A high-sensitivity temperature sensor and modulation method and system thereof

Abstract

The present invention provides a high-sensitivity temperature sensor and its modulation method and system, including erbium-doped fiber EDF and coreless fiber CLF, the two ends of the erbium-doped fiber EDF are fused and cascaded with the coreless fiber CLF; and the other end of each coreless fiber CLF away from the erbium-doped fiber EDF is fused and cascaded with the single-mode fiber SMF; the two coreless fiber CLFs are of equal length and have a linear relationship with the length of the erbium-doped fiber EDF; the interference intensity between the core mode and / or cladding mode of each single-mode fiber SMF, coreless fiber CLF and erbium-doped fiber EDF is positively correlated with the effective refractive index difference between the core mode and / or cladding mode. In order to solve the problems of insufficient sensitivity, great difficulty in design and debugging, and limited application range of traditional temperature and curvature sensors, the present invention uses Er in EDF to generate a high-sensitivity temperature sensor. 3+ The characteristics of ions achieve a temperature sensitivity of up to 0.415dB / ℃ in the temperature range of 24℃ to 40℃ and a ‑1 ‑6.469dB / m within the curvature range ‑1 The curvature sensitivity of the nanostructured carbon nanotubes has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a high-sensitivity temperature sensor and a modulation method and system thereof. Background Art

[0002] Fiber optic sensors detect changes in physical quantities or environmental parameters by sensing changes in optical signals.

[0003] Compared with traditional sensors, fiber optic sensors have the characteristics of strong anti-electromagnetic interference ability, high measurement accuracy, miniaturization and high durability. In recent years, the research on fiber optic sensors has made extensive development and has excellent performance, and is used in aerospace, environmental monitoring, medical and other fields.

[0004] At present, it is known that a variety of optical fiber sensor structures have been proposed to detect temperature and curvature, such as peanut-shaped structure, side-polished type, spherical, conical structure and sensor based on Mach-Zehnder interferometer (MZI) structure. Among them, MZI sensor has high sensitivity, simple structure, excellent anti-environmental interference ability, and can be better put into practical application.

[0005] Erbium-doped fiber is a special type of optical fiber in which erbium ions (Er 3+ ), erbium ion is one of the rare earth ions, with high gain characteristics in the 1550 nanometer wavelength range. In fiber optic sensors, erbium-doped fiber can be used to measure temperature, pressure, strain and chemical parameters.

[0006] Currently, fiber optic sensors are designed for specific applications. The design and implementation of high-precision temperature curvature sensors involve complex optical, electronic, and signal processing technologies, which undoubtedly increases the difficulty of design and debugging, and also limits its applicability in other scenarios.

[0007] Based on this, the present invention proposes to cascade erbium-doped fiber and coreless fiber to form a sensing system in a fiber MZI structure, and realize the sensing characteristics of erbium-doped fiber through its advantages of high sensitivity, good linearity and simple structure. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention aims to provide a high-sensitivity temperature sensor and its modulation method and system, which form a Mach-Zehnder interferometer MZI through a cascade structure, realize high-sensitivity temperature and curvature detection capabilities, and have the characteristics of simple structure, low cost, strong anti-interference ability and miniaturization, so that it has broad application prospects in the fields of industrial manufacturing, aerospace and environmental monitoring. Solve the problems raised in the above background technology.

[0009] In order to achieve the above object, the present invention is implemented through the following technical solution: a high-sensitivity temperature sensor, comprising:

[0010] Erbium-doped fiber EDF and coreless fiber CLF, among which,

[0011] The two ends of the erbium-doped optical fiber EDF are fused and cascaded with the coreless optical fiber CLF to achieve light splitting or coupling; and the other end of each coreless optical fiber CLF away from the erbium-doped optical fiber EDF is fused and cascaded with the single-mode optical fiber SMF to achieve optical signal input and output;

[0012] The two sections of coreless optical fiber CLF are of equal length and have a linear relationship with the length of the erbium-doped optical fiber EDF; this determines the sensitivity and measurement range of the sensor;

[0013] The interference intensity between the core modes and / or cladding modes of the single-mode optical fiber SMF, coreless optical fiber CLF and erbium-doped optical fiber EDF is positively correlated with the effective refractive index difference between their core modes and / or cladding modes, so as to realize accurate sensing of the optical signal.

[0014] As a second aspect of the present invention, a high-sensitivity temperature sensor modulation method is proposed, comprising the following steps:

[0015] Temperature response characteristic test: the temperature of the sensor is controlled by a constant temperature box, the temperature is gradually lowered, and the changes in the transmission spectrum are recorded. Then, the response of the transmission spectrum to temperature changes is analyzed to evaluate the sensitivity of the sensor to temperature changes.

[0016] Curvature response characteristic test: Use the curvature measurement platform to apply different curvatures to the sensor, record the corresponding displacement changes, observe and analyze the impact of the curvature change on the sensor transmission spectrum, obtain the change of dip characteristics and wavelength shift in the sensor transmission spectrum, and evaluate the sensor's response characteristics to curvature changes;

[0017] Performance optimization,Based on the above test results, the length and structure of the optical fiber are adjusted to optimize the performance of the sensor and ensure that it can provide stable and accurate measurement results under different environmental conditions.

[0018] As a third aspect of the present invention, a high-sensitivity temperature sensor modulation system is provided, comprising:

[0019] At least one processor and a memory that establishes an information interaction channel with at least one of the processors, wherein:

[0020] Each of the memories stores a computer program executable by at least one of the processors;

[0021] The computer program is executed by at least one of the processors to enable the at least one of the processors to execute the high-sensitivity temperature sensor and / or the modulation method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In order to solve the problems of insufficient sensitivity, great difficulty in design and debugging, and limited application range of traditional temperature and curvature sensors, the present invention proposes a new type of high-sensitivity sensor based on Mach-Zehnder interferometer (MZI) composed of erbium-doped fiber EDF cascaded coreless fiber CLF. 3+ The characteristics of ions achieve a temperature sensitivity of up to 0.415dB / ℃ in the temperature range of 24℃ to 40℃ and a -1 Reach -6.469dB / m within the curvature range -1 The advantages of excellent curvature sensitivity and high linearity make the present invention have broad application prospects in the fields of industrial manufacturing, aerospace and environmental monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The disclosure of the present invention is described with reference to the accompanying drawings. It should be understood that the drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings, the same reference numerals are used to refer to the same components. Among them:

[0025] Figure 1 It is a structural schematic diagram of a high-sensitivity temperature sensor proposed in one embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the sensor transmission spectrum when the length of the erbium-doped fiber EDF is fixed at 3 cm and the length of the coreless fiber CLF is 10 mm, 12 mm, and 15 mm respectively, as proposed in one embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the influence on the sensor performance when the length of the coreless fiber CLF is fixed at 1.2 cm and the lengths of the erbium-doped fiber EDF are 2 cm, 3 cm, and 4 cm respectively, as proposed in one embodiment of the present invention;

[0028] Figure 4 A schematic diagram of the structure of an experimental device for a high-sensitivity temperature sensor measurement and modulation system proposed in one embodiment of the present invention;

[0029] Figure 5 It is a schematic diagram of evaluating the response characteristics of a sensor to temperature at 24° C. to 40° C. proposed in one embodiment of the present invention;

[0030] Figure 6 It is a schematic diagram of the structure of a curvature measurement platform proposed in one embodiment of the present invention;

[0031] Figure 7 When the curvature changes from 0m -1Change to 0.30036m -1 Schematic diagram of evaluating the sensor's response characteristics to curvature changes. DETAILED DESCRIPTION

[0032] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the present invention.

[0033] The present invention is further described in detail below with reference to the accompanying drawings, but is not intended to limit the present invention.

[0034] As an understanding of the technical concept and implementation principle of the present invention, the high-sensitivity temperature sensor modulation method proposed in the present invention is mainly aimed at solving the problems of insufficient sensitivity, great difficulty in design and debugging, and limited application range of traditional temperature and curvature sensors.

[0035] Therefore, the present invention is a novel high-sensitivity sensor based on Mach-Zehnder interferometer (MZI) composed of erbium-doped fiber EDF cascaded coreless fiber CLF, by utilizing Er in EDF 3+ The characteristics of ions achieve a temperature sensitivity of up to 0.415dB / ℃ in the temperature range of 24℃ to 40℃ and a -1 Reach -6.469dB / m within the curvature range -1 The advantages of excellent curvature sensitivity and high linearity make the present invention have broad application prospects in the fields of industrial manufacturing, aerospace and environmental monitoring.

[0036] When implementing it, Figure 1 As shown, as an embodiment of the present invention, a high-sensitivity temperature sensor is proposed, including an erbium-doped fiber EDF and a coreless fiber CLF, wherein two ends of the erbium-doped fiber EDF are fused and cascaded with the coreless fiber CLF to achieve light splitting or coupling; and the other end of each section of the coreless fiber CLF away from the erbium-doped fiber EDF is fused and cascaded with the single-mode fiber SMF to achieve optical signal input and output.

[0037] It should be noted that the two sections of coreless optical fiber CLF are of equal length, and the length of the erbium-doped optical fiber EDF satisfies a linear relationship, the purpose of which is to determine the sensitivity and measurement range of the sensor; at the same time, the interference intensity between the core mode and / or cladding mode of each single-mode optical fiber SMF, coreless optical fiber CLF and erbium-doped optical fiber EDF is positively correlated with the effective refractive index difference between their core mode and / or cladding mode, so as to achieve accurate sensing of optical signals.

[0038] It can be understood that the interference intensity proposed in the present invention is generated by the mutual interference of light in the core mode and the cladding mode. This interference effect depends on the phase difference between the two modes, and the phase difference is caused by the optical path difference of light propagating in two different modes, that is, the optical path difference is related to the propagation constant of the light wave in the optical fiber (related to the refractive index). Therefore, when the effective refractive index difference increases, the phase difference will also change accordingly, causing the interference pattern (that is, the interference intensity) to change. This change can be detected by the output end of the interferometer, so it can be used to measure the changes in the refractive index. These changes may be caused by temperature, pressure, curvature or other environmental factors.

[0039] In sensors, erbium-doped fiber (EDF) has a special Er 3+ Ion doping is sensitive to temperature, which makes it advantageous in temperature sensing. Since coreless fiber (CLF) lacks a core, light mainly propagates in the cladding, and its effective refractive index is greatly affected by environmental conditions. Single-mode fiber (SMF) provides a stable reference optical path, and the effective refractive index difference between its core and cladding is relatively stable.

[0040] In one embodiment of the present invention, the proposed high-sensitivity temperature sensor is designed and constructed by a fiber optic fusion splicer, such as FFS, Furukawa S178C. During specific implementation, the manufacturing process is as follows: first, the coating layer of the optical fiber is stripped off, a certain length of EDF and two sections of CLF of the same length are selected, and the two sections of CLF are respectively welded at both ends of the EDF using a fusion splicer, and then SMF is welded at both ends of the CLF to complete the preparation of the proposed sensor.

[0041] It can be understood that the sensor is composed of a single-mode optical fiber SMF, an erbium-doped optical fiber EDF and a coreless optical fiber CLF, forming a structure constructed by sequentially fusion-joining SMF-CLF-EDF-CLF-SMF, wherein the single-mode optical fiber SMF, as the input and output end of the sensor, provides the input of optical signals and receives output signals; the coreless optical fiber CLF1, connected after the SMF, plays the role of splitting and diverging the light beam. After the light beam passes through the SMF and enters the CLF1, since the CLF1 has only a cladding but no core, the light beam is The erbium-doped fiber EDF is located after CLF1 and serves as the sensing area. Part of the input light enters the core of the EDF, and the rest of the light is transmitted through the cladding of the EDF, exciting higher-order modes and enhancing the energy of the cladding mode. Coreless fiber CLF2 is located after the EDF and plays a coupling role. After the light propagates in the CLF2, the cladding mode light is recoupled into the core at the fusion point of CLF2 and SMF. The single-mode fiber SMF, as the other end of the sensor, receives the optical signal after coupling by CLF2.

[0042] It should be noted that, based on the influence of optical fiber on energy concentration and interference spectrum intensity, in order to make the high-order mode of the sensor stronger and higher in order and improve the sensitivity of the sensor, the length of the coreless optical fiber CLF proposed in the present invention is 10mm~15mm, and the length of the erbium-doped optical fiber EDF is 2cm~4cm, forming MZI. At the same time, the SMF used in practice adopts Corning, SMF-28e, the diameters of the SMF core and cladding are 8.5μm and 125μm respectively, the coating diameter is 250μm, the refractive indexes of the core and cladding of the SMF are 1.4682 and 1.4629 respectively, the CLF only has a cladding with a diameter of 125μm and a refractive index of 1.444, and the diameters of the EDF core and cladding are 5.0μm and 125μm respectively.

[0043] The working principle of the above sensor is as follows: when the input light enters CLF1 through SMF, since there is only cladding in CLF, the light beam is completely diverged in CLF. When passing through EDF, part of the light enters the core of EDF, and the rest of the light is transmitted through the cladding of EDF. The energy of the cladding mode becomes stronger. When the light propagates in CLF2, the cladding mode will be recoupled into the core mode of the core at the fusion point of CLF2 and SMF. Since the effective RI (Refractive Index) of the core and cladding is different, that is, the refractive index is different, the optical path difference between the core and cladding modes forms MZI, forming a transmission spectrum with a stable output distribution at the output end.

[0044] It can be understood that since the CLFs at both ends of the EDF have the function of splitting / coupling, the middle EDF serves as the sensing area. As the temperature changes, the optical path difference between the core mode and the cladding mode will change accordingly because the refractive index of the cladding is greatly affected by temperature, resulting in an interference spectrum shift. Therefore, the measured temperature sensitivity can be obtained by monitoring the displacement.

[0045] As a second aspect of the present invention, a high-sensitivity temperature sensor modulation method is proposed, comprising the steps of:

[0046] S1: Apply the sensing principle and conduct performance test: In specific implementation, since CLF is responsible for beam splitting and coupling, EDF is the sensing part. The input light enters the CLF through the SMF and diverges. Part of the light enters the EDF core, and the rest is transmitted through the cladding to form the core mode and cladding mode. The effective refractive index (RI) of the core and cladding is different, resulting in an optical path difference and forming an MZI interference pattern. Therefore, in this step, the effect of EDFs of different lengths on the sensor performance can be tested, and the interference spectrum can be monitored by a spectrum analyzer:

[0047] S1-1, such as Figure 1As shown, the sensor is based on MZI and is composed of EDF cascaded CLF. Therefore, the intensity of its output light is determined by the interference between the light transmitted in the cladding and the core. When the temperature rises, the refractive index of the optical fiber material will change. The refractive index changes of the cladding and the core are different. The cladding material usually has a large thermal expansion coefficient, so its refractive index changes greatly, while the refractive index change of the core is relatively small. When light is transmitted in the optical fiber, it will be affected by the change of the refractive index, causing the propagation speed and path of the light to change, causing the light beam to split during transmission. Splitting will change the amount of light transmitted in the cladding and the core, resulting in a change in its light intensity, that is, I1 and I2 change in the following formula (1), which in turn causes a change in the interference intensity I.

[0048] Therefore, the present invention stipulates that the interference intensity between the core modes and / or cladding modes of each pair of single-mode optical fibers SMF, coreless optical fibers CLF and erbium-doped optical fibers EDF is positively correlated with the effective refractive index difference between their core modes and / or cladding modes:

[0049]

[0050] Where I1 and I2 represent the light intensity of the core mode and high-order cladding mode propagating in the fiber core, respectively. It should be noted that the core mode (core mode) generally refers to the light mode propagating in the core of an optical fiber. Since the core is the thicker part at the center of the optical fiber and has a higher refractive index than the cladding, light mainly propagates in the core in the core in the core mode. The core mode generally has a higher light intensity, and since the refractive index of the core is higher, the propagation path of light in the core is shorter. When the input light enters the coreless optical fiber (CLF) through the single-mode optical fiber (SMF), the light beam will diverge in the CLF. When this part of the light passes through the erbium-doped optical fiber (EDF), part of the light will enter the core of the EDF to form a core mode, while the other part of the light will be transmitted through the cladding of the EDF to form a cladding mode. The purpose is to form an interference pattern together with the cladding mode of the sensor based on the interferometer principle, so that the sensor can respond to changes in environmental factors such as temperature and curvature; φ is represented by the phase difference between the core mode and the high-order cladding mode; wherein,

[0051]

[0052] Where Δneff is the effective refractive index difference between the core mode and the higher-order cladding mode; L is the interference length; λ is the interference wavelength; the interference wavelength is expressed as:

[0053]

[0054] When m is an integer, the interference intensity is minimum.

[0055] It can be understood that, since the cladding refractive index of the sensor matches the external temperature and the core is not in contact with the outside, the effective refractive index of the cladding mode is not only related to the incident wavelength of the transmitted light, but also to the external temperature, while the effective refractive index of the core mode is only related to the incident wavelength of the transmitted light. Therefore, the present invention stipulates that the effective refractive index between the cladding modes of each single-mode optical fiber SMF, coreless optical fiber CLF and erbium-doped optical fiber EDF satisfies a functional relationship with the incident wavelength of the sensor transmitted light and the external temperature; while the effective refractive index between the core modes only satisfies this functional relationship with the incident wavelength of the transmitted light.

[0056] Specifically, when the external temperature changes, Δneff changes, resulting in a wavelength drift Δλ. The functional relationship satisfied by the effective refractive index, the incident wavelength and the external temperature is:

[0057]

[0058] Where δ represents the thermo-optical coefficient of the optical fiber; k represents the thermal expansion coefficient of the optical fiber; and ΔT represents the temperature change during the measurement process.

[0059] Based on the above technical concept, it should be noted that the change of external temperature affects the wavelength δ and k of the interference spectrum through the thermo-optic effect and the thermal expansion effect. Therefore, the calculation method of the change of external temperature is:

[0060]

[0061] In the formula, Expressed as the rate at which the refractive index changes with temperature; Expressed as the rate at which the fiber length changes with temperature;

[0062] Therefore, it can be seen from the above formula that, compared with ordinary single-mode optical fiber, the sensor structure proposed with erbium-doped optical fiber as the main body has a stronger thermo-optical effect and can effectively improve its temperature sensitivity.

[0063] In one embodiment of the present invention, the CLF is used as a beam splitter and coupler in the designed sensor, such as Figure 2 As shown in the figure, the three curves are the transmission spectra of the sensor when the EDF is in the range of 2cm to 4cm in length and the fixed length is 3cm, and the CLF lengths are 10mm, 12mm, and 15mm respectively. As the part of the splitting / coupling function, the most important thing about CLF is its splitting and coupling capabilities. It can be clearly seen from the figure that when the CLF length is 12mm, the energy is more concentrated than that at 15mm, and the intensity is higher than that at 10mm. Therefore, in order to make the high-order modes of the sensor stronger and of higher order and improve the sensitivity of the sensor, the CLF length is selected to be 12mm.

[0064] At the same time, Figure 3 As shown in FIG. 1 , in order to explore the effect of EDF length on sensor performance, the present invention fixes the CLF (beam splitter / coupler) length to 1.2 cm, and makes sensors with EDF lengths of 2 cm, 3 cm, and 4 cm, respectively, and observes the transmission spectrum of each sensor as shown in FIG. Figure 3 As shown in (a): Figure 3 It can be seen that as the length of EDF increases, the free spectral range (FSR) of the spectrum decreases, which is consistent with theoretical research. By comparing the transmission spectra of the three sensors, it can be found that when the EDF is 3cm, the maximum loss of the spectrum ( / OSNR) is greater than that of the sensors with EDF lengths of 2cm and 4cm, which ensures excellent sensing performance while also having a large FSR. The sensing performance of the sensor is positively correlated with the order of the high-order modes formed by itself, that is, the higher the order of the high-order modes formed in the MZI, the better the performance of the sensor. This is a known theorem. Figure 3 (b) is the FFT frequency domain diagram of the three sensors. It can be clearly seen that compared with the sensors composed of 2cmEDF and 4cmEDF, when the EDF length is 3cm, the high-order mode of the sensor is stronger and has a higher order, which is beneficial to improving the sensitivity of the sensor.

[0065] Based on this, the sensor proposed in the present invention can achieve the optimal performance of the sensor when the CLF length is 1.2 cm and the EDF length is 3 cm, including high sensitivity, a large free spectral range (FSR), excellent temperature and curvature response characteristics, and good linearity. These characteristics make the sensor have potential application prospects in industrial manufacturing, environmental monitoring, aerospace and other fields.

[0066] To further verify the above conclusion, as an embodiment of the present invention, Figures 4 to 6 As shown, continue to modulate the high-sensitivity temperature sensor, that is, the steps are proposed:

[0067] S2, experimental verification of temperature and curvature sensitivity, firstly conduct temperature sensitivity experiment:

[0068] Fix the sensor in a constant temperature box, cool it down from 40℃ to 24℃, and record the changes in the transmission spectrum. The specific implementation steps are:

[0069] S2-1. Use a broadband light source BBS with an output power of 5mw as the input light source, and connect it to an external spectrum analyzer to analyze the transmission spectrum. Straighten the sensor horizontally and fix it in a constant temperature box to avoid being affected by external force or bending. At the same time, set the initial temperature of the constant temperature box to be higher than 40℃ to pave the way for precise temperature control.

[0070] S2-2, temperature control and data acquisition: gradually cool down from above 40℃ in steps of 2℃ until it drops to 24℃. At the same time, during this cooling process, record the change in the transmission spectrum every 2℃ change to obtain the sensor's response data to temperature changes in the range of 24℃ to 40℃: Figure 5 As shown in (a), the change of the transmission spectrum of the sensor at 24-40℃ is shown. Figure 5 The overall trend of dip can be seen in (b). As the temperature increases, the transmission spectrum undergoes a red shift. The fitting curve of the wavelength drift is shown in Figure 5 As shown in (c), its sensitivity is 0.826nm / ℃ and its linearity is 0.997. In addition, from the perspective of intensity, it can be seen that the intensity change is 6.482dB and the intensity increases with the increase of temperature. Figure 5 It can be seen from (b) that the maximum temperature sensitivity of the sensor is 0.415dB / ℃ and the linearity reaches 0.996.

[0071] Therefore, according to the experimental results, it can be obtained that the sensor has a maximum temperature sensitivity of 0.415dB / ℃ and a linearity of 0.996 in the range of 24℃ to 40℃.

[0072] Next, the present invention continues to conduct curvature sensitivity experiments to evaluate the response characteristics of the sensor to curvature changes, such as Figure 6 As shown, the specific implementation steps are:

[0073] S2-3. Place the sensor on the curvature measurement platform, where the optical fiber is fixed on the optical fiber bracket. The curvature of the sensor platform position can be changed by turning the knob. The displacement is represented by x, such as Figure 7 As shown, the dip and linear fitting curves selected for the curvature experiment of the sensor are shown. It can be seen that when the curvature changes from 0m -1 Change to 0.30036m -1 When the sensor dip is reduced by 1.796dB and the wavelength is blue-shifted, the wavelength shifts toward the short-wave direction as the curvature increases. Figure 7 As shown in (c), the sensitivity of the sensor is -2.266nm / m -1 , the linearity is 0.998.

[0074] The calculation formula for different sensor curvatures generated by the knob fixed on the curvature measurement platform is:

[0075]

[0076] In the formula, C represents the curvature; R represents the radius of curvature; X represents the displacement of the curvature measurement platform, and L1 represents the distance between the two curvature measurement platforms;

[0077] Based on this, we can obtain that the maximum curvature sensitivity of the sensor with an EDF length of 3 cm and a CLF length of 1.2 cm is -6.469 dB / ℃, with good linearity and R 2 It is 0.993.

[0078] Based on the above technical concept, it should be noted that the cross sensitivity of the proposed sensor is analyzed because the sensitivity matrix form of curvature and temperature measurement is monitored separately. Therefore, when the external temperature changes, the curvature and external temperature of the sensor proposed in the present invention need to satisfy the relationship matrix of curvature and temperature to accurately distinguish and quantify the response of the sensor to the curvature and temperature changes:

[0079] Given the temperature sensitivity of Dip1, we obtain the temperature sensitivity of another spectrum in the same temperature range and step size, which is Dip2, i.e. K T1 and K T2 In addition, the sensitivities of Dip1 and Dip2, namely KC1 and KC2, are obtained. Therefore, the equation of curvature and temperature can be expressed as:

[0080] ΔR1=K C1 ΔC+K T1 ΔT

[0081] ΔR2=KC2ΔC+K T2 ΔT(7)

[0082] Where ΔR1, KC1 and KT1 are the intensity offset, curvature sensitivity and temperature sensitivity of the first trough in the sensor transmission spectrum; ΔR2, KC2 and KT2 are the offset, curvature sensitivity and temperature sensitivity of the other trough, and are the changes in curvature and temperature around the sensor;

[0083] Get the relationship matrix between curvature and temperature:

[0084]

[0085] It should be noted that in the specific implementation, KC1 is taken as -6.469, K C2 is -5.773, K T1 and K T2 are 0.415 and 0.290 respectively, so the matrix can be derived as:

[0086]

[0087] As an embodiment of the present invention, the following table is a sensitivity comparison table of intensity modulation sensors:

[0088]

[0089]

[0090] It can be understood that when the sensor as a whole uses a CLF length of 1.2 cm and an EDF length of 3 cm, the maximum curvature sensitivity of the sensor is -6.469 dB / ℃, the linearity is very good, and R2 is 0.993. At the same time, the highest temperature sensitivity is 0.415 dB / ℃, and the linearity reaches 0.996, which is the highest among the currently known intensity-modulated temperature sensors. In addition, the present invention uses a special optical fiber EDF to explore the sensing characteristics of EDF, and at the same time has good curvature sensitivity and a wide sensing range, within the range of 0-0.30036 m. -1 The highest curvature sensitivity in the range is -6.469dB / ℃, and the linearity is 0.993. These parameters can illustrate that the sensor has the advantages of simple structure, low cost, high temperature sensitivity, wide detection range of curvature sensitivity, and high linearity, and has potential application prospects in the field of sensing.

[0091] As a third aspect of the present invention, a high-sensitivity temperature sensor modulation system is proposed, comprising at least one processor and a memory that establishes an information interaction channel with the at least one processor, wherein each memory stores a computer program that can be executed by the at least one processor; the computer program is executed by the at least one processor so that the at least one processor performs modulation of the high-sensitivity temperature sensor and / or the above-mentioned modulation method.

[0092] In specific implementation, the high-sensitivity temperature sensor modulation system proposed in the present invention includes a broadband light source BBS module, which provides a stable and continuous optical signal; an optical fiber transmission link module, which transmits the optical signal to the sensor; the sensor includes an erbium-doped optical fiber EDF and a coreless optical fiber CLF, wherein the two ends of the erbium-doped optical fiber EDF are fused and cascaded with the coreless optical fiber CLF to achieve light splitting or coupling; and the other end of each section of the coreless optical fiber CLF away from the erbium-doped optical fiber EDF is fused and cascaded with the single-mode optical fiber SMF to achieve optical signal input and output; a constant temperature box module, in which the sensor is fixedly installed, for testing the temperature response of the sensor; a spectrum analysis module, which receives the optical signal returned from the sensor, analyzes the changes in its wavelength and intensity, and forms spectrum data; a data processing module, which is respectively connected to the broadband light source BBS module, the constant temperature box module, the spectrum analysis module and the data recording and analysis module, records and analyzes the spectrum data, and calculates the temperature sensitivity and linearity of the sensor.

[0093] The technical scope of the present invention is not limited to the contents in the above description. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of ​​the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A high-sensitivity temperature sensor, characterized in that: Including erbium-doped fiber EDF and coreless fiber CLF, among which, The two ends of the erbium-doped optical fiber EDF are fused and cascaded with the coreless optical fiber CLF to achieve light splitting or coupling; and the other end of each coreless optical fiber CLF away from the erbium-doped optical fiber EDF is fused and cascaded with the single-mode optical fiber SMF to achieve optical signal input and output; The two sections of coreless optical fiber CLF are of equal length and have a linear relationship with the length of the erbium-doped optical fiber EDF; the interference intensity between the core mode and / or cladding mode of the single-mode optical fiber SMF, the coreless optical fiber CLF and the erbium-doped optical fiber EDF is positively correlated with the effective refractive index difference between the core mode and / or cladding mode, so as to realize accurate sensing of the optical signal; The effective refractive index between the cladding modes of the single-mode optical fiber SMF, coreless optical fiber CLF and erbium-doped optical fiber EDF satisfies a functional relationship with the incident wavelength of the sensor transmitted light and the external temperature; while the effective refractive index between the core modes only satisfies the functional relationship with the incident wavelength of the transmitted light; the length of the coreless optical fiber CLF is 10mm~15mm, and when the length of the coreless optical fiber CLF is 10mm~15mm, the length of the erbium-doped optical fiber EDF is 2cm~4cm.

2. A high-sensitivity temperature sensor according to claim 1, characterized in that: The positive correlation between the interference intensity and the effective refractive index difference is: Where I1 and I2 represent the light intensity of the core mode and high-order cladding mode propagating in the fiber core respectively; φ represents the phase difference between the core mode and the high-order cladding mode; where, Where Δneff is the effective refractive index difference between the core mode and the higher-order cladding mode; L is the interference length; λ is the interference wavelength; In the formula, when m is an integer, the interference intensity is the smallest.

3. A high-sensitivity temperature sensor according to claim 1, characterized in that: When the external temperature changes, the incident wavelength of the sensor transmission light shifts by Δλ. The functional relationship between the effective refractive index, the incident wavelength and the external temperature is: Where δ represents the thermo-optical coefficient of the optical fiber; k represents the thermal expansion coefficient of the optical fiber; ΔT represents the temperature change during the measurement process; The change in external temperature is calculated from the wavelength δ and k of the interference spectrum affected by the thermo-optical effect and thermal expansion effect: In the formula, Expressed as the rate at which the effective refractive index changes with temperature; Expressed as the rate at which the fiber length changes with temperature.

4. A high-sensitivity temperature sensor according to claim 1, characterized in that: When the external temperature changes, the curvature of the sensor and the external temperature satisfy: In the formula, ΔR1, K C1 and K T1 They are respectively represented by the intensity offset, curvature sensitivity and temperature sensitivity of the first trough in the sensor transmission spectrum; ΔR2, K C2 and K T2 They are respectively represented as the offset of another trough in the sensor transmission spectrum, the curvature sensitivity and the temperature sensitivity, where: ΔR1=K C1 ΔC+K T1 ΔT ΔR2=K C2 ΔC+K T2 ΔT。 5. A high-sensitivity temperature sensor modulation method, characterized in that: The modulation of the high-sensitivity temperature sensor according to claims 1 to 4 comprises the following steps: Temperature response characteristic test: the temperature of the sensor is controlled by a constant temperature box, the temperature is gradually lowered, and the changes in the transmission spectrum are recorded. Then, the response of the transmission spectrum to temperature changes is analyzed to evaluate the sensitivity of the sensor to temperature changes. Curvature response characteristic test: Use the curvature measurement platform to apply different curvatures to the sensor, record the corresponding displacement changes, observe and analyze the impact of the curvature change on the sensor transmission spectrum, obtain the change of dip characteristics and wavelength shift in the sensor transmission spectrum, and evaluate the sensor's response characteristics to curvature changes; Performance optimization,Based on the above test results, the length and structure of the optical fiber are adjusted to optimize the performance of the sensor and ensure that it can provide stable and accurate measurement results under different environmental conditions.

6. A high-sensitivity temperature sensor modulation method according to claim 5, characterized in that: The specific method for evaluating the sensor's response characteristics to temperature is: a1) Experimental preparation and setup: A broadband light source BBS with an output power of 5 mW was used as the input light source, and an external spectrum analyzer was connected to analyze the transmission spectrum. The sensor was horizontally straightened and fixed in a constant temperature box to avoid being affected by external force or bending. At the same time, the initial temperature of the constant temperature box was set to be higher than 40°C; a2) Temperature control and data acquisition: gradually cool down the temperature from above 40°C in steps of 2°C until it drops to 24°C. At the same time, during the cooling process, record the change in the transmission spectrum every 2°C change to obtain the response data of the sensor to the temperature change in the range of 24°C to 40°C; The specific method for evaluating the response characteristics of the sensor to curvature changes is: b1) Curvature sensing experiment setup: The sensor is placed on a curvature measurement platform, and different sensor curvatures are generated by a knob fixed to the curvature measurement platform, where the custom displacement is represented by x, and the sensor curvature is obtained from 0m -1 Change to 0.30036m -1 The impact on sensor output; b2) Curvature sensitivity analysis: Establish a curvature-temperature relationship matrix to accurately distinguish and quantify the sensor's response to curvature and temperature changes.

7. A high-sensitivity temperature sensor modulation system, based on the modulation method according to any one of claims 5 to 6, characterized in that: include: At least one processor and a memory that establishes an information interaction channel with at least one of the processors, wherein: Each of the memories stores a computer program executable by at least one of the processors; The computer program is executed by at least one of the processors to enable the at least one processor to perform the modulation of the high-sensitivity temperature sensor according to any one of claims 1 to 4 and / or the modulation method according to any one of claims 5 to 6.

Images