WO2020056820A1 - Method and device for measuring temperature and/or deformation according to brillouin shift - Google Patents

Abstract

The present application relates to a method and device for measuring the temperature and/or deformation according to Brillouin shift. A section of bent optical fiber having both ends fixed is used, the effect of the strain on the Brillouin shift after the optical fiber is bent and both ends thereof are fixed is ignored to measure the Brillouin shift of the section of optical fiber, and the temperature can be obtained according to the relation between the Brillouin shift and the temperature. The Brillouin shift of a section of unfixed optical fiber at the certain temperature is then measured, and the strain is obtained through calculation. According to the present application, the temperature and the strain of an optical fiber node can be independently measured, the calculation is simple, and the result is accurate.

Description

Method and device for measuring temperature and / or deformation according to Brillouin frequency shift Technical field

The present application belongs to the technical field of optical fiber distributed temperature sensors, and particularly relates to a method and device for independently measuring the temperature of an infrastructure node.

Background technique

Optical fiber distributed temperature and strain sensor FDTSS (Fiber Distributed Temperature and Stress Sensor). The system uses the Brillouin optical time domain reflection technology (BOTDR, Brillouin Optical Time Domain Reflectometry), which has developed rapidly in recent years, using single-mode fiber and photonic crystal The optical fiber temperature measurement node enables the optical fiber to be used as a signal transmission medium while measuring the temperature and strain distribution on the optical fiber path by sensing the medium. This system takes advantage of the nonlinear effect of light-the Brillouin frequency shift of the incident light is proportional to the strain and temperature loaded on the fiber, and it can measure the signal power of the single-frequency or multi-frequency time-domain reflected power spectrum. The influence of temperature and strain on the Brillouin frequency shift, in order to predict the changes in the infrastructure structure, and to prevent the occurrence of safety accidents by means of maintenance, maintenance and repair of the infrastructure in advance. The measurement device based on BOTDR technology has a Brillouin reflection spectral line with a small light intensity distribution. Therefore, special encoding / decoding and signal processing are required for pulse pumping and receiving spectral line processing. In addition, because the Brillouin frequency shift is simultaneously proportional to the temperature and strain acting on the fiber, the Brillouin frequency shift is the result of the simultaneous action of temperature and strain, so it is not possible to independently measure the temperature and strain acting on the fiber node. Value.

Summary of the Invention

The technical problem to be solved by the present invention is: in order to solve the above-mentioned shortcomings in the prior art, a method and device for measuring temperature and / or deformation according to a Brillouin frequency shift, which can independently measure the temperature and strain of an optical fiber node, are provided.

The technical solutions adopted by the present invention to solve its technical problems are:

A method for measuring temperature based on a Brillouin frequency shift includes the following steps:

S1: Take a piece of bent and fixed optical fiber and place the optical fiber in a cylinder with a linear expansion coefficient of ± 0.007 × 10 ^-6 K ^-1 ;

S2: Measure the Brillouin frequency shift V _B1 of the fiber, then the temperature value T = (V _B1 -V ₀₁ ) / △ V _B ; where △ V _B is the frequency shift constant corresponding to temperature, and V ₀₁ is the frequency shift constant .

A method for measuring deformation according to a Brillouin frequency shift includes the following steps:

S1: Take a piece of bent and fixed optical fiber, and place the optical fiber in a cylinder with good thermal conductivity and linear expansion coefficient between ± 0.007 × 10 ^-6 K ^-1 ;

S2: measure the Brillouin frequency shift V _B1 of the fiber;

S3: Measure the Brillouin frequency shift V _{B2 of} an unfixed fiber at the same temperature.

Where C _r is the frequency shift constant and V ₀₁ and V ₀₂ are frequency shift constants, respectively.

A method for measuring temperature and deformation based on a Brillouin frequency shift includes the following steps:

S1: Take a piece of bent and fixed optical fiber, and place the optical fiber in a cylinder with good thermal conductivity and linear expansion coefficient between ± 0.007 × 10 ^-6 K ^-1 ;

S2: Measure the Brillouin frequency shift V _B1 of the fiber, and the temperature value T = (V _B1 -V ₀₁ ) / △ V _B ; where △ V _B is the frequency shift constant corresponding to temperature, and V ₀₁ is the frequency shift constant;

S3: Measure the Brillouin frequency shift V _{B2 of} an unfixed fiber at the same temperature.

Where C _r is the frequency shift constant and V ₀₂ is the frequency shift constant.

Preferably, in the method of the present invention, the cylinder is a lithium aluminosilicate glass ceramic, and the cylinder is provided with a through hole.

Preferably, in the method of the present invention, the bending angle of the optical fiber is less than 7 °.

Preferably, in the method of the present invention, the optical fiber is a photonic crystal polarization maintaining fiber.

A device for measuring temperature according to Brillouin frequency shift, including:

A hollow cylinder, fixed buckles provided at both ends of the cylinder, and a bent optical fiber fixed between two fixed buckles;

The Brillouin frequency shift sensor is connected to the bent optical fiber and is used to measure the Brillouin frequency shift V _{B1 of the} fiber;

The temperature calculation module calculates the temperature T according to the formula T = (V _B1 -V ₀₁ ) / △ V _B , where C _r is the frequency conversion constant and V ₀₁ and V ₀₂ are frequency shift constants, respectively.

A device for measuring deformation according to a Brillouin frequency shift includes:

A hollow cylinder, fixed buckles provided at both ends of the cylinder, and a bent optical fiber fixed between two fixed buckles;

A section of unfixed fiber;

Brillouin frequency shift sensor, an optical fiber connection and the curved fiber-free fixing, for measuring the bending of the optical fiber at the same temperature Brillouin frequency shift V _B1 of the optical fiber and no fixed Brillouin frequency shift V _B2;

Deformation calculation module according to formula

The strain ε is calculated, where C _r is the frequency shift constant.

A device for measuring temperature and deformation according to Brillouin frequency shift, including:

A hollow cylinder, a fixed buckle provided at both ends of the cylinder, and a bent optical fiber fixed between the two fixed buckles;

A section of unfixed fiber;

Brillouin frequency shift sensor, an optical fiber connection and the curved fiber-free fixing, for measuring the bending of the optical fiber at the same temperature Brillouin frequency shift V _B1 of the optical fiber and no fixed Brillouin frequency shift V _B2;

The temperature calculation module calculates the temperature T according to the formula T = (V _B1 -V ₀₁ ) / △ V _B , where △ V _B is a frequency shift constant corresponding to temperature, and V ₀₁ is a frequency shift constant;

Deformation calculation module according to formula

Calculate the strain variable ε, where C _r is the frequency shift constant and V ₀₂ is the frequency shift constant.

The beneficial effects of the present invention are:

According to the method and device for measuring temperature and / or deformation according to the Brillouin frequency shift of the present application, the influence of the strain on the Brillouin frequency shift after the fiber is bent and fixed at both ends through a section of the bent and fixed fiber is negligible The Brillouin frequency shift V _B1 of the fiber is measured, and the temperature can be obtained according to the relationship between the Brillouin frequency shift and temperature. Then measure the Brillouin frequency shift V _{B2 of} a section of unfixed fiber at a certain temperature, and then calculate the strain. The application can independently measure the temperature and strain of the optical fiber node, and has the advantages of simple calculation and accurate results.

BRIEF DESCRIPTION OF THE DRAWINGS

The technical solution of the present application is further described below with reference to the accompanying drawings and embodiments.

1 is a schematic structural diagram of an optical fiber fixing structure according to an embodiment of the present application;

The reference numerals in the figure are:

Cylinder 1, fixed buckle 2, optical fiber 9.

detailed description

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

In the description of this application, it should be understood that the terms "center", "vertical", "horizontal", "upper", "down", "front", "rear", "left", "right", " The orientations or positional relationships indicated by "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing this application and The simplified description does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the scope of protection of this application. In addition, the terms “first”, “second”, and the like are used for descriptive purposes only, and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise stated, "multiple" means two or more.

In the description of this application, it should be noted that the terms "installation", "connected", and "connected" should be understood in a broad sense unless explicitly stated and limited otherwise. For example, they may be fixed connections or removable. Connected or integrated; it can be mechanical or electrical; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood through specific situations.

The technical solution of the present application will be described in detail below with reference to the drawings and embodiments.

This application is based on the relationship between Brillouin frequency shift and temperature and strain: V _B = V ₀ + C _r ε + △ V _B T, where v _B is the Brillouin frequency shift, and C _r is the frequency conversion constant, which is Known values, ε is a strain variable, Δv _B is a frequency shift constant corresponding to temperature, is a known value, T is temperature, and v ₀ is a frequency shift constant, is a known value.

The formula shows that the Brillouin frequency shift (v _B ) cannot be measured separately due to the influence of temperature and strain simultaneously, so it can be distinguished independently by the two-parameter matrix method. The principle of this algorithm is to use two sets of equations to describe the effect of temperature and strain on the Brillouin frequency shift, and one of them is not sensitive to strain. That is, in different states (whether the two ends are fixed or not fixed), the Brillouin frequency shift can be measured by measuring multiple temperature and strain values, and then the Brillouin frequency shift can be obtained by the dual parameter matrix method. The relationship between temperature and strain value can be finally applied to the calculation of strain value in the following. Therefore, through prior experiments, the following V ₀₁ , V ₀₂ and △ V _{B are obtained.}

When the two ends of the fiber are fixed, the effect of its strain on the Brillouin frequency shift is negligible, so C _r ε can be ignored. At this time, V _B1 = V ₀₁ + △ V _B T (Equation 1); Brillouin frequency shift V _B1 can be obtained by Brillouin frequency shift induction, and V ₀₁ is a constant frequency shift when fixed at both ends of the fiber. According to Equation 1, when the Brillouin frequency shift V _B1 is known, the temperature T = (V _B1 -V ₀₁ ) / ΔV _B can be obtained.

When the two ends of the optical fiber are not fixed, in a free state, V _B2 = V ₀₂ + C _r ε + △ V _B T (Equation 2); Brillouin frequency shift V _B2 can be obtained by Brillouin frequency shift induction, V ₀₂ It is the frequency shift constant when fixed at both ends of the fiber.

Equations 1 and 2 can be used to find the dependent variable

V ₀₂ is the frequency shift constant when there are no fixed ends of the fiber.

Therefore, through the above method, the temperature constant of the environment where the fiber is located and the stress of the fiber can be obtained by measuring the frequency shift constants when the two ends of the fiber are fixed and when the two ends of the fiber are not fixed at the same temperature.

Example 1

This embodiment provides a method for measuring temperature according to a Brillouin frequency shift, including the following steps:

S1: Take a section of bent and fixed optical fiber and place the fiber into the barrel. The barrel is preferably lithium aluminosilicate glass ceramic. The barrel is provided with through holes (through holes can be circular or stripe). In order not to introduce high bending loss and reflection, the bending angle of the optical fiber is preferably less than 7 °, and the optical fiber is preferably a photonic crystal polarization maintaining fiber. When a photonic crystal polarization maintaining fiber is generally used, the influence of the bending angle of the fiber on the bending loss and reflection can be can be ignored;

S2: Measure the Brillouin frequency shift V _B1 of the fiber, and calculate the temperature T, T = (V _B1 -V ₀₁ ) / △ V _B ; where △ V _B1 is the frequency shift constant corresponding to temperature, and V ₀₁ is Frequency shift constant; △ V _B is the frequency shift constant corresponding to the temperature, which is a known value, and T is the temperature.

In this implementation, the ambient temperature can be directly obtained through the Brillouin frequency shift.

Example 2

This embodiment provides a method for measuring deformation according to a Brillouin frequency shift, including the following steps:

S1: Take a section of the optical fiber 9 that is bent and fixed at both ends, and place the optical fiber 9 in a cylinder. The cylinder is preferably a cylinder, preferably lithium aluminosilicate glass ceramic. The cylinder is provided with a through hole. High bending loss and reflection, the bending angle of the optical fiber 9 is preferably less than 7 °, and the optical fiber is preferably a photonic crystal polarization maintaining fiber. When a photonic crystal polarization maintaining fiber is generally used, the influence of the bending angle of the optical fiber 9 on the bending loss and reflection is negligible;

S2: measure the Brillouin frequency shift V _B1 of the fiber;

S3: Measure the Brillouin frequency shift V _{B2 of} a section of unfixed optical fiber at a certain temperature.

V ₀₁ and V ₀₂ are frequency shift constants; △ V _B is a frequency shift constant corresponding to temperature, which is a known value.

This implementation does not need to calculate the temperature, and directly obtains the strain variable through the Brillouin frequency shift.

Example 3

This embodiment provides a method for measuring temperature and deformation according to a Brillouin frequency shift, including the following steps:

S1: Take a section of the optical fiber 9 that is bent and fixed at both ends, and place the optical fiber 9 in a cylinder. The cylinder is preferably a lithium aluminosilicate glass ceramic. The cylinder is provided with a through hole so as not to introduce high bending loss. And reflection, the bending angle of the optical fiber 9 is preferably less than 7 °, and the optical fiber 9 is preferably a photonic crystal polarization maintaining fiber. When a photonic crystal polarization maintaining fiber is generally used, the influence of the bending angle of the optical fiber 9 on bending loss and reflection is negligible;

S2: Measure the Brillouin frequency shift V _B1 of the fiber, and calculate the temperature T, T = (V _B1 -V ₀₁ ) / △ V _B ; where △ V _B1 is the frequency shift constant corresponding to temperature, and V ₀₁ is Frequency shift constant; △ V _B is the frequency shift constant corresponding to the temperature, which is a known value, and T is the temperature;

S3: Measure the Brillouin frequency shift V _{B2 of} a section of unfixed fiber at a certain temperature.

Is the frequency shift constant and is a known value.

In this implementation, the ambient temperature and the strain amount are obtained through the Brillouin frequency shift.

Example 4

This embodiment provides a device for measuring temperature according to a Brillouin frequency shift. As shown in FIG. 1, the device includes:

Hollow cylinder 1, fixed buckles 2 provided at both ends of the cylinder 1, and a bent optical fiber 9 fixed between two fixed buckles 2; the cylinder is preferably a lithium aluminosilicate glass ceramic, so as not to introduce high Bending loss and reflection, the bending angle of the optical fiber 9 is preferably less than 7 °, and the optical fiber is preferably a photonic crystal polarization maintaining fiber. When a photonic crystal polarization maintaining fiber is generally used, the influence of the bending angle of the optical fiber 9 on the bending loss and reflection is negligible;

The Brillouin frequency shift sensor is connected to the bent optical fiber and is used to measure the Brillouin frequency shift V _{B1 of the} fiber;

The temperature calculation module calculates the temperature T according to the formula T = (V _B1 -V ₀₁ ) / △ V _B , where C _r is a constant frequency shift constant and is a known value.

Example 5

This embodiment provides a device for measuring deformation according to a Brillouin frequency shift. As shown in FIG. 1, the device includes:

Hollow cylinder 1, fixed buckles 2 provided at both ends of cylinder 1, and curved optical fiber fixed between two fixed buckles 2; the cylinder is preferably a lithium aluminosilicate glass ceramic, in order not to introduce a higher Bending loss and reflection, the bending angle of the optical fiber is preferably less than 7 °, and the optical fiber is preferably a photonic crystal polarization maintaining fiber. When a photonic crystal polarization maintaining fiber is generally used, the influence of the bending angle of the fiber on the bending loss and reflection is negligible;

A section of unfixed fiber;

Brillouin frequency shift sensor, an optical fiber connection and the curved fiber-free fixing, for measuring the bending of the optical fiber at the same temperature Brillouin frequency shift V _B1 of the optical fiber and no fixed Brillouin frequency shift V _B2;

Deformation calculation module according to formula

The strain ε is calculated, where C _r is the constant frequency shift constant and is a known value.

Example 6

This embodiment provides a device for measuring temperature and deformation according to a Brillouin frequency shift. As shown in FIG. 1, the device includes:

Hollow cylinder 1, fixed buckles 2 provided at both ends of cylinder 1, and curved optical fiber fixed between two fixed buckles 2; the cylinder is preferably a lithium aluminosilicate glass ceramic, in order not to introduce a higher Bending loss and reflection, the bending angle of the optical fiber is preferably less than 7 °, and the optical fiber is preferably a photonic crystal polarization maintaining fiber. When a photonic crystal polarization maintaining fiber is generally used, the influence of the bending angle of the fiber on the bending loss and reflection is negligible;

A section of unfixed fiber;

Brillouin frequency shift sensor, an optical fiber connection and the curved fiber-free fixing, for measuring the bending of the optical fiber at the same temperature Brillouin frequency shift V _B1 of the optical fiber and no fixed Brillouin frequency shift V _B2;

The temperature calculation module calculates the temperature T according to the formula T = (V _B1 -V ₀₁ ) / △ V _B , where V _B is a frequency shift constant corresponding to temperature, and V ₀₁ is a frequency shift constant;

Deformation calculation module according to formula

The strain ε is calculated, where △ C _r is the constant frequency shift constant and is a known value.

It should be noted that, in Examples 1-6, the linear expansion coefficient of the cylinder 1 is between ± 0.007 × 10 ^-6 K ^-1 to prevent the thermal deformation of the cylinder 1 from affecting the optical fiber.

Taking the above-mentioned ideal embodiment based on the present application as a revelation, through the above-mentioned description content, the related staff members can make various changes and modifications within the scope that does not deviate from the technical idea of this application. The technical scope of this application is not limited to the content of the description, and its technical scope must be determined according to the scope of the claims.

Claims (9)

1. A method for measuring temperature according to a Brillouin frequency shift, characterized in that it includes the following steps:

   S1: Take a piece of bent and fixed optical fiber and place the optical fiber in a cylinder with a linear expansion coefficient of ± 0.007 × 10 ^-6 K ^-1 ;

   S2: Measure the Brillouin frequency shift V _B1 of the fiber, then the temperature value T = (V _B1 -V ₀₁ ) / △ V _B ; where △ V _B is the frequency shift constant corresponding to temperature, and V ₀₁ is the frequency shift constant .
2. A method for measuring deformation according to a Brillouin frequency shift is characterized in that it includes the following steps:

   S1: Take a piece of bent and fixed optical fiber, and place the optical fiber in a cylinder with good thermal conductivity and linear expansion coefficient between ± 0.007 × 10 ^-6 K ^-1 ;

   S2: measure the Brillouin frequency shift V _B1 of the fiber;

   S3: Measure the Brillouin frequency shift V _{B2 of} an unfixed fiber at the same temperature.

   

   Where C _r is the frequency shift constant and V ₀₁ and V ₀₂ are frequency shift constants, respectively.
3. A method for measuring temperature and deformation according to a Brillouin frequency shift, characterized in that it includes the following steps:

   S1: Take a piece of bent and fixed optical fiber, and place the optical fiber in a cylinder with good thermal conductivity and linear expansion coefficient between ± 0.007 × 10 ^-6 K ^-1 ;

   S2: Measure the Brillouin frequency shift V _B1 of the fiber, and the temperature value T = (V _B1 -V ₀₁ ) / △ V _B ; where △ V _B is the frequency shift constant corresponding to temperature, and V ₀₁ is the frequency shift constant;

   S3: Measure the Brillouin frequency shift V _{B2 of} an unfixed fiber at the same temperature.

   

   Where C _r is the frequency shift constant and V ₀₂ is the frequency shift constant.
4. The method according to any one of claims 1-3, wherein the cylinder is a lithium aluminosilicate glass ceramic, and the cylinder is provided with a through hole.
5. The method according to claim 4, wherein the bending angle of the optical fiber is less than 7 °.
6. The method according to claim 4 or 5, wherein the optical fiber is a photonic crystal polarization maintaining fiber.
7. A device for measuring temperature according to Brillouin frequency shift, characterized in that it includes:

   A hollow cylinder (1), fixed clips (2) provided at both ends of the cylinder (1), and a bent optical fiber fixed between the two fixed clips (2);

   The Brillouin frequency shift sensor is connected to the bent optical fiber and is used to measure the Brillouin frequency shift V _{B1 of the} fiber;

   The temperature calculation module calculates the temperature T according to the formula T = (V _B1 -V ₀₁ ) / △ V _B , where C _r is the frequency conversion constant and V ₀₁ and V ₀₂ are frequency shift constants, respectively.
8. A device for measuring deformation according to a Brillouin frequency shift is characterized in that it includes:

   A hollow cylinder (1), fixed clips (2) provided at both ends of the cylinder (1), and a bent optical fiber fixed between the two fixed clips (2);

   A section of unfixed fiber;

   Brillouin frequency shift sensor, an optical fiber connection and the curved fiber-free fixing, for measuring the bending of the optical fiber at the same temperature Brillouin frequency shift V _B1 of the optical fiber and no fixed Brillouin frequency shift V _B2;

   Deformation calculation module according to formula

   

   The strain ε is calculated, where C _r is the constant frequency shift constant.
9. A device for measuring temperature and deformation according to a Brillouin frequency shift, characterized in that it includes:

   A hollow cylinder (1), fixed clips (2) provided at both ends of the cylinder (1), and a bent optical fiber fixed between the two fixed clips (2);

   A section of unfixed fiber;

   Brillouin frequency shift sensor, an optical fiber connection and the curved fiber-free fixing, for measuring the bending of the optical fiber at the same temperature Brillouin frequency shift V _B1 of the optical fiber and no fixed Brillouin frequency shift V _B2;

   The temperature calculation module calculates the temperature T according to the formula T = (V _B1 -V ₀₁ ) / △ V _B , where △ V _B is a frequency shift constant corresponding to temperature, and V ₀₁ is a frequency shift constant;

   Deformation calculation module according to formula

   

   Calculate the strain variable ε, where C _r is the frequency shift constant and V ₀₂ is the frequency shift constant.

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