Temperature strain sensor based on optical fiber over-coupling structure, method and application
阅读说明：本技术 基于光纤过耦合结构的温度应变传感器、方法及应用 (Temperature strain sensor based on optical fiber over-coupling structure, method and application ) 是由 柳春郁 江升旭 苏杭 于 2020-05-20 设计创作，主要内容包括：本发明属于光纤传感技术领域,本发明公开了一种基于光纤过耦合结构的温度应变传感器、方法及应用。其中,传感器包括依次连接的光源、导入单模光纤、光纤过耦合结构、导出单模光纤、耦合器和检测单元；所述的检测单元包括光功率计和光谱仪；所述的光纤过耦合结构包括第一耦合光纤和第二耦合光纤,所述的第一耦合光纤中部和第二耦合光纤中部耦合形成耦合区。本发明的传感器可以同时测量两个参量,灵敏度水平较高。(The invention belongs to the technical field of optical fiber sensing, and discloses a temperature strain sensor based on an optical fiber over-coupling structure, a method and application. The sensor comprises a light source, a lead-in single mode fiber, a fiber over-coupling structure, a lead-out single mode fiber, a coupler and a detection unit which are connected in sequence; the detection unit comprises an optical power meter and a spectrometer; the optical fiber over-coupling structure comprises a first coupling optical fiber and a second coupling optical fiber, wherein the middle part of the first coupling optical fiber and the middle part of the second coupling optical fiber are coupled to form a coupling area. The sensor of the invention can measure two parameters simultaneously and has higher sensitivity level.)
1. A temperature strain sensor based on an optical fiber over-coupling structure is characterized by comprising a light source, a lead-in single mode optical fiber, an optical fiber over-coupling structure, a lead-out single mode optical fiber, a coupler and a detection unit which are sequentially connected;
the detection unit comprises an optical power meter and a spectrometer;
the optical fiber over-coupling structure comprises a first coupling optical fiber and a second coupling optical fiber, wherein the middle part of the first coupling optical fiber and the middle part of the second coupling optical fiber are coupled to form a coupling area.
2. The fiber optic over-coupling structure based temperature strain sensor of claim 1, wherein the first coupling fiber is a single mode fiber, a polarization maintaining fiber or a multimode fiber.
3. The fiber optic over-coupling structure based temperature strain sensor of claim 1, wherein the second coupling fiber is a single mode fiber, a polarization maintaining fiber or a multimode fiber.
4. The fiber optic over-coupling structure based temperature strain sensor of claim 1, wherein the first coupling fiber and the second coupling fiber are of the same fiber type.
5. The fiber optic over-coupling structure-based temperature strain sensor of claim 1, wherein the light source is an ASE broadband light source.
6. The fiber optic over-coupling structure based temperature strain sensor of claim 1, wherein the coupler is a 3dB coupler.
7. The fiber optic over-coupling structure based temperature strain sensor of claim 1, wherein the first coupling fiber is a straight-through arm fiber and the second coupling fiber is a coupling arm fiber.
8. A method for preparing a temperature strain sensor based on an optical fiber over-coupling structure, wherein the sensor is the sensor of any one of claims 1 to 7, comprising the following steps:
(1) preparing an optical fiber over-coupling structure: cutting the end faces of the first coupling optical fiber and the second coupling optical fiber to be flat, and respectively welding two jumper wires with two ends of the first coupling optical fiber to form a straight-through arm optical fiber; welding one jumper wire and one end of a second optical fiber to form a coupling arm optical fiber, controlling the loss in the welding process to be 0.01dB to 0.02dB, and performing welding when the angles of the end faces of the optical fibers are consistent, wherein the splitting ratio is adjusted to 50 percent to be used as a pre-tapering process; when the splitting ratio reaches 50: 50, the total loss is less than or equal to 0.2dB, and the hydrogen flow is ensured to be stable and continuous under the condition of 60 percent; by setting the splitting ratio not equal to 1, the cone drawing can be ensured to be continuously carried out; continuously tapering continuously, observing that the curve period of the light energy in the monitoring interface vibrates violently, and stopping tapering when the oscillation period is 60 ℃ and tends to be stable; obtaining an optical fiber over-coupling structure;
(2) and the light source, the lead-in single mode fiber, the fiber over-coupling structure, the lead-out single mode fiber, the coupler and the detection unit are connected in sequence.
9. Use of a temperature strain sensor based on an optical fiber over-coupling structure, characterized in that the sensor according to any of claims 1-7 is used for temperature and stress change sensitivity measurements.
10. Use according to claim 9,
the measurement of the temperature sensitivity comprises the following steps:
turning on a light source, transmitting an optical signal emitted by the light source to a detection unit through a leading-in single mode fiber, a fiber over-coupling structure, a leading-out single mode fiber and a coupler in sequence, and changing the temperature of a space where the sensor is located to obtain transmission spectra at different temperatures;
the measurement of the sensitivity to stress variations comprises the following steps:
and opening the light source, transmitting the optical signal emitted by the light source to the detection unit through the lead-in single-mode optical fiber, the optical fiber over-coupling structure, the lead-out single-mode optical fiber and the coupler in sequence, and applying different stresses to the sensor to obtain the transmission spectra under different stresses.
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a temperature strain sensor based on an optical fiber over-coupling structure, a method and application.
Background
The description of the background of the invention pertaining to the related art to which this invention pertains is given for the purpose of illustration and understanding only of the summary of the invention and is not to be construed as an admission that the applicant is explicitly or implicitly admitted to be prior art to the date of filing this application as first filed with this invention.
The basic working principle of the optical fiber sensor is that light beams incident from a light source are transmitted to a modulator through an optical fiber, interact with external measured parameters in the modulator, change optical properties (such as intensity, wavelength, frequency, phase, polarization state and the like) of the light to form modulated light signals, and then the modulated light signals are transmitted through the optical fiber and demodulated through a demodulator to obtain corresponding measured parameters. The optical fiber sensor is continuously developed towards high sensitivity, high accuracy, strong adaptability, structure precision and intellectualization. In recent years, a great number of optical fiber sensors of various novel structures have been reported, and the research on optical fiber couplers is also being intensively carried out; in early studies, the fiber coupler was simple in structure and not very functional. Most function as an optical signal transmission medium. Nowadays, optical fiber couplers are continuously developed, and innovations and breakthroughs in structure and performance are already made, so that the optical fiber couplers have wide development prospects in the field of optical fiber sensing.
Current sensors have difficulty measuring dual parameters at high levels.
Disclosure of Invention
The embodiment of the invention aims to provide a temperature strain sensor based on an optical fiber over-coupling structure, a method and application.
A temperature strain sensor based on an optical fiber over-coupling structure comprises a light source, a lead-in single mode optical fiber, an optical fiber over-coupling structure, a lead-out single mode optical fiber, a coupler and a detection unit which are connected in sequence;
the detection unit comprises an optical power meter and a spectrometer;
the optical fiber over-coupling structure comprises a first coupling optical fiber and a second coupling optical fiber, wherein the middle part of the first coupling optical fiber and the middle part of the second coupling optical fiber are coupled to form a coupling area.
Further, the first coupling fiber is a single mode fiber, a polarization maintaining fiber or a multimode fiber.
Further, the second coupling optical fiber is a single mode optical fiber, a polarization maintaining optical fiber or a multimode optical fiber.
Further, the first coupling fiber and the second coupling fiber have the same fiber type.
Further, the light source is an ASE broadband light source.
Further, the coupler is a 3dB coupler.
Further, the first coupling optical fiber is a straight-through arm optical fiber, and the second coupling optical fiber is a coupling arm optical fiber.
In a second aspect, the present invention provides a method for preparing a temperature strain sensor based on an optical fiber over-coupling structure, where the sensor is the above-mentioned sensor, and the method includes the following steps:
(1) preparing an optical fiber over-coupling structure: cutting the end faces of the first coupling optical fiber and the second coupling optical fiber to be flat, and respectively welding two jumper wires with two ends of the first coupling optical fiber to form a straight-through arm optical fiber; welding one jumper wire and one end of a second optical fiber to form a coupling arm optical fiber, controlling the loss in the welding process to be 0.01dB to 0.02dB, and performing welding when the angles of the end faces of the optical fibers are consistent, wherein the splitting ratio is adjusted to 50 percent to be used as a pre-tapering process; when the splitting ratio reaches 50: 50, the total loss is less than or equal to 0.2dB, and the hydrogen flow is ensured to be stable and continuous under the condition of 60 percent; by setting the splitting ratio not equal to 1, the cone drawing can be ensured to be continuously carried out; continuously tapering continuously, observing that the curve period of the light energy in the monitoring interface vibrates violently, and stopping tapering when the oscillation period is 60 ℃ and tends to be stable; obtaining an optical fiber over-coupling structure;
(2) and the light source, the lead-in single mode fiber, the fiber over-coupling structure, the lead-out single mode fiber, the coupler and the detection unit are connected in sequence.
In a third aspect, the invention provides an application of a temperature strain sensor based on an optical fiber over-coupling structure, and the sensor is applied to measurement of temperature sensitivity and stress change sensitivity.
Further, the measurement of the temperature sensitivity comprises the following steps:
turning on a light source, transmitting an optical signal emitted by the light source to a detection unit through a leading-in single mode fiber, a fiber over-coupling structure, a leading-out single mode fiber and a coupler in sequence, and changing the temperature of a space where the sensor is located to obtain transmission spectra at different temperatures;
the measurement of the sensitivity to stress variations comprises the following steps:
and opening the light source, transmitting the optical signal emitted by the light source to the detection unit through the lead-in single-mode optical fiber, the optical fiber over-coupling structure, the lead-out single-mode optical fiber and the coupler in sequence, and applying different stresses to the sensor to obtain the transmission spectra under different stresses.
The embodiment of the invention has the following beneficial effects:
the all-fiber sensing device utilizes an all-fiber structure for sensing, and has the advantages of electromagnetic interference resistance, electric insulation, high sensitivity, small volume, light weight, flexible and changeable appearance structure, strong adaptability, wide application range, high reliability and the like.
The sensor of the application has the effect of measuring temperature and strain sensitivity simultaneously, and the sensitivity of temperature and strain has higher level.
The method introduces a double-parameter demodulation method and a sensitivity matrix mode to solve the problem of cross sensitivity of temperature and strain, and can eliminate the mutual influence of wavelength on temperature and strain responsivity.
When the temperature and the strain in the external environment change simultaneously, the wavelength change of the interference valley image of the optical fiber over-coupler can be expressed as
Δλi＝k,iΔ+kT,iΔT
Where Δ is the amount of change in stress, Δ T is the amount of change in temperature, k,iAnd kΤ,iRespectively, a stress response sensitivity value and a temperature response sensitivity value.
There may be a matrix equation of response values as:
drawings
Fig. 1 is a schematic structural diagram of a sensor in an embodiment of a temperature strain sensor based on an optical fiber over-coupling structure according to the present invention.
FIG. 2 is a diagram illustrating the relationship between the interference wavelength of the optical fiber over-coupling structure and the temperature variation;
FIG. 3 is a diagram showing the fitting of the interference wavelength to the temperature change in the embodiment;
FIG. 4 is a diagram illustrating the variation of interference wavelength with strain of an optical fiber over-coupling structure according to an embodiment;
FIG. 5 is a diagram illustrating the fitting of the interference wavelength to the strain change in the embodiment.
Detailed Description
The present application is further described below with reference to examples.
In the following description, different "one embodiment" or "an embodiment" may not necessarily refer to the same embodiment, in order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art. Various embodiments may be replaced or combined, and other embodiments may be obtained according to the embodiments without creative efforts for those skilled in the art.
With reference to fig. 1, a temperature strain sensor based on an optical fiber over-coupling structure includes a light source 1, a lead-in single mode fiber 2, an optical fiber over-coupling structure 3, a lead-out single mode fiber 4, a coupler 5 and a detection unit, which are connected in sequence;
the detection unit comprises an optical power meter 6 and a spectrometer 7;
the optical fiber over-coupling structure comprises a first coupling optical fiber 3-1 and a second coupling optical fiber 3-3, wherein the middle part of the first coupling optical fiber and the middle part of the second coupling optical fiber are coupled to form a coupling area 3-2.
In some embodiments of the present invention, the first coupling fiber 3-1 is a single mode fiber, a polarization maintaining fiber or a multimode fiber.
In some embodiments of the present invention, the second coupling fiber 3-2 is a single mode fiber, a polarization maintaining fiber or a multimode fiber.
In some embodiments of the present invention, the first coupling fiber 3-1 and the second coupling fiber 3-2 are of the same fiber type.
In some embodiments of the present invention, the light source 1 is an ASE broadband light source.
In some embodiments of the present invention, the coupler 5 is a 3dB coupler.
In some embodiments of the present invention, the first coupling fiber 3-1 is a through-arm fiber, and the second coupling fiber 3-2 is a coupling-arm fiber.
A preparation method of a temperature strain sensor based on an optical fiber over-coupling structure is provided, wherein the sensor is the above sensor, and comprises the following steps:
(1) preparing an optical fiber over-coupling structure: the end faces of the first coupling optical fiber 3-1 and the second coupling optical fiber 3-2 are cut to be flat, and two jumper wires are respectively welded with the two ends of the first coupling optical fiber 3-1 to form a straight-through arm optical fiber; welding one jumper wire and one end of the second optical fiber 3-2 to form a coupling arm optical fiber, controlling the loss in the welding process to be 0.01dB to 0.02dB, and performing welding when the angles of the end faces of the optical fibers are consistent, wherein the splitting ratio is adjusted to 50 percent to be used as a pre-tapering process; when a preset parameter value is reached, the cone drawing can be ensured to be continuously carried out by setting the splitting ratio not to be equal to 1; when the curve period oscillation of the light energy in the observation and monitoring interface is most violent, the oscillation period is small enough and tends to be stable, the tapering is stopped; obtaining an optical fiber over-coupling structure;
(2) and the light source 1, the lead-in single mode fiber 2, the fiber over-coupling structure 3, the lead-out single mode fiber 4, the coupler 5 and the detection unit are connected in sequence.
The application of the temperature strain sensor based on the optical fiber over-coupling structure is to apply the sensor to the measurement of temperature sensitivity and stress change sensitivity.
In some embodiments of the invention, the measuring of the temperature sensitivity comprises the steps of:
the method comprises the following steps that a light source 1 is turned on, an optical signal sent by the light source 1 is transmitted to a detection unit through a leading-in single-mode optical fiber 2, an optical fiber over-coupling structure 3, a leading-out single-mode optical fiber 4 and a coupler 5 in sequence, and the temperature of a space where a sensor is located is changed to obtain transmission spectra at different temperatures;
the measurement of the sensitivity to stress variations comprises the following steps:
and (2) opening the light source 1, transmitting the optical signal emitted by the light source 1 to the detection unit through the leading-in single-mode optical fiber 2, the optical fiber over-coupling structure 3, the leading-out single-mode optical fiber 4 and the coupler 5 in sequence, and applying different stresses to the sensor to obtain transmission spectra under different stresses.
The length of the tapering is in the range of 22000-23000, and the tapering speed is adjusted to 100.
The sensing area is made of a traditional single mode optical fiber. In the sensing analysis, from the perspective of optical fiber energy coupling, the temperature and the strain are measured by utilizing the characteristic that the over-coupling structure is easily influenced by the environment. The sensing structure has the advantages of low cost, compact structure, convenient use and the like.
In the optical fiber-based over-coupling structure, the tapering speed is ensured to be kept constant, and the tapering length is maintained between 22000 μm and 23000 μm. By optimization, the contrast of the stripes in the interval can reach 19.70dB at most.
Light is transmitted to the first coupling optical fiber 3-1 and the second coupling optical fiber 3-2, the normalized frequency of the optical fiber is gradually reduced due to the fact that the fiber core is wide and narrow in the fused cone structure, and light energy starts to enter the cladding from the fiber core; when light is output from the first coupling optical fiber 3-1 and the second coupling optical fiber 3-2, the fiber core becomes thicker continuously, the normalized frequency of the optical fiber is increased again, and light energy gradually returns to the fiber core from the cladding.
When the over-coupling structure realizes temperature sensing, the structure can realize measurement of strain sensing at the same time.
Analyzing the responsivity of wavelength aiming at the optical fiber over-coupling structure tapered to 22000 mu m, substituting the stress response sensitivity and the temperature response sensitivity into a response value matrix equation,
a sensitivity matrix of general form can be obtained:
it shows that the wavelength of the interference valley image of the optical fiber over-coupling structure changes when the temperature and the strain in the external environment change simultaneously.
In some embodiments of the present invention, in conjunction with FIGS. 2-5, an ASE broadband light source with a wavelength range of 1520 and 1565nm is used in the sensing device, and an Agilent 86142B spectrometer (wavelength resolution of 0.06nm) is used in the detection section. When an optical signal is emitted from the ASE light source and then transmitted to the over-coupling structure through the single-mode fiber 2, the interference pattern signal is transmitted to the optical power meter 6 and the spectrometer 7 through the derived single-mode fiber 4. The experimental analysis of the temperature strain sensor characteristics of the present example includes the following steps:
a temperature sensing characteristic
Putting the optical fiber coupler structure 3 into a thermostat, performing a heating test, measuring a plurality of groups of temperatures, selecting three groups of data of 36 ℃, 38 ℃ and 40 ℃, wherein the step length is 2 ℃, recording spectral data in the optical spectrum analyzer 7 after the temperature of the thermostat reaches an expected temperature and is stable, and detecting the wavelength drift amount of the sensor; the transmission spectrum of the optical fiber sensor in the temperature rise process is shown in fig. 2, and as can be known from the attached fig. 2, the interference spectrum of the sensor undergoes a significant blue shift with the temperature rise.
The temperature response characteristic curve in the temperature rise process shown in fig. 3 is drawn by taking the temperature change as the horizontal axis and the wave trough position as the vertical axis, as shown in the figure, when the temperature rises from 36 ℃ to 40 ℃, the wavelength linearly increases, the temperature and the resonance wavelength are in a linear function relationship, the linearity is 0.986, and the sensitivity reaches 110 pm/DEG C.
Two strain sensing characteristic
Fixing the optical fiber over-coupling structure 3 on an optical adjusting frame, wherein one end of the optical fiber over-coupling structure is fixed, the other end of the optical fiber over-coupling structure is adjusted to move through a micron-sized displacement platform, and micro-strain is applied to the optical fiber over-coupling structure 3; experimental data are collected by a spectrum analyzer 7, micro stress is applied to the over-coupling structure 3 in a stretching mode, three groups of data with stretching lengths of 10 micrometers, 20 micrometers and 30 micrometers are selected, and the step length is 10 micrometers. The spectral change in the loading process is shown in fig. 4, the interference spectrum undergoes an obvious blue shift as the optical fiber over-coupling structure 3 is stretched and the strain response characteristic curve shown in fig. 5 is drawn by taking the strain change as the horizontal axis and the wavelength as the vertical axis, and the experimental result shows that as the strain increases, the wavelength linearly decreases, the strain and the resonant wavelength have a good linear relationship, the linearity is as high as 0.996, and the strain sensitivity is about-21.3.
The temperature response value of the wavelength change is about 110 pm/DEG C according to data analysis; the strain response for the wavelength change was about-21.3.
It should be noted that the above embodiments can be freely combined as necessary. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.