pulse tester 6 are different from each other. It is possible to judge the difference in the set temperature (temperature step) (in this case, if the optical fibers are reciprocally arranged in the length direction so that the distances are different, the temperature sources may be at substantially the same position. 7).

FIG. 7 shows a case where three kinds of shape memory alloys are used.
The example which comprises one optical fiber temperature sensor is shown. Here, the detected data from the optical fiber temperature sensor is stored in the storage section 6h and displayed on the CRT display section 6f after the calculation processing in the calculation processing section 6g. Further, the storage unit 6h stores specific values of the attenuation amounts corresponding to the previously detected temperature of each optical fiber temperature sensor 5 and the distance on the optical fiber. The difference between the measurement data is calculated by the calculation processing unit 6g to determine the actual set temperature which is changed stepwise. Alternatively, the set temperature is judged from the difference in the distance. Then, the result can be displayed on the CRT display unit 6f as necessary. According to the method of this embodiment, since the arithmetic processing unit 6g is provided with the comparing and judging means, by comparing the difference between the stored previous temperature data and the present data, and judging sequentially, It is also possible to detect the temperature cycle in the target optical fiber temperature sensor 5.

[Application of the Invention of the Present Application] Next, as an application of the present application, a case of operating as an automatic temperature monitoring / warning device will be described. When using an automatic device, switch circuit 6
Turn j on. The comparison detection unit 6k is a storage unit 6h.
Then, the intensity information of the backscattered light from each temperature sensor when the detected temperature has not been reached is obtained and stored as a reference value together with the installation distance information. It receives measurement data obtained at each monitoring from the arithmetic processing unit 6g, compares it with the reference value, and if the difference exceeds the judgment value, sends a signal to the alarm unit 6l, and sends it to the CRT via the signal processing unit 6f. An alarm is displayed on the display section 6f, and the audible alarm for the operator is activated by operating the audible alarm device 6m.

This alarm monitoring / warning function is provided by the reset unit 6.
It is reset by n. The judgment value is set to a value equal to or less than the increase value of the propagation loss when the optical fiber is bent to the specified curvature. In addition, this function can generate a fault alarm when a fault occurs in the optical pulse tester or the optical fiber and the backscattered light is blocked or extremely lowered.
Furthermore, by observing the waveform displayed by the optical pulse tester whether the device is operating or not, it is possible to know the occurrence of defects such as burnout or disconnection of the optical fiber and temperature sensor, and the location It can be discovered and also restored.

[Effect of Embodiment 1] A plurality of optical fiber temperature sensors having different detection temperatures can be installed in various places of one optical fiber to detect and monitor temperature changes at a plurality of places. [Effect of Embodiment 2] The shape memory alloy has two protective plates (7,
It is guided so that it can freely deform and move in the plane of 8), and it is kept at an angle that bends the optical fiber beyond the specified curvature at the set temperature and the length before and after bending of the optical fiber in the optical fiber temperature sensor. Are kept the same length, so no excessive force is applied to the outside of the temperature sensor. Also,
Since the temperature sensor can be retrofitted, there is an effect that the sensor can be installed without cutting the optical fiber. [Effect of Embodiment 3] Even when the temperature periodically changes in a cycle of several hours or one day, the state can be detected.
Moreover, it is possible to detect stepwise changes in temperature in detail, including observing and recording the presence or absence of a predetermined temperature.

[0033]

As described above, the optical fiber temperature monitoring apparatus of the present invention uses the optical fiber as a temperature sensor and a transmission line for detection, and one optical fiber can detect different detected temperatures. Multiple optical fiber temperature sensors can be installed to detect and monitor temperature changes at multiple locations. In addition, this temperature detection and monitoring can be performed from both ends of the optical fiber, and when a failure occurs, the failure part can be automatically detected, so a temperature monitoring device that is simple, reliable, and easy to maintain Can be provided.

[Brief description of drawings]

FIG. 1 is an overall perspective view showing an outline of an optical fiber temperature monitoring device of the present invention.

FIG. 2 shows an internal detailed view and an external view of the optical fiber temperature sensor of the present invention.

FIG. 3 (a) is a diagram showing transmission of light in an optical fiber. (B) The figure which shows the bending angle of an optical fiber, and the leak of light.

FIG. 4 is a block diagram showing an outline of an optical pulse tester of the present invention.

FIG. 5 is a flowchart showing an outline of backscattered light level changes during non-temperature sensing and temperature sensing, which are operations of the present invention. (A)
FIG. 4 is a diagram showing the level of a transmission light pulse. (B) is a figure which shows the backscattered light level change at the time of non-sensing temperature. (C) is a figure which shows the backscattered light level change at the time of temperature sensing.

FIG. 6 is a diagram showing a state of a waveform displayed on the CRT display unit of the optical pulse tester of the present invention.

FIG. 7 is a diagram showing an embodiment in which a plurality of temperature sensors are connected in series and a plurality of set temperatures can be detected.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical fiber, 2 ... Core, 3,3a, 3b, 13 ... Shape memory alloy, 4 ... Optical connector, 5, 5b, 5x ... Optical fiber temperature sensor, 6 ... Optical pulse tester, 6a ... Optical pulse generating circuit, 6b ... Optical pulse transmitting means (optical pulse transmitting section), 6c ... Transmission / reception coupling means (transmission / reception coupling section), 6d ... Light receiving means ( Optical pulse light receiving section), 6e ... Signal processing means (signal processing section), 6f ... Display means (CRT display section), 6g ... Arithmetic processing means (arithmetic processing section), 6h ... Storage means (Memory unit), 7 ... Rear surface protection plate, 8 ... Front surface protection plate, 9 ... Fixed frame (means for bending the optical fiber beyond a specified curvature), 10 ... Clad, 11. ..Optical signals, 14 ... Screws, 15 ... Grooves, 71 ... Optical pulses

[Procedure amendment]

[Submission date] February 13, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

FIG. 5 is a flowchart showing an outline of backscattered light level changes during non-temperature sensing and temperature sensing, which are operations of the present invention.
From the top, a, b, and c are shown in the order of the transmission light pulse level, the backscattered light level change when the temperature is not sensed, and the backscattered light level change when the temperature is sensed.

Claims (1)

[Claims] 1. An optical fiber temperature sensor (5) provided at a plurality of desired positions of an optical fiber (1), and an optical signal connected to one end of the optical fiber, the optical signal being sent to the optical fiber,
An optical fiber temperature monitoring device comprising: an optical pulse tester (6) for receiving return light from the optical fiber and performing a bending process on the return light, wherein the optical fiber temperature sensor (5) is deformed at a set temperature. A shape memory alloy (3) and a means (9) for bending the optical fiber by the shape memory alloy to a specified curvature or more, and the optical pulse tester (6) transmits and receives an optical signal. Coupling means (6c) and optical pulse sending means (6b)
A light receiving means (6d) for converting the return light from the optical fiber into an electric signal, a signal processing means (6e) for processing an output signal of the light receiving means, an arithmetic processing means (6g), and a display means (6f). ) And storage means (6h), the temperature signals from each of the optical fiber temperature sensors (5) provided at the plurality of positions are subjected to folding processing to automatically change the temperature at each position. An optical fiber temperature monitoring device characterized by detecting the occurrence of