Static ice pressure and temperature compensation sensor and system based on double-fiber annular ring-down cavity

Abstract

The invention belongs to the technical field of optical fiber sensing, and discloses a static ice pressure and temperature compensation sensor based on a double-optical-fiber annular ring-down cavity, which comprises a cavity substrate, an H-shaped base is arranged on the bottom surface of the cavity substrate, a first long groove and a second long groove are respectively formed in the upper surface and the lower surface of the H-shaped base, a first optical fiber is arranged in the first long groove, and a second optical fiber is arranged in the second long groove; the upper surface of the cavity substrate is provided with an elastic membrane used for sealing the cavity, the bottom of the elastic membrane is provided with a protrusion, the first optical fiber and the second optical fiber are provided with a first fiber bragg grating and a second fiber bragg grating respectively, the first fiber bragg grating is fixedly connected with the protrusion, and the second fiber bragg grating is fixedly connected with the protrusion. The second fiber bragg grating is fixedly connected with the second long groove; two ends of the first optical fiber and the second optical fiber are led out from two ends of the cavity substrate and then are respectively connected with an optical fiber annular ring-down cavity. According to the invention, the static ice pressure sensing precision can be improved.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing technology, specifically designing a static ice pressure and temperature compensation sensor and system based on a dual-fiber ring decay cavity. Background Technology

[0002] Static ice pressure refers to the stress caused by the temperature gradient within the ice body due to changes in water and air temperature during ice formation and melting. As the temperature drops, the ice expands internally (frost heave), and when heated, it expands thermally. These expansion effects affect structures such as river channels, dams, hydraulic engineering projects, and offshore platforms through horizontal thrust on surrounding boundaries. When this thrust exceeds the structure's bearing capacity, it can cause damage such as compression, bending, or cracking, interfering with river ice condition warnings and ice prevention operations, and potentially causing casualties and significant economic losses. However, the unique regional and physical complexity of ice bodies presents numerous technical challenges to the monitoring and assessment of static ice pressure. Fiber Bragg gratings (FBGs) can independently respond to temperature and strain changes, achieving temperature compensation through multiple sensors to ensure high-precision pressure measurement. Furthermore, FBG sensors are extremely sensitive to minute pressure changes, supporting large-scale distributed monitoring, and possess advantages such as resistance to electromagnetic interference, corrosion, and high temperature and pressure, enabling long-term stable operation in extreme environments. They are small in size and flexible in installation, making them ideal for high-precision, harsh-environment monitoring scenarios of hydraulic structures.

[0003] In real-world scenarios, changes in ambient temperature can affect the center wavelength of the static ice pressure sensor (FBG), indicating a temperature cross-sensitivity problem. This makes it difficult to accurately determine whether the FBG wavelength is affected by the measured quantity or other physical quantities. Therefore, temperature compensation is needed for traditional static ice pressure sensors to eliminate the influence of temperature variations. Summary of the Invention

[0004] To address the technical problem that traditional sensors are easily affected by temperature changes, this invention proposes a static ice pressure temperature compensation sensor based on a dual-fiber ring decay cavity, which solves the problem of traditional sensors being easily affected by temperature changes and improves the accuracy of static ice pressure sensing.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a static ice pressure temperature compensation sensor based on a dual-fiber annular ring decay cavity, comprising: a cavity substrate, an H-shaped base disposed on the bottom surface of the cavity substrate, a first long groove and a second long groove respectively disposed on the upper and lower surfaces of the H-shaped base, a first optical fiber disposed in the first long groove, a second optical fiber disposed in the second long groove, an elastic diaphragm for sealing the cavity disposed on the upper surface of the cavity substrate, a protrusion disposed at the bottom of the elastic diaphragm, a first fiber grating and a second fiber grating respectively disposed on the first and second optical fibers, the first fiber grating being fixedly connected to the protrusion, and the second fiber grating being fixedly connected to the second long groove; the two ends of the first and second optical fibers are led out from the two ends of the cavity substrate and respectively connected to an optical fiber annular ring decay cavity.

[0006] The cavity substrate is elongated, and the first and second elongated grooves are arranged along the length of the cavity substrate; the depth of the first and second elongated grooves is 0.1 ~ 0.3 mm.

[0007] The length and width of the H-shaped base are the same as the length and width of the cavity inside the cavity base.

[0008] The protrusion is circular and located at the center of the cavity base, with a radius of 8 to 15 mm and a thickness of 0.3 to 0.5 mm.

[0009] The elastic diaphragm is made of 304 stainless steel; The elastic diaphragm has a length of 60-90 mm, a width of 20-40 mm, and a thickness of 0.5-0.8 mm.

[0010] The first fiber grating and the second fiber grating have different center wavelengths.

[0011] Furthermore, the present invention also provides a static ice pressure and temperature compensation sensing system based on a dual-fiber ring ring decay cavity, including the aforementioned static ice pressure and temperature compensation sensor based on a dual-fiber ring ring decay cavity, and further including a laser, a first coupler, a first isolator, a second isolator, a first fiber ring decay cavity, a second fiber ring decay cavity, a first photodetector, a second photodetector, and a computing unit; the first fiber is disposed in the first fiber ring decay cavity, and the second fiber is disposed in the second fiber ring decay cavity; The laser output from the laser is split into two beams by the first coupler. One beam enters the first fiber ring decay cavity after passing through the first isolator, and the other beam enters the second fiber ring decay cavity after passing through the second isolator. The signals output from the first fiber ring decay cavity and the second fiber ring decay cavity are detected by the first photodetector and the second photodetector, respectively, and then transmitted to the computing unit. The calculation unit is used to perform temperature compensation on the signal detected by the first photodetector based on the signal detected by the second photodetector, and obtain the temperature-compensated static ice pressure.

[0012] The specific method by which the computing unit performs temperature compensation on the signal detected by the first photodetector based on the signal detected by the second photodetector to obtain the temperature-compensated static ice pressure is as follows: based on the ring-down time of the signal detected by the second photodetector, the center wavelength drift of the second fiber grating is obtained to achieve temperature-induced demodulation; it is also used to obtain the center wavelength drift of the first fiber grating () based on the ring-down time of the signal detected by the first photodetector, and combine the temperature change with the static ice pressure to demodulate the static ice pressure to obtain the temperature-compensated static ice pressure.

[0013] The demodulation formula is: ; ; in, Indicates pressure sensitivity. and These represent the temperature sensitivity of the first fiber Bragg grating and the second fiber Bragg grating, respectively. and These represent the center wavelength drift of the first fiber grating and the center wavelength drift of the second fiber grating, respectively.

[0014] The first fiber ring decay cavity includes a second coupler and a third coupler; the first branch port of the second coupler is connected to the output of the first isolator, the second branch port is connected to one end of the first fiber, the other end of the first fiber is connected to the second branch port of the third coupler, the main port of the second coupler is connected to the main port of the third coupler through a single-mode fiber, and the first branch port of the third coupler is connected to the first photodetector. The second fiber ring fading cavity includes a fourth coupler and a fifth coupler; the first branch port of the fourth coupler is connected to the output of the second isolator, the second branch port is connected to one end of the second optical fiber, the other end of the second optical fiber is connected to the second branch port of the fifth coupler, the main port of the fourth coupler is connected to the main port of the fifth coupler through a single-mode optical fiber, and the first branch port of the fifth coupler is connected to the second photodetector.

[0015] Compared with the prior art, the present invention has the following advantages: This invention proposes a static ice pressure temperature compensation sensor and sensing system based on a dual-fiber ring ring cavity. By integrating two fiber gratings into the sensor and combining them with the two fiber gratings using a dual-fiber ring ring cavity structure, the temperature is measured using one of the fiber gratings. Temperature compensation demodulation is then performed on the pressure sensing information based on the temperature, thereby improving the measurement accuracy of static ice pressure. In addition, the sensor in this invention is elongated, which can be applied to the installation requirements of complex or narrow spaces. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a static ice pressure and temperature compensation sensor based on a dual-fiber ring decay cavity provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the elastic diaphragm structure in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the cavity substrate in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the H-shaped base in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the optical path structure of a static ice pressure and temperature compensation sensing system based on a dual-fiber ring decay cavity, provided in Embodiment 2 of the present invention. Figure 6 This is a graph showing the trend of measured stress versus pressure for one of the fiber Bragg gratings in an embodiment of the present invention. Figure 7 This is a graph showing the trend of the center wavelength of the first fiber optic grating as a function of pressure in an embodiment of the present invention. Figure 8 The curves showing the relationship between the center wavelength of the first and second fiber gratings and temperature under stress-free conditions in this embodiment of the invention are shown. Figure 9 This is a schematic diagram of the temperature error obtained by measuring two fiber optic gratings in different temperature ranges in an embodiment of the present invention; In the figure, 1 is an H-shaped base, 2 is a protrusion, 3 is an elastic diaphragm, 4 is a first fiber grating (FBG), 5 is a first long slot, 6 is a first optical fiber, 7 is a cavity substrate, 8 is a second long slot, 9 is a second fiber grating, 10 is a second optical fiber, 11 is a laser, 12 is a first coupler, 13 is a first isolator, 14 is a second isolator, 15 is a first fiber ring attenuation cavity, 16 is a second fiber ring attenuation cavity, 17 is a first photodetector, 18 is a second photodetector, 19 is an oscilloscope, 20 is a second coupler, 21 is a third coupler, 22 is a fourth coupler, and 23 is a fifth coupler. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 like Figures 1-4 As shown, Embodiment 1 of the present invention provides a static ice pressure temperature compensation sensor based on a dual-fiber annular ring decay cavity, comprising: a cavity substrate 7, an H-shaped base 1 disposed on the bottom surface of the cavity substrate 7, a first long groove 5 and a second long groove 8 disposed on the upper and lower surfaces of the H-shaped base 1 respectively, a first optical fiber 6 disposed in the first long groove, a second optical fiber 10 disposed in the second long groove 8, an elastic diaphragm 3 for sealing the cavity disposed on the upper surface of the cavity substrate 7, a protrusion 2 disposed at the bottom of the elastic diaphragm 3, a first fiber grating 4 and a second fiber grating 9 disposed on the first optical fiber 6 and the second optical fiber 10 respectively, the first fiber grating 4 being fixedly connected to the protrusion 2, and the second fiber grating 9 being fixedly connected to the second long groove 8; the two ends of the first optical fiber 6 and the second optical fiber 10 are led out from the two end sidewalls of the cavity substrate 7 and respectively connected to an optical fiber annular ring decay cavity.

[0019] Specifically, such as Figure 3 As shown, in this embodiment, the H-shaped base 1 is elongated, with its external dimensions smaller than the cavity within the cavity base 7. Its length is along the length of the cavity base 7 and located at the center of the cavity base 7. The first elongated groove 5 and the second elongated groove 8 are arranged along the length of the cavity base 7; the depth of the first elongated groove 5 and the second elongated groove 8 is 0.1~0.3 mm. Figure 2 As shown, in this embodiment, the length and width of the elastic diaphragm 3 are consistent with those of the cavity substrate 7.

[0020] Furthermore, in this embodiment, the length and width of the H-shaped base 1 can be set to be the same as the length and width of the cavity inside the cavity base 7, so that the H-shaped base 1 maintains close contact with the inner wall of the cavity base 7. Additionally, the H-shaped base 1 can be integrally formed with the cavity base 7.

[0021] Specifically, in this embodiment, the material of the elastic diaphragm 3 is 304 stainless steel; the diaphragm 3 and the protrusion 2 can be integrally formed from 304 stainless steel, which not only has a high elastic limit and excellent fatigue strength, with a tensile strength of up to 625.55 MPa and a yield strength of 263.80 MPa, but also has a very small hysteresis effect that can effectively reduce measurement hysteresis error.

[0022] Specifically, in this embodiment, the elastic diaphragm 3 has a length of 60-90 mm, a width of 20-40 mm, and a thickness of 0.5-0.8 mm. The protrusion 2 is circular and located at the center of the cavity substrate 7, with a radius of 8-15 mm and a thickness of 0.3-0.5 mm, ensuring uniform stress distribution and optimal sensitivity. This layered design of the elastic diaphragm 3 and the protrusion 2 can concentrate the originally uniformly distributed stress at the protrusion, while optimizing the stress-bearing area.

[0023] Specifically, in this embodiment, the cavity substrate 7 is made of high-strength resin material and is integrally formed by 3D printing, which ensures both structural stability and precision protection. The synergistic effect of the above components enables the fiber optic grating 4 to respond only to static ice pressure—maintaining maximum measurement sensitivity and significantly enhanced long-term stability even under complex operating conditions.

[0024] To ensure the repeatability of the elastic diaphragm 3, the maximum deflection of the elastic diaphragm 3 shall not exceed the thickness of the diaphragm. The parameters of the elastic diaphragm 3 can be derived from formula (1).

[0025] (1) In the above formula, P is the pressure; R is the working radius of the diaphragm; E is the elastic modulus of the elastic diaphragm material; and μ is the Poisson's ratio of the elastic diaphragm material. Let be the displacement of the center of the elastic diaphragm; h be the thickness of the elastic diaphragm. The Poisson's ratio μ for the metallic material is 0.3. Substituting these values ​​into the formula, the thickness of the elastic diaphragm 3 is obtained as follows: , The value range is the film thickness. To ensure that no plastic deformation occurs within the maximum side surface area, the pressure value should be 1 to 2 times the maximum measured value. Since the elastic diaphragm 3 is rectangular, an equivalent formula is derived based on the circular thin-plate theory, and the elongated diaphragm is designed as an equivalent circular diaphragm; the formula of the small deflection bending theory of circular thin plates is referenced. The elastic modulus of the elastic diaphragm 3 is 193 GPa. h, P=500kPa, length is 80mm, width is 30mm, and substituting into the formula, we get the thickness of elastic diaphragm 3 as h=0.52mm, the radius of the protrusion is 10mm, and the thickness as h=0.42mm.

[0026] Specifically, in this embodiment, the elastic diaphragm 3 has a length of 80 mm, a width of 30 mm, and a thickness of 0.52 mm. The protrusion 2 has a thickness of 0.42 mm and a radius of 10 mm.

[0027] Specifically, in this embodiment, the width of the first long slot 5 and the second long slot 8 are comparable to those of the optical fiber, and the depth is 0.2 mm. The first long slot 5 and the second long slot 8 can keep the sensitive element, the first fiber grating 4, at a safe distance from other media. The H-shaped base isolates the first fiber grating 4 and the second fiber grating 9, effectively shielding mechanical vibration and ensuring that the second fiber grating 9 is not subjected to static ice pressure and only responds to temperature.

[0028] Specifically, in this embodiment, the center wavelengths of the first fiber grating 4 and the second fiber grating 9 are different.

[0029] In this embodiment, when the sensor encounters static ice pressure, the elastic diaphragm 3 deforms, causing the first fiber optic grating 4 to elongate axially. This change causes an axial shift in the center wavelength of the reflection spectrum of the first fiber optic grating 4, thus affecting the ring-down time. By analyzing the changes in the ring-down time, the static ice pressure can be measured, and its specific magnitude can be obtained. The second fiber optic grating 9, isolated from the first fiber optic grating 4 by the H-shaped base 1, is therefore unaffected by static ice pressure, only by temperature. The temperature can be measured through the second fiber optic grating 9, thereby compensating for the temperature-induced effect on the center wavelength of the first fiber optic grating 4, achieving accurate measurement of static ice pressure.

[0030] In this embodiment, multiple optimizations were made to the sensor's structural design to ensure that the sensor maintains high sensitivity and long-term stability under complex environments. Firstly, a first elongated groove 5 is formed at the bottom of the first fiber Bragg grating 4 via an H-shaped base, creating a physical isolation barrier that completely separates the first fiber Bragg grating 4 from the external medium. This effectively blocks the erosion of external contaminants and avoids interference from accidental mechanical stress, thereby significantly improving the sensor's anti-interference capability. The groove depth is strictly controlled within the range of 0.1 to 0.3 mm to ensure sufficient isolation without affecting the overall compactness of the sensor.

[0031] Example 2 like Figure 5 As shown, Embodiment 2 of the present invention provides a static ice pressure and temperature compensation sensing system based on a dual-fiber ring ring decay cavity, including the static ice pressure and temperature compensation sensor based on a dual-fiber ring ring decay cavity described in Embodiment 1, and further including a laser 11, a first coupler 12, a first isolator 13, a second isolator 14, a first fiber ring decay cavity 15, a second fiber ring decay cavity 16, a first photodetector 17, a second photodetector 18, and a computing unit; the first fiber 6 is disposed in the first fiber ring decay cavity 15, and the second fiber 10 is disposed in the second fiber ring decay cavity 16.

[0032] In this embodiment, the laser output from the laser 11 is split into two beams by the first coupler 12. One beam enters the first fiber ring attenuation cavity 15 after passing through the first isolator 13, and the other beam enters the second fiber ring attenuation cavity 16 after passing through the second isolator 14. The signals output from the first fiber ring attenuation cavity 15 and the second fiber ring attenuation cavity 16 are detected by the first photodetector 17 and the second photodetector 18, respectively, and then transmitted to the computing unit. The computing unit is used to perform temperature compensation on the signal detected by the first photodetector 17 based on the signal detected by the second photodetector 18, and obtain the temperature-compensated static ice pressure.

[0033] Specifically, such as Figure 5 As shown, in this embodiment, the first fiber ring fading cavity 15 includes a second coupler 21 and a third coupler 22; the first branch port of the second coupler 21 is connected to the output end of the first isolator 13, the second branch port is connected to one end of the first fiber 6, the other end of the first fiber 6 is connected to the second branch port of the third coupler 22, the main port of the second coupler 21 is connected to the main port of the third coupler 22 through a single-mode fiber, and the first branch port of the third coupler 22 is connected to the first photodetector 17; Specifically, such as Figure 5 As shown, in this embodiment, the second fiber ring fading cavity 16 includes a fourth coupler 23 and a fifth coupler 24; the first branch port of the fourth coupler 23 is connected to the output end of the second isolator 14, the second branch port is connected to one end of the second fiber 10, the other end of the second fiber 10 is connected to the second branch port of the fifth coupler 24, the main port of the fourth coupler 23 is connected to the main port of the fifth coupler 24 through a single-mode fiber, and the first branch port of the fifth coupler 24 is connected to the second photodetector 18.

[0034] Specifically, in this embodiment, the splitting ratio of the two split ports of the first coupler 12 is 50:50; the splitting ratio of the first split port and the second split port of the second coupler 21, the third coupler 22, the fourth coupler 23, and the fifth coupler 24 is 10:90.

[0035] In this embodiment, laser 11 is a pulsed laser with a broadband optical signal in the 1550 nm band. The center wavelength of the first fiber grating 4 is λ1 = 1550 nm, and the center wavelength of the second fiber grating 9 is λ2 = 1550.5 nm. The pulsed laser output from laser 11 enters the first fiber ring attenuation cavity 15 and the second fiber ring attenuation cavity 16 via the second coupler 21 and the fourth coupler 23, respectively. The second fiber grating 9 in the second fiber ring attenuation cavity 16 is almost unaffected by pressure. By synchronously triggering laser pulses and acquiring the attenuation intensity curves of the two cavities through the first photodetector 17 and the second photodetector 18, the corresponding attenuation times τ1 and τ2 can be extracted to obtain the center wavelength shift of the two fiber gratings.

[0036] When measuring static ice pressure, multiple sets of ring-down pulse peaks can be acquired using an oscilloscope 19. The specific measurement principle is as follows: static ice pressure acts on the elastic diaphragm of the sensor, causing elastic deformation. The measuring grating attached to the diaphragm undergoes axial strain, resulting in a shift in the center wavelength of the measuring grating. This wavelength shift causes a change in the ring-down time of the fiber optic ring-down cavity. To obtain the ring-down time, a peak-finding algorithm is used to process the acquired pulse peaks and accurately identify each peak. Then, an exponential function is used to fit all peak data points. Since the ring-down process exhibits a single exponential decay characteristic, the fitting process outputs the corresponding result, thus obtaining the ring-down time. Subsequently, the temperature and stress demodulation are achieved using the ring-down time.

[0037] Specifically, in this embodiment, the calculation unit performs temperature compensation on the signal detected by the first photodetector 17 based on the signal detected by the second photodetector 18 to obtain the temperature-compensated static ice pressure. The specific method is as follows: based on the decay time of the signal detected by the second photodetector 18, the center wavelength drift of the second fiber grating 9 is obtained to achieve temperature-induced demodulation; it is also used to obtain the center wavelength drift of the first fiber grating 4 based on the decay time of the signal detected by the first photodetector 17, and combine the temperature change with the static ice pressure to demodulate the static ice pressure to obtain the temperature-compensated static ice pressure.

[0038] Wherein: the demodulation formula is: ; (2) ; (3) in, Indicates pressure sensitivity. and These represent the temperature sensitivity of the first fiber grating 4 and the second fiber grating 9, respectively. and These represent the center wavelength drift of the first fiber grating 4 and the center wavelength drift of the second fiber grating 9, respectively.

[0039] The temperature compensation principle of this invention is described below.

[0040] The decay time in an optical fiber ring cavity can be expressed as: (4) Where L is the geometric length of the fiber ring cavity, n represents the fixed refractive index of the fiber, c is the speed of light, and A is the inherent loss of the ring cavity. Indicates the inherent decay time.

[0041] When a sensor is connected to an optical fiber loop, an additional loss B is introduced into the loop. The light intensity can be written as: ; (5) This is the light intensity value. Let be the initial intensity of the output optical pulse signal. The ring-down time can be obtained from formula (5): (6) Combining formulas (4) and (6), the principle of the annular ring-down cavity can be expressed as: (7) When the FBG is subjected to pressure, the center wavelength will change. The offset, at which point the additional loss of the device is We can obtain: (8) Similarly, when FBG is affected by temperature, we can obtain: (9) in, and These represent coefficients related to pressure and temperature, respectively. Therefore, after calibrating these coefficients, the decay time can be measured. Determine the center wavelength offset of the FBG .

[0042] When the ring-down times of the two fiber ring cavities are measured, the center wavelength drift of the first fiber grating 4 can be determined by combining formulas (8) and (9). The center wavelength drift of the second fiber grating 9 and Substituting into formulas (2) and (3), the temperature and static ice pressure can be demodulated. Moreover, the static ice pressure obtained by demodulation achieves temperature compensation, which improves the measurement accuracy.

[0043] In addition, before the formal measurement, the sensitivity coefficients in formulas (2) and (3) need to be calibrated. , and For pressure sensitivity calibration, firstly, in a constant temperature environment, a stepped static ice pressure (in 50 kPa increments) within the range of 0–500 kPa was applied to the sensor; then, the decay time of the first fiber ring decay cavity at each pressure point was recorded. Simultaneously, the center wavelength of the first fiber grating is calibrated using a spectrometer or other instruments to obtain the center wavelength offset of the first FBG. ; final fitting The linear relationship between the pressure P and the pressure sensitivity is represented by the slope. Furthermore, the pressure coefficient Kp can be obtained by fitting the relationship between the ring-down time and the center wavelength shift under pressure conditions using equation (8). For temperature sensitivity calibration, in a pressureless environment, the sensor is placed in a temperature-controlled chamber of -25℃ to 5℃ (in 5℃ increments), and each temperature point is kept at that temperature for 30 minutes. The ring-down time of the dual-ring-down cavity at each temperature point is recorded. , Simultaneously, the center wavelengths of the two fiber gratings are calibrated using a spectrometer or other instruments, and the center wavelength offset of the two fiber gratings is calculated. , Finally, they were fitted separately. , and The linear relationship, the slope of which is the sensitivity. and Furthermore, the temperature coefficient K can be obtained by fitting the relationship between the ring-down time and the center wavelength shift under temperature variation conditions using equation (9). T .

[0044] During the actual measurement process, the decay time of the dual-decay cavity was acquired in real time. , Demodulation is achieved through formulas (8) and (9) , The temperature change is calculated from the second FBG data using formula (3), and the pressure after temperature compensation is calculated from the first FBG data using formula (2).

[0045] The pressure and sensitivity coefficients of the two FBGs should meet the following requirements: (10) During specific measurements, the sensor is fixed to the surface of the ice layer to be measured, ensuring that the elastic diaphragm 3 is in close contact with the contact surface to eliminate the influence of air gaps on pressure transmission. The orientation of the cavity substrate 7 is finely adjusted to ensure that the optical axes of the first fiber grating 4 and the second fiber grating 9 are aligned with the principal component of the ice layer pressure, thereby maximizing the sensitivity of strain detection. The decay time of the two fiber gratings is extracted by collecting the decay pulse peaks in the two fiber ring decay cavities. , ) to obtain the center wavelength offset ( , Based on this, a sensitivity matrix equation is established. By inverting the matrix, the mixed response can be separated into independent pressure components; then, combined with the pre-calibrated sensitivity coefficients and formulas (2) to (3), the static ice pressure is accurately calculated. Finally, the temperature drift error is dynamically corrected in the algorithm, and the final pressure data after temperature compensation is output.

[0046] Figure 6 and Figure 7The values ​​represent the trends of strain and center wavelength of the FBG as a function of applied pressure, respectively. This experiment was conducted by applying a vertical unidimensional force ranging from 0 kPa to 500 kPa in 50 kPa increments above the elastic diaphragm 1, and recording the diaphragm displacement. Figure 6 It can be seen that strain and pressure have a highly linear relationship; from Figure 5 It can be seen that the center wavelength of the FBG exhibits a good linear relationship with the pressure. Further fitting of this data to the relationship between strain, wavelength, and pressure, as shown in the figure, not only verifies the theoretical analysis results such as the diaphragm center displacement, but also provides a basis for predicting the sensor's mechanical response, stability, service life, and fatigue strength, thus helping to optimize sensor design and improve performance.

[0047] Furthermore, to analyze the adaptability of the pressure sensor to temperature variations, temperature compensation performance tests were conducted. The unloaded sensor was placed in a constant temperature environment, with the test temperature range set from -25℃ to 5℃, and gradient control was performed in 5℃ increments. Each temperature node was maintained in a stable state for 30 minutes to ensure that the device reached sufficient thermal equilibrium, and the center wavelength data of the dual FBGs were collected simultaneously. Figure 8 The temperature-sensitive characteristics of the two FBG devices without temperature correction are demonstrated. Figure 9 The results show the measurement deviations of the two FBG devices in different temperature regions. Experimental data shows that under zero pressure, the temperature sensitivity coefficients of the first fiber grating 4 and the second fiber grating 9 are 7.75 pm / ℃ and 7.56 pm / ℃, respectively. Their linear fits are 0.9900 and 0.9902, respectively, showing a high linear correlation, which lays the foundation for constructing a temperature compensation model. It is worth noting that the temperature sensitivity response of the first fiber grating 4 is slightly higher than that of the second fiber grating 9. This difference is mainly due to the additional stress caused by the thermal expansion effect of the material. Due to the difference in thermal properties between the square diaphragm and the substrate material, the dual FBGs experience asymmetric thermal strain. Therefore, temperature compensation is performed using a dual-fiber ring-wavelength matrix method.

[0048] In summary, the static ice pressure temperature compensation sensor based on a dual-fiber ring ring decay cavity proposed in this invention has significant advantages in terms of measurement range, detection sensitivity, anti-interference capability, structural design, and reliability. Based on the FBG pressure sensing principle, it can accurately measure static ice pressure, ensuring data accuracy and stability. Its measurement range is wide, covering 0 kPa to 500 kPa, suitable for different environments and operating conditions, meeting various application needs. Furthermore, to further improve measurement accuracy, this invention employs a temperature compensation method based on a dual-wavelength matrix. Since changes in ambient temperature may affect the measurement results of the FBG sensor, this invention utilizes dual-wavelength matrix technology to compensate for temperature drift in real time, effectively eliminating temperature interference with the measurement data and ensuring high accuracy and reliability of pressure measurement. This temperature compensation strategy not only enhances the sensor's adaptability but also enables it to operate stably under harsh climatic conditions, making it particularly suitable for static ice pressure monitoring in low-temperature environments. At the same time, the sensor has a simple structural design, relatively simple manufacturing process, facilitates large-scale production and subsequent maintenance, and has a long service life and high stability. With its superior anti-interference capabilities, the sensor effectively resists the influence of external environmental factors on measurement results, further improving data reliability. Therefore, this sensor can be widely used in key areas such as dam engineering and hydropower projects in cold regions for static ice pressure monitoring and early warning, demonstrating extremely broad application prospects. Combining its accurate measurement, temperature compensation capabilities, and strong adaptability, this sensor possesses high competitiveness in the field of static ice pressure detection and provides reliable technical support for research and engineering applications in related fields.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A static ice pressure and temperature compensation sensor based on a dual-fiber annular ring-attenuation cavity, characterized in that, include: A cavity substrate (7) is provided with an H-shaped base (1) on its bottom surface. The upper and lower surfaces of the H-shaped base (1) are respectively provided with a first long groove (5) and a second long groove (8). A first optical fiber (6) is provided in the first long groove and a second optical fiber (10) is provided in the second long groove (8). An elastic diaphragm (3) for sealing the cavity is provided on the upper surface of the cavity substrate (7). A protrusion (2) is provided at the bottom of the elastic diaphragm (3). A first fiber grating (4) and a second fiber grating (9) are respectively provided on the first optical fiber (6) and the second optical fiber (10). The first fiber grating (4) is fixedly connected to the protrusion (2), and the second fiber grating (9) is fixedly connected to the second long groove (8). The two ends of the first optical fiber (6) and the second optical fiber (10) are led out from the two ends of the cavity substrate (7) and respectively connected to an optical fiber ring decay cavity.

2. The static ice pressure and temperature compensation sensor based on a dual-fiber annular ring decay cavity according to claim 1, characterized in that, The cavity substrate (7) is elongated, and the first long groove (5) and the second long groove (8) are arranged along the length of the cavity substrate (7); the depth of the first long groove (5) and the second long groove (8) is 0.1 ~ 0.3 mm.

3. The static ice pressure and temperature compensation sensor based on a dual-fiber annular ring decay cavity according to claim 1, characterized in that, The length and width of the H-shaped base (1) are the same as the length and width of the cavity inside the cavity base (7).

4. The static ice pressure and temperature compensation sensor based on a dual-fiber annular ring decay cavity according to claim 1, characterized in that, The protrusion (2) is circular and is located at the center of the cavity base (7), with a radius of 8 to 15 mm and a thickness of 0.3 to 0.5 mm.

5. A static ice pressure and temperature compensation sensor based on a dual-fiber annular ring-wake cavity according to claim 1, characterized in that, The elastic diaphragm (3) is made of 304 stainless steel; The elastic diaphragm (3) has a length of 60-90 mm, a width of 20-40 mm, and a thickness of 0.5-0.8 mm.

6. The static ice pressure and temperature compensation sensor based on a dual-fiber annular ring decay cavity according to claim 1, characterized in that, The center wavelengths of the first fiber grating (4) and the second fiber grating (9) are different.

7. A static ice pressure and temperature compensation sensing system based on a dual-fiber ring decay cavity, characterized in that, The static ice pressure temperature compensation sensor based on a dual-fiber ring ring cavity as described in claim 1 further includes a laser (11), a first coupler (12), a first isolator (13), a second isolator (14), a first fiber ring ring cavity (15), a second fiber ring ring cavity (16), a first photodetector (17), a second photodetector (18), and a computing unit; the first fiber (6) is disposed in the first fiber ring ring cavity (15), and the second fiber (10) is disposed in the second fiber ring ring cavity (16); The laser output from the laser (11) is split into two beams by the first coupler (12). One beam enters the first fiber ring attenuation cavity (15) after passing through the first isolator (13), and the other beam enters the second fiber ring attenuation cavity (16) after passing through the second isolator (14). The signals output from the first fiber ring attenuation cavity (15) and the second fiber ring attenuation cavity (16) are respectively detected by the first photodetector (17) and the second photodetector (18) and then transmitted to the computing unit. The calculation unit is used to perform temperature compensation on the signal detected by the first photodetector (17) based on the signal detected by the second photodetector (18) to obtain the static ice pressure after temperature compensation.

8. The static ice pressure and temperature compensation sensing system based on a dual-fiber ring decay cavity according to claim 7, characterized in that, The specific method for the calculation unit to perform temperature compensation on the signal detected by the first photodetector (17) based on the signal detected by the second photodetector (18) to obtain the temperature-compensated static ice pressure is as follows: the center wavelength drift of the second fiber grating (9) is obtained based on the decay time of the signal detected by the second photodetector (18) to achieve temperature-induced demodulation; it is also used to obtain the center wavelength drift of the first fiber grating (4) based on the decay time of the signal detected by the first photodetector (17), and combine the temperature change with the static ice pressure to demodulate the static ice pressure to obtain the temperature-compensated static ice pressure.

9. A static ice pressure and temperature compensation sensing system based on a dual-fiber ring decay cavity according to claim 8, characterized in that, The demodulation formula is: ； ； in, Indicates pressure sensitivity. and These represent the temperature sensitivities of the first fiber grating (4) and the second fiber grating (9), respectively. and These represent the center wavelength drift of the first fiber grating (4) and the center wavelength drift of the second fiber grating (9), respectively.

10. A static ice pressure and temperature compensation sensing system based on a dual-fiber annular ring decay cavity according to claim 8, characterized in that, The first fiber ring decay cavity (15) includes a second coupler (20) and a third coupler (21); the first branch port of the second coupler (20) is connected to the output end of the first isolator (13), the second branch port is connected to one end of the first fiber (6), the other end of the first fiber (6) is connected to the second branch port of the third coupler (21), the main port of the second coupler (20) is connected to the main port of the third coupler (21) through a single-mode fiber, and the first branch port of the third coupler (21) is connected to the first photodetector (17); The second fiber ring decay cavity (16) includes a fourth coupler (23) and a fifth coupler (24); the first branch port of the fourth coupler (23) is connected to the output end of the second isolator (14), the second branch port is connected to one end of the second fiber (10), the other end of the second fiber (10) is connected to the second branch port of the fifth coupler (24), the main port of the fourth coupler (23) is connected to the main port of the fifth coupler (24) through a single-mode fiber, and the first branch port of the fifth coupler (24) is connected to the second photodetector (18).

Images