Double-parameter optical fiber sensor based on double interference effect and preparation method thereof

Abstract

The invention relates to the technical field of optical fiber sensors, in particular to a double-parameter optical fiber sensor based on a double interference effect and a preparation method thereof.The sensor comprises a sensing unit 5 based on a Fabry-Perot interferometer and a sensing unit 6 based on a Mach-Zehnder interferometer, and the two sensing units form a cascade structure; mutual reference probes can be realized when different parameters are measured; according to the invention, an approximate free spectral range is obtained by controlling the cavity length, a remarkable vernier effect is formed, the air pressure and temperature sensitivity can be calculated by tracking the drift of the envelope, the measurement accuracy can be effectively improved, and the device has the advantages of simple structure and small volume.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensor technology, specifically to a dual-parameter fiber optic sensor based on the dual interference effect and its fabrication method. Background Technology

[0002] In recent years, fiber optic sensing technology has developed rapidly. Fiber optic sensors, with their advantages of small size, compact structure, long transmission distance, resistance to electromagnetic interference, and resistance to chemical corrosion, have been widely used in marine engineering, aerospace, industrial production, life sciences, and national defense, becoming an important scientific research technology related to national welfare and people's livelihood. Common fiber optic sensor measurement parameters include temperature, air pressure, strain, humidity, and acceleration, among which air pressure and temperature are particularly important parameters in many application areas.

[0003] In the research process of improving the measurement range and sensitivity of existing fiber optic sensors, crosstalk between air pressure and temperature has affected the accuracy and judgment of the sensing to some extent. Therefore, many current sensing structures can only measure a single parameter. Fiber optic sensors capable of measuring two parameters and possessing good sensitivity have become a hot topic for future research.

[0004] In summary, there is an urgent need to provide a fiber optic sensor capable of measuring both air pressure and temperature parameters with good sensitivity. Summary of the Invention

[0005] This invention addresses the technical problem of how to provide a fiber optic sensor capable of measuring both air pressure and temperature with good sensitivity.

[0006] To achieve the above objectives, a first aspect of the present invention provides a dual-parameter fiber optic sensor based on a dual interference effect, the dual-parameter fiber optic sensor comprising:

[0007] Sensing unit 5 based on Fabry-Perot interferometer and sensing unit 6 based on Mach-Zehnder interferometer;

[0008] The sensing unit 5 based on the Fabry-Perot interferometer includes a first single-mode fiber 501, a hollow fiber 502, and a second single-mode fiber 503 fused together in sequence.

[0009] The aspect ratio of the hollow optical fiber 502 is 2-4:1;

[0010] The cladding of the hollow fiber 502 has through holes as temperature sensing channels 504, so that the air cavity of the hollow fiber 502 is connected to the outside. The air cavity of the hollow fiber 502 is filled with PDMS.

[0011] The radial cross-sectional area of ​​the temperature sensing channel 504 accounts for 5-10% of the outer surface area of ​​the hollow fiber 502;

[0012] The sensing unit 6 based on the Mach-Zehnder interferometer includes a third single-mode fiber 601, a first multimode fiber 602, a special fiber 603, a second multimode fiber 604, and a fourth single-mode fiber 605, which are fused together in sequence.

[0013] The special optical fiber 603 includes a cladding, an air cavity inside the cladding, and a fiber core. The fiber core is located at the center of the special optical fiber, and the air cavity is arranged around the fiber core. A through hole is formed on the cladding of the special optical fiber 603 as a pressure sensing channel 606.

[0014] The radial cross-sectional area of ​​the pressure sensing channel 606 accounts for 10-20% of the outer surface area of ​​the special optical fiber 603;

[0015] The length ratio of the first multimode fiber 602, the special fiber 603, and the second multimode fiber 604 is 0.65-1:1:0.65-1.

[0016] A second aspect of the present invention provides a method for fabricating the above-mentioned dual-parameter fiber optic sensor based on the dual interference effect, comprising the following steps:

[0017] S1. Take a section of single-mode fiber, remove the coating layer, wipe it with ethanol solution, cut the end face of the single-mode fiber flat, and clean the end face of the single-mode fiber by discharge to obtain the first single-mode fiber 501. Process a section of hollow fiber using the same steps to obtain hollow fiber 502. Fiber one end of the first single-mode fiber 501 is fused to the hollow fiber 502.

[0018] Cut the hollow fiber 502, remove the coating layer, wipe it with ethanol solution, cut the end face of the hollow fiber 502 flat, and fuse the second single-mode fiber 503 to the other end of the hollow fiber 502.

[0019] A temperature sensing channel 504 is constructed by drilling holes in the cladding of hollow fiber 502 using a femtosecond laser device.

[0020] An elastomer polymer and an auxiliary curing solution are mixed at a mass ratio of 10:1 and allowed to stand for 1 hour until the bubbles disappear to obtain a PDMS solution. Then, the PDMS solution is coated onto the temperature sensing channel 504 on the surface of the hollow fiber 502. The PDMS solution is then filled into the air cavity of the hollow fiber 502 through the temperature sensing channel 504 using the capillary effect until the air cavity of the hollow fiber 502 is completely filled. The fiber is then placed in a drying oven at 100°C and baked for 80 minutes to cure, thus obtaining a sensing unit 5 based on a Fabry-Perot interferometer.

[0021] Take a section of single-mode fiber, remove the coating layer, use ethanol solution to wipe the end face of the single-mode fiber to cut it flat, and clean the end face of the single-mode fiber by discharge to obtain the third single-mode fiber 601. Use the same steps to process the multimode fiber to obtain the first multimode fiber 602, and fusion splice one end of the third single-mode fiber 601 and the first multimode fiber 602.

[0022] Cut the first multimode fiber 602, remove the coating layer, wipe it with ethanol solution, and cut the end face of the first multimode fiber 602 flat. Fusion one end of the special fiber 603 to the other end of the first multimode fiber 602. Fusion the other end of the special fiber 603 to the second multimode fiber 604 and the fourth single-mode fiber 605 in sequence to form a symmetrical structure.

[0023] A femtosecond laser device is used to drill holes in the cladding of a special optical fiber 603 to build a pressure sensing channel 606, thereby obtaining a sensing unit 6 based on a Mach-Zehnder interferometer.

[0024] S2. The sensing unit 5 based on the Fabry-Perot interferometer and the sensing unit 6 based on the Mach-Zehnder interferometer are cascaded to obtain a dual-parameter fiber optic sensor based on the dual interference effect.

[0025] The beneficial effects of this invention are as follows:

[0026] 1. By cascading a sensing structure based on a Fabry-Perot interferometer and a sensing structure based on a Mach-Zehnder interferometer to form a dual interference effect, namely the optical vernier effect, and in conjunction with a specially configured temperature sensing channel and a pressure sensing channel, the sensitivity of the sensor to pressure and temperature can be improved.

[0027] 2. By using the envelope tracking method to measure parameters and observing the envelope drift, the sensitivity of air pressure and temperature can be calculated; by changing the reference cavity, the crosstalk problem of air pressure and temperature is overcome, and dual-parameter measurement is realized. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a dual-parameter fiber optic sensor based on the dual interference effect of the present invention.

[0029] Figure 2 This is a schematic diagram of the sensing unit based on a Fabry-Perot interferometer in the sensor.

[0030] Figure 3 This is a schematic diagram of the sensing unit based on a Mach-Zehnder interferometer in a sensor.

[0031] In the diagram: 1. Supercontinuum Light Source (YSL); 2. Spectrometer; 3. Fiber Optic Circulator; 4. Dual-parameter sensor based on dual interference effect; 5. Sensing unit based on Fabry-Perot interferometer; 6. Sensing unit based on Mach-Zehnder interferometer; 501. First single-mode fiber; 502. Hollow-core fiber; 503. Second single-mode fiber; 504. Temperature sensing channel; 601. Third single-mode fiber; 602. First multimode fiber; 603. Special fiber; 604. Second multimode fiber; 605. Fourth single-mode fiber; 606. Pressure sensing channel; 01. Circulator line 1; 02. Circulator line 2; 03. Circulator line 3. Detailed Implementation

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] The first aspect of this invention provides a dual-parameter fiber optic sensor based on a dual interference effect, characterized in that the dual-parameter fiber optic sensor comprises:

[0034] Sensing unit 5 based on Fabry-Perot interferometer and sensing unit 6 based on Mach-Zehnder interferometer;

[0035] The sensing unit 5 based on the Fabry-Perot interferometer includes a first single-mode fiber 501, a hollow fiber 502, and a second single-mode fiber 503 fused together in sequence.

[0036] The aspect ratio of the hollow optical fiber 502 is 2-4:1;

[0037] The cladding of the hollow fiber 502 has through holes as temperature sensing channels 504, so that the air cavity of the hollow fiber 502 is connected to the outside. The air cavity of the hollow fiber 502 is filled with PDMS.

[0038] The radial cross-sectional area of ​​the temperature sensing channel 504 accounts for 5-10% of the outer surface area of ​​the hollow fiber 502;

[0039] The sensing unit 6 based on the Mach-Zehnder interferometer includes a third single-mode fiber 601, a first multimode fiber 602, a special fiber 603, a second multimode fiber 604, and a fourth single-mode fiber 605, which are fused together in sequence.

[0040] The special optical fiber 603 includes a cladding, an air cavity inside the cladding, and a fiber core. The fiber core is located at the center of the special optical fiber, and the air cavity is arranged around the fiber core. A through hole is formed on the cladding of the special optical fiber 603 as a pressure sensing channel 606.

[0041] The radial cross-sectional area of ​​the pressure sensing channel 606 accounts for 10-20% of the outer surface area of ​​the special optical fiber 603;

[0042] The length ratio of the first multimode fiber 602, the special fiber 603, and the second multimode fiber 604 is 0.65-1:1:0.65-1.

[0043] According to the present invention, the diameter of the first single-mode fiber 501 is 120-130 μm, and the diameters of the first single-mode fiber 501, the hollow fiber 502 and the second single-mode fiber 503 are the same.

[0044] According to the present invention, the diameter of the air cavity of the hollow optical fiber 502 is 95-105 μm.

[0045] According to the present invention, the diameter of the third single-mode optical fiber 601 is 120-130 μm;

[0046] The third single-mode fiber 601, the first multimode fiber 602, the special fiber 603, the second multimode fiber 604, and the fourth single-mode fiber 605 have the same diameter.

[0047] The core diameter of the first multimode optical fiber 602 is 100-110 μm, and the sensing cavity length is 0.9-1.3 mm.

[0048] The second multimode fiber 604 has a core diameter of 100-110 μm and a sensing cavity length of 0.9-1.3 mm.

[0049] According to the present invention, the diameter of the air cavity of the special optical fiber 603 is 45-55 μm.

[0050] In this invention, during use, the dual-parameter fiber optic sensor consists of a Fabry-Perot interferometer-based sensing unit 5 and a Mach-Zehnder interferometer-based sensing unit 6 forming a dual-parameter sensing structure 4 based on the double interference effect. Together with the supercontinuum light source YSL1, the spectrometer 2, and the fiber optic circulator 3, it forms a sensing structure for parameter measurement.

[0051] A second aspect of the present invention provides a method for fabricating the above-mentioned dual-parameter fiber optic sensor, comprising the following steps:

[0052] S1. Take a section of single-mode fiber, remove the coating layer, wipe it with ethanol solution, cut the end face of the single-mode fiber flat, and clean the end face of the single-mode fiber by discharge to obtain the first single-mode fiber 501. Process a section of hollow fiber using the same steps to obtain hollow fiber 502. Fiber one end of the first single-mode fiber 501 is fused to the hollow fiber 502.

[0053] Cut the hollow fiber 502, remove the coating layer, wipe it with ethanol solution, cut the end face of the hollow fiber 502 flat, and fuse the second single-mode fiber 503 to the other end of the hollow fiber 502.

[0054] A temperature sensing channel 504 is constructed by drilling holes in the cladding of hollow fiber 502 using a femtosecond laser device.

[0055] An elastomer polymer and an auxiliary curing solution are mixed at a mass ratio of 10:1 and allowed to stand for 1 hour until the bubbles disappear to obtain a PDMS solution. Then, the PDMS solution is coated onto the temperature sensing channel 504 on the surface of the hollow fiber 502. The PDMS solution is then filled into the air cavity of the hollow fiber 502 through the temperature sensing channel 504 using the capillary effect until the air cavity of the hollow fiber 502 is completely filled. The fiber is then placed in a drying oven at 100°C and baked for 80 minutes to cure, thus obtaining a sensing unit 5 based on a Fabry-Perot interferometer.

[0056] Take a section of single-mode fiber, remove the coating layer, use ethanol solution to wipe the end face of the single-mode fiber to cut it flat, and clean the end face of the single-mode fiber by discharge to obtain the third single-mode fiber 601. Use the same steps to process the multimode fiber to obtain the first multimode fiber 602, and fusion splice one end of the third single-mode fiber 601 and the first multimode fiber 602.

[0057] Cut the first multimode fiber 602, remove the coating layer, wipe it with ethanol solution, and cut the end face of the first multimode fiber 602 flat. Fusion one end of the special fiber 603 to the other end of the first multimode fiber 602. Fusion the other end of the special fiber 603 to the second multimode fiber 604 and the fourth single-mode fiber 605 in sequence to form a symmetrical structure.

[0058] A femtosecond laser device is used to drill holes in the cladding of a special optical fiber 603 to build a pressure sensing channel 606, thereby obtaining a sensing unit 6 based on a Mach-Zehnder interferometer.

[0059] S2. The sensing unit 5 based on the Fabry-Perot interferometer and the sensing unit 6 based on the Mach-Zehnder interferometer are cascaded to obtain a dual-parameter fiber optic sensor based on the dual interference effect.

[0060] In this invention, during use, the dual-parameter fiber optic sensor consists of a Fabry-Perot interferometer-based sensing unit 5 and a Mach-Zehnder interferometer-based sensing unit 6 forming a dual-parameter sensing structure 4 based on the double interference effect. Together with the supercontinuum light source YSL1, the spectrometer 2, and the fiber optic circulator 3, it forms a sensing structure for parameter measurement.

[0061] According to the present invention, the diameter of the first single-mode fiber 501 is 120-130 μm, and the diameters of the first single-mode fiber 501, the hollow fiber 502 and the second single-mode fiber 503 are the same.

[0062] According to the present invention, the aspect ratio of the hollow optical fiber 502 is 2-4:1.

[0063] According to the present invention, the setting parameters of the femtosecond laser device include:

[0064] The laser's center wavelength is set at 520 nm, the repetition rate is 20 kHz, the focusing objective is a 20× objective, the laser power is 15-30 μW, the open-cavity laser power is 50-60 μW, the writing speed is 70 μm / s, and the pulse width is 30-50 ms.

[0065] According to the present invention, a through hole is formed on the cladding of the hollow optical fiber 502 as a temperature sensing channel 504, so that the air cavity of the hollow optical fiber 502 is connected to the outside.

[0066] The radial cross-sectional area of ​​the temperature sensing channel 504 accounts for 5-10% of the outer surface area of ​​the hollow fiber 502.

[0067] According to the present invention, the special optical fiber 603 includes a cladding, an air cavity inside the cladding, and a fiber core. The fiber core is disposed at the center of the special optical fiber, and the air cavity is disposed around the fiber core. A through hole is formed on the cladding of the special optical fiber 603 as a pressure sensing channel 606.

[0068] The radial cross-sectional area of ​​the pressure sensing channel 606 accounts for 10-20% of the outer surface area of ​​the special optical fiber 603;

[0069] The length ratio of the first multimode fiber 602, the special fiber 603, and the second multimode fiber 604 is 0.65-1:1:0.65-1;

[0070] The diameter of the third single-mode fiber 601 is 120-130 μm;

[0071] The third single-mode fiber 601, the first multimode fiber 602, the special fiber 603, the second multimode fiber 604, and the fourth single-mode fiber 605 have the same diameter.

[0072] The sensing cavity length of the special optical fiber 603 is 1 mm;

[0073] The diameter of the third single-mode fiber (601) is 125 μm, and the diameter of the fourth single-mode fiber (605) is 125 μm.

[0074] According to the present invention, the air pressure sensing channel 606 occupies 10-20% of the outer surface area of ​​the special optical fiber 603.

[0075] In this invention, according to the appendix to the specification Figure 1 The light beam emitted from the supercontinuum light source YSL is guided to the circulator via line 01, then guided out via line 02, and subsequently enters the FPI structure. Assuming the light field intensity carried by the light exiting line 02 is denoted as Ei, the field intensities of the two reflected beams on the two reflecting surfaces of the FPI can be expressed as follows:

[0076]

[0077] The coefficient R in the above formula f1 and R f2 Δφ represents the reflectivity of the two reflective surfaces within the FPI structure. F This represents the phase delay of light at the second reflecting surface relative to light at the first reflecting surface. Its value is defined as:

[0078]

[0079] Where n and L f Let λ represent the effective refractive index of the material and the length of the FP cavity, and λ represent the wavelength of the beam. The electric field intensity of the beam after reflection through the FPI structure is:

[0080]

[0081] The beam is guided into the MZI structure through line 03 of the circulator. Within the MZI structure, the influence of the lengths of the MMF and DSHF segments in the SMF-MMF-DSHF-MMF-SMF configuration on the transmitted optical field intensity can be investigated. The findings indicate that as the MMF length increases, the mode field diameter of the emitted light also increases, meaning that more energy can be coupled into the DSHF cladding. The transmitted light magnitudes for the base cladding mode and base air mode can be expressed as:

[0082]

[0083]

[0084] I core and I air I represents the transmitted light intensity between the fiber core and the air pores in the MZI structure, respectively. clad ϕ is the transmitted light intensity of the cladding in the MZI structure. air and ϕclad The cladding represents the phase difference between the MZI core and the air holes and the cladding, respectively. The specific formula is as follows:

[0085]

[0086]

[0087] and The expression is:

[0088]

[0089]

[0090] At this point, the electric field intensity in the fundamental-air mode of the MZI is:

[0091]

[0092] In the above formula and These are the electric field strengths of the beam passing through the air hole and the fiber core region, respectively. In the above formula... It can be expressed by the following formula:

[0093]

[0094] This formula represents the transfer matrix of MZI. and This represents the amplitude division ratio of the optical field in different transmission paths, while and These represent the total phase difference in the air hole path and the fiber core path, respectively. The cumulative phase difference of the optical column along the air hole and fiber core boundaries is expressed as:

[0095]

[0096] Corresponding to the effective refractive index difference between the air pores and the quartz cladding, This represents the length of the DSHF, i.e., the optical path length of the MZI interferometer cavity. In summary, the output electric field of the fundamental mode-air mode combination of the MZI is as follows:

[0097]

[0098] This is the electric field intensity output by the MZI from the fundamental-air mode combination. In summary, the final output light intensity can be deduced as:

[0099]

[0100] Each parameter in this formula represents the following:

[0101]

[0102] Therefore, the MZI structure along the fundamental mode-cladding mode combination is similar to that along the fundamental mode-air mode combination, except that the parameters related to the pore region in the formula are replaced with parameters related to the DSHF cladding. Ultimately, the output electric field and field strength of the entire MZI structure are the superposition of the electric field and the optical field intensity.

[0103] When two cascaded interferometers have similar but unequal FSRs, they can produce an optical vernier effect after superimposing the two interference spectra, resulting in regular interference envelope fringes. The angular wavelength and FSR of the envelope are as follows:

[0104]

[0105]

[0106]

[0107]

[0108] In the above equation, This indicates the wavelength at which p-order envelope fringes appear. Similarly, , and These correspond to the envelope-free spectral ranges generated by FPI, MZI, and the vernier effect, respectively. When external environmental factors (temperature and air pressure) change, the refractive index and cavity length of MZI and FPI also change, resulting in changes in their respective FSRs. The tilt wavelength shifts of MZI and FPI caused by environmental disturbances are as follows:

[0109]

[0110]

[0111] in and This represents the spectral region where the interference tilt angles of the two interference structures are located. If the external environment changes, the cursor envelope curve will also shift accordingly.

[0112]

[0113] When the peak values ​​of the corresponding curves from two interferometers coincide, it represents the wavelength corresponding to the maximum value of the envelope on the vernier spectrum. The intrinsic relationship between the independent wavelength shifts of the two interference structures and the shift of the envelope curve in the vernier envelope curve is as follows:

[0114]

[0115] in:

[0116]

[0117]

[0118] and These are the sensitivity coefficients of the envelope formed by combining individual FPIs and MZIs, respectively. Therefore, the amplified sensitivity of the vernier effect can be determined by the envelope FSR. According to the formula, the smaller the FSR difference between the two interferometers, the higher the sensitivity amplification factor. However, it should be noted that an excessively high amplification factor may make it difficult to accurately track the envelope. Therefore, in the actual development of the sensor, it is necessary to adjust the FSR of the interferometers to achieve an appropriate balance of sensitivity within the obtained comb-shaped envelope.

[0119] Furthermore, a sensitivity matrix can be constructed to demodulate the dual-parameter measurement data. When measuring temperature parameters, FPI is used as the sensing cavity and MZI as the reference cavity, and the pressure crosstalk of the MZI interferometer cavity can be ignored; when measuring pressure parameters, MZI is used as the sensing cavity and FPI as the reference cavity, and the temperature crosstalk of the FPI interferometer cavity can be ignored.

[0120] Specifically, the process involves the following steps:

[0121] S1. Take a section of single-mode fiber, remove the coating layer, wipe it with ethanol solution, cut the end face of the single-mode fiber flat with a cleaver, place it in a fusion splicer, and clean the end face of the single-mode fiber by discharge to obtain the first single-mode fiber 501. Process a section of hollow fiber using the same steps to obtain hollow fiber 502. Fiber one end of the first single-mode fiber 501 into the hollow fiber 502.

[0122] Use a fixed-length cutting machine to cut the hollow fiber 502, remove the coating layer, wipe it with ethanol solution, cut the end face of the hollow fiber 502 flat, and fuse the second single-mode fiber 503 to the other end of the hollow fiber 502.

[0123] A temperature sensing channel 504 is constructed by drilling holes in the cladding of hollow fiber 502 using a femtosecond laser device.

[0124] An elastomer polymer and an auxiliary curing solution are mixed at a mass ratio of 10:1 and allowed to stand for 1 hour until the bubbles disappear to obtain a PDMS solution. Then, the PDMS solution is coated onto the temperature sensing channel 504 on the surface of the hollow fiber 502. The PDMS solution is then filled into the air cavity of the hollow fiber 502 through the temperature sensing channel 504 using the capillary effect until the air cavity of the hollow fiber 502 is completely filled. The fiber is then placed in a drying oven at 100°C and baked for 80 minutes to cure, thus obtaining a sensing unit 5 based on a Fabry-Perot interferometer.

[0125] Take a section of single-mode fiber, remove the coating layer, wipe it with ethanol solution, cut the end face of the single-mode fiber flat with a cleaver, place it in a fusion splicer, and clean the end face of the single-mode fiber by discharge to obtain the third single-mode fiber 601. Process the multimode fiber in the same way to obtain the first multimode fiber 602, and fusion splice one end of the third single-mode fiber 601 and the first multimode fiber 602.

[0126] The first multimode fiber 602 is cut with a fixed-length cutting machine to remove the coating layer. It is then wiped with an ethanol solution to make the end face of the first multimode fiber 602 flat. The other end of the first multimode fiber 602 is fused to one end of a special fiber 603. The other end of the special fiber 603 is then fused to the second multimode fiber 604 and the fourth single-mode fiber 605 in sequence to form a symmetrical structure.

[0127] A femtosecond laser device is used to drill holes in the cladding of a special optical fiber 603 to build a pressure sensing channel 606, thereby obtaining a sensing unit 6 based on a Mach-Zehnder interferometer.

[0128] S2. The sensing unit 5 based on the Fabry-Perot interferometer and the sensing unit 6 based on the Mach-Zehnder interferometer are cascaded to obtain a dual-parameter fiber optic sensor based on the dual interference effect.

[0129] The settings parameters for the femtosecond laser device include:

[0130] The laser's center wavelength was set at 520 nm, the repetition rate at 20 kHz, the focusing objective at 20×, the laser power at 20 μW, the open-cavity laser power at 50 μW, the writing speed at 70 μm / s, and the pulse width at 40 ms.

[0131] The hollow optical fiber 502 has an opening in its cladding to serve as a temperature sensing channel 504.

[0132] The radial cross-sectional area of ​​the temperature sensing channel 504 accounts for 7.5% of the outer surface area of ​​the hollow optical fiber 502;

[0133] The radial cross-sectional area of ​​the pressure sensing channel 606 accounts for 15% of the outer surface area of ​​the special optical fiber 603.

[0134] Measurements are taken by integrating the entire sensing structure.

[0135] The sensor based on the Fabry-Perot interferometer includes two single-mode optical fibers and one hollow-core optical fiber. The single-mode optical fiber (SMF) and the hollow-core optical fiber (HCF) have a diameter of 125 μm. The materials are connected sequentially in the order of SMF-HCF-SMF to build a symmetrical structure.

[0136] The sensor based on the Mach-Zehnder interferometer includes two single-mode optical fibers, two multimode optical fibers, and one special optical fiber. The single-mode fiber (SMF) has a diameter of 125 μm, the multimode fiber (MMF) has a diameter of 125 μm, and the core diameter is 105 μm. The special optical fiber (DSHF) matches the size of the single-mode and multimode optical fibers used. The cladding contains a pair of double-sided air holes with a diameter of 50 μm. The materials are connected sequentially in the order of SMF-MMF-DSHF-MMF-SMF to build a symmetrical structure.

[0137] The diameters of the first single-mode fiber 501, the hollow fiber 502, and the second single-mode fiber 503 are 125 μm, and the length of the sensing cavity of the hollow fiber 502 is 300 μm.

[0138] The length ratio of the first multimode fiber 602, the special fiber 603, and the second multimode fiber 604 is 0.7:1:0.7.

[0139] The diameters of the third single-mode fiber 601, the first multimode fiber 602, the special fiber 603, the second multimode fiber 604, and the fourth single-mode fiber 605 are 125 μm.

[0140] The core diameter of the first multimode fiber 602 and the second multimode fiber 604 is 105 μm, and the length of the sensing cavity is 1 mm.

[0141] The diameter of the air cavity in hollow fiber 502 is 100μm, and the diameter of the air cavity in special fiber 603 is 50μm.

[0142] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A dual-parameter fiber optic sensor based on a dual interference effect, characterized in that, The dual-parameter fiber optic sensor includes: Sensing unit (5) based on Fabry-Perot interferometer and sensing unit (6) based on Mach-Zehnder interferometer. The sensing unit (5) based on the Fabry-Perot interferometer includes a first single-mode fiber (501), a hollow fiber (502), and a second single-mode fiber (503) fused together in sequence. The aspect ratio of the hollow optical fiber (502) is 2-4:1; The hollow fiber (502) has through holes in its cladding as temperature sensing channels (504), so that the air cavity of the hollow fiber (502) is connected to the outside, and the air cavity of the hollow fiber (502) is filled with PDMS. The radial cross-sectional area of ​​the temperature sensing channel (504) accounts for 5-10% of the outer surface area of ​​the hollow fiber (502); The sensing unit (6) based on the Mach-Zehnder interferometer includes a third single-mode fiber (601), a first multimode fiber (602), a special fiber (603), a second multimode fiber (604), and a fourth single-mode fiber (605) that are fused together in sequence. The special optical fiber (603) includes a cladding, an air cavity inside the cladding, and a fiber core. The fiber core is located at the center of the special optical fiber, and the air cavity is arranged around the fiber core. A through hole is opened on the cladding of the special optical fiber (603) as a pressure sensing channel (606). The radial cross-sectional area of ​​the pressure sensing channel (606) accounts for 10-20% of the outer surface area of ​​the special optical fiber (603); The length ratio of the first multimode fiber (602), the special fiber (603), and the second multimode fiber (604) is 0.65-1:1:0.65-1.

2. The dual-parameter fiber optic sensor according to claim 1, characterized in that, The diameter of the first single-mode fiber (501) is 120-130μm, and the diameters of the first single-mode fiber (501), the hollow fiber (502), and the second single-mode fiber (503) are the same.

3. The dual-parameter fiber optic sensor according to claim 1, characterized in that, The diameter of the third single-mode fiber (601) is 120-130 μm; The third single-mode fiber (601), the first multimode fiber (602), the special fiber (603), the second multimode fiber (604), and the fourth single-mode fiber (605) have the same diameter; The core diameter of the first multimode optical fiber (602) is 100-110 μm, and the sensing cavity length is 0.9-1.3 mm; The second multimode fiber (604) has a core diameter of 100-110 μm and a sensing cavity length of 0.9-1.3 mm.

4. The method for fabricating the dual-parameter fiber optic sensor based on the dual interference effect as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Take a section of single-mode fiber, remove the coating layer, wipe it with ethanol solution, cut the end face of the single-mode fiber flat, and clean the end face of the single-mode fiber by discharge to obtain the first single-mode fiber (501). Process a section of hollow fiber using the same steps to obtain hollow fiber (502). Fiber one end of the first single-mode fiber (501) is fused to the hollow fiber (502). Cut the hollow fiber (502), remove the coating layer, wipe with ethanol solution, cut the end face of the hollow fiber (502) flat, and fuse the second single-mode fiber (503) to the other end of the hollow fiber (502). A temperature sensing channel (504) is constructed by drilling holes in the cladding of a hollow optical fiber (502) using a femtosecond laser device. The elastomer polymer and the auxiliary curing solution were mixed at a mass ratio of 10:1 and allowed to stand for 1 hour until the bubbles disappeared to obtain a PDMS solution. Then, the PDMS solution was coated onto the temperature sensing channel (504) on the surface of the hollow fiber (502). The PDMS solution was then used to fill the air cavity of the hollow fiber (502) through the temperature sensing channel (504) using the capillary effect until the air cavity of the hollow fiber (502) was completely filled. The fiber was then placed in a drying oven at 100°C and baked for 80 minutes to cure, thus obtaining a sensing unit (5) based on a Fabry-Perot interferometer. Take a section of single-mode fiber, remove the coating layer, wipe the end face of the single-mode fiber with ethanol solution to cut it flat, and clean the end face of the single-mode fiber by discharge to obtain the third single-mode fiber (601). Process the multimode fiber in the same way to obtain the first multimode fiber (602). Fusion splice one end of the third single-mode fiber (601) and the first multimode fiber (602). Cut the first multimode fiber (602), remove the coating layer, wipe with ethanol solution, cut the end face of the first multimode fiber (602) flat, and fuse one end of the special fiber (603) to the other end of the first multimode fiber (602). The other end of the special fiber (603) is then fused to the second multimode fiber (604) and the fourth single-mode fiber (605) in sequence to form a symmetrical structure. A femtosecond laser device is used to drill holes in the cladding of a special optical fiber (603) to build a pressure sensing channel (606) and obtain a sensing unit (6) based on a Mach-Zehnder interferometer. S2. The sensing unit (5) based on the Fabry-Perot interferometer and the sensing unit (6) based on the Mach-Zehnder interferometer are cascaded to obtain a dual-parameter fiber optic sensor based on the dual interference effect.

5. The preparation method according to claim 4, characterized in that, The diameter of the first single-mode fiber (501) is 120-130μm, and the diameters of the first single-mode fiber (501), the hollow fiber (502), and the second single-mode fiber (503) are the same.

6. The preparation method according to claim 4, characterized in that, The aspect ratio of the hollow optical fiber (502) is 2-4:

1.

7. The preparation method according to claim 4, characterized in that, The settings parameters for the femtosecond laser device include: The laser's center wavelength is set at 520 nm, the repetition rate is 20 kHz, the focusing objective is a 20× objective, the laser power is 15-30 μW, the open-cavity laser power is 50-60 μW, the writing speed is 70 μm / s, and the pulse width is 30-50 ms.

8. The preparation method according to claim 4, characterized in that, The hollow fiber (502) has through holes in its cladding as temperature sensing channels (504), so that the air cavity of the hollow fiber (502) is connected to the outside. The radial cross-sectional area of ​​the temperature sensing channel (504) accounts for 5-10% of the outer surface area of ​​the hollow fiber (502).

9. The preparation method according to claim 4, characterized in that, The special optical fiber (603) includes a cladding, an air cavity inside the cladding, and a fiber core. The fiber core is located at the center of the special optical fiber, and the air cavity is arranged around the fiber core. A through hole is opened on the cladding of the special optical fiber (603) as a pressure sensing channel (606). The radial cross-sectional area of ​​the pressure sensing channel (606) accounts for 10-20% of the outer surface area of ​​the special optical fiber (603); The length ratio of the first multimode fiber (602), the special fiber (603), and the second multimode fiber (604) is 0.65-1:1:0.65-1; The diameter of the third single-mode fiber (601) is 120-130 μm; The third single-mode fiber (601), the first multimode fiber (602), the special fiber (603), the second multimode fiber (604), and the fourth single-mode fiber (605) have the same diameter; The sensing cavity length of the special optical fiber (603) is 1 mm; The diameter of the third single-mode fiber (601) is 125 μm, and the diameter of the fourth single-mode fiber (605) is 125 μm.

10. The preparation method according to claim 4, characterized in that, The air pressure sensing channel (606) occupies 10-20% of the outer surface area of ​​the special optical fiber (603).

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