JP4458058B2 - Optical fiber sensor external force detection method and optical fiber sensor external force detection device - Google Patents

Description

  In the present invention, light is incident on an optical fiber having a fiber Bragg grating (hereinafter simply referred to as “FBG”) sensor, and the wavelength shift of the reflected light by the FBG sensor is measured for each wavelength. The present invention relates to an external force detection method for an optical fiber sensor that detects the presence or absence of an external force by a person or the like, and an external force detection device thereof.

  Conventionally, as an external force detection device (intrusion detection device) for an optical fiber sensor, a device using a combination of a polarization fluctuation detector (OTDR) and an FBG sensor for detecting breakage at a sensor installation location such as a fence. (For example, see Patent Document 1).

Japanese Patent Laying-Open No. 2005-32224 (FIG. 1)

  As an intrusion detection device using an optical fiber sensor, there has heretofore been a device that measures a wavelength shift amount or polarization fluctuation of reflected light by an FBG sensor and detects an external force or an optical fiber cut by an intruder or the like. However, this type of conventional apparatus detects the external force by an intruder by measuring the wavelength displacement (shift) amount of the installed FBG sensor. However, the FBG sensor is used for intrusion detection outdoors or in places where temperature changes occur. It is often installed, and changes in the refractive index due to ambient temperature fluctuations and wind disturbances, which are the characteristics of the original optical fiber, are not always constant. Therefore, external force is applied to the reflected light from the FBG sensor. There is a problem that a wavelength shift that is not the influence of the error occurs, and this wavelength shift is erroneously detected as an external force by an intruder or the like, or cannot be detected (hereinafter, both cases are referred to as false detection). It was. In addition, since this type of conventional apparatus does not have a temperature compensation function (including disturbance compensation) for an FBG sensor or an optical fiber, it is possible to determine whether or not this type of apparatus / system is operating normally. There was a problem that it was difficult.

  The present invention has been made to solve the above-described problems, and is a novel optical fiber sensor having a temperature compensation function that does not falsely detect an external force even if the refractive index changes due to a change in the ambient temperature of the FBG sensor. It is an object of the present invention to provide an inspection method and an inspection apparatus therefor.

External force detecting method for the optical fiber sensor according to claim 1, Bragg grating frequency than is Do different incident light into an optical fiber having a plurality of Bragg gratings sensors with different reference resonant reflection wavelengths, each Bragg grating sensor calculating an average value of the wavelength of the received reflected light reflected, among the intensity distribution for each wavelength of the received reflected light, the reflected light coming is successively reflected by the Bragg grating sensor corresponding to the wavelength is the peak by In the intensity distribution for each wavelength of the reflected light, the primary detection reflected light wavelength , which is the wavelength of the reflected light whose absolute value of the difference between the peak wavelength and the corresponding reference resonant reflection wavelength exceeds a predetermined value , is detected. when the, if the absolute value of the difference between said average value and said primary detecting reflected light wavelengths to the primary reflected light detected wavelength that is detected exceeds the predetermined value, the primary reflected light detected Bragg grating sensor corresponding to the length is intended determines that external force is applied.

External force detecting method for the optical fiber sensor according to claim 2, Bragg grating frequency than is Do different incident light into an optical fiber having a plurality of Bragg gratings sensors with different reference resonant reflection wavelengths, each Bragg grating sensor calculating an average value of the wavelength of the received reflected light reflected, among the intensity distribution for each wavelength of the received reflected light, the reflected light coming is successively reflected by the Bragg grating sensor corresponding to the wavelength is the peak by and, among the intensity distribution for each wavelength of the reflected light, detecting a predetermined value in the reflected light wavelength which is the wavelength of the reflected light of the absolute value of the predetermined value of the difference between the reference resonant reflection wavelength corresponding to the wavelength is the peak and, when the absolute value of the difference between said average value and said predetermined value in the reflected light wavelength to the predetermined value in the reflected light wavelength is detected exceeds the predetermined value, to respond to the predetermined value in the reflected light wavelength The Bragg grating sensor is intended determines that external force is applied.

External force detecting device for an optical fiber sensor according to claim 3, Bragg grating frequency than is Do different, outgoing optical fiber having a plurality of Bragg grating sensors having different reference resonant reflection wavelength, respectively, the light to the optical fiber A light source that receives the reflected light of each wavelength reflected by each Bragg grating sensor, and a spectrum detector that detects a peak wavelength among the intensity distributions of the received reflected light for each wavelength. And an average value calculation for calculating an average value of the wavelengths of the reflected light sequentially reflected by the Bragg grating sensor corresponding to the peak wavelength in the intensity distribution for each wavelength of the reflected light received by the light receiving unit. in parts and, among the intensity distribution for each wavelength of the reflected light, the wavelength of the reflected light absolute value exceeds a predetermined value of the difference between the reference resonant reflection wavelength corresponding to the wavelength is the peak Primary detecting reflected light wavelength detector for detecting a primary reflected light detected wavelength that, the average value of up to primary reflected light detected wavelength that is detected from the average calculation unit, the primary detection and the average value A secondary detection reflected light wavelength detection unit that detects a secondary detection reflected light wavelength that is a wavelength of reflected light that has an absolute value of a difference from the reflected light wavelength that exceeds the predetermined value, and a secondary detection reflected light wavelength detection unit. A sensor specifying unit that specifies a Bragg grating sensor corresponding to the detected secondary detection reflected light wavelength, and determines that an external force is applied to the Bragg grating sensor specified by the sensor specifying unit .

External force detecting device for an optical fiber sensor according to claim 4, Bragg grating frequency than is Do different, outgoing optical fiber having a plurality of Bragg grating sensors having different reference resonant reflection wavelength, respectively, the light to the optical fiber A light source that receives the reflected light of each wavelength reflected by each Bragg grating sensor, and a spectrum detector that detects a peak wavelength among the intensity distributions of the received reflected light for each wavelength. And an average value calculation for calculating an average value of the wavelengths of the reflected light sequentially reflected by the Bragg grating sensor corresponding to the peak wavelength in the intensity distribution for each wavelength of the reflected light received by the light receiving unit. and parts, of the intensity distribution for each wavelength of the reflected light, the absolute value of the difference between the reference resonant reflection wavelength corresponding to the wavelength is the peak is a wavelength of the reflected light within a predetermined value Obtaining a predetermined value in the reflected light wavelength detector for detecting the value within the reflection wavelength, the average value up to the predetermined value in the reflected light wavelength is detected from the average calculation unit, the predetermined and the average value A secondary detection reflected light wavelength detection unit that detects a secondary detection reflected light wavelength that is a wavelength of reflected light whose absolute value of the difference from the reflected light wavelength within the value exceeds the predetermined value, and this secondary detection reflected light wavelength detection A sensor specifying unit that specifies a Bragg grating sensor corresponding to the secondary detection reflected light wavelength detected by the unit , and determines that an external force is applied to the Bragg grating sensor specified by the sensor specifying unit .

As described above, according to the first aspect of the invention, the average value until the primary detection reflected light wavelength is detected (the average value of the wavelengths of the reflected light sequentially reflected by the corresponding Bragg grating sensor) and the primary value. If the absolute value of the difference from the detected reflected light wavelength exceeds a predetermined value, it is determined that an external force has been applied to the Bragg grating sensor corresponding to the primary detected reflected light wavelength. There exists an effect that the external force detection method of a fiber sensor can be provided.

According to the second aspect of the present invention, the average value until the reflected light wavelength within the predetermined value is detected (the average value of the wavelengths of the reflected light sequentially reflected by the corresponding Bragg grating sensor) and the reflected light within the predetermined value. When the absolute value of the difference from the wavelength exceeds a predetermined value, it is determined that an external force has been applied to the Bragg grating sensor corresponding to the reflected light wavelength within the predetermined value, so the optical fiber sensor is independent of the ambient temperature fluctuation of the Bragg grating sensor. It is possible to provide an external force detection method.

According to the invention of claim 3, the average value until the primary detection reflected light wavelength is detected (the average value of the wavelengths of the reflected light sequentially reflected by the corresponding Bragg grating sensor), and the primary detection reflected light wavelength, If the absolute value of the difference exceeds a predetermined value, the sensor identification unit identifies the Bragg grating sensor when an external force is applied to the Bragg grating sensor corresponding to the primary detection reflected light wavelength, which is related to fluctuations in the ambient temperature of the Bragg grating sensor. And an external force detecting device for an optical fiber sensor can be provided.

According to the fourth aspect of the present invention, the average value until the reflected light wavelength within the predetermined value is detected (the average value of the wavelengths of the reflected light sequentially reflected by the corresponding Bragg grating sensor) and the reflected light within the predetermined value. If the absolute value of the difference between the wavelength exceeds a predetermined value, the sensor specifying unit and external force is applied to the Bragg grating sensor corresponding to a predetermined value in the reflected light wavelength so identify the Bragg grating sensor, the Bragg grating sensor ambient temperature There is an effect that an external force detection device for an optical fiber sensor can be provided regardless of fluctuations.

Embodiment 1 FIG.
Hereinafter, an external force detection device for an optical fiber sensor according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a system configuration diagram of an external force detection device for an optical fiber sensor according to a first embodiment. 2A and 2B are basic operation diagrams of the Bragg grating sensor. FIG. 2A is a perspective view of the optical fiber sensor, FIG. 2B is an enlarged view of the Bragg grating, and FIG. 3 is a reflection due to an external force of the Bragg grating. FIG. 4 is a detailed diagram of a specific part of the external force detection device of the optical fiber sensor according to the first embodiment. FIG. 5 is a wavelength shift diagram of reflected light due to fluctuations in the ambient temperature of the Bragg grating. FIG. 6A is a time variation diagram of the reflected light of the optical fiber sensor according to the first embodiment. FIG. 6A shows the detection of the wavelength shift amount based on the reference resonance reflection wavelength, and FIG. Change to reflection wavelength moving average value, FIG. 6C is a wavelength shift amount detection by resonant reflection wavelength moving average value, FIG. 7 is a time change diagram of reflected light of the optical fiber sensor according to the first embodiment, FIG. 7A shows the wavelength shift due to the reference resonance reflection wavelength. Detection, FIG. 7 (b), a change from the reference resonant reflection wavelength to the resonant reflection wavelength moving average value, FIG. 7 (c) is a wavelength shift amount detection by the resonant reflection wavelength moving average. 1 to 7, reference numeral 1 denotes an optical fiber, and 2 denotes a plurality of Bragg grating sensors provided in the optical fiber 1 with different Bragg grating intervals, and includes a surface vibration sensor, a tension sensor, and a load sensor, as will be described later. . The Bragg grating sensor 2 includes a case where a plurality of types of these sensors are used and a case where only one type of each of these sensors is used, and is appropriately used depending on the application. Reference numeral 3 denotes a light source including a laser light source that makes light (transmission light) incident on the optical fiber 1. Light emitted from the light source is supplied to the optical fiber 1, and the light source 3 and the optical fiber 1 are optically coupled. ing. Reference numeral 4 denotes an optical receiver that receives reflected light of each wavelength reflected from each Bragg grating sensor 2. Reference numeral 5 denotes a circulator for making light (transmission light) from the light source 3 incident on the optical fiber 1 and sending reflected light from each Bragg grating sensor 2 provided on the optical fiber 1 to the light receiving unit 4. 6 is a spectrum detector that detects the intensity distribution for each wavelength of the reflected light received by the light receiver 4, and 7 is the peak wavelength among the intensity distributions for each wavelength detected by the spectrum detector 6. the absolute value of the difference between the reference resonant reflection wavelength is detected what exceeds a predetermined value Δλ is a threshold, a specifying unit for specifying a Bragg grating sensor 2 corresponding to the wavelength is the peak. Further, 8 is a fence in which the Bragg grating sensor 2 of the surface vibration sensor is installed, 9 is a fence in which a tension sensor is installed, and 10 is a wall surface on which a load sensor is installed. Reference numeral 11 denotes a detection line connected to the vicinity of the Bragg grating sensor 2 of the optical fiber 1 provided on the fence 9 and stretched on the top of the fence 9. 12 is a top plate provided on the upper surface of the wall surface 10, 13 is a flexural elastic body provided at the lower portion of the top plate 12 and straddling the Bragg grating sensor 2 of the optical fiber 1, and 14 is an optical fiber 1. A clad 15 is an optical fiber core.

Reference numeral 19 denotes a control unit that sends and controls a control signal, a command signal, and the like to the entire apparatus including the specifying unit 7. 20 is an operation unit for operating the control unit 19, 21 is an output unit for displaying a test result of the specifying unit 7 (sensor specifying unit 18), and the storage unit 17 and the sensor specifying unit 18 are It may be provided outside. 24, primary detection reflected light wavelength detection for detecting a primary detection reflected light wavelength in which an absolute value of a difference between a peak wavelength and a corresponding reference resonant reflection wavelength exceeds a predetermined value as a threshold value in the intensity distribution for each wavelength. And 25, a predetermined value for detecting a reflected light wavelength within a predetermined value within a predetermined value Δλ in which an absolute value of a difference between the peak wavelength and the corresponding reference resonant reflection wavelength is a threshold value in the intensity distribution for each wavelength. inner reflected light wavelength detector, 26 is sequentially reflected by the Bragg grating sensor corresponding to the primary reflected light detected wavelength to the primary reflected light detected wavelength is detected, among the intensity distribution for each wavelength spectrum detector detects An average value calculating unit 27 for calculating a resonance reflection wavelength moving average value of the peak wavelength, and 27 is an absolute value of a difference between the resonance reflection wavelength moving average value and the primary detection reflected light wavelength ( reflected light wavelength within a predetermined value ). Predetermined threshold A secondary detection reflected light wavelength detection unit that detects a secondary detection reflected light wavelength exceeding the value Δλ, 17 is a storage unit that stores a wavelength at which resonance reflection occurs for each Bragg grating sensor 2, and 18 is a secondary detection reflected light. The sensor identifying unit identifies the Bragg grating sensor 2 corresponding to the matching wavelength by comparing the wavelength of the reflected light detected by the wavelength detecting unit 27 with the wavelength stored in the storage unit 17. In addition, 22 is an optical connector including the optical fiber 1 provided with the Bragg grating sensor 2, and for example, a load sensor, a tension sensor and a surface vibration sensor are connected to each other as shown in FIG. Here, i in the figure and in the specification is i = 1, 2,..., 6 and is generally i = N (integer). The average value calculation unit 26 may be provided outside the secondary detection reflected light wavelength detection unit 27. In the drawings, the same reference numerals denote the same or corresponding parts, and detailed descriptions thereof are omitted.

First, the basic operation of the external force detection device for an optical fiber sensor according to the first embodiment will be described with reference to FIGS. First, as shown in FIG. 2, the Bragg grating sensor 2 used as an optical fiber sensor has a wavelength (reference resonance reflection wavelength) λΒ, a grating interval ( Assuming that (period length) Λ and the refractive index n of the core 15, the relationship of λΛ = 2nΛ holds, and the light incident on the optical fiber has a characteristic of reflecting light of wavelength λΒ in the Bragg grating. On the other hand, when an external force is applied to the optical fiber and a deflection or distortion occurs in the Bragg grating, the Bragg grating interval changes, and the wavelength of reflected light shifts. Therefore, by measuring (observing) the wavelength shift, when an intruder or the like enters the position where the optical fiber sensor is installed, the external force is applied to the Bragg grating sensor, which can be used for intrusion detection. As shown in FIG. 3, when the reference resonance reflection wavelength, which is the peak wavelength, is the wavelength λ (i) in the intensity distribution for each wavelength of the reflected light, the wavelength shift is caused by the deflection or distortion of the Bragg grating. It shows shifting before and after λ (i). ± Δλ is a threshold value for detecting a wavelength shift due to an external force.

  In FIG. 1, the light source 3 uses a broadband Amplified Spontaneous Emission (ASE) light source. There are various types of broadband ASE light sources such as wavelength ranges of 1530 nm to 1570 nm, 1520 to 1620 nm, and an appropriate one may be selected from the number of Bragg grating sensors and their resonant reflection wavelengths. Light (transmission light) transmitted from the light source 3 is transmitted to an optical fiber provided with the Bragg grating sensor 2 having wavelengths λ (1) to λ (6) whose resonance reflection wavelength is included in the wavelength range of the broadband ASE light source. . Note that λ (1) to λ (6) are arranged in order of increasing wavelength, and the Bragg grating sensor 2 of λ (1) and λ (2) is a surface vibration sensor, and λ (3) to λ (5). The Bragg grating sensor 2 is installed as a tension sensor (tension sensor), and the λ (6) Bragg grating sensor 2 is installed as a load sensor. Here, regarding the resonance reflection wavelengths λ (1) to λ (6), the band interval of the Bragg grating sensor 2 may be about 5 nm when the threshold ± Δλ detected by the wavelength shift is 1 nm.

Next, the specific operation of the external force detection device for the optical fiber sensor will be described. Transmitted light from the light source 3 is sent from the circulator 5 to the optical fiber 1, and reflected light returns from each Bragg grating sensor 2 to the circulator 5. The reflected light is sent to the light receiving unit 4 by the circulator 5. The optical receiver 4 receives the reflected light, generates a received video signal of the reflected light, and sends it to the spectrum detector 6. The spectrum detector 6 detects the peak wavelength in the intensity distribution for each wavelength of the received video signal, and the specifying unit 7 sets the threshold wavelength Δλ to the wavelength shift amount of the peak wavelength in the intensity distribution for each wavelength. It is determined whether or not an external force is applied to the Bragg grating sensor based on whether or not it exceeds (FIG. 3). The threshold value can be changed for each Bragg grating sensor, and the sensitivity of the sensor can be changed according to the environment of the installation location. The output unit 21 includes a display device and an audio output device, and displays information indicating that an external force has been detected on the display according to the determination result sent from the specifying unit 7, and also outputs audio. Output by sound (alarm sound) from the device. In FIG. 1, the state where an external force is applied is
“When the fence 8 is vibrated by an intruder or the like, an external force is applied to the Bragg grating sensor 2 of the surface vibration sensor knitted into the net of the fence 8 to cause a wavelength shift of the reflected light.”
“When an intruder or the like touches the detection line 11 stretched on the top of the fence 9 and is vibrated, an external force is applied to the Bragg grating sensor 2 of the tension sensor, causing a wavelength shift of the reflected light.”
“When an intruder or the like climbs on the top plate 12 provided on the upper surface of the wall surface 10, the bending elastic body 13 located at the lower portion of the top plate 12 and straddling the Bragg lattice sensor 2 of the load sensor is bent, and the Bragg lattice An external force is applied to the sensor 2 and a wavelength shift of the reflected light occurs.
It is.

Next, details of the external force detection apparatus for an optical fiber sensor according to the present invention will be described with reference to FIGS. The control unit 19 responds to internal processing at a preset timing and an operation command sent from the operation unit 20 in response to various control signals and commands for executing external force detection of the optical fiber sensor 1. A signal is generated to control the entire optical fiber sensor inspection device and the operation timing of each unit. Note that the preset timing assumes periodic external force detection and the like. When the external force detection is executed, a transmission light emission command signal is sent from the control unit 19 to the light source 3, and transmission light is sent from the light source 3 to the circulator 5. The circulator 5 sends the transmission light sent from the light source 3 to the optical fiber 1, and sends the reflected light from each Bragg grating sensor 2 provided on the optical fiber 1 to the light receiving unit 4. The light receiving unit 4 takes in the reflected light sent from the circulator 5, A / D converts the analog signal of the reflected light into a digital signal, and sends it to the spectrum detecting unit 6 as a received video signal of the reflected light. The spectrum detector 6 performs fast Fourier transform (FFT) on the received video signal of the digital signal sent from the light receiver 4 according to the command signal of the controller 19 to obtain the intensity distribution for each wavelength of the reflected light. The specific unit 7 determines whether an external force is applied to which Bragg grating sensor 2 depending on whether or not the wavelength shift amount of the peak wavelength in the intensity distribution for each wavelength exceeds the threshold Δλ. However, as shown in FIG. 5, the refractive index n of the Bragg grating changes due to fluctuations in the ambient temperature of the Bragg grating sensor 2 or disturbances such as wind, and the reflected light of intensity P (peak) is reflected. A wavelength shift may occur, and if the amount of wavelength shift is close to the threshold Δλ for detecting an external force or exceeds the threshold Δλ, it may be erroneously detected that an external force is applied to the Bragg grating sensor 2. Therefore, it is necessary to perform temperature compensation in order to prevent erroneous detection by determining whether or not the wavelength shift amount exceeds the threshold value Δλ. In the case of erroneous detection, it is roughly classified into a case where it is determined that an external force is not applied to the Bragg grating sensor 2 due to a change in the refractive index n of the Bragg grating due to a change in the ambient temperature (case 1; FIG. 6). Actually, there are two patterns when external force is applied to the Bragg grating sensor 2 but it is determined that external force is not applied (Case 2; FIG. 7). 6 and 7 show the wavelength shift of the resonant reflection wavelength due to the time change of the reflected light from one of the Bragg grating sensors 2 detected by the spectrum detector 6, where the horizontal axis is wavelength and the vertical axis is time. Yes. Hereinafter, with reference to FIGS. 6 and 7, the wavelengths of time τ ₀ , time τ ₁ , and time τ ₂ will be described.

In the case 1, in FIG. 6A, the resonance reflection wavelength is hardly shifted from the reference resonance reflection wavelength λ (i) at the wavelength of time τ ₀ , but at time τ ₁ and time τ ₂ . In terms of wavelength, the wavelength shift is large and exceeds the range of ± Δλ that is the threshold for detecting external force. Since it cannot be determined whether the wavelength shift is due to external force applied to the Bragg grating sensor 2 or due to a temperature change around the Bragg grating sensor 2, the control unit 19 sends a control / command signal to the determination unit 7. The absolute value of the difference between the primary detection reflected light wavelength detection unit 24 and the reference resonance reflection wavelength corresponding to the peak wavelength in the intensity distribution for each wavelength transmitted from the spectrum detection unit 6 is the predetermined value Δλ. While detecting the primary detected reflected light wavelength exceeding, the average value calculating unit 26 sequentially reflects the Bragg grating sensor corresponding to the primary detected reflected light wavelength until the primary detected reflected light wavelength is detected, and the spectrum detecting unit 6 The resonance reflection wavelength moving average value λ _ave (i) of the peak wavelength in the intensity distribution for each wavelength detected by is calculated. As shown in FIG. 6B, the value of Δλ, which is a threshold for detecting external force, is fixed, and the resonance reflection wavelength moving average value λ calculated by the average value calculation unit for the reference resonance reflection wavelength λ (i) serving as the central axis. change to _ave (i), and the secondary detection reflected light wavelength detector 27 causes the absolute value of the difference between the resonant reflection wavelength moving average value λ _ave (i) and the primary detection reflected light wavelength to exceed the predetermined value Δλ. When the secondary detection reflected light wavelength is detected, as shown in FIG. 6C, the secondary detection reflected light wavelength is detected only at the time τ ₂ out of the wavelengths at time τ ₁ and τ _2. is there. This is because the reference resonance reflection wavelength λ (i) is changed to the resonance reflection wavelength moving average value λ _ave (i), and the temperature compensation is performed for the wavelength of the time τ _{1 when} the resonance reflection wavelength is moved by the wavelength shift due to the temperature change. As a result, the wavelength at time τ ₁ that has exceeded the threshold Δλ with respect to the reference resonance reflection wavelength λ (i) is determined not to have undergone a wavelength shift due to external force.

In case 2, the resonance reflection wavelength is hardly shifted from the reference resonance reflection wavelength λ (i) at the wavelengths of time τ ₀ , τ ₁ , τ ₂ in FIG. A wavelength shift occurs due to a temperature change around the sensor 2. Whether external force is applied to the Bragg grating sensor 2 and the wavelength shifts in the opposite direction to the wavelength shift due to temperature change, and is within the range of ± Δλ which is the threshold for detecting external force, or is the external force merely applied? Therefore, the control unit 19 sends a control / command signal to the determination unit 7, and the reflected light wavelength detection unit 25 within the predetermined value is included in the intensity distribution for each wavelength transmitted from the spectrum detection unit 6. , while the absolute value of the difference between the reference resonant reflection wavelength wavelength is the peak corresponding to detecting a predetermined value in the reflected light wavelength in the predetermined value [Delta] [lambda], the average value calculating section 26, to a predetermined value in the reflected light wavelength The resonance reflection wavelength moving average value λ _ave (i) of the peak wavelength is calculated from the intensity distribution for each wavelength sequentially reflected by the corresponding Bragg grating sensor and detected by the spectrum detector 6. As shown in FIG. 7B, the value of Δλ, which is a threshold for detecting external force, is fixed, and the resonance reflection wavelength moving average value λ calculated by the average value calculation unit for the reference resonance reflection wavelength λ (i) serving as the central axis. _By changing to _ave (i), the absolute value of the difference between the resonant reflection wavelength moving average value λ _ave (i) and the reflected light wavelength within the predetermined value exceeds the predetermined value Δλ by the secondary detection reflected light wavelength detection unit 27. When the secondary detection reflected light wavelength is detected, as shown in FIG. 7C, among the wavelengths of time τ ₀ , τ ₁ , τ ₂ , the secondary detection reflected light wavelength is detected at time τ _2. Only the wavelength. This reference resonant reflection wavelength lambda (i) to change the resonant reflection wavelength moving average lambda _{ave (i),} the moved time tau ₀ of the resonant reflection wavelength by the wavelength shift due to temperature _change, to the wavelength of tau ₁ As a result of the temperature compensation, the wavelength of time τ ₂ that was within the threshold Δλ with respect to the reference resonance reflection wavelength λ (i) was determined to have been determined to have a wavelength shift due to external force. Yes.

Next, when the secondary detection reflected light wavelength detection unit 27 detects the secondary detection reflected light wavelength , the sensor specifying unit 18 determines that the ambient temperature of the secondary detection reflected light wavelength is The “original resonant resonance reflection wavelength considering the amount of wavelength shift due to external force” and the “reference resonant reflection wavelength for each Bragg grating sensor 2 stored in the storage unit 17” are collated, and the Bragg grating sensor corresponding to the matching wavelength is used. 2 is specified. That is, the reference resonance reflection wavelength λ (i) obtained by subtracting the wavelength shift amount due to temperature change or external force from the peak wavelength in the intensity distribution for each wavelength detected by the secondary detection reflected light wavelength detection unit 27 is, for example, , Λ (4), the reflected light of λ (4) having the same wavelength among the reference resonance reflection wavelengths λ (1) to λ (6) of each Bragg grating sensor 2 stored in the storage unit 17 is used. It can be identified that it is a corresponding Bragg grating sensor. Further, the resonance reflection wavelength moving average value calculated by the average value calculation unit 26 is sent to the storage unit 17, and the corresponding reference resonance reflection wavelengths λ (1) to λ (6) are set to the resonance reflection wavelength moving average value λ _ave (1). -Λ _ave (6) is sequentially changed / updated, and the sensor specifying unit 18 stores “the original resonance reflection wavelength considering the amount of wavelength shift due to the external force of the secondary detection reflected light wavelength” and “stored in the storage unit 17. You may collate with "resonance reflection wavelength moving average value". If the threshold Δλ = 1 nm for detecting the amount of wavelength shift is set to 1 nm, the resonance reflection wavelength of each Bragg grating sensor 2 can be determined by selecting the band interval of the resonance reflection wavelengths of the Bragg grating sensors 2 to be set to about 5 nm. Since the maximum width for wavelength shift is included, the possibility that the adjacent Bragg grating sensors 2 having the resonance reflection wavelength are subjected to wavelength shift is low.

Further, after specifying the Bragg grating sensor 2 corresponding to the detected secondary detection reflected light wavelength , a command is sent from the control unit 19 to the specifying unit 7 to send the specifying result of the sensor specifying unit 18 to the output unit 21. The output unit 21 outputs a message indicating that an external force has been applied to the Bragg grating sensor 2 using an external force detection display or sound. Here, if the installation position of the Bragg grating sensor 2 having the wavelength stored in the storage unit 17 is known, the installation position of the specified Bragg grating sensor 2 can also be known. In the case of FIG. 1, if the reference resonance reflection wavelength λ (i) at which an external force is detected is λ (4), the external force is applied to the Bragg grating sensor λ (4) provided as a tension sensor on the fence 9. Can be identified. Therefore, information such as the installation position is stored in the storage unit 17 according to the identification result of the sensor identification unit 18, and information indicating that an external force is applied to which Bragg grating sensor 2 is output in the output unit 21. You may output by a display or an audio | voice.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to FIGS. FIG. 8 is a detailed diagram of a specific part of the external force detection device for an optical fiber sensor according to the second embodiment. FIG. 9 is a flowchart of the external force detection device for an optical fiber sensor according to the second embodiment. 8 and 9, reference numeral 28 denotes a temperature in which the functions of the primary detection reflected light wavelength detection unit 24, the reflected light wavelength detection unit 25 within the predetermined value, the average value calculation unit 26, and the secondary detection reflected light wavelength detection unit 27 are incorporated. This is a compensated reflected light wavelength detector. In the drawings and the specification, i is a sensor number, i = 1, 2,..., 6, generally i = N (integer), and the total number of Bragg grating sensors 2, t is The number of times the external force (secondary detection reflected light wavelength ) is detected, m is the number of data processing of the resonance reflection wavelength moving average value. In the first embodiment, the secondary detection reflected light wavelength is detected separately for case 1 and case 2, but the primary detection reflected light wavelength and the reflected light wavelength within a predetermined value may be detected in an integrated manner. . In the second embodiment, an integrated operation of the external force detection device for the optical fiber sensor will be described.

In the second embodiment, when the temperature compensation process is performed, the control unit 19 first sends a control / instruction signal for performing the temperature compensation process to the specifying unit 19. Hereinafter, the detection processing of the secondary detection reflected light wavelength of the temperature compensated reflected light wavelength detection unit 24 provided in the specifying unit 7 will be described. The received video signal of the reflected light sent from the optical receiver 4 is sent to the spectrum detector 6. The spectrum detector 6 performs fast Fourier transform (FFT) on the received video signal of the digital signal sent from the light receiver 4 according to the command signal of the controller 19 to obtain the intensity distribution for each wavelength of the reflected light. This is sent to the temperature compensated reflected light wavelength detection unit 28 in the specifying unit 7. In STEP 1, as the initial value setting, the resonance reflection wavelength moving average value λ _ave (i, t−1) of each Bragg grating sensor 2 and the reference resonance reflection wavelength λ (i, t) of each Bragg grating sensor are detected. The number of processing executions t = 1 and the Bragg grating sensor i = 1 are set. The total number of Bragg grating sensors is N, the number of data processing of the resonant reflection wavelength moving average value is m, and an arbitrary value is set. In FIG. 1, N = 6. Next, in STEP 2, the first Bragg grating sensor, that is, the Bragg grating sensor 2 (FIG. 1) of λ (1), λ (1,1) and the resonant reflection wavelength moving average of the first Bragg grating sensor. A difference from a value (reference resonance reflection wavelength) λ _ave (i, 0) is obtained, and it is determined whether or not the absolute value exceeds a threshold value Δλ for determining the presence or absence of an external force. As a result, if it exceeds a predetermined value Δλ is the threshold value, it is determined that there external force, and recorded that there external force first Bragg grating sensors in STEP3, perform the following STEP4. On the other hand, if the predetermined value Δλ is not exceeded, the next STEP 4 is executed.

In STEP 4, it is compared whether the detection processing execution count t is larger than the data processing count m of the resonant reflection wavelength moving average value. As a result, when the detection processing execution count t is smaller, STEP 6 is executed. If the detection processing execution count t is large, STEP5 is executed. In STEP 5, it is determined whether the number of data necessary for the resonant reflection wavelength moving average process can be secured. At this time, if it is determined that there is no intrusion in all m external force detection processes from the current detection process execution count t to the detection process execution count {t− (m−1)}, STEP 7 is executed. On the other hand, if it is not determined that there is no external force, STEP 6 is executed because the number m of data processing necessary for calculating the resonant reflection wavelength moving average value cannot be secured. In STEP 6, as a measure when the resonant reflection wavelength moving average value cannot be calculated, the latest moving average value λave (i, t) is used as the moving average value λave (i, t, when the number of detection processing executions is (t−1). After replacing t-1), the next STEP8 is executed. In STEP 7, the resonance reflection wavelength moving average value is obtained using the wavelength values from the current detection processing execution count to m times before, and this resonance reflection wavelength moving average value is obtained as the latest resonance reflection wavelength moving average value λave (n, t), the next STEP8 is executed. In STEP 8, the difference between λ (1,1) and the moving average value λave (i, t) of the first Bragg grating sensor is obtained based on the presence or absence of the external force obtained in STEP2 and STEP3. It is determined whether or not the absolute value exceeds a threshold value Δλ for determining the presence or absence of an external force.

  Next, in order to perform temperature compensation processing for all the Bragg grating sensors, in STEP 9, the number i of the Bragg grating sensor is incremented in order to perform determination processing for the next Bragg grating sensor. In STEP 10, the number i of the Bragg grating sensor is compared with the total number N of Bragg grating sensors, and the processing from STEP 2 to STEP 9 is repeatedly executed until the number i of the Bragg grating sensor exceeds the total number N of Bragg grating sensors. On the other hand, when the number i of the Bragg grating sensors exceeds the total number N of Bragg grating sensors, the next STEP 11 is executed. In STEP 11, it is determined whether or not the external force detection is continued. When the external force detection is continued, the detection processing execution count t is incremented in STEP 12 and the processes after STEP 2 are repeatedly executed. After the completion, the external force detection result is sent to the control unit 19 and the sensor specifying unit 18. Based on the result received from the determination unit 7, the control unit 19 generates a message indicating the presence or absence of an intruder and sends it to the output unit 8. Note that the processing statuses of STEP 8, STEP 11, and STEP 1 to 12 as a whole may be sequentially sent to the control unit 19.

From the external force detection result, the sensor specifying unit 18 stores the “original reference resonance reflection wavelength considering the amount of wavelength shift due to the external force of the peak wavelength in the detected intensity distribution for each wavelength” and “stored in the storage unit 17. The Bragg grating sensor 2 corresponding to the matching wavelength is identified by comparing with the “resonance reflection wavelength moving average value”. That is, the secondary reflected light detected wavelength detector 27 the reference resonant reflection wavelength lambda by subtracting the wavelength shift amount reflected light wavelength is detected by a temperature change or an external force by (i) is, for example, if the lambda (4), It is a Bragg grating sensor corresponding to the reflected light of λ (4) having the matching wavelength among the reference resonance reflection wavelengths λ (1) to λ (6) of each Bragg grating sensor 2 stored in the storage unit 17. Can be identified. Further, the resonance reflection wavelength moving average value calculated by the average value calculation unit 26 is sent to the storage unit 17, and the corresponding reference resonance reflection wavelengths λ (1) to λ (6) are set to the resonance reflection wavelength moving average value λ _ave (1). -Λ _ave (6) is sequentially changed / updated, and the sensor specifying unit 18 stores “the original resonance reflection wavelength considering the amount of wavelength shift due to the external force of the secondary detection reflected light wavelength” and “stored in the storage unit 17. You may collate with "resonance reflection wavelength moving average value". If the threshold Δλ = 1 nm for detecting the amount of wavelength shift is set to 1 nm, the resonance reflection wavelength of each Bragg grating sensor 2 can be determined by selecting the band interval of the resonance reflection wavelengths of the Bragg grating sensors 2 to be set to about 5 nm. Since the maximum width for wavelength shift is included, the possibility that the adjacent Bragg grating sensors 2 having the resonance reflection wavelength are subjected to wavelength shift is low. Further, a command is sent from the control unit 19 to the specifying unit 7 to send the specifying result of the sensor specifying unit 18 to the output unit 21, and a message indicating that an external force is applied to the Bragg grating sensor 2 is displayed in the output unit 21. Output by detection display and sound. Here, if the installation position of the Bragg grating sensor 2 having the wavelength stored in the storage unit 17 is known, the installation position of the specified Bragg grating sensor 2 can also be known. In the case of FIG. 1, if the reference resonance reflection wavelength λ (i) at which an external force is detected is λ (4), the external force is applied to the Bragg grating sensor λ (4) provided as a tension sensor on the fence 9. Can be identified. Therefore, information such as the installation position is stored in the storage unit 17 according to the identification result of the sensor identification unit 18, and information indicating that an external force is applied to which Bragg grating sensor 2 is output in the output unit 21. You may output by a display or an audio | voice.

  As described above, the resonance reflection wavelength moving average value of the wavelength obtained when the reflected light from the Bragg grating sensor 2 is subjected to frequency analysis processing is obtained and used as the reference value for detecting the external force. With a simple system configuration that does not require any special hardware in the detection device, it is possible to prevent erroneous detection of the external force detection of the optical fiber sensor due to the temperature compensation process. Since the configuration is such that the number of data processing m can be set, setting corresponding to the installation environment is possible, and the flexibility of the system can be improved. Further, as shown in FIG. 1, since the optical fiber 1 in which the optical connector 22 is disposed between the Bragg grating sensors 2 is installed, the replacement of the Bragg grating sensor 2 is easy.

It is a system configuration | structure figure of the external force detection apparatus of the optical fiber sensor which concerns on Embodiment 1 and 2. FIG. It is a basic operation | movement figure of a Bragg grating sensor. It is a wavelength shift figure of the reflected light by the external force of a Bragg grating. 3 is a detailed view of a specific part of the external force detection device for the optical fiber sensor according to Embodiment 1. FIG. It is a wavelength shift figure of reflected light by change of ambient temperature of a Bragg grating. It is a time change figure of the reflected light of the optical fiber sensor concerning Embodiment 1. It is a time change figure of the reflected light of the optical fiber sensor concerning Embodiment 1. FIG. 10 is a detailed view of a specific part of the external force detection device for an optical fiber sensor according to a second embodiment. 6 is a flowchart of an external force detection device for an optical fiber sensor according to Embodiment 2. FIG.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber, 2 ... Bragg grating sensor, 3 ... Light source, 4 ... Light receiving part, 5 ... Circulator, 6 ... Spectrum detection part, 7 ... Specific part, 8 ... Fence, 9 ... Fence, 10 ... Wall surface, 11 ... Detection line, 12 ... top plate, 13 ... flexible elastic body, 14 ... clad, 15 ... core, 17 ... storage unit, 18 ... sensor specifying unit, 19 ... control unit, 20 ... operation unit, 21 ... output unit, 22 ... Optical connector, 24 ... primary detection reflected light wavelength detector, 25 ... reflected light wavelength detector within predetermined value, 26 ... average value calculator, 27 ... secondary detected reflected light wavelength detector, 28 ... temperature compensated reflected light wavelength Detection unit .

Claims (4)

Bragg grating frequency than is Do different, the light incident on the optical fiber having a plurality of Bragg grating sensors having different reference resonant reflection wavelength respectively, receiving said reflected light reflected by the Bragg grating sensors, is the received Of the intensity distribution for each wavelength of the reflected light, calculate the average value of the wavelength of the reflected light sequentially reflected by the Bragg grating sensor corresponding to the peak wavelength, and among the intensity distribution for each wavelength of the reflected light, when the absolute value of the difference between the wavelength and the corresponding reference resonant reflection wavelength is the peak detects the primary reflected light detected wavelength is the wavelength of the reflected light exceeds a predetermined value, the primary reflected light detected wavelength that is detected If the absolute value of the difference between the average value and the primary reflected light detected wavelengths up exceeds a predetermined value, external force is applied to the Bragg grating sensors corresponding to the primary reflected light detected wavelength External force detecting method for determining optical fiber sensor. Bragg grating frequency than is Do different, the light incident on the optical fiber having a plurality of Bragg grating sensors having different reference resonant reflection wavelength respectively, receiving said reflected light reflected by the Bragg grating sensors, is the received Of the intensity distribution for each wavelength of the reflected light, calculate the average value of the wavelength of the reflected light sequentially reflected by the Bragg grating sensor corresponding to the peak wavelength, and among the intensity distribution for each wavelength of the reflected light, Until the reflected light wavelength within the predetermined value, which is the wavelength of the reflected light whose absolute value of the difference between the peak wavelength and the corresponding reference resonant reflection wavelength is within the predetermined value, is detected, and the reflected light wavelength within the predetermined value is detected wherein when the absolute value of the difference between the average value and the predetermined value in the reflected light wavelength exceeds the predetermined value, determines light external force to the Bragg grating sensor corresponding to the predetermined value in the reflected light wavelength is applied for External force detection method of Aibasensa. Bragg grating frequency than is Do different, an optical fiber having a plurality of Bragg grating sensors having different reference resonant reflection wavelength, respectively, a light source for emitting light to the optical fiber, each of said reflected by the Bragg grating sensors a light receiving unit for receiving a reflected light of a wavelength, of the intensity distribution of each wavelength of the received reflected light, and the spectrum detecting unit for detecting the wavelength is the peak wavelength of the reflected light which the light receiving unit receives Out of the intensity distribution of each of the reflected light, the average value calculating unit for calculating the average value of the wavelengths of the reflected light sequentially reflected by the Bragg grating sensor corresponding to the peak wavelength, primary detecting reflected light waves for detecting a primary reflected light detected wavelength absolute value of the wavelength of the reflected light exceeds a predetermined value of the difference between the reference resonant reflection wavelength corresponding to the wavelength is the peak A detection unit, the average value of up to primary reflected light detected wavelength that is detected from the average calculation unit, the absolute value of the difference between the average value the primary detecting reflected light wavelength of said predetermined value a secondary reflected light detected wavelength detector for detecting a secondary detection light reflected wavelength is the wavelength of the reflected light exceeds a Bragg grating sensor secondary reflected light detected wavelength detecting unit corresponds to the secondary detection reflection wavelength detected And an external force detection device for an optical fiber sensor that determines that an external force is applied to the Bragg grating sensor specified by the sensor specification unit . Bragg grating frequency than is Do different, an optical fiber having a plurality of Bragg grating sensors having different reference resonant reflection wavelength, respectively, a light source for emitting light to the optical fiber, each of said reflected by the Bragg grating sensors a light receiving unit for receiving a reflected light of a wavelength, of the intensity distribution of each wavelength of the received reflected light, and the spectrum detecting unit for detecting the wavelength is the peak wavelength of the reflected light which the light receiving unit receives Out of the intensity distribution of each of the reflected light, the average value calculating unit for calculating the average value of the wavelengths of the reflected light sequentially reflected by the Bragg grating sensor corresponding to the peak wavelength, , the absolute value is a predetermined value in the reflected light wavelength detection for detecting a predetermined value in the reflected light wavelength which is the wavelength of the reflected light within a predetermined value of the difference between the reference resonant reflection wavelength corresponding to the wavelength is the peak Parts and, the mean value to the predetermined value in the reflected light wavelength is detected from the average value calculator, an absolute value of the predetermined value of the difference between the average value and the predetermined value in the reflected light wavelength Secondary detection reflected light wavelength detection unit for detecting the secondary detection reflected light wavelength that is the wavelength of the reflected light exceeding the wavelength, and a Bragg grating corresponding to the secondary detection reflected light wavelength detected by the secondary detection reflected light wavelength detection unit and a sensor specifying unit for specifying a sensor, external force detecting device determines optical fiber sensor and the sensor specifying unit external force is applied to the Bragg grating sensor identified.

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