KR101030728B1 - monitoring system using dual wavelength fiber bragg grating sensor and method thereof - Google Patents

Abstract

Disclosed are a monitoring system and method using a dual wavelength FBG (Fiber Bragg Grating) sensor according to the present invention. The dual wavelength FBG sensor according to the present invention is formed to have three grating portions having different physical characteristics, and is formed to reflect the first reflected wavelength signal for the first optical wavelength signal to a core of the first outer diameter in a predetermined region in the optical fiber. 1 lattice portion; A second grating part connected to the first grating part and configured to reflect a second reflected wavelength signal with respect to the first optical wavelength signal to a core having a second outer diameter; And a third grating portion connected to the second grating portion and configured to reflect a third reflected wavelength signal with respect to a second optical wavelength signal to a core having the second outer diameter. Through this, the present invention can simultaneously detect the temperature and strain, and further expand the detection range, that is, the number of FBG sensors.

Fiber optic, FBG, fiber bragg grating, sensor, temperature, strain

Description

Monitoring system using dual wavelength fiber bragg grating sensor and method

The present invention relates to a monitoring system and method using a dual wavelength FBG (Fiber Bragg Grating) sensor.

In general, the optical fiber sensor has a function of optical and electrical signal conversion, as well as a measurement signal, information transmission, as well as a simple sensing element, unlike the conventional electrical sensor, it is also called an optical fiber application measuring device.

Such an optical fiber sensor may measure a change in physical quantity to be measured using amplitude, phase, or polarization of light passing through the optical fiber, that is, intensity, rotation rate, temperature, pressure, water level, sound, gas concentration, etc. of an electromagnetic field. In addition, the optical fiber sensor can configure a measuring system having characteristics such as induction, insulation, and explosion-proof stability of the optical and optical fibers, and is excellent in matching with the electronic technology represented by microcomputer and minicom. In other words, the optical fiber sensor can be connected to a computer to collect, process and analyze the measured information.

However, fiber optic sensors usually have a low signal-to-noise figure, and to measure a specific point, a fiber optic sensor needs to be cut and coated or another specially treated fiber optic sensor.

Thus, the optical fiber Bragg grating (FBG) using a Bragg grating, which transmits ultraviolet light to the surface of the optical fiber and changes the chemical bond of the optical fiber, reflects only a desired wavelength at a specific portion of the optical fiber. The sensor is attracting attention. In particular, the FBG sensor has a high sensitivity without being affected by electromagnetic interference, and has a merit that it can be effectively used in a dangerous place where a normal sensor cannot be used or a special purpose requiring high sensitivity because it is small and light.

When an external physical quantity such as temperature, strain, or pressure is applied to an FBG sensor that exhibits such reflection characteristics, these values change, and the reflected wavelength changes. The strain or temperature change can be measured using the change amount of the wavelength.

However, since the wavelength reflected from the FBG sensor is not changed only by one of the strain and the temperature, it is difficult to distinguish when the strain and the temperature change occur at the same time.

The present invention is to solve the problems of the prior art as described above, by forming a Fiber Bragg Grating (FBG) sensor having three gratings with different physical properties, dual wavelength FBG to detect the temperature and strain at the same time The present invention provides a monitoring system using a sensor and a method thereof.

In addition, the present invention forms a FBG sensor having three grating portions having different physical properties, but having different reflection wavelengths, so that the detection range, that is, the monitoring using the dual-wavelength FBG sensor to further expand the number of FBG sensors It is to provide a system and a method thereof.

To this end, the dual wavelength FBG sensor according to an aspect of the present invention comprises: a first grating portion formed to reflect a first reflected wavelength signal for a first optical wavelength signal on a core of a first outer diameter in a predetermined region in the optical fiber; A second grating part connected to the first grating part and configured to reflect a second reflected wavelength signal with respect to the first optical wavelength signal to a core having a second outer diameter; And a third grating part connected to the second grating part and formed to reflect a third reflected wavelength signal for a second optical wavelength signal to a core having the second outer diameter.

Preferably, the first outer diameter may be smaller than the second outer diameter. In addition, the first optical wavelength signal may mean a wavelength of a predetermined band having a center wavelength of 1550 nm, and the second optical wavelength signal may mean a wavelength of a predetermined band having a center wavelength of 1310 nm.

According to another aspect of the present invention, a monitoring system using a dual wavelength FBG sensor includes: a fiber bragg grating (FBG) sensor having three grating portions having different physical characteristics in a predetermined region of an optical fiber; A first optical coupler receiving a first reflected wavelength signal and a second reflected wavelength signal for the first optical wavelength signal reflected from the FBG sensor; A second optical coupler receiving a third reflected wavelength signal with respect to the second optical wavelength signal reflected from the FBG sensor; And an estimator configured to estimate changes in temperature and strain based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal.

Preferably, the FBG sensor comprises: a first grating portion formed to reflect a first reflected wavelength signal with respect to a first optical wavelength signal in a predetermined region of the optical fiber to a core having a first outer diameter; A second grating part connected to the first grating part and configured to reflect a second reflected wavelength signal with respect to the first optical wavelength signal to a core having a second outer diameter; And a third grating part connected to the second grating part and formed to reflect a third reflected wavelength signal for a second optical wavelength signal to a core having the second outer diameter.

The first optical coupler provides a first optical wavelength signal generated from a first light source unit to one side of the FBG sensor, and receives the first and second reflected wavelength signals reflected from the FBG sensor. The first reflected wavelength signal and the second reflected wavelength signal may be provided to the estimator.

The second optical coupler provides a second optical wavelength signal generated from a second light source unit to the other side of the FBG sensor, and receives the third reflected wavelength signal reflected from the FBG sensor to receive the third reflected wavelength signal. It can be provided to the estimator.

Preferably, the estimator estimates an amount of change of strain with respect to a point where the FBG sensor is located based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal, and estimates the estimated strain. The amount of change in temperature with respect to the point can be estimated based on the amount of change in.

If necessary, the estimator includes: a first arrayed waveguide grating (AWG) for processing the first reflected wavelength signal and the second reflected wavelength signal; A second AWG for processing the third reflected wavelength signal; And an optical spectrum analyzer for analyzing the spectrum of the signal processed in the first AWG and the second AWG.

According to another aspect of the present invention, a surveillance system using a dual wavelength FBG sensor includes: a fiber bragg grating (FBG) sensor having three grating portions having different physical characteristics in a predetermined region of an optical fiber; A first optical circulator configured to receive a first reflected wavelength signal and a second reflected wavelength signal for the first optical wavelength signal reflected from the FBG sensor; A second optical circulator for receiving a third reflected wavelength signal with respect to the second optical wavelength signal reflected from the FBG sensor; And an estimator configured to estimate changes in temperature and strain based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal.

According to another aspect of the present invention, a monitoring method using a dual-wavelength FBG sensor includes a first method for a first optical wavelength signal from a fiber bragg grating (FBG) sensor having three grating portions having different physical characteristics in a predetermined region of an optical fiber. Receiving a reflected wavelength signal and a second reflected wavelength signal; Receiving a third reflected wavelength signal for a second optical wavelength signal from the FBG sensor; And estimating an amount of change in temperature and strain based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal.

Preferably, the estimating may include estimating an amount of change of strain with respect to a point where the FBG sensor is located based on the received first and second reflected wavelength signals; Estimating an amount of change in temperature with respect to the point based on the estimated amount of change in strain; And estimating a point at which the FBG sensor is located based on the received third reflected wavelength signal.

Hereinafter, a monitoring system using a dual wavelength FBG (Fiber Bragg Grating) sensor and a method thereof according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 5. The present invention aims to detect temperature and strain simultaneously by forming an FBG sensor having three grating portions having different physical characteristics, for example, an outer diameter or diameter of a core, a gap between gratings, and the like, in a predetermined region of an optical fiber.

1 is an exemplary view showing the structure of a dual wavelength FBG sensor according to an embodiment of the present invention.

As shown in FIG. 1, the dual wavelength FBG sensor according to the present invention may include a first grating part 110, a second grating part 120, a third grating part 130, and the like having different physical characteristics. Can be.

In this case, the FBG sensor transmits ultraviolet light to the surface of the optical fiber to change the chemical bonding of the optical fiber, so that a Bragg grating that uses a Bragg grating that exhibits reflection characteristics only for a desired wavelength at a specific portion of the optical fiber whose chemical bonding has changed is used. Can mean. In particular, the dual wavelength FBG sensor according to the present invention may be formed to have three grating portions having different physical properties.

That is, the FBG sensor according to the present invention generates the reflected wavelength signal signal for the first optical wavelength signal, the first grating unit 110 is the first reflected wavelength signal for the first optical wavelength signal in the core of the first outer diameter d1 The grating may be formed to generate the grating, and the grating may be formed on the second grating part 120 to reflect the second reflected wavelength signal with respect to the first optical wavelength signal to the core having the second outer diameter d2. In this case, the first outer diameter d1 of the first grating part 110 is preferably smaller than the second outer diameter d2 of the second grating part 120.

As described above, the present invention intends to use the principle that the reaction due to strain is different from each other because of the same wavelength shift characteristics due to temperature but different outer diameters because the same material is used when two optical fiber gratings having different outer diameters of the core are used.

In addition, the FBG sensor according to the present invention, in order to detect the reflected wavelength signal for the second optical wavelength signal, the third grating portion is a grating to reflect the third reflected wavelength signal for the second optical wavelength signal on the core of the second outer diameter d2 Can be formed.

In this case, the first optical wavelength signal may mean a wavelength of a predetermined band having a center wavelength of 1550 nm, and the second optical wavelength signal may mean a wavelength of a predetermined band having a center wavelength of 1310 nm. In addition, the length l1 of the first grating part 110, the length l2 of the second grating part 120, and the length l3 of the third grating part 130 are preferably formed in the same manner.

2 is an exemplary view showing a monitoring system using a dual wavelength FBG sensor according to an embodiment of the present invention.

As shown in FIG. 2, the monitoring system according to the present invention includes a first light source unit 210, a first optical coupler or a first optical circulator 220, an FBG sensor 230, It may be configured to include a second optocoupler or a second optical circulator 240, a second light source 250, the estimator 260 and the like.

When a first optical wavelength signal, for example, a wavelength of a predetermined band having a center wavelength of 1550 nm is provided from the first light source unit 210, the first optical coupler 220 provides the first optical wavelength signal to one side of the FBG sensor 230. Wavelengths reflected from the first and second grating portions of the FBG sensor 230, that is, the first and second reflected wavelength signals for the first optical wavelength signal, may be respectively received. Then, the first optocoupler 220 may provide the first reflected wavelength signal and the second reflected wavelength signal to the estimator 260.

Similarly, when a second optical wavelength signal, for example, a wavelength of a predetermined band having a center wavelength of 1310 nm is provided from the second light source unit 250, the second optical coupler 240 transmits the second optical wavelength signal to the other side of the FBG sensor 230. And receive a wavelength reflected from the FBG sensor 230, that is, a third reflected wavelength signal for the second optical wavelength signal. The second optocoupler 240 may provide the received third reflected wavelength signal to the estimator 260.

In this case, since the first optical coupler provides the first and second reflected wavelength signals to the first light source unit as well as the estimator, the first optical coupler blocks the first and second reflected wavelength signals flowing into the first light source unit. In order to do so, a first optical isolator may be connected in series with the first light source unit, and likewise, a second optical isolator may be connected in series with the second light source unit.

Accordingly, the estimator 260 simultaneously adjusts the amount of change of strain and the amount of change of temperature with respect to the point where the FBG sensor 230 is located based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal. It can be estimated. That is, the estimator 260 estimates an amount of change of strain with respect to a point where the FBG sensor 230 is located, based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal. Based on the change amount of the strain, the change amount of the temperature for the point where the FBG sensor 230 is located is estimated again.

For example, the estimator 260 may include a first arrayed waveguide grating (AWG) 261 for processing a first reflected wavelength signal and a second reflected wavelength signal, a second AWG 262 for processing a third reflected wavelength signal, And an optical spectrum analyzer 263 for analyzing the spectrum of the signal processed in the first AWG and the second AWG.

3 is an exemplary view showing a measuring method using a dual wavelength FBG sensor according to an embodiment of the present invention.

As shown in FIG. 3, when the first light source generates the first optical wavelength signal (S310), the first optical coupler provides the first optical wavelength signal to the FBG sensor (S320) and reflects at least one reflected from the FBG sensor. A wavelength signal can be received. That is, the first optical coupler receives the first reflection wavelength of the first optical wavelength signal from the first grating portion of the FBG sensor and the second reflection wavelength signal of the first optical wavelength signal from the second grating portion (S330). ).

Accordingly, the first optocoupler may provide the received first reflected wavelength signal and the second reflected wavelength signal to the estimator (S340).

Similarly, when the second light source generates the second optical wavelength signal (S312), the second optical coupler may provide the second optical wavelength signal to the FBG sensor (S322) to receive the reflected wavelength signal reflected from the FBG sensor. That is, the second optical coupler receives the third reflected wavelength signal for the second optical wavelength signal from the third grating portion of the FBG sensor (S332).

Accordingly, the second optocoupler may provide the received third reflected wavelength signal to the estimator (S342).

The estimator receives the first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal when the first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal are received from the first and second optical couplers. Based on the reflected wavelength signal, it is possible to estimate the amount of change in strain and temperature at the point where the FBG sensor is located.

At this time, the change amount Δλ _B of the wavelength with respect to the optical wavelength signal is represented by the following [Equation 1].

[Equation 1]

Δλ _B = k _ε Δε + k _T ΔT

Here, Δε may mean an amount of change in strain (longitudinal strain), ΔT may mean an amount of change in temperature, and k _ε , k _T may mean a strain and a temperature coefficient, respectively.

The change amounts of wavelengths Δλ _{B1 and} Δλ _B2 for the first and second reflected wavelength signals reflected from the first and second grating portions of the FBG sensor are represented by the following Equations 2 and 3 Same as

[Equation 2]

&Quot; (3) "

Here, d may mean a core outer diameter of the grating portion, and l may mean a length of the grating portion.

Based on the above [Equation 2] and [Equation 3], the change amount Δλ ₂₁ of the wavelength difference between the first reflected wavelength signal and the second reflected wavelength signal can be expressed as Equation 4 below.

&Quot; (4) "

Through Equation 4, the estimator can estimate the variation Δε of the strain with respect to the point where the FBG sensor is located (S350), because it knows k _ε , d ₁ , d ₂ , l ₁ , l _2, etc. It is possible. Then, the estimator estimates the temperature change ΔT by applying the estimated change of strain Δε to the above Equation 2 or Equation 3 (S360), which is also k _ε, Δε, k _T It is possible because we know back.

In addition, the estimator may estimate a location where the FBG sensor is located based on the third reflected wavelength signal (S370).

The reason for estimating the point where the FBG sensor is located by using the third reflected wavelength signal is described as follows. When the wavelength range of the light wavelength signal is 40 nm and the band is 1 nm, the present invention can estimate the change in the wavelength of a total of 40 FBG sensors using only the first light wavelength signal of the band having the center wavelength of 1550 nm. However, when the first optical wavelength signal in the band having a center wavelength of 1550 nm and the second optical wavelength signal in the band having a center wavelength of 1310 nm are used, it is possible to estimate the change in the wavelength of a total of 160 FBG sensors.

As described above, the present invention provides a FBG sensor having three grating portions having different physical properties in a predetermined region of the optical fiber, thereby simultaneously detecting temperature and strain, and further detecting the detection range, that is, the number of FBG sensors. Can be extended

As described above, a simulation model of a monitoring system using a dual wavelength FBG sensor having three grating portions having different physical characteristics and a result thereof will be described with reference to FIGS. 4 to 5.

4 is an exemplary view showing a simulation model according to an embodiment of the present invention.

As shown in FIG. 4, for the simulation of the monitoring system according to the present invention, four dual wavelength FBG sensors are used, and light wavelength signals having wavelengths of 1550 nm and 1310 nm are used as light sources, and the strain range is 0. It can be seen that the simulation model is set to a temperature range of 20 ~ 100 ℃ ℃ ~ 2500 με.

5 is an exemplary view showing a simulation result according to an embodiment of the present invention.

As shown in FIG. 5, the simulation was performed using the previous simulation model, in which (a) shows a temperature change of 20 ° C. but no strain change. And a case where there is a change in strain.

In the figure (a), when the optical wavelength signal having a band having a center wavelength of 1550 nm is injected, the reflected wavelength signal is uniformly displayed for the optical wavelength signals reflected from the four FBG sensors, so that not only the strain but also the temperature change can be seen. It can be seen that there is no.

However, when the optical wavelength signal having a band having a center wavelength of 1550 nm is injected in the drawing (b), the reflected wavelength signal for the optical wavelength signal reflected from the second FBG sensor among the reflected wavelength signals for the optical wavelength signal reflected from the four FBG sensors You can see that there has been a change. That is, the reflected wavelength signal for the optical wavelength signal reflected from the second FBG sensor is divided into two, so that the change of strain and the resulting temperature change can be estimated simultaneously through this change.

The monitoring system and method using the dual wavelength FBG (Fiber Bragg Grating) sensor according to the present invention can be modified and applied in various forms within the scope of the technical idea of the present invention and are not limited to the above embodiments. In addition, the embodiments and drawings are merely for the purpose of describing the contents of the invention in detail, not intended to limit the scope of the technical idea of the invention, the present invention described above is common knowledge in the technical field to which the present invention belongs As those skilled in the art can have various substitutions, modifications, and changes without departing from the technical spirit of the present invention, it is not limited to the above embodiments and the accompanying drawings, of course, and not only the claims to be described below but also claims Judgment should be made including scope and equivalence.

1 is an exemplary view showing the structure of a dual wavelength FBG sensor according to an embodiment of the present invention,

2 is an exemplary view showing a monitoring system using a dual wavelength FBG sensor according to an embodiment of the present invention,

3 is an exemplary view showing a measuring method using a dual wavelength FBG sensor according to an embodiment of the present invention,

4 is an exemplary view showing a simulation model according to an embodiment of the present invention,

5 is an exemplary view showing a simulation result according to an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

110: first grid portion

120: second lattice portion

130: third grid portion

210: first light source unit

220: first optical coupler or first optical circulator

230: FBG sensor

240: second optocoupler or second optocirculator

250: second light source

260: estimator

Claims (13)

A first grating portion formed in a predetermined region of the optical fiber to reflect a first reflected wavelength signal with respect to the first optical wavelength signal to a core having a first outer diameter; A second grating part connected to the first grating part and configured to reflect a second reflected wavelength signal with respect to the first optical wavelength signal to a core having a second outer diameter; And A third grating part connected to the second grating part and formed to reflect a third reflected wavelength signal for a second optical wavelength signal to a core having the second outer diameter; Dual wavelength FBG sensor comprising a. According to claim 1, The first outer diameter is, Dual-wavelength FBG sensor, characterized in that formed smaller than the second outer diameter. The method according to claim 1 or 2, The first optical wavelength signal refers to a wavelength of a predetermined band having a center wavelength of 1550 nm, and the second wavelength means a wavelength of a predetermined band having a center wavelength of 1310 nm, respectively. A fiber bragg grating (FBG) sensor having three grating portions having different physical characteristics in a predetermined region of the optical fiber; A first optical coupler receiving a first reflected wavelength signal and a second reflected wavelength signal for the first optical wavelength signal reflected from the FBG sensor; A second optical coupler receiving a third reflected wavelength signal with respect to the second optical wavelength signal reflected from the FBG sensor; And An estimator estimating an amount of change in temperature and strain based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal Surveillance system using a dual wavelength FBG sensor comprising a. 5. The method of claim 4, The FBG sensor, A first grating portion formed in a predetermined region of the optical fiber to reflect a first reflected wavelength signal with respect to the first optical wavelength signal to a core having a first outer diameter; A second grating part connected to the first grating part and configured to reflect a second reflected wavelength signal with respect to the first optical wavelength signal to a core having a second outer diameter; And And a third grating portion connected to the second grating portion and configured to reflect a third reflected wavelength signal for a second optical wavelength signal to a core of the second outer diameter. The method according to claim 4 or 5, The first optocoupler, Providing a first light wavelength signal generated from a first light source to one side of the FBG sensor, And receiving the first reflection wavelength signal and the second reflection wavelength signal reflected from the FBG sensor and providing the received first reflection wavelength signal and the second reflection wavelength signal to the estimator. Surveillance system using FBG sensor. The method according to claim 4 or 5, The second optocoupler, Providing a second light wavelength signal generated from a second light source to the other side of the FBG sensor, And receiving the third reflected wavelength signal reflected from the FBG sensor and providing the received third reflected wavelength signal to the estimator. The method according to claim 4 or 5, The estimating unit, Estimating an amount of change of strain with respect to a point where the FBG sensor is located based on the received first and second reflected wavelength signals, Estimating a change in temperature with respect to the point based on the estimated change in strain, And estimating a point at which the FBG sensor is located based on the received third reflected wavelength signal. The method according to claim 4 or 5, The estimating unit, A first arrayed waveguide grating (AWG) for processing the first reflected wavelength signal and the second reflected wavelength signal; A second AWG for processing the third reflected wavelength signal; And And a light spectrum analyzer for analyzing the spectrum of the signal processed in the first AWG and the second AWG. The method according to claim 4 or 5, A first optical isolator connected in series between the first light source unit and the first optical coupler; And A second optical isolator connected in series between the second light source unit and the second optical coupler Surveillance system using a dual wavelength FBG sensor further comprising. A fiber bragg grating (FBG) sensor having three grating portions having different physical characteristics in a predetermined region of the optical fiber; A first optical circulator configured to receive a first reflected wavelength signal and a second reflected wavelength signal for the first optical wavelength signal reflected from the FBG sensor; A second optical circulator for receiving a third reflected wavelength signal with respect to the second optical wavelength signal reflected from the FBG sensor; And An estimator estimating an amount of change in temperature and strain based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal Surveillance system using a dual wavelength FBG sensor comprising a. Receiving a first reflected wavelength signal and a second reflected wavelength signal for the first optical wavelength signal from a fiber bragg grating (FBG) sensor having three grating portions having different physical characteristics in a predetermined region of the optical fiber; Receiving a third reflected wavelength signal for a second optical wavelength signal from the FBG sensor; And Estimating changes in temperature and strain based on the received first reflected wavelength signal, the second reflected wavelength signal, and the third reflected wavelength signal; Monitoring method using a dual wavelength FBG sensor comprising a. 13. The method of claim 12, The estimating step, Estimating an amount of change of strain with respect to a point where the FBG sensor is located based on the received first and second reflected wavelength signals; Estimating an amount of change in temperature with respect to the point based on the estimated amount of change in strain; And And estimating a point at which the FBG sensor is located based on the received third reflected wavelength signal.

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