Two-parameter synchronous measurement method and system and optical fiber sensor thereof

Abstract

The invention relates to a two-parameter synchronous measurement method and system and an optical fiber sensor thereof, and the method comprises the steps: obtaining the superposition interference spectrum of a first sensing interferometer and a second sensing interferometer, carrying out the spectrum analysis of the superposition interference spectrum, and obtaining the interference spectrum of the first sensing interferometer and the interference spectrum of the second sensing interferometer; setting a virtual interference spectrum, and superposing the virtual interference spectrum with the interference spectrum of the first sensing interferometer and the interference spectrum of the second sensing interferometer respectively to generate a first vernier effect and a second vernier effect respectively; when the two to-be-measured parameters change, the interference spectrum envelopes in the first vernier effect and the second vernier effect are translated, and a first translation amount and a second translation amount are obtained; and establishing a two-dimensional matrix equation based on the first translation amount and the second translation amount, and obtaining the to-be-measured parameters of the two to-be-measured parameters through the two-dimensional matrix equation.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to a method and system for synchronously measuring dual parameters and an optical fiber sensor thereof. Background Art

[0002] Fiber optic sensors use optical fiber as the basic carrier and have the advantages of compact structure, resistance to electromagnetic interference, low cost, small size, and easy multiplexing. They can realize real-time, efficient, rapid, in-situ, and large-scale continuous monitoring of environmental parameters.

[0003] In recent years, researchers have achieved multi-parameter simultaneous measurement of interferometric fiber optic sensors. However, most of the current multi-parameter sensors are completed by connecting multiple interferometers in series or parallel. The signal light received by its spectrometer must also pass through multiple interferometers. Its structure and interference spectrum are relatively complex, and the changes in the measured parameters cannot be expressed intuitively. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to propose a method, system and optical fiber sensor for synchronous measurement of dual parameters. The sensor is composed of two interferometers connected in parallel. The sensor interferometer 1 and the sensor interferometer 2 produce a vernier effect. By performing spectrum analysis on the complex interference spectrum received by the spectrometer, the interference spectra of the two interferometers are obtained. On this basis, the interference spectrum of the virtual interferometer is superimposed. The sensor interferometer 1 and the sensor interferometer 2 respectively produce a vernier effect with the virtual interferometer to obtain the interference spectrum envelopes produced by two different vernier effects, thereby realizing the simultaneous measurement of two parameters to be measured. The sensor not only improves the sensitivity by using the vernier effect, but also realizes the simultaneous measurement of dual parameters.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A method for synchronously measuring two parameters, comprising:

[0007] Acquire a superimposed interference spectrum of a first sensor interferometer and a second sensor interferometer, perform spectrum analysis on the superimposed interference spectrum, and acquire an interference spectrum of the first sensor interferometer and an interference spectrum of the second sensor interferometer;

[0008] Setting a virtual interference spectrum, and superimposing the virtual interference spectrum with the interference spectrum of the first sensor interferometer and the second sensor interferometer, respectively, to generate a first vernier effect and a second vernier effect;

[0009] When the two parameters to be measured change, the interference spectrum envelopes in the first vernier effect and the second vernier effect are translated to obtain a first translation amount and a second translation amount;

[0010] A two-dimensional matrix equation is established based on the first translation amount and the second translation amount, and measured parameters of two measured parameters are obtained through the two-dimensional matrix equation.

[0011] Optionally, a method for obtaining the interference spectrum of the first sensor interferometer and the interference spectrum of the second sensor interferometer is:

[0012]

[0013] Among them, A 1 , A 2 are the amplitude of the first interferometer, A 3 , A 4 are the intensities of the two reflected lights of the second interferometer, L 1 , L 2 are the cavity lengths of the first interferometer and the second interferometer, n 1 and n 2 are the refractive indices of the intracavity media of the first interferometer, the second interferometer, and the cavity respectively.

[0014] Optionally, the free spectral range of the first sensor interferometer and the second sensor interferometer is:

[0015] FSR 1 =λ 2 / 2n 1 L 1

[0016] FSR 2 =λ 2 / 2n 2 L 2

[0017] Where, λ is the wavelength of the signal light, n 1 is the refractive index of the first sensing interferometer, n 2 is the refractive index of the first sensing interferometer.

[0018] Optionally, the method for obtaining the first translation amount and the second translation amount is:

[0019]

[0020] Among them, ΔT and ΔS represent the first parameter to be measured and the second parameter to be measured relative to the calibration point (T 0 ,S 0 ) changes, Δλ 13 , Δλ 23 They are the interference spectrum envelope I en-13 ,I en-23 The translation of the interference spectrum envelope relative to the calibration point, α 1 and β 1 They are the interference spectrum envelope Ien-13 The sensitivity of the first parameter to be measured and the second parameter to be measured; α 2 and β 2 They are the interference spectrum envelope I en-23 The sensitivity of the first parameter to be measured and the second parameter to be measured.

[0021] Optionally, the method of establishing the two-dimensional matrix equation is:

[0022]

[0023] Among them, ΔT and ΔS represent the first parameter to be measured and the second parameter to be measured relative to the calibration point (T 0 ,S 0 ) changes, Δλ 13 , Δλ 23 They are the interference spectrum envelope I en-13 ,I en-23 The translation of the interference spectrum envelope relative to the calibration point, α 1 and β 1 They are the interference spectrum envelope I en-13 The sensitivity of the first parameter to be measured and the second parameter to be measured; α 2 and β 2 They are the interference spectrum envelope I en-23 The sensitivity of the first parameter to be measured and the second parameter to be measured.

[0024] Optionally, the method for obtaining the measured parameters of the two measured parameters is:

[0025]

[0026] Wherein, T and S represent the first parameter to be measured and the second parameter to be measured respectively, and ΔT and ΔS represent the first parameter to be measured and the second parameter to be measured relative to the calibration point (T 0 ,S 0 )’s change.

[0027] To achieve the above objectives, the present invention also provides an optical fiber sensor for synchronous measurement of dual parameters, including a first sensing interferometer and a second sensing interferometer, the first sensing interferometer and the second sensing interferometer are connected in parallel, the first sensing interferometer is made by staggered fusion of three single-mode optical fibers, the second sensing interferometer is made by fusion of a single-mode optical fiber and a hollow-core optical fiber, and PDMS is injected into the hollow-core optical fiber to form an air cavity.

[0028] Optionally, the misalignment of the first sensing interferometer is 65-70 microns, and the free spectral range of the first sensing interferometer is 1.01-1.1 times the free spectral range of the virtual interferometer.

[0029] Optionally, the free spectral range of the air cavity is 0.90-0.99 times the free spectral range of the virtual interferometer.

[0030] To achieve the above-mentioned purpose, the present invention also provides a dual-parameter synchronous measurement system, comprising: a broadband light source, wherein the broadband light source emits light to a fiber coupler, wherein the fiber coupler distributes the light source to a fiber sensor, wherein the fiber sensor comprises a first sensor interferometer and a second sensor interferometer connected in parallel, wherein the reflected light of the first sensor interferometer and the second sensor interferometer is received by a spectrometer after passing through the fiber coupler.

[0031] The beneficial effects of the present invention are:

[0032] The present invention cascades or connects two interferometers in parallel to produce a vernier effect, which is a common method to improve the measurement sensitivity of the sensor. However, the interference spectrum envelope produced by the vernier effect can only measure a single parameter. The present invention uses spectrum analysis combined with a virtual auxiliary interferometer method to achieve dual-parameter simultaneous measurement. The specific scheme is as follows: First, the mixed interference spectrum of the two interferometers is subjected to spectrum analysis to restore the interference spectrum of each of the two interferometers. Then, the interference spectra of the two interferometers are superimposed with the interference spectrum of the virtual auxiliary interferometer to produce a vernier effect respectively, and two different interference spectrum envelopes are obtained. Finally, the sensitivity matrix equation is established by utilizing the characteristics that the two interference spectrum envelopes are simultaneously sensitive to dual parameters. By solving the matrix equation, the two measured parameters can be obtained.

[0033] The invention has the advantages of not only improving the measurement sensitivity by utilizing the vernier effect, but also realizing the simultaneous measurement of dual parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 A schematic diagram of a method for synchronously measuring dual parameters according to an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the structure of the sensor interferometer according to the embodiment of the present invention; wherein (a) is the interferometer 1; (b) is the interferometer 2;

[0037] Figure 3 A schematic diagram of a complex multi-cavity interference spectrum according to an embodiment of the present invention;

[0038] Figure 4Schematic diagram of interference spectrum of an embodiment of the present invention; wherein (a) is the interference spectrum of interferometer 1, and (b) is the interference spectrum of interferometer 2;

[0039] Figure 5 The interference spectrum envelope Ien-13 of the embodiment of the present invention; wherein (a) is the calibration temperature and salinity (T0, S0) and (b) is the temperature and salinity to be measured.

[0040] Figure 6 It is the interference spectrum envelope Ien-23 of an embodiment of the present invention; wherein, (a) is the calibration temperature and salinity (T0, S0) and (b) is the temperature and salinity to be measured. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] In this embodiment, the measurement of temperature and salinity is taken as an example. The first parameter to be measured and the second parameter to be measured in the embodiment represent temperature and salinity respectively. It should be noted here that in addition to being applied to the measurement of temperature and salinity, this embodiment can also be used for the measurement of other parameters.

[0044] This embodiment proposes a method for dual-parameter synchronous measurement and its optical fiber sensor. The sensor is composed of two sensor interferometers with different structures connected in parallel. To achieve dual-parameter synchronous measurement, the interference spectra of the two interferometers are superimposed with the interference spectrum of the virtual interferometer during data processing to form two interference spectrum envelopes, and the synchronous measurement of the two parameters is achieved based on the movement of the envelopes.

[0045] The sensor of this embodiment uses only two interferometers in the structure, which can more simply and conveniently obtain the interference spectrum envelopes of the two parameters. First, the complex interference spectrum received by the spectrometer is spectrally analyzed to reconstruct the interference spectrum of the two interferometers, and then the individual interference spectra are superimposed on the interference spectrum of the virtual reference interferometer to obtain the interference spectrum envelope expressing the two parameters, that is, the interference spectrum envelope between the sensor interferometer 1 and the virtual interference spectrum, and the interference spectrum envelope between the sensor interferometer 2 and the virtual interference spectrum. According to the translation of the two interference spectrum envelopes relative to the experimentally calibrated interference spectrum envelope (corresponding to a specific parameter), a relationship matrix between the two interference spectrum envelope translations and the two parameters to be measured is established, and the simultaneous measurement of the two parameters is achieved by solving the relationship matrix.

[0046] The present embodiment discloses a method for synchronous measurement of two parameters, including: obtaining a superimposed interference spectrum of a first sensing interferometer and a second sensing interferometer, performing spectrum analysis on the superimposed interference spectrum, and obtaining the interference spectrum of the first sensing interferometer and the interference spectrum of the second sensing interferometer; setting a virtual interference spectrum, and superimposing the virtual interference spectrum with the interference spectrum of the first sensing interferometer and the second sensing interferometer, respectively, to generate a first vernier effect and a second vernier effect, respectively; when two parameters to be measured change, the interference spectrum envelopes in the first vernier effect and the second vernier effect are translated, and a first translation amount and a second translation amount are obtained; based on the first translation amount and the second translation amount, a two-dimensional matrix equation is established, and the measured parameters of the two parameters to be measured are obtained through the two-dimensional matrix equation.

[0047] like Figure 1 As shown, the incident light emitted by the broadband light source enters the sensor interferometer 1 and the sensor interferometer 2 respectively through the coupler, is reflected by the sensor interferometer 1 and the sensor interferometer 2, and is received by the spectrometer after passing through the optical fiber coupler.

[0048] The interference spectra of sensor interferometers 1 and 2 can be expressed as:

[0049]

[0050] Among them, A 1 , A 2 are the amplitude of interferometer 1, A 3 , A 4 are the intensities of the two reflected lights of interferometer 2, L 1 , L 2 are the cavity lengths of interferometer 1 and interferometer 2, respectively, n 1 and n 2 are the refractive indices of the cavity media of interferometer 1 and interferometer 2 respectively. The interference spectrum received by the spectrometer is a complex interference spectrum superimposed by two interference spectra, which can be approximately expressed as:

[0051] I=I 1 (λ)+I2 (λ) (3)

[0052] The free spectral range of interferometer 1 and interferometer 2 can be expressed as:

[0053] FSR 1 =λ 2 / 2n 1 L 1

[0054] FSR 2 =λ 2 / 2n 2 L 2 (4)

[0055] Since the free spectral ranges of interferometer 1 and interferometer 2 are close but not equal, a cursor effect will occur between interferometers 1 and 2, resulting in the interference spectrum envelope I en-12 It can be expressed as:

[0056]

[0057] Among them, E 12 is the interference spectrum envelope amplitude; M 12 is the magnification of the cursor effect between interferometers 1 and 2, that is, the interference spectrum envelope I en-12 The sensitivity of the first parameter to be measured and the second parameter to be measured is M of a single interferometer 2 12 times.

[0058] Since the spectrometer obtains the complex interference spectrum of the light source after two interferometers are connected in parallel, in order to obtain the interference spectrum I 1 ,I 2 , it is necessary to perform spectrum analysis on the complex interference spectrum to obtain the interference spectra of the two interferometers, and then obtain the interference spectrum envelope I by superimposing them with the interference spectrum 3. en-13 ,I en-23 ,like Figure 5 (a)-(b) and Figure 6 As shown in (a)-(b).

[0059] When the first parameter to be measured and the second parameter to be measured change, the interference spectrum envelope I en-13和 I en-23 The translation Δλ 13 and Δλ 23 They can be expressed as:

[0060]

[0061] The corresponding matrix equation can be expressed as:

[0062]

[0063] Among them, ΔT and ΔS represent the first parameter to be measured and the second parameter to be measured relative to the calibration point (T 0 ,S 0 ) change; Δλ 13 , Δλ 23 They are the interference spectrum envelope I en-13 ,I en-23 The translation of the interference spectrum envelope relative to the calibration point; α 1 and β 1 They are the interference spectrum envelope I en-13 The sensitivity of the first parameter to be measured and the second parameter to be measured is a constant and can be measured by experiment; α 2 and β 2 They are the interference spectrum envelope I en-23 The sensitivity of the first parameter to be measured and the second parameter to be measured is a constant and can be measured by experiment. By solving the matrix equation, the first parameter to be measured T and the second parameter to be measured S can be obtained, respectively:

[0064]

[0065] Since what is received is the complex interference spectrum after multi-cavity coupling, such as Figure 3 As shown, the complex interference spectrum can be analyzed by Fourier transform to extract the interference spectrum of each cavity I 1 (λ), I 2 (λ), such as Figure 4 (a)-(b), The free spectral ranges of the three interferometers are very close and unequal, and can be cascaded to produce a Vernier effect.

[0066] This embodiment also discloses an optical fiber sensor for dual-parameter synchronous measurement, including: a broadband light source, the broadband light source transmits light to an optical fiber coupler, the optical fiber coupler distributes the light to a first sensor interferometer and a second sensor interferometer, and the reflected light of the first sensor interferometer and the second sensor interferometer is received by a spectrometer after passing through the optical fiber coupler.

[0067] Specifically, optical fiber sensors such as Figure 2 As shown, it is composed of a wide-spectrum light source (1400nm-1600nm), a fiber coupler, an interferometer 1, an interferometer 2 and a spectrometer. The light emitted by the light source passes through the fiber coupler and enters the sensor interferometer 1 and the sensor interferometer 2 respectively. The reflected light of the sensor interferometer 1 and the sensor interferometer 2 is received by the spectrometer after passing through the fiber coupler. The spectrum received by the spectrometer is a complex interference spectrum of the parallel structure of the two interferometers. In order to obtain the interference spectrum envelope generated by the vernier effect, it is necessary to perform frequency domain analysis on the complex interference spectrum measured by the spectrometer. The interference spectrum of the two interferometers is reconstructed, and then the interference spectrum envelope between the sensor interferometer 1 and the virtual interferometer and the sensor interferometer 2 and the virtual interferometer is obtained by superposition of the interference spectrum.

[0068] The sensing interferometer 1 is made of three single-mode optical fibers that are staggered and fused, with a stagger of 65-70 microns. The free spectral range of the interferometer 1 is about 1.01-1.1 times the free spectral range of the virtual interferometer 3, so as to ensure that the interferometer 1 and the interferometer 2 and the virtual interferometer 3 have a vernier effect.

[0069] The sensing interferometer 2 is formed by fusion splicing a single-mode optical fiber with a hollow-core optical fiber, and PDMS is injected into the hollow-core optical fiber to form an air cavity. The free spectral range of the air cavity is approximately 0.90-0.99 times the free spectral range of the virtual interferometer 3 to ensure a vernier effect between the interferometer 2 and the virtual interferometer 3.

[0070] This embodiment also discloses a system for synchronous measurement of dual parameters, including: a broadband light source, which emits light to a fiber coupler, and the fiber coupler distributes the light to a fiber sensor, the fiber sensor includes a first sensor interferometer and a second sensor interferometer connected in parallel, and reflected light from the first sensor interferometer and the second sensor interferometer is received by a spectrometer after passing through the fiber coupler.

[0071] The above embodiments are only descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for synchronously measuring two parameters, characterized in that: include: Acquire a superimposed interference spectrum of a first sensor interferometer and a second sensor interferometer, perform spectrum analysis on the superimposed interference spectrum, and acquire an interference spectrum of the first sensor interferometer and an interference spectrum of the second sensor interferometer; Setting a virtual interference spectrum, and superimposing the virtual interference spectrum with the interference spectrum of the first sensor interferometer and the second sensor interferometer, respectively, to generate a first vernier effect and a second vernier effect; When the two parameters to be measured change, the interference spectrum envelopes in the first vernier effect and the second vernier effect are translated to obtain a first translation amount and a second translation amount; A two-dimensional matrix equation is established based on the first translation amount and the second translation amount, and measured parameters of two measured parameters are obtained through the two-dimensional matrix equation.

2. The method for dual-parameter synchronous measurement according to claim 1, characterized in that: The method of obtaining the interference spectrum of the first sensor interferometer and the interference spectrum of the second sensor interferometer is: Among them, A1 and A2 are the amplitudes of the first interferometer, A3 and A4 are the intensities of the two reflected lights of the second interferometer, L1 and L2 are the cavity lengths of the first interferometer and the second interferometer, n1 and n2 are the refractive indices of the cavity media of the first interferometer and the second interferometer, respectively.

3. The method for dual-parameter synchronous measurement according to claim 1, characterized in that: The free spectral range of the first sensor interferometer and the second sensor interferometer is: FSR1=λ 2 / 2n1L1 FSR2=λ 2 / 2n2L2 Wherein, λ is the laser wavelength, n1 is the refractive index of the first sensing interferometer, and n2 is the refractive index of the first sensing interferometer.

4. The method for dual-parameter synchronous measurement according to claim 1, characterized in that: The method for obtaining the first translation and the second translation is: Wherein, ΔT and ΔS represent the changes of the first parameter to be measured and the second parameter to be measured relative to the calibration point (T0, S0), respectively, and Δλ 13 , Δλ 23 They are the interference spectrum envelope I en-13 ,I en-23 Relative to the translation of the interference spectrum envelope of the calibration point, α1 and β1 are the interference spectrum envelope I en-13 The sensitivity of the first parameter to be measured and the second parameter to be measured; α2 and β2 are the interference spectrum envelope I en-23 The sensitivity of the first parameter to be measured and the second parameter to be measured.

5. The method for dual-parameter synchronous measurement according to claim 1, characterized in that: The method of establishing the two-dimensional matrix equation is: Wherein, ΔT and ΔS represent the changes of the first parameter to be measured and the second parameter to be measured relative to the calibration point (T0, S0), respectively, and Δλ 13 , Δλ 23 They are the interference spectrum envelope I en-13 ,I en-23 Relative to the translation of the interference spectrum envelope of the calibration point, α1 and β1 are the interference spectrum envelope I en-13 The sensitivity of the first parameter to be measured and the second parameter to be measured; α2 and β2 are the interference spectrum envelope I en-23 The sensitivity of the first parameter to be measured and the second parameter to be measured.

6. The method for dual-parameter synchronous measurement according to claim 1, characterized in that: The method of obtaining the measured parameters of the two measured parameters is: Wherein, T and S represent the first parameter to be measured and the second parameter to be measured respectively, and ΔT and ΔS represent the changes of the first parameter to be measured and the second parameter to be measured relative to the calibration point (T0, S0) respectively.

7. An optical fiber sensor for dual-parameter synchronous measurement, characterized in that: The invention comprises a first sensor interferometer and a second sensor interferometer, wherein the first sensor interferometer is connected in parallel with the second sensor interferometer, the first sensor interferometer is made by staggered fusion of three single-mode optical fibers, the second sensor interferometer is made by fusion of a single-mode optical fiber and a hollow-core optical fiber, and PDMS is injected into the hollow-core optical fiber to form an air cavity.

8. The optical fiber sensor for dual-parameter synchronous measurement according to claim 7, characterized in that: The misalignment of the first sensing interferometer is 65-70 microns, and the free spectral range of the first sensing interferometer is 1.01-1.1 times the free spectral range of the virtual interferometer.

9. The optical fiber sensor for dual-parameter synchronous measurement according to claim 7, characterized in that: The free spectral range of the air cavity is 0.90-0.99 times the free spectral range of the virtual interferometer.

10. A dual-parameter synchronous measurement system, used to implement the method according to any one of claims 1 to 6, characterized in that: include: A broadband light source, wherein the broadband light source emits light to a fiber coupler, wherein the fiber coupler distributes the light to the fiber sensor according to any one of claims 7 to 9, wherein the fiber sensor comprises a first sensor interferometer and a second sensor interferometer connected in parallel, wherein reflected light from the first sensor interferometer and the second sensor interferometer is received by a spectrometer after passing through the fiber coupler.

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