Dual-parameter sensing system for magnetic field and stress based on near-infrared band dual-peak PCF

Abstract

The present invention provides a dual-parameter sensing device and method for magnetic field and stress based on a dual-peak photonic crystal fiber (PCF) in the near-infrared band. It includes a light source (1), a single-mode optical fiber (2), a sensing unit (3), a spectral analyzer (4), a photoelectric converter (5), a signal processing module (6), and a computer (7). By utilizing the surface plasmon resonance principle, the magnetic field and stress are detected through the spacing between two resonance peaks of a photonic crystal fiber with a special structure, and the results are displayed in the computer. The present invention replaces the traditional wavelength sensitivity calculation method with a dual-peak sensitivity formula. The proposed new sensing device adopts a dual-peak sensitivity sensing method, which has the advantages of high sensitivity, flexible design, compact structure, and strong stability, and has extremely high application value in the fields of industrial applications, medical and health, consumer electronics, scientific research and development, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber optic sensing, and particularly relates to a dual-parameter sensing system for magnetic field and stress based on a near-infrared band dual-peak PCF. Background Art

[0002] As one of the top ten leading technologies to be prioritized in the 21st century, sensing technology will develop towards miniaturization, integration, multi-functionality, and systematization in the future. Metal surface plasmons (SPs) can not only break through the diffraction limit of traditional optics and achieve light transmission at the nanoscale, but are also extremely sensitive to changes in the refractive index of the surrounding dielectric. Photonic crystal fiber (PCF) has advantages such as light weight, small size, and electromagnetic interference resistance. Therefore, the combination of metal surface plasmon resonance (SPR) technology and fiber technology provides new research ideas and new development space for realizing sensors with high sensitivity, high reliability, miniaturization, and easy integration. Optical sensors mostly achieve sensing by converting the information changes of biological, chemical, and other molecules into changes in parameters such as the refractive index of the medium or spectral absorbance, and have different sensing models such as waveguide structures (grating coupling, resonant mirror), mode interference measurement methods, and surface plasmon resonance (SPR). Maxwell's theory shows that electromagnetic waves can propagate on the metal surface or in the metal thin film, and the characteristic frequency of this type of electromagnetic wave is between w = 0 and , and the specific dispersion characteristic w kRelated to the incident light wave and with a wave vector greater than that of the light wave at the same energy, this type of electromagnetic wave is called the Surface Plasmon Wave (SPW), also known as the Surface Plasmon Polaritions (SPPs), which is an important extension of plasma physics. SPPs propagate along the surface of the medium, with an extremely high electromagnetic field intensity at the surface and exponentially decaying in the space perpendicular to the surface, having a very strong electromagnetic wave confinement ability. In addition, the wave vector of the metal SPPs is related to the dielectric constant of the surrounding dielectric, which helps to realize high-precision, miniaturized, and integrated optical sensors using metal SPPs technology. The principle of Surface Plasmon Resonance (SPR) is that light undergoes total internal reflection on the surface of the metal medium, and the total internal reflection evanescent wave is used to excite the Surface Plasmon Polaritions (SPR), that is, the Surface Plasmon Wave, resulting in a significant attenuation of the total internal reflection energy. The generated metal SPPs modes are extremely sensitive to changes in the refractive index of the surrounding dielectric, that is, the wave vector characteristics of the SPPs modes change with the change of the refractive index of the dielectric, thus causing a change in the phase matching condition between the SPPs mode and the incident light wave. Therefore, by monitoring the changes in parameters such as the light wavelength, angle, and absorption intensity when the metal SPR effect occurs, information sensing in fields such as biology, drug detection, magnetic field detection, and environmental monitoring can be achieved. The principle of the SPR sensor is precisely to measure the refractive index of the measured substance based on the different attenuation peaks of different measured substances. Due to its high sensitivity, no background interference, sample without labels, no need for further purification, real-time and rapid detection, etc., the SPR sensing technology has become a multi-functional tool for monitoring the refractive index of analytes, filtering light of specific frequencies, and detecting the formation of nano-biofilms. In recent years, SPR sensors based on Photonic Crystal Fibers (PCF) have received extensive attention. Photonic crystal fibers have extremely strong anti-bending characteristics, flexible dispersion tailoring characteristics, good nonlinear characteristics, and unique photonic bandgap characteristics. Therefore, dispersion, birefringence, nonlinearity, etc. can be customized through different air hole arrangements, and these aspects make photonic crystal fibers particularly eye-catching in many fields. In 2010, H.Y. Fu et al. proposed (Fu H Y, Wu C, Tse M, et al. High pressure sensor based on photonic crystal fiber for downhole application[J]. Ao / 49 / 14 / ao Pdf, 2010, 49(14):2639-0) a Sagnac interferometer based on polarization-maintaining photonic crystal fiber (PCF) for downhole high-pressure sensing. The PM-PCF is used as a direct pressure probe, enhancing the long-term sensing stability. In addition, the PM-PCF coiled into a smaller diameter can meet the size requirements for downhole applications, achieving high-pressure measurements up to 20 megapascals.In 2014, Jonas H. Osório et al. developed a pressure sensor for dual environment monitoring by adjusting PCF (Osório, Jonas H, Hayashi JG, Espinel YAV, et al. Photonic-crystal fiber-based pressure sensor for dual environment monitoring[J]. Applied Optics, 2014, 53(17): 3668 - 72), which can allow independent acquisition of the individual responses of two optical fibers. The structure has two sensitive regions that can be used in dual environment pressure sensing for monitoring.

[0003] Magnetic Fluids (MFs), also known as magnetic liquids, ferrofluids or magnetic fluids, are a kind of stable colloidal liquid. They are a new type of functional material formed by uniformly dispersing strongly magnetic nanoparticles (such as Fe3O4, Fe, CoFe2O4 or MnFe2O4, etc.) coated with surfactants (such as carboxyl or hydroxyl groups, etc.) in a base carrier liquid (such as water, hydrocarbons, organic solvents or oils, etc.). They have both the fluidity of a liquid and the magnetism of a solid magnetic material. Although MFs themselves do not have magnetism, under the action of an external magnetic field, MFs not only have magnetism but are also extremely sensitive to changes in the magnetic field. Their sensitive characteristics are mainly manifested in that the refractive index changes with the change of the magnitude or direction of the external magnetic field. Since the tunable refractive index characteristic of MFs can be used to conveniently monitor and sense external magnetic field signals, MFs are often used as magnetic sensitive materials in magnetic field sensing. With the development of SPR technology and MFs technology, many scholars have begun to study the realization of magnetic field sensing by using the fiber optic SPR effect and the MFs filling method. In 2016, Weng et al. proposed (Weng S, Pei L, Wang J, et al. High sensitivity side-hole fiber magnetic field sensor based on surface plasmon resonance[J]. Chinese Optics Letters, 2016, 14(011):19-22) a magnetic field sensor based on the SPR effect and MFs filling. This sensor digs a large-aperture channel above and below the fiber core, coats the Au film in the channel, and fills MFs to achieve magnetic field sensing. Under the optimized structure, this sensor can achieve sensing in the magnetic field strength range of 30 - 210.9 Oe, and the sensitivity can reach 1.063 nm / Oe. In 2017, Liu et al. proposed (Liu H, Wang Y, Wei S, et al. Simultaneous dual-parameter measurement based on dual-channel surface plasmon resonance in photonic crystal fiber[J]. Optik, 2017, 145:582-588) a dual-parameter SPR sensor based on a dual-channel photonic crystal fiber. This sensor has two channels. Among them, channel 1 is coated with the Au film, channel 2 is filled with Au nanowires, and MFs are filled in both channels simultaneously to achieve dual-parameter sensing of temperature and magnetic field. Under the optimized structure, the magnetic field sensitivity of the sensor can reach 1.08 nm / mT, and the temperature sensitivity can reach -0.2269 nm / ℃.At Harbin University of Science and Technology, Shen Tao et al. proposed (Shen Tao, Zhang Zhiwen, Wang Shaofeng, etc. A Magnetic Field Sensitive Sensing Device and Method Based on SPR of D-Type Photonic Crystal Fiber) a photonic crystal fiber magnetic field sensing device. Using the SPR sensing mechanism, it converts the tiny change in the refractive index RI of the magnetic fluid into the change of the measurable loss peak to achieve refractive index sensing, and then realizes the detection of the magnetic field intensity. It has the advantages of high sensitivity, flexible design, compact structure, strong stability, etc., and has very high practical value in the field of magnetic field intensity detection. Limited by the performance of the spectrometer, most current PCF-SPR sensors only exist in the simulation theory, and the sensitivity of the sensors in actual manufacturing often fails to reach the theoretical level. Therefore, it is very important to propose a new practical PCF structure and detection method working in the near-infrared band. Summary of the Invention

[0004] Aiming at the above problems, the technical problem to be solved by the present invention is to propose a magnetic field and stress dual-parameter sensing system based on a near-infrared band double-peak PCF, and propose a new method for determining the state of the analyte (including refractive index, stress or magnetic field) and a stable sensitivity calculation method.

[0005] The technical solution adopted by the present invention to solve its technical problems is as follows:

[0006] Technical solution: A magnetic field and stress dual-parameter sensing system based on a near-infrared band double-peak PCF, characterized in that it is composed of a light source (1), a single-mode fiber (2), a sensing unit (3), a spectral analyzer (4), a photoelectric converter (5), a signal processing module (6) and a computer (7);

[0007] Furthermore, the sensing unit (3) is a photonic crystal fiber (3-1); it is composed of a cladding (3-2), a silver film (3-7), a zinc oxide thin film (3-8) and an analysis liquid (3-9); the cladding (3-2) includes: 20 circular air holes (3-3), 5 circular air holes (3-4), 2 elliptical air holes (3-5), 3 elliptical air holes (3-6); the circular air holes (3-3), circular air holes (3-4), elliptical air holes (3-5) and elliptical air holes (3-6) are arranged symmetrically about the y-axis of the fiber; the circular air holes (3-4) are located between the circular air holes (3-3) and the elliptical air holes (3-5); the silver film (3-7) and the zinc oxide thin film (3-8) are at the junction of the cladding (3-2) and the analysis liquid (3-9);

[0008] Furthermore, for the sensing unit (3), the diameter of the cladding (3-2) is 15 μm, the diameter of the circular air hole (3-3) is 1.5 μm, the diameter of the circular air hole (3-4) is 2 μm, the major axis of the elliptical air hole (3-5) is 3 μm, and the minor axis is 2 μm; the major axis of the elliptical air hole (3-6) is 4 μm, and the minor axis is 3 μm; the thickness of the silver film (3-7) is 20 nm; the thickness of the zinc oxide thin film (3-8) is 18 nm; the cladding material is fused silica, and its refractive index is defined by the Sellmeier formula;

[0009] Furthermore, the photonic crystal fiber (3-1) is prepared by the stacking-drawing technique. The length of the photonic crystal fiber (3-1) is 20 mm. The silver film (3-7) can be obtained by the radio frequency magnetron sputtering method. The stacking-drawing technique is as follows: First, the quartz sleeve is pretreated, and the capillary is drawn according to the parameters in a ultra-clean environment. The drawing temperature is 1900 °C - 2000 °C. Then, the two ends of the capillary are tapered and sealed with a hydrogen-oxygen flame. The capillary is stacked in the quartz sleeve according to the design requirements to form the required structure. The voids are filled with a pure quartz rod. The quartz sleeve and the capillary are sintered together with an oxyacetylene flame. The photonic crystal fiber is made by using the double-drawing technique on the drawing tower;

[0010] Furthermore, the analysis liquid (3-9) is magnetic fluid (MFs). The change of the magnetic field will change the refractive index of the magnetic fluid (MFs), making the resonance loss peak change significantly; and the stress will change the refractive index of the cladding of the sensing unit (3), which will also make the resonance loss peak change significantly.

[0011] Furthermore, for the near-infrared band dual-peak PCF magnetic field and stress dual-parameter sensing system, the light signal emitted by the light source (1) is transmitted to the sensing unit (3) through the single-mode fiber (2). The sensing unit (3) outputs to the spectral analyzer (4) and the photoelectric converter (5). The photoelectric converter (5) converts the light signal into an electrical signal and outputs it to the signal processing module (6), and finally it is displayed in the computer (7);

[0012] Furthermore, the light source (1) outputs a light signal in the band of 750 - 2000 nm;

[0013] Furthermore, the light signal is transmitted to the sensing unit (3) through the single-mode fiber (2). The wave vector of the surface plasmon wave excited on the surface of the silver film (3-7) and the wave vector of the incident light field reach phase matching in a specific wavelength range, resulting in two couplings and two resonance loss peaks. Surface plasmon resonance (SPR) is very sensitive to the dielectric environment. The change of the refractive index RI of the analysis liquid (3-9) or the cladding (3-2) will change the resonance condition, resulting in significant changes in the two resonance loss peaks;

[0014] Furthermore, for the dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF, an optical signal is emitted by a light source (1) and transmitted to a sensing unit (3) through a single-mode optical fiber (2). When the refractive index of the analysis liquid (3-9) changes, the conditions for the plasma resonance phenomenon of the photonic crystal fiber (3-1) change, and the two coupling modes change. The distance Δλ between the two peaks displayed in the spectral analyzer (4) peak changes significantly. When the refractive index of the analysis liquid (3-9) or the cladding (3-2) increases, the distance between the two peaks decreases; when the refractive index of the analysis liquid (3-9) or the cladding (3-2) decreases, the distance between the two peaks increases. The sensitivity is calculated using the dual-peak sensitivity formula.

[0015] The dual-peak sensitivity formula is as follows:

[0016] s = (Δλ peak2 - Δλ peak1 ) / Δn a (1)

[0017] In the formula, (Δλ peak2 - Δλ peak1 ) is the wavelength difference between the two loss peaks at different refractive indices, Δn a is the change in magnetic field / stress, and s is the obtained dual-peak sensitivity. Among them, Δλ peak1 and Δλ peak2 correspond to the humidity and stress states of the sensing unit (3); the sensing unit (3) transmits the optical signal carrying the value of (Δλ peak2 - Δλ peak1 ) to the photoelectric converter (5), and the photoelectric converter (5) converts the optical signal into an electrical signal and outputs it to the signal processing module (6), and finally the information of the analysis liquid (3-7) is displayed in the computer (7);

[0018] Furthermore, for the dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF, the following formula needs to be used for calculation when measuring stress and magnetic field simultaneously:

[0019]

[0020] In formula (2), Δλ 1 is the change in the distance between the two peaks after the change in magnetic field intensity, Δλ 2 is the change in the distance between the two peaks after the change in stress, S T , S N are the sensitivities of magnetic field and stress respectively, and ΔT and ΔN are the changes in magnetic induction intensity and stress respectively. Furthermore, the changes in magnetic induction intensity and stress can be obtained from formula (3).

[0021] Structural Invention: Dual-parameter Sensing System of Magnetic Field and Stress Based on Near-infrared Band Dual-peak PCF

[0022] Compared with the publicly disclosed technologies, the beneficial effects of this invention patent are as follows:

[0023] 1. The dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF described in this invention has a special structure, which greatly increases the birefringence characteristics and dispersion characteristics, is conducive to the maintenance of polarization state, and can be widely applied in fields such as polarization control and precision optical fiber sensing.

[0024] 2. The dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF described in this invention has two confinement loss peaks. By calculating with the dual-peak sensitivity formula proposed in this invention, it solves the problems of poor sensitivity measurement accuracy and poor actual test effect of traditional PCF-SPR sensors, and increases the stability of the measurement system.

[0025] 3. The working wavelength of the dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF described in this invention is in the near-infrared band, and the interference of external environmental light on the sensor can be ignored.

[0026] 4. The dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF described in this invention uses silver as the SPR excitation material and MFs as the analysis liquid, can realize the measurement of dual parameters of magnetic field and stress, and reaches the maximum sensitivity of 1.16 nm / Oe and 1.3×10 -3 nm / mpa. Description of the Drawings

[0027] Figure 1 This is the device diagram of the dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF provided by this invention.

[0028] Figure 2 This is the cross-sectional view of the sensing unit of the dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF provided by this invention.

[0029] Figure 3 This is the coupling diagram of the dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF provided by this invention.

[0030] Figure 4 This is the result diagram of the dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF provided by this invention. Detailed Embodiments

[0031] The following combines the drawings to illustrate the detailed embodiments of the dual-parameter sensing system of magnetic field and stress based on near-infrared band dual-peak PCF proposed by this invention.

[0032] As shown in Figure 1As shown in the figure, the present invention provides a device diagram of a dual-parameter sensing system for magnetic field and stress based on a near-infrared band dual-peak PCF. The light signal emitted by the light source (1) is transmitted to the sensing unit (3) through a single-mode optical fiber (1). When the light is transmitted to the silver film (3-6), due to the inconsistent refractive indices of the analysis liquid (3-7) and the cladding (3-2), surface plasmon polariton phenomenon occurs at the silver film (3-6), and two confinement loss peaks appear. The sensing unit (3) outputs to the spectral analyzer (4) and the photoelectric converter (5). The photoelectric converter (5) converts the light signal into an electrical signal and outputs it to the signal processing module (6), and finally displays it in the computer (7);

[0033] As Figure 2 shown in the figure, it is a cross-sectional view of the sensing unit of the dual-parameter sensing system for magnetic field and stress based on a near-infrared band dual-peak PCF provided by the present invention. The sensing unit (3) is a photonic crystal fiber (3-1); it is composed of a cladding (3-2), a silver film (3-7), a zinc oxide thin film (3-8), and an analysis liquid (3-9); the cladding (3-2) includes: 22 circular air holes (3-3), 5 circular air holes (3-4), 2 elliptical air holes (3-5), 3 elliptical air holes (3-6), a silver film (3-7), zinc oxide (3-8), and an analysis liquid (3-9); its characteristics are: the air holes (3-3), air holes (3-4), elliptical air holes (3-5), and elliptical air holes (3-6) are arranged symmetrically about the y-axis of the optical fiber; the air hole (3-4) is located between the air hole (3-3) and the elliptical air hole (3-5); the silver film (3-7) and the zinc oxide thin film (3-8) are at the junction of the cladding (3-2) and the analysis liquid (3-9); the air holes affect the mode properties and can confine the light in the core. The silver film (3-7) is at the junction of the cladding (3-2) and the analysis liquid (3-9). When the light signal is transmitted to the photonic crystal fiber (3-1), the presence of the silver film (3-7) causes the occurrence of surface plasmon resonance phenomenon, thereby realizing high-sensitivity detection;

[0034] As Figure 3 shown in the figure, it is a two-coupling diagram of the dual-parameter sensing system for magnetic field and stress based on a near-infrared band dual-peak PCF provided by the present invention. When the working wavelength is 1200 - 2000 nm, two confinement loss peaks can be detected by this sensing system, and two couplings between the core and the silver film (3-7) occur.

[0035] As Figure 4As shown in the figure, the present invention provides the loss spectra of a dual-parameter sensing system for magnetic field and stress based on near-infrared band dual-peak PCF at a magnetic induction intensity of 10 kA / m, a stress of 40 kN, and a magnetic induction intensity of 20 kA / m, a stress of 55 kN. By calculating the change in the loss value when the stress ranges from 40 kN to 50 kN and the magnetic induction intensity ranges from 10 kA / m to 20 kA / m respectively, the maximum sensitivity for magnetic field measurement can be obtained as 1.16 nm / Oe, and the maximum sensitivity for stress measurement is 1.3×10 -3 nm / mpa.

Claims

1. A dual-parameter sensing system for magnetic field and stress based on a near-infrared band dual-peak PCF, characterized in that: it is composed of a light source (1), a single-mode optical fiber (2), a sensing unit (3), a spectral analyzer (4), a photoelectric converter (5), a signal processing module (6) and a computer (7); the sensing unit (3) is a photonic crystal fiber (3-1); it is composed of a cladding (3-2), a silver film (3-7), a zinc oxide thin film (3-8) and an analysis liquid (3-9); the cladding (3-2) includes: 20 circular air holes (3-3), 5 circular air holes (3-4), 2 elliptical air holes (3-5), 3 elliptical air holes (3-6); the circular air holes (3-3), the circular air holes (3-4), the elliptical air holes (3-5) and the elliptical air holes (3-6) are arranged symmetrically about the y-axis of the optical fiber; the circular air holes (3-4) are located between the circular air holes (3-3) and the elliptical air holes (3-5); the silver film (3-7) and the zinc oxide thin film (3-8) are at the junction of the cladding (3-2) and the analysis liquid (3-9); for the described sensing unit (3), the diameter of the cladding (3-2) is 15μm, the diameter of the circular air holes (3-3) is 1.5μm, the diameter of the circular air holes (3-4) is 2μm, the major axis of the elliptical air holes (3-5) is 3μm, and the minor axis is 2μm; the major axis of the elliptical air holes (3-6) is 4μm, and the minor axis is 3μm; the thickness of the silver film (3-7) is 20nm; the thickness of the zinc oxide thin film (3-8) is 18nm; the cladding material is fused silica, and its refractive index is defined by the Sellmeier formula; the silver film (3-7) is coated by the radio frequency magnetron sputtering method; the photonic crystal fiber (3-1) is prepared by the stacking-drawing technique, and the length of the photonic crystal fiber (3-1) is 20mm. The specific preparation method is: First, the quartz sleeve is pretreated, and the capillary is drawn according to the parameters in a super-clean environment. The drawing temperature is 1900℃-2000℃. Then, the two ends of the capillary are tapered and sealed with a hydrogen-oxygen flame. The capillary is stacked in the quartz sleeve according to the design requirements to form the required structure. The voids are filled with a pure quartz rod. The quartz sleeve and the capillary are sintered together with an oxyacetylene flame, and the photonic crystal fiber is made by using the two-time drawing technique on the drawing tower; the analysis liquid (3-9) is a magnetic fluid (MFs). The change of the magnetic field will change the refractive index of the magnetic fluid (MFs), making the resonance loss peak change significantly; and the stress will change the refractive index of the cladding of the sensing unit (3), which will also make the resonance loss peak change significantly. Therefore, the purpose of dual-parameter measurement can be achieved; the light source (1) outputs an optical signal in the 750-2000nm band; For the dual-parameter sensing system of magnetic field and stress based on near-infrared band double-peak PCF, the optical signal emitted by the light source (1) is transmitted to the sensing unit (3) through the single-mode optical fiber (2). The sensing unit (3) outputs to the spectral analyzer (4) and the photoelectric converter (5). The photoelectric converter (5) converts the optical signal into an electrical signal and outputs it to the signal processing module (6), and finally displays it in the computer (7). The optical signal is transmitted to the sensing unit (3) through the single-mode optical fiber (2). The wave vector of the surface plasmon wave excited on the surface of the silver film (3-7) and the wave vector of the incident optical field reach phase matching within a specific wavelength range, resulting in two couplings and two resonance loss peaks. Surface plasmon resonance (SPR) is very sensitive to the dielectric environment. Changes in the refractive index RI of the analysis liquid (3-9) and the cladding (3-2) will change the resonance conditions, causing significant changes in the two resonance loss peaks. The described dual-parameter sensing system for magnetic field and stress based on near-infrared band dual-peak PCF emits an optical signal from a light source (1), which is transmitted through a single-mode optical fiber (2) to a sensing unit (3). When the refractive index of the analysis liquid (3-9) changes, the conditions for the plasmon resonance phenomenon of the photonic crystal fiber (3-1) change, and the two coupling modes change. The distance Δλ between the two peaks displayed in the spectral analyzer (4) peak changes significantly. When the refractive index of the analysis liquid (3-9) or the cladding (3-2) increases, the distance between the two peaks decreases. When the refractive index of the analysis liquid (3-9) or the cladding (3-2) decreases, the distance between the two peaks increases. The sensitivity is calculated using the dual-peak sensitivity formula; The formula for the double-peak sensitivity is as follows: s = (Δλ peak2 - Δλ peak1 ) / Δn a (1) where (Δλ peak2 -Δλ peak1 ) is the wavelength difference between two loss peaks at different refractive indices, Δn a is the change in magnetic field / stress, and s is the obtained double-peak sensitivity; where Δλ peak1 and Δλ peak2 correspond to the humidity and stress states of the sensing unit (3); the sensing unit (3) transmits an optical signal carrying the value of (Δλ peak2 -Δλ peak1 ) to the photoelectric converter (5), and the photoelectric converter (5) converts the optical signal into an electrical signal and outputs it to the signal processing module (6), and finally the information of the analysis solution (3-9) is displayed in the computer (7); For the dual-parameter sensing system of magnetic field and stress based on near-infrared band double-peak PCF, the following formula needs to be used for calculation when measuring stress and magnetic field simultaneously: Δλ in formula (2) 1 is the change in the peak spacing after the magnetic field changes, and Δλ 2 is the change in the peak spacing after the stress changes. S T , S N are the sensitivities of the magnetic induction intensity and the stress respectively. ΔT and ΔN are the changes in the magnetic induction intensity and the stress respectively. Furthermore, the changes in the magnetic induction intensity and the stress can be obtained from formula (3).

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