An interferometric temperature and humidity sensing device and method based on fiber grating Fabry-Perot

Abstract

The present invention discloses an interferometric temperature and humidity sensing device and method based on fiber grating Fabry-Perot. The device includes a light source, an optical circulator, a temperature and humidity sensing unit, a first detector, a second detector and a demodulator in sequence along the propagation direction of the optical signal; the light source is used to generate continuous light; the optical circulator inputs the continuous light to the temperature and humidity sensor unit; the temperature and humidity sensing unit is used to generate a reflected light signal and a transmitted light signal according to the continuous light, and input the reflected light signal to the first detector, and input the transmitted light signal to the second detector; the demodulator is used to demodulate the signal detected by the detector to obtain temperature information and humidity information respectively. The present invention realizes the synchronous measurement of the dual parameters of temperature and humidity.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to an interferometric temperature and humidity sensing device and method based on optical fiber grating Fabry-Perot. Background Art

[0002] Accurately measuring the temperature and humidity of the environment is of great significance to structural health, industrial production, etc., such as safety monitoring of large buildings, subways, traffic tunnels, temperature monitoring of oil production, etc. Traditional electrical temperature and humidity sensing devices have low measurement accuracy, poor long-term stability, poor anti-electromagnetic interference ability, high cost, and are difficult to achieve large-scale engineering detection.

[0003] Fiber Bragg grating has the advantages of small size, anti-electromagnetic interference, fast response, and easy networking. Among the many fiber optic temperature and humidity sensors, the fiber optic temperature and humidity sensor composed of fiber optic interferometer has high sensitivity and simple structure, and has received special attention. Compared with other interference sensors, such as Mach-Zehnder interference fiber optic humidity sensor, Michelson interference fiber optic humidity sensor, Sagnac interference fiber optic humidity sensor, etc., the Fabry-Perot interference fiber optic humidity sensor has many advantages such as simple production, good reliability, flexible production, and high sensitivity. However, the number of FP cavities that can be constructed by traditional Fabry-Perot sensors is extremely limited. Most sensors only construct a single FP cavity based on the end face of the optical fiber, which can only complete the measurement of a single parameter, and are difficult to produce and have poor repeatability. Summary of the invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, provide an interferometric temperature and humidity sensing device and method based on fiber grating Fabry-Perot, and solve the technical problem that the temperature and humidity sensor in the prior art can only measure a single parameter.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides an interferometric temperature and humidity sensing device based on fiber grating Fabry-Perot

[0007] The optical circulator includes a light source, an optical circulator, a temperature and humidity sensing unit, a first detector, a second detector and a demodulator in sequence along the propagation direction of the optical signal; the light source is used to generate continuous light and transmit the continuous light to the input port of the optical circulator;

[0008] The optical circulator is used to collect the continuous light and input the continuous light into the temperature and humidity sensor unit through the first outlet;

[0009] The temperature and humidity sensing unit is connected to the first outlet of the optical circulator, for generating a reflected light signal and a transmitted light signal according to the continuous light, and inputting the reflected light signal to the first detector, and inputting the transmitted light signal to the second detector;

[0010] The first detector is communicatively connected to the second outlet of the optical circulator, and is used to collect the reflected light signal and convert the reflected light signal into an electrical signal containing temperature information;

[0011] The second detector is in communication with the temperature and humidity sensing unit, and is used to collect the transmitted light signal and convert the transmitted light signal into an electrical signal containing humidity information;

[0012] The demodulator is communicatively connected with the first detector and the second detector, and is used to collect the reflected electrical signal and the transmitted electrical signal, and to demodulate and analyze the reflected electrical signal to determine the ambient temperature, and to demodulate and analyze the transmitted electrical signal to determine the ambient humidity.

[0013] In some embodiments, the temperature and humidity sensing unit includes a fiber Bragg grating (FBG) Fabry-Perot interferometer and a fiber Bragg grating (FBG); the reflected light signal is acquired through the fiber Bragg grating (FBG) Fabry-Perot interferometer and the fiber Bragg grating, and the transmitted light signal is acquired through the fiber Bragg grating (FBG) Fabry-Perot interferometer.

[0014] In some embodiments, the surface of the fiber Bragg grating is coated with a moisture sensitive material.

[0015] In some embodiments, the fiber Bragg grating Fabry-Perot interferometer and the fiber Bragg grating have different temperature sensitivity coefficients and different humidity sensitivity coefficients.

[0016] In some embodiments, the central wavelength of the fiber Bragg grating Fabry-Perot interferometer is a first wavelength, the central wavelength of the fiber Bragg grating is a second wavelength, and the first wavelength is not equal to the second wavelength.

[0017] In some embodiments, the demodulator includes a data acquisition unit, a data demodulation unit, a data processing unit, and a temperature and humidity feedback unit;

[0018] The data acquisition unit is in communication with the first detector and the second detector, and is used to acquire the reflected electrical signal and the transmitted electrical signal;

[0019] The data demodulation unit is communicatively connected to the data acquisition unit, and is used to demodulate the reflected electrical signal to obtain a first demodulation result, and to demodulate the transmitted electrical signal to obtain a second demodulation result, and transmit the first demodulation result and the second demodulation result to the data processing unit;

[0020] The data processing unit is in communication with the data demodulation unit, and is used to determine the ambient temperature according to the first demodulation result based on a preset temperature calculation method; and to determine the ambient humidity according to the second demodulation result based on a preset humidity calculation method;

[0021] The temperature and humidity feedback unit is in communication with the data processing unit, and is used to collect relevant information of the ambient temperature and the ambient humidity, and feed back the relevant information to the user.

[0022] In some embodiments, the preset temperature calculation method and the preset humidity calculation method can be expressed by the following formula:

[0023]

[0024]

[0025] Among them, α T1 is the temperature sensitivity caused by the fiber Bragg grating Fabry-Perot interferometer, α RH1 is the humidity sensitivity caused by the fiber Bragg grating Fabry-Perot interferometer, α T2 is the temperature sensitivity caused by the fiber Bragg grating, α RH2 is the humidity sensitivity caused by the fiber Bragg grating, OPD is the optical path difference of the interference spectrum formed by the transmitted light, Δλ is the offset of the central wavelength of the reflected light, ΔT is the ambient temperature, and ΔRH is the ambient humidity.

[0026] In some embodiments, an isolator is further included, the isolator being connected to the light source and the first inlet of the optical circulator, for isolating the light reflected by the optical circulator and transmitting the continuous light to the optical circulator.

[0027] In some embodiments, a polarization controller is further included, one end of the polarization controller is communicatively connected to the isolator, and the other end of the polarization controller is communicatively connected to the optical circulator, and is used to control the polarization state of the continuous light.

[0028] In a second aspect, the present invention further provides an interferometric temperature and humidity sensing method based on fiber grating Fabry-Perot, which is applied to any of the interferometric temperature and humidity sensing devices based on fiber grating Fabry-Perot described above, and the method comprises:

[0029] Acquiring the reflected light signal and the transmitted light signal;

[0030] Determine the ambient temperature using a preset temperature calculation method according to the reflected light signal;

[0031] The ambient humidity is determined according to the transmitted light signal using a preset humidity calculation method.

[0032] Compared with the prior art, the interferometric temperature and humidity sensing device and method based on fiber Bragg grating Fabry-Perot provided by the present invention generates continuous light through a light source, and inputs the continuous light into a temperature and humidity sensing unit through a circulator to obtain a reflected light signal and a transmitted light signal. Subsequently, the temperature and humidity sensing unit transmits the reflected light signal to a first detector through an optical circulator, and transmits the transmitted light signal to a second detector, and converts the reflected light signal through the first detector to obtain a reflected electrical signal, and converts the transmitted light signal through the second detector to obtain a transmitted electrical signal, and finally uses a demodulator to determine the ambient temperature according to the reflected electrical signal, and determines the ambient humidity according to the transmitted electrical signal. The present invention not only forms a Fabry-Perot interferometer through a fiber Bragg grating, and effectively improves the measurement sensitivity and measurement accuracy by using an interference measurement method, but also realizes simultaneous measurement of temperature and humidity by multiplexing a fiber Bragg grating Fabry-Perot interferometer and a fiber Bragg grating with different central wavelengths and using a dual parameter matrix method. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of an interferometric temperature and humidity sensing device based on fiber grating Fabry-Perot provided by the present invention;

[0034] Figure 2 It is a structural schematic diagram of a demodulator in the interferometric temperature and humidity sensing device based on fiber grating Fabry-Perot provided by the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] The embodiment of the present invention provides an interferometric temperature and humidity sensing device 1 based on fiber grating Fabry-Perot. Figure 1 , along the propagation direction of the optical signal, it includes a light source 11, an optical circulator 12, a temperature and humidity sensor unit 13, a first detector 14, a second detector 15 and a demodulator 16;

[0037] The light source 11 is used to generate continuous light and transmit the continuous light to the input port of the optical circulator 12;

[0038] The optical circulator 12 is used to collect the continuous light and input the continuous light into the temperature and humidity sensor unit 13 through the first outlet;

[0039] The temperature and humidity sensing unit 13 is connected to the first outlet of the optical circulator 12, and is used to generate a reflected light signal and a transmitted light signal according to the continuous light, and input the reflected light signal to the first detector 14, and input the transmitted light signal to the second detector 15;

[0040] The first detector 14 is communicatively connected to the second outlet of the optical circulator 12, and is used to collect the reflected light signal and convert the reflected light signal into an electrical signal containing temperature information;

[0041] The second detector 15 is in communication with the temperature and humidity sensing unit 13, and is used to collect the transmitted light signal and convert the transmitted light signal into an electrical signal containing humidity information;

[0042] The demodulator 16 is communicatively connected with the first detector 14 and the second detector 15, and is used to collect the reflected electrical signal and the transmitted electrical signal, and demodulate and analyze the reflected electrical signal to determine the ambient temperature, and demodulate and analyze the transmitted electrical signal to determine the ambient humidity.

[0043] Continuous light is generated by the light source 11, and the continuous light is input to the temperature and humidity sensing unit 13 through the circulator 12 to obtain a reflected light signal and a transmitted light signal. Then the temperature and humidity sensing unit 13 transmits the reflected light signal to the first detector 14 through the optical circulator 12, and transmits the transmitted light signal to the second detector 15, and the reflected light signal is converted to an electrical signal by the first detector 14 and the transmitted light signal is converted to an electrical signal by the second detector 15, and finally the ambient temperature and humidity are determined according to the electrical signal by the demodulator 16. The present invention not only forms a Fabry-Perot interferometer through a fiber Bragg grating, and effectively improves the measurement sensitivity and measurement accuracy by using the interference measurement method, but also realizes the simultaneous measurement of temperature and humidity by multiplexing a fiber Bragg Fabry-Perot interferometer and a fiber Bragg grating with different central wavelengths and using a dual parameter matrix method.

[0044] Furthermore, this fiber Bragg Fabry-Perot interferometric temperature and humidity sensing system is easy to integrate and package. It can be laid on roads and tunnels, and can also be integrated into cable structures, thereby realizing temperature and humidity detection in various complex environments. It is worthy of vigorous promotion.

[0045] In some embodiments, the temperature and humidity sensing unit 13 includes a fiber Bragg grating (FBG) Fabry-Perot interferometer and a fiber Bragg grating (FBG); the reflected light signal is obtained through the fiber Bragg grating (FBG) Fabry-Perot interferometer and the fiber Bragg grating, and the transmitted light signal is obtained through the fiber Bragg grating (FBG) Fabry-Perot interferometer.

[0046] In this embodiment, the composition structure and connection method of the fiber Bragg grating Fabry-Perot interferometer and the fiber Bragg grating are conventional forms of the prior art. The distance between the fiber Bragg grating Fabry-Perot interferometer and the fiber Bragg grating is relatively far, and the transmission light of the fiber Bragg grating and the fiber Bragg grating Fabry-Perot interferometer will not cause secondary interference, and the interference spectrum of the interferometer can be directly obtained.

[0047] In some embodiments, the surface of the fiber Bragg grating is coated with a moisture sensitive material.

[0048] In this embodiment, the applied moisture-sensitive material includes, but is not limited to, polyimide, polyvinyl alcohol, agar and agarose coating, titanium dioxide metal oxide, graphene oxide, and nanocomposite hydrogel.

[0049] Furthermore, the volume of the coated hygroscopic material changes as it absorbs or releases water molecules in the air, thereby generating strain, which causes the change in the cavity length of the fiber grating Fabry-Perot interferometer, and ultimately causes the movement of the interference spectrum. Therefore, by detecting the change in the interference spectrum (formed by transmission), the measurement of ambient temperature and humidity can be achieved.

[0050] In some embodiments, the fiber Bragg grating Fabry-Perot interferometer and the fiber Bragg grating have different temperature sensitivity coefficients and different humidity sensitivity coefficients.

[0051] In this embodiment, the multiplexed fiber Bragg Fabry-Perot interferometer and fiber Bragg grating have different temperature sensitivity coefficients and humidity sensitivity coefficients, and can achieve simultaneous measurement of temperature and humidity.

[0052] Furthermore, the fiber Bragg grating Fabry-Perot interferometer and fiber Bragg grating in the temperature and humidity sensor array have a linear response to temperature and humidity. Therefore, the temperature sensitivity caused by the fiber Bragg grating Fabry-Perot interferometer is α T1 , the humidity sensitivity caused is α RH1 , the temperature sensitivity caused by the fiber Bragg grating is α T2 , the humidity sensitivity caused is α RH2 , the two can establish the following formula (1):

[0053]

[0054] Formula (1) is further simplified into formulas (2) and (3), thereby obtaining the temperature and humidity at the measurement unit:

[0055]

[0056]

[0057] Among them, α T1 is the temperature sensitivity caused by the fiber Bragg grating Fabry-Perot interferometer, α RH1 is the humidity sensitivity caused by the fiber Bragg grating Fabry-Perot interferometer, α T2 is the temperature sensitivity caused by the fiber Bragg grating, α RH2 is the humidity sensitivity caused by the fiber Bragg grating, OPD is the optical path difference of the interference spectrum formed by the transmitted light, Δλ is the offset of the central wavelength of the reflected light, ΔT is the ambient temperature, and ΔRH is the ambient humidity.

[0058] Furthermore, the interferometric temperature and humidity sensing device based on fiber grating Fabry-Perot is characterized in that α T1 and α T2 Not equal, α RH1 and α RH2 They are not equal, so the temperature and humidity are decoupled using the dual parameter matrix method.

[0059] In some embodiments, the central wavelength of the fiber Bragg grating Fabry-Perot interferometer is a first wavelength, the central wavelength of the fiber Bragg grating is a second wavelength, and the first wavelength is not equal to the second wavelength.

[0060] In this embodiment, the central wavelength of the fiber Bragg grating constituting the Fabry-Perot interferometer is λ1, the central wavelength of the fiber Bragg grating multiplexed with the interferometer is λ2, and λ1≠λ2. By detecting the central wavelength offset of the fiber Bragg grating reflected light, the ambient humidity can be measured.

[0061] In some embodiments, see Figure 2 , the demodulator 16 includes a data acquisition unit 161, a data demodulation unit 162, a data processing unit 163 and a temperature and humidity feedback unit 164;

[0062] The data acquisition unit 161 is in communication with the first detector 14 and the second detector 15, and is used to collect electrical signals;

[0063] The data demodulation unit 162 is in communication with the data acquisition unit 161, and is used to demodulate the electrical signal to obtain a first demodulation result and a second demodulation result, and transmit the first demodulation result and the second demodulation result to the data processing unit 163;

[0064] The data processing unit 163 is in communication with the data demodulation unit 162, and is used to determine the ambient temperature according to the first demodulation result based on a preset temperature calculation method; and to determine the ambient humidity according to the second demodulation result based on a preset humidity calculation method;

[0065] The temperature and humidity feedback unit 164 is in communication with the data processing unit 163 and is used to collect relevant information of the ambient temperature and the ambient humidity and feed back the relevant information to the user.

[0066] In this embodiment, the reflected electrical signal and the transmitted electrical signal are collected by the data acquisition unit 161, and then the reflected electrical signal and the transmitted electrical signal are demodulated by the data demodulation unit 162 to obtain a first demodulation result and a second demodulation result. The data processing unit 163 uses a temperature calculation method to determine the ambient temperature according to the first demodulation result, and uses a humidity calculation method to determine the ambient humidity according to the second demodulation result. Finally, the ambient temperature and ambient humidity information are fed back to the terminal or user through the temperature and humidity feedback unit 164, thereby achieving the purpose of simultaneous measurement of both temperature and humidity parameters.

[0067] In some embodiments, an isolator 17 is further included, which is connected to the light source 11 and the first inlet of the optical circulator 12 and is used to isolate the light reflected by the optical circulator 12 and transmit the continuous light to the optical circulator 12.

[0068] In this embodiment, the isolator is located between the light source 11 and the optical circulator 12. On the one hand, it is used to input the continuous light generated by the light source 11 into the optical circulator 12, and on the other hand, it can isolate the light reflected by the optical circulator 12, thereby avoiding the influence of the reflected light on the continuous light, resulting in reduced measurement accuracy.

[0069] In some embodiments, a polarization controller 18 is further included, one end of which is communicatively connected to the isolator and the other end of which is communicatively connected to the optical circulator 12, for controlling the polarization state of the continuous light.

[0070] In this embodiment, the polarization controller is used to control the polarization state of the continuous light according to the set optical path to obtain a better interference phenomenon.

[0071] Based on the above-mentioned interferometric temperature and humidity sensing device based on fiber Bragg Fabry-Perot, an embodiment of the present invention further provides an interferometric temperature and humidity sensing method based on fiber Bragg Fabry-Perot, the method comprising:

[0072] Acquiring the reflected light signal and the transmitted light signal;

[0073] Determine the ambient temperature using a preset temperature calculation method according to the reflected light signal;

[0074] The ambient humidity is determined according to the transmitted light signal using a preset humidity calculation method.

[0075] In this embodiment, the ambient temperature is determined according to the reflected light signal, and the ambient humidity is determined according to the transmitted light signal, thereby achieving the purpose of dual-parameter synchronous measurement.

[0076] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An interferometric temperature and humidity sensing device based on fiber grating Fabry-Perot, characterized in that: The optical signal transmission direction includes a light source, an optical circulator, a temperature and humidity sensing unit, a first detector, a second detector and a demodulator; The light source is used to generate continuous light and transmit the continuous light to the input port of the optical circulator; The optical circulator is used to collect the continuous light and input the continuous light into the temperature and humidity sensing unit through the first outlet; The temperature and humidity sensing unit is connected to the first outlet of the optical circulator, and is used to generate a reflected light signal and a transmitted light signal according to the continuous light, and input the reflected light signal to the first detector, and input the transmitted light signal to the second detector; the temperature and humidity sensing unit includes a fiber Bragg grating Fabry-Perot interferometer and a fiber Bragg grating; the reflected light signal is obtained through the fiber Bragg grating Fabry-Perot interferometer and the fiber Bragg grating, and the transmitted light signal is obtained through the fiber Bragg grating Fabry-Perot interferometer; the surface of the fiber Bragg grating is coated with a humidity-sensitive material; the central wavelength of the fiber Bragg grating Fabry-Perot interferometer is a first wavelength, and the central wavelength of the fiber Bragg grating is a second wavelength, and the first wavelength is not equal to the second wavelength; the fiber Bragg grating Fabry-Perot interferometer and the fiber Bragg grating have different temperature sensitivity coefficients and different humidity sensitivity coefficients; The first detector is communicatively connected to the second outlet of the optical circulator, and is used to collect the reflected light signal and convert the reflected light signal into an electrical signal; The second detector is in communication with the temperature and humidity sensing unit and is used to collect the transmitted light signal and convert the transmitted light signal into an electrical signal; The demodulator is communicatively connected with the first detector and the second detector, and is used for demodulating the electrical signals detected by the detectors to obtain temperature information and humidity information.

2. The interferometric temperature and humidity sensing device based on fiber grating Fabry-Perot according to claim 1 is characterized in that: The fiber Bragg grating Fabry-Perot interferometer and the fiber Bragg grating have different temperature sensitivity coefficients and different humidity sensitivity coefficients.

3. The interferometric temperature and humidity sensor device based on fiber grating Fabry-Perot according to claim 1 is characterized in that: The demodulator includes a data acquisition unit, a data demodulation unit, a data processing unit and a temperature and humidity feedback unit; The data acquisition unit is in communication with the first detector and the second detector, and is used to collect electrical signals; The data demodulation unit is communicatively connected to the data acquisition unit, and is used to demodulate the reflection signal to obtain a first demodulation result, and to demodulate the transmission signal to obtain a second demodulation result, and transmit the first demodulation result and the second demodulation result to the data processing unit; The data processing unit is communicatively connected to the data demodulation unit, and is used to determine the ambient temperature according to the first demodulation result based on a preset temperature calculation method; and determining the ambient humidity according to the second demodulation result based on a preset humidity calculation method; The temperature and humidity feedback unit is in communication with the data processing unit, and is used to collect relevant information of the ambient temperature and the ambient humidity, and feed back the relevant information to the user.

4. The interferometric temperature and humidity sensing device based on fiber grating Fabry-Perot according to claim 3 is characterized in that: The preset temperature calculation method and the preset humidity calculation method can be expressed by the following formula: in, is the temperature sensitivity caused by the fiber Bragg grating Fabry-Perot interferometer, is the humidity sensitivity caused by the fiber Bragg grating Fabry-Perot interferometer, is the temperature sensitivity caused by the fiber Bragg grating, is the humidity sensitivity caused by the fiber Bragg grating, OPD is the optical path difference of the interference spectrum formed by the transmitted light, is the shift of the central wavelength of the reflected light, is the ambient temperature, is the ambient humidity.

5. The interferometric temperature and humidity sensor device based on fiber grating Fabry-Perot according to claim 1, characterized in that: An isolator is also included. The isolator is connected to the light source and the first inlet of the optical circulator and is used to isolate the light reflected by the optical circulator and transmit the continuous light to the optical circulator.

6. The interferometric temperature and humidity sensing device based on fiber grating Fabry-Perot according to claim 5 further comprises a polarization controller, one end of which is communicatively connected to the isolator and the other end of which is communicatively connected to the optical circulator, for controlling the polarization state of the continuous light.

7. An interferometric temperature and humidity sensing method based on fiber Bragg Fabry-Perot, applied to the interferometric temperature and humidity sensing device based on fiber Bragg Fabry-Perot as claimed in any one of claims 1 to 6, characterized in that: The method comprises: Acquiring the reflected light signal and the transmitted light signal; Determine the ambient temperature using a preset temperature calculation method according to the reflected light signal; The ambient humidity is determined according to the transmitted light signal using a preset humidity calculation method.

Images