Differential vernier effect-based probe, manufacturing method, and ocean temperature sensor

Abstract

The present invention relates to the technical field of fiber optic sensors. Disclosed are a differential vernier effect-based probe, a manufacturing method, and an ocean temperature sensor. In the present invention, a fiber optic cable is connected to a fiber optic coupler / splitter, the fiber optic coupler / splitter being further connected to sensing arm A and sensing arm B; sensing arm A extends into a temperature sensing tube fixed in a quartz tube; sensing arm B extends into the quartz tube; sensing arm B is located outside the temperature sensing tube; reflective film A and reflective film B are fixedly connected to the end of the temperature sensing tube away from the fiber optic coupler / splitter, reflective film A being located inside the temperature sensing tube; a cavity between sensing arm A and reflective film A forms a main scale cavity; reflective film B is located outside the temperature sensing tube, the ends of reflective film B and sensing arm B extending into the quartz tube being arranged opposite to each other; and a cavity between sensing arm B and reflective film B forms a vernier cavity. The probe further comprises an evacuated unit, the evacuated unit being fixed on a sensor base. The sensor probe of the present application can effectively improve the signal-to-noise ratio and sensitivity.

Description

Probe based on differential vernier effect, preparation method thereof, and ocean temperature sensor Technical Field

[0001] The present invention relates to the technical field of optical fiber sensors, and in particular to a probe based on a differential vernier effect, a preparation method thereof, and an ocean temperature sensor. Background Art

[0002] Ocean observation primarily involves the exploration of unknown sea areas, islands, and landforms, the investigation of new marine species, and the detailed study of ocean parameters in order to forecast future climate change, monsoons, and other factors. In the field of seawater observation, high-precision measurement of seawater temperature has always been an important research topic. This is primarily because accurate seawater temperature measurement is of great significance to marine ranching, shipping, and the military. For example, in marine ranching, real-time, dynamic, and high-precision monitoring of seawater temperature changes can provide a reference for seafood farming, thereby improving aquaculture efficiency. In shipping and the military, high-precision measurement of underwater seawater temperature stratification and the determination of underwater internal wave distribution provide the necessary data support for submarine stealth and safe navigation of ships.

[0003] Fiber optic temperature sensors are an important measurement tool for high-precision measurement of seawater temperature. Currently, commonly used fiber optic temperature sensors include those based on fiber Bragg gratings, those based on interferometers, and those based on the fiber fluorescence effect. Interferometer-based fiber optic temperature sensors are often used for high-sensitivity detection due to their sensitive response to temperature and pressure. However, when faced with the need to measure temperature under the background of small fluctuations in ocean water temperature, the sensitivity of the sensor still needs to be greatly improved. Therefore, some researchers have proposed a method to improve the measurement accuracy of temperature sensors by using the spectral vernier effect. However, most temperature sensors that use the spectral vernier effect to improve measurement accuracy suffer from poor signal-to-noise ratio and low sensitivity.

[0004] To this end, the present application proposes a probe and a preparation method based on the differential vernier effect, as well as an ocean temperature sensor. Summary of the Invention

[0005] In order to make up for the deficiencies of the prior art, the present application provides a probe based on the differential vernier effect, a preparation method thereof, and an ocean temperature sensor.

[0006] The technical solution of the present invention is as follows: A sensor probe based on the differential vernier effect includes a sensor base, an optical fiber cable, an optical fiber coupling splitter, a sensing arm A, a sensing arm B, and a sealing sleeve. A portion of the optical fiber cable, the optical fiber coupling splitter, the sensing arm A, the sensing arm B, and the sealing sleeve are fixedly arranged on the sensor base; the remaining portion of the optical fiber cable not fixed to the sensor base is used to connect to a fiber circulator; the optical fiber cable is connected to the optical fiber coupling splitter, and the optical fiber coupling splitter is also connected to the sensing arm A and the sensing arm B respectively. The sensing arm A extends into a temperature sensing tube fixedly arranged in a quartz tube, and the sensing arm B extends into the quartz tube. The sensing arm B is located outside the temperature sensing tube, and the end of the temperature sensing tube away from the optical fiber coupling splitter is fixedly connected to a reflective film A and a reflective film B, wherein the reflective film A is located inside the temperature sensing tube, and the cavity between the sensing arm A and the reflective film A constitutes one interference cavity in the vernier differential interference double cavity, namely the main scale cavity, and the reflective film B is located outside the temperature sensing tube, and the reflective film B is arranged opposite to the end of the sensing arm B extending into the quartz tube, and the cavity between the sensing arm B and the reflective film B constitutes the other interference cavity in the vernier differential interference double cavity, namely the vernier cavity; and it also includes a vacuum unit, which is fixed on the sensor base.

[0007] Preferably, the quartz tube, the sensing arm A and the sensing arm B are all made of quartz glass, and the temperature sensing tube is made of beryllium copper alloy material.

[0008] Preferably, the vacuum unit includes an external pressure balance hole, a sealing sleeve, and a vacuum tube; the temperature sensing tube and the quartz tube are both provided with internal and external pressure balance holes, the quartz tube is fixedly sleeved in the sealing sleeve, the sealing sleeve is fixedly connected to the vacuum tube, the sealing sleeve is communicated with the vacuum tube, and after the vacuum tube is vacuumed, the vacuum tube is melted and sealed; the vacuum tube is fixed on the sensor base.

[0009] Preferably, a layer of heat-conducting material is filled between the temperature-sensing tube and the quartz tube and / or between the quartz tube and the sealing sleeve.

[0010] Preferably, the thermally conductive material layer is one of a metal wool layer, a metal fiber mesh and an asbestos mesh.

[0011] Preferably, at room temperature, the length of the main ruler cavity is greater than or equal to twice the length of the vernier cavity or less than or equal to 1 / 2 of the length of the vernier cavity.

[0012] Preferably, at room temperature, the length of the main ruler cavity is 2-30 times the length of the vernier cavity or the length of the main ruler cavity is 1 / 30-1 / 2 the length of the vernier cavity.

[0013] Preferably, the sensor base is a heat-conducting metal shell, which is provided with a cavity for installing optical fiber cables, optical fiber coupling splitters, sensing arms A and B, sealing sleeves and vacuum tubes.

[0014] Preferably, a portion of the optical fiber cable, the optical fiber coupling splitter, the sensing arm A, the sensing arm B, the sealing sleeve and the vacuum tube are placed in the cavity of the heat-conducting metal shell and fixedly connected to the heat-conducting metal shell through a thermal grease layer.

[0015] A method for preparing a sensor probe based on a differential vernier effect, comprising the following steps: first, fixing a reflective film A and a reflective film B on a temperature-sensing tube, wherein the reflective film A is located inside the temperature-sensing tube and the reflective film B is located outside the temperature-sensing tube; then, extending one end of the sensing arm A into the temperature-sensing tube with an internal and external pressure balance hole, and fixing the sensing arm A and the temperature-sensing tube together at a fixed point A; then, extending the temperature-sensing tube with the reflective film A, the reflective film B and the sensing arm A into a quartz tube with an internal and external pressure balance hole, and fixing the temperature-sensing tube and the quartz tube together at a fixed point A; then, inserting the quartz tube into a sealing sleeve fixedly connected to the vacuum tube, and fixing the quartz tube and the sealing sleeve together at a fixed point A; then, inserting one end of the sensing arm B into the sealing sleeve and into the quartz tube in sequence, and the sensing arm B is located outside the temperature-sensing tube, Then, at the fixed point B, the sensing arm B and the quartz tube are fixed together, and the connection between the sensing arm B and the sealing sleeve is sealed so that the sealing sleeve seals the quartz tube, and the sensing arm B located between the quartz tube and the sealing sleeve is in a relaxed state; the cavity between the sensing arm A and the reflective film A constitutes the main scale cavity, and the cavity between the sensing arm B and the reflective film B constitutes the vernier cavity. At room temperature, the length of the main scale cavity is greater than or equal to times the length of the vernier cavity or less than or equal to 1 / 2 of the vernier cavity; then, vacuum is applied to the vacuum tube. After the vacuum tube is evacuated, the vacuum tube is melted and sealed, and then the sensing arm A and the sensing arm B are connected to the optical fiber coupling splitter, and then the optical fiber coupling splitter is connected to the optical fiber cable; finally, a portion of the optical fiber cable, the optical fiber coupling splitter, the sensing arm A, the sensing arm B, the sealing sleeve, and the vacuum tube are fixed to the sensor base.

[0016] Preferably, the temperature sensing tube with the reflective film A, the reflective film B and the sensing arm A is inserted into a quartz tube with internal and external pressure balance holes, and then a layer of heat conductive material is filled between the temperature sensing tube and the quartz tube; then, the temperature sensing tube and the quartz tube are fixed together at the fixed point A.

[0017] Preferably, the quartz tube is inserted into a sealing sleeve fixedly connected to the vacuum tube, and then a heat conductive material layer is filled between the quartz tube and the sealing sleeve, and then the quartz tube and the sealing sleeve are fixed together at a fixing point A.

[0018] An ocean temperature sensor includes a wide-spectrum light source, a spectrum demodulator, a fiber optic circulator, and a sensor probe; the wide-spectrum light source is connected to the first port of the fiber optic circulator, the spectrum demodulator is connected to the third port of the fiber optic circulator, and the fiber optic cable in the sensor probe is connected to the second port of the fiber optic circulator.

[0019] In the present application, a wide-spectrum light source is used to emit a broadband spectrum, and a fiber circulator is used to isolate the broadband spectrum signal emitted by the wide-spectrum light source and the composite envelope interference spectrum signal output by the sensor probe; in the present application, the broadband spectrum emitted by the wide-spectrum light source is input into the sensor probe through the fiber circulator, and the main scale cavity, the vernier cavity, and the fiber coupling splitter connected to the sensor arm A and the sensor B in the sensor probe constitute a vernier composite unit. The broadband spectrum input into the sensor probe forms a composite envelope interference spectrum under the action of the vernier composite unit and in the fiber coupling splitter. Then, the composite envelope interference spectrum is transmitted to the fiber circulator via the optical fiber cable for isolation, and then transmitted back to the spectrum demodulator through the optical fiber circulator to realize spectrum demodulation. The ocean temperature sensor prepared in the present application can meet the accuracy requirements of remote measurement.

[0020] A method for obtaining temperature using peak wavelength tracking begins with measuring water temperature with an ocean temperature sensor, continuously locks and tracks the movement trajectory of the composite envelope interference spectrum in the spectral data output by the ocean temperature sensor's spectral demodulator, determines the accurate composite envelope interference spectrum used to calculate temperature, and then calculates the corresponding temperature based on the determined composite envelope interference spectrum peak value.

[0021] Compared with the prior art, the beneficial technical effects of the present application are as follows: 1. The sensor probe constructed in the present application is a linear self-compensating structure. Specifically, the main scale cavity formed by the cavity between the sensing arm A and the reflecting film A and the vernier cavity formed by the cavity between the sensing arm B and the reflecting film B are located on the same straight line, so that when measuring temperature, the main scale cavity and the vernier cavity can produce a differential effect; furthermore, in the present application, the main scale cavity and the vernier cavity are spatially encapsulated in the same probe at the same time, so that the main scale cavity and the vernier cavity can be in the same measured environment at the same time, so that the main scale cavity and the vernier cavity can remain synchronized under the influence of external temperature changes, avoiding the problem of asynchronous temperature response caused by the separation of the main scale cavity and the vernier cavity in other vernier effect temperature measurement schemes, and effectively improving the consistency and synchronization of the temperature sensor. 2. The quartz tube, sensor arm A, and sensor arm B in the sensor probe of this application are all made of an inert material, quartz glass. Firstly, quartz glass, an inert material, is very susceptible to very small deformation due to temperature changes, is acid-resistant and corrosion-resistant, and has high strength. Secondly, when the quartz tube, sensor arm A, and sensor arm B undergo slight deformation due to temperature changes, the quartz tube, sensor arm A, and sensor arm B deform synchronously, which can greatly offset the deformation effect caused by temperature changes. The thermal expansion coefficient of the quartz glass material used in the quartz tube, sensor arm A, and sensor arm B is significantly different from the thermal expansion coefficient of the beryllium copper alloy material of the temperature sensing tube. Specifically, the thermal expansion coefficient of the quartz glass material used in the quartz tube, sensor arm A, and sensor arm B is approximately 5.5×10 - 7 / ℃, the thermal expansion coefficient of the beryllium copper alloy material used in the temperature sensing tube is about 1.7×10 -5 / ℃, therefore, under the same heating conditions, the expansion degree of the quartz tube, sensor arm A and sensor arm B is significantly smaller than that of the temperature sensing tube. At this time, the main scale cavity and the vernier cavity caused by the expansion and contraction of the temperature sensing tube, sensor arm A and sensor arm B in response to temperature changes are in opposite directions, forming a differential effect. Specifically, when the temperature rises, the temperature sensing tube is affected by the temperature increase and the elongation length is longer, and the quartz tube, sensor arm A and sensor arm B are affected by the temperature increase and the elongation length is relatively shorter. At this time, the main scale cavity between the sensor arm A and the reflex arc A fixed between the temperature sensing tubes will become larger. At the same time, the vernier cavity between the sensor arm B and the reflex arc B fixed between the temperature sensing tubes will become smaller, thereby forming a more significant sensitivity enhancement effect. 3. In the present application, the main scale cavity and the vernier cavity can respectively make the input broadband spectrum generate comb spectra with different interference periods to simulate the main scale and the vernier scale. The comb spectrum reflected back by the main scale cavity and the comb spectrum reflected back by the vernier cavity are coupled at the fiber-coupled splitter to form a composite envelope interference spectrum. Therefore, the present application can convert the tiny interference period change of a single interference cavity into a large-range movement change of the composite envelope interference spectrum, thereby achieving the purpose of improving the temperature measurement sensitivity; the temperature sensitivity of the sensor probe prepared in the present application can reach 0.000096°C. 4. In addition, the main scale cavity and the vernier cavity in the present application are essentially connected in parallel. Therefore, the existence of the main scale cavity and the vernier cavity effectively avoids the problem of large loss caused by the series or nested cavities used in the prior art, as well as the problem of poor contrast of the composite envelope interference spectrum caused by loss mismatch. The main scale cavity and the vernier cavity in the present application are essentially connected in parallel, with high reflection efficiency, low loss, strong signal, and small difference in the intensity of the reflection spectrum between the main scale cavity and the vernier cavity. Moreover, the comb spectrum reflected back by the main scale cavity and the comb spectrum reflected back by the vernier cavity in the present application are coupled at the fiber coupling splitter, forming The composite envelope interference spectrum has a strong contrast. Therefore, the main scale cavity and the vernier cavity provided in the present application are beneficial to improving the demodulation signal-to-noise ratio of the temperature sensor. In addition, the main scale cavity and the vernier cavity in the present application are connected in parallel, which has a simple structure, high reflectivity and good consistency. There is neither the problem of the reference cavity and the sensing cavity being sensitive to temperature in the same direction as in the series FP cavity structure, nor the problem of the interference cavity embedded in the bubble structure requiring strict control of the bubble size. At the same time, the problem of inconsistent reflectivity and low reflectivity of the two FP cavities in the series FP cavity structure is avoided.5. In order to achieve high-precision and fast demodulation, the present application adopts a method of obtaining temperature by peak wavelength tracking to demodulate the spectral data collected by the spectral demodulator. Specifically, the present application starts from measuring the water temperature with the ocean temperature sensor, continuously locks and tracks the moving trajectory of the composite envelope interference spectrum in the spectral data output by the spectral demodulator of the ocean temperature sensor, and determines the accurate composite envelope interference spectrum used to calculate the temperature. Then, the corresponding temperature is calculated based on the composite envelope interference spectrum peak of the determined composite envelope interference spectrum. This can effectively avoid the problem that when the spectrum demodulated by the spectral demodulator has multiple composite envelope interference spectra at the same time, the composite envelope interference spectrum used to calculate the temperature cannot be accurately determined, thereby affecting the accuracy of the temperature calculation. 6. The sensor probe in the present application is provided with a vacuum tube. After the vacuum tube is evacuated, the vacuum tube is melted and sealed. At this time, the internal vacuum state formed in the sealing sleeve enables the sealing sleeve to remain in a sealed state for a long time, which can effectively eliminate the change in gas density caused by thermal expansion and contraction of the gas due to residual gas in the sealing sleeve, thereby causing interference errors on the effective cavity length of the main scale cavity and the vernier scale; in addition, after the sealing sleeve is evacuated, the influence of the external environmental pressure on the various components in the sealing sleeve can also be avoided. 7. In the present application, the space between the sealing sleeve and the quartz tube and / or between the quartz tube and the temperature sensing tube is filled with a layer of thermal conductive material, and then the air inside the sealing sleeve is discharged through the vacuum tube, which can effectively ensure that the external temperature is fully conducted in the sensor probe, solves the problem of slow temperature transfer caused by temperature isolation of the vacuum tube, and avoids the problem of liquid thermal conductive agents such as thermal grease volatilizing in a vacuum state and fluidity contaminating the reflectivity of the interference cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the structure of the ocean temperature sensor of the present application. Figure 2 is a schematic diagram of the structure of the sensor probe of the present application. Figure 3 is a differential composite vernier interferometer cavity spectrum obtained by the ocean temperature sensor of the present application at 24°C-32°C. Figure 4 is a graph of temperature calibration test data obtained by the ocean temperature sensor of the present application at 24°C-32°C.

[0023] In the figure: 1-broad spectrum light source, 2-spectral demodulator, 3-fiber circulator, 4-fiber optic cable, 5-sensor probe, 6-fiber optic coupling splitter, 7-sensing arm A, 8-sensing arm B, 9-temperature sensing tube, 10-reflection film A, 11-reflection film B, 12-internal and external pressure balance holes, 13-quartz tube, 14-thermal conductive material layer, 15-sealing sleeve, 16-evacuation tube, 17-fixing point A, 18-fixing point B, 19-sensor base. DETAILED DESCRIPTION

[0024] Some embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0025] As shown in Figure 2, a sensor probe based on the differential vernier effect includes a sensor base 19, an optical fiber cable 4, an optical fiber coupling splitter 6, a sensing arm A7, a sensing arm B8 and a sealing sleeve 15. A portion of the optical fiber cable 4, the optical fiber coupling splitter 6, the sensing arm A7, the sensing arm B8 and the sealing sleeve 15 are fixedly arranged on the sensor base 19. In this embodiment, the optical fiber cable 4 is connected to the optical fiber coupling splitter 6, and the optical fiber coupling splitter 6 is connected to the sensing arm A7 and the sensing arm B8 respectively. The sensing arm A7 extends to the temperature sensing tube 9 fixedly set in the quartz tube 13, and the sensing arm B8 extends into the quartz tube 13, and the sensing arm B8 is located outside the temperature sensing tube 9. The end of the temperature sensing tube 9 away from the optical fiber coupling splitter 6 is fixedly connected to the reflecting film A10 and the reflecting film B11. The reflecting film A10 is located in the temperature sensing tube 9. The cavity between the sensing arm A7 and the reflecting film A10 constitutes one of the interference cavities in the vernier differential interference double cavity, namely the main scale cavity, and the reflecting film B11 is located outside the temperature-sensing tube 9, and the reflective film B11 is arranged opposite to the end of the sensing arm B8 extending into the quartz tube 13. The cavity between the sensing arm B8 and the reflective film B11 constitutes another interference cavity in the vernier differential interference double cavity, namely the vernier cavity; in this embodiment, at room temperature, the length of the main scale cavity is greater than or equal to 2 times the length of the vernier cavity or less than or equal to 1 / 2 of the length of the vernier cavity. Specifically in this embodiment, at room temperature, the length of the main scale cavity is 18 times the length of the vernier cavity; in this embodiment, the quartz tube, sensing arm A and sensing arm B are all made of quartz glass, and the temperature-sensing tube is made of beryllium copper alloy. This embodiment also includes a vacuum unit, which is fixed on the sensor base 19; the vacuum unit includes an external pressure balance hole 12, a sealing sleeve 15, and a vacuum tube 16; the temperature sensing tube 9 and the quartz tube 13 are both provided with internal and external pressure balance holes 12, the quartz tube 13 is fixedly sleeved in the sealing sleeve 15, the sealing sleeve 15 is fixedly connected to the vacuum tube 16, and the sealing sleeve 15 is communicated with the vacuum tube 16. After the vacuum tube 16 is evacuated, the vacuum tube 16 is melted and sealed. The sensor base 19 is a heat-conducting metal shell, which is provided with a cavity for installing the optical fiber cable 4, the optical fiber coupling splitter 6, the sensing arm A7, the sensing arm B8, the sealing sleeve 15 and the vacuum tube 16; a part of the optical fiber cable 4, the optical fiber coupling splitter 6, the sensing arm A7, the sensing arm B8, the sealing sleeve 15 and the vacuum tube 16 are placed in the cavity of the heat-conducting metal shell and fixedly packaged together with the heat-conducting metal shell through a thermal grease layer. The remaining part of the optical fiber cable 4 not fixed on the sensor base 19 is used to connect to the optical fiber circulator 3; in addition, in this embodiment, a heat-conducting material layer 14 is filled between the temperature sensing tube 9 and the quartz tube 13, and between the quartz tube 13 and the sealing sleeve 15, and the heat-conducting material layer 14 is a metal wool layer.

[0026] A method for preparing a sensor probe based on the differential vernier effect includes the following steps: First, a reflective film A10 and a reflective film B11 are fixed to a temperature-sensing tube 9, wherein reflective film A10 is located inside the temperature-sensing tube 9 and reflective film B11 is located outside the temperature-sensing tube 9. Next, one end of a sensing arm A7 is inserted into the temperature-sensing tube 9, which has an internal and external pressure balancing hole 12, and the sensing arm A7 and the temperature-sensing tube 9 are fixed together at a fixing point A17. Next, the temperature-sensing tube 9 with reflective films A10, B11, and sensing arm A7 is inserted into a quartz tube 13, which has an internal and external pressure balancing hole 12. A thermally conductive material layer 14 is then filled between the temperature-sensing tube 9 and the quartz tube 13. In this embodiment, the thermally conductive material layer 14 is a layer of metal wool. Finally, the temperature-sensing tube 9 and the quartz tube 13 are fixed together at a fixing point A17. Then, the quartz tube 13 is inserted into the sealing sleeve 15, which is fixedly connected to the vacuum tube 16. A thermally conductive material layer 14 is then filled between the quartz tube 13 and the sealing sleeve 15. The quartz tube 13 and the sealing sleeve 16 are then fixed together at a fixing point A17. One end of the sensing arm B8 is then inserted into the sealing sleeve 15 and the quartz tube 13, respectively, with the sensing arm B8 positioned outside the temperature-sensing tube 9. The sensing arm B8 and the quartz tube 13 are then fixed together at a fixing point B18. The connection between the sensing arm B8 and the sealing sleeve 15 is sealed, ensuring that the sealing sleeve 16 seals the quartz tube 13. The sensing arm B8, located between the quartz tube 13 and the sealing sleeve 15, is in a relaxed state, as shown in FIG2 . The purpose is to ensure that the sensing arm B8 located between the sealing sleeve 15 and the optical fiber quartz tube 13 does not exert tension, thereby avoiding error interference. In this application, the cavity between the sensing arm A7 and the reflective film A10 constitutes the main scale cavity, and the cavity between the sensing arm B8 and the reflective film B11 constitutes the vernier cavity. At room temperature, the length of the main scale cavity is greater than or equal to twice the length of the vernier cavity or less than or equal to 1 / 2 the length of the vernier cavity. In this embodiment, at room temperature, the length of the main scale cavity is 18 times the length of the vernier cavity. Then, vacuum is applied to the vacuum tube 16. After vacuuming, the vacuum tube 16 is fused and sealed. Then, the sensing arms A7 and B8 are connected to the optical fiber coupling splitter 6, and the optical fiber coupling splitter 6 is then connected to the optical fiber cable 4. Finally, a portion of the optical fiber cable 4, the optical fiber coupling splitter 6, the sensing arm A7, the sensing arm B8, the sealing sleeve 15 and the vacuum tube 16 are placed in the cavity of the heat-conducting metal shell of the sensor base 19 and fixedly encapsulated together with the heat-conducting metal shell through a thermal grease layer.

[0027] As shown in Figures 1 and 2, an ocean temperature sensor includes a wide-spectrum light source 1, a spectrum demodulator 2, a fiber optic circulator 3, and a sensor probe 5. The spectrum demodulator in this embodiment can use a common spectrum demodulation module currently sold on the market, such as the I-MON 256 OEM demodulation module, Bayspec's FBGA-S-1510-1590-FA, etc. Specifically, in this embodiment, the spectrum demodulator used in this embodiment is the I-MON 256 OEM demodulation module; in this application, the wide-spectrum light source 1 is connected to the first port of the fiber optic circulator 3, the spectrum demodulator 2 is connected to the third port of the fiber optic circulator 3, and the end of the optical fiber cable 4 in the sensor probe 5 that is not fixed on the sensor base is connected to the second port of the fiber optic circulator 3.

[0028] In this embodiment, the broadband light source 1 emits a broadband spectrum with a wavelength range of 1450nm-1650nm. The broadband spectrum emitted by the broadband light source is input into the sensor probe 5 through the fiber optic circulator 3. The main scale cavity, vernier cavity, and fiber optic coupling splitter 6 connected to the sensor arm A7 and sensor B8 in the sensor probe 5 constitute a vernier composite unit. Under the action of the vernier composite unit and in the fiber optic coupling splitter 6, the broadband spectrum input into the sensor probe 5 forms a composite envelope interference spectrum. The composite envelope interference spectrum is then transmitted to the fiber optic circulator 3 via the optical fiber cable 4 for isolation, and then transmitted back to the spectrum demodulator 2 through the fiber optic circulator 3 to achieve spectral demodulation.

[0029] In order to verify the temperature sensitivity performance of the ocean temperature sensor of the present application, the present application conducted a temperature calibration test on the ocean temperature sensor obtained in this embodiment. The test results are shown in Figure 4. It can be seen from Figure 4 that the temperature sensitivity of the ocean temperature sensor obtained in this embodiment can reach 10.4nm / ℃. The spectrum demodulator in this embodiment adopts the I-MON 256 OEM demodulation module. The demodulation accuracy of the spectrum demodulator is 1pm. According to the demodulation accuracy of the spectrum demodulator, the temperature sensitivity of the ocean temperature sensor of the present application can reach 0.000096℃; while in the prior art, the temperature sensitivity of the temperature sensor is usually required to be no higher than 0.005℃ to meet the requirements of high-sensitivity ocean temperature detection. That is to say, the sensitivity of the ocean temperature sensor prepared by the present application is improved by nearly two orders of magnitude compared with the sensitivity required for high-sensitivity ocean temperature detection in the prior art.

[0030] In addition, the present application also uses a method of obtaining temperature by peak wavelength tracking to demodulate the data collected by the spectrum demodulator 2. The specific principle is that starting from the ocean temperature sensor measuring the water temperature, the moving trajectory of the composite envelope interference spectrum in the spectral data output by the spectrum demodulator of the ocean temperature sensor is continuously locked and tracked to determine the accurate composite envelope interference spectrum used to calculate the temperature, and then, the corresponding temperature is calculated based on the composite envelope interference spectrum peak value of the determined composite envelope interference spectrum; specifically, starting from the starting temperature, the moving trajectory of the composite envelope interference spectrum is continuously tracked, and after determining the accurate composite envelope interference spectrum, the wavelength value of the lower composite envelope interference spectrum is extracted from the data collected by the spectrum demodulator 2 and the peak wavelength value or trough value of the lower composite envelope interference spectrum is calculated, and then the specific temperature value is calculated based on the pre-calibrated correspondence between the composite envelope interference spectrum and the temperature value. In conjunction with this embodiment, the sensor probe is first placed in a standard constant temperature water area (displaying the precise water area temperature value), and then the spectrum is read from the spectrum demodulator. The spectrum graph read in this embodiment is shown in Figure 3. Then, the peak value or trough value of the composite envelope interference spectrum in the spectrum is extracted as the corresponding composite envelope interference spectrum peak value (the trough value is used in this embodiment, as shown in Figure 3), forming a calibration data value of "temperature + composite envelope interference spectrum peak value"; after changing the temperature of the standard constant temperature water bath, the above steps are repeated to obtain the calibration data value of "temperature + composite envelope interference spectrum peak value" at other temperatures. After multiple calibrations, a calibration value correspondence table can be formed. After obtaining the calibration value temperature-composite envelope interference spectrum peak corresponding data table, a temperature-wavelength linear fitting formula can be fitted, as shown in Figure 4.

[0031] When the sensor probe prepared in the present application is used for actual temperature measurement, a new spectrum will be generated when the sensor probe is placed in the measured area. After obtaining the peak value of the composite envelope interference spectrum, the corresponding actual temperature value can be inversely calculated according to the fitting formula.

[0032] In the prior art, multiple envelopes exist simultaneously in the composite envelope interference spectrum. If a specific envelope is not locked as the designated envelope for temperature measurement, it will cause misjudgment and form a jump phenomenon in the temperature measurement. The method used in this application to obtain temperature by peak wavelength tracking starts from the starting temperature and continuously measures and tracks. It takes advantage of the physical property that the temperature of the ocean water body changes continuously and slowly. After the system is running, the demodulator continuously records the peak value of the composite envelope interference spectrum, forming a continuous tracking of the movement and change of the composite envelope interference spectrum, thereby avoiding the influence of other envelopes and achieving a continuous temperature measurement effect.

Claims

1. A sensor probe based on differential vernier effect, characterized in that: It includes a sensor base, an optical fiber cable, an optical fiber coupling splitter, a sensor arm A, a sensor arm B and a sealing sleeve, wherein a part of the optical fiber cable, the optical fiber coupling splitter, the sensor arm A, the sensor arm B and the sealing sleeve are fixedly arranged on the sensor base; The optical fiber cable is connected to the optical fiber coupling splitter, and the optical fiber coupling splitter is also connected to the sensing arm A and the sensing arm B respectively. The sensing arm A extends to the temperature sensing tube fixedly arranged in the quartz tube, and the sensing arm B extends into the quartz tube, and the sensing arm B is located outside the temperature sensing tube. The temperature sensing tube is fixedly connected with a reflection film A and a reflection film B at one end away from the optical fiber coupling splitter, wherein the reflection film A is located in the temperature sensing tube, and the cavity between the sensing arm A and the reflection film A constitutes the main scale cavity, and the reflection film B is located outside the temperature sensing tube. B is arranged opposite to one end of the sensing arm B extending into the quartz tube, and the cavity between the sensing arm B and the reflecting film B constitutes a vernier cavity; it also includes a vacuum unit, which is fixed on the sensor base; the vacuum unit includes a pressure balance hole, a sealing sleeve, and a vacuum tube; the temperature sensing tube and the quartz tube are both provided with a pressure balance hole, the quartz tube is fixedly sleeved in the sealing sleeve, the sealing sleeve is fixedly connected to the vacuum tube, and after the vacuum tube is vacuumed, the vacuum tube is melted and sealed; the vacuum tube is fixed on the sensor base.

2. The sensor probe based on differential vernier effect according to claim 1, characterized in that: The quartz tube, the sensing arm A and the sensing arm B are all made of quartz glass, and the temperature sensing tube is made of beryllium copper alloy material.

3. The sensor probe based on differential vernier effect according to claim 1, characterized in that: A heat-conducting material layer is filled between the temperature sensing tube and the quartz tube and / or between the quartz tube and the sealing sleeve.

4. The sensor probe based on differential vernier effect according to claim 1, characterized in that: At room temperature, the length of the main ruler cavity is greater than or equal to twice the length of the vernier cavity or less than or equal to 1 / 2 of the length of the vernier cavity.

5. The sensor probe based on differential vernier effect according to claim 4, characterized in that: At room temperature, the length of the main ruler cavity is 2-30 times the length of the vernier cavity or the length of the main ruler cavity is 1 / 30-1 / 2 of the length of the vernier cavity.

6. The sensor probe based on differential vernier effect according to claim 1, characterized in that: The sensor base is a heat-conducting metal shell, and a cavity for installing optical fiber cables, optical fiber coupling splitters, sensor arms A and B, sealing sleeves and vacuum tubes is provided on the heat-conducting metal shell.

7. The sensor probe based on differential vernier effect according to claim 6, characterized in that: A portion of the optical fiber cable, the optical fiber coupling splitter, the sensing arm A, the sensing arm B, the sealing sleeve and the vacuum tube are placed in the cavity of the heat-conducting metal shell and fixedly connected to the heat-conducting metal shell through a heat-conducting silicone grease layer.

8. A method for preparing a sensor probe based on a differential vernier effect, characterized in that: The steps include: First, a reflective film A and a reflective film B are fixed on the temperature sensing tube, wherein the reflective film A is located inside the temperature sensing tube and the reflective film B is located outside the temperature sensing tube; Then, one end of the sensing arm A is inserted into the temperature sensing tube with a pressure balance hole, and the sensing arm A and the temperature sensing tube are fixed together at the fixed point A; Then, the temperature sensing tube with the reflection film A, the reflection film B and the sensing arm A is inserted into the quartz tube with the pressure balance hole, and the temperature sensing tube and the quartz tube are fixed together at the fixed point A; Then, the quartz tube is inserted into the sealing sleeve fixedly connected to the vacuum tube, and the quartz tube and the sealing sleeve are fixed together at the fixed point A; Then, one end of the sensing arm B is inserted into the sealing sleeve and the quartz tube in turn, and the sensing arm B is located outside the temperature sensing tube. Then, at the fixed point B, the sensing arm B and the quartz tube are fixed together, and a sealing treatment is performed at the connection between the sensing arm B and the sealing sleeve, so that the sealing sleeve seals the quartz tube, and the sensing arm B located between the quartz tube and the sealing sleeve is in a relaxed state; the cavity between the sensing arm A and the reflecting film A constitutes a main scale cavity, and the cavity between the sensing arm B and the reflecting film B constitutes a vernier cavity. At room temperature, the length of the main scale cavity is greater than or equal to times the length of the vernier cavity or less than or equal to 1 / 2 of the vernier cavity; Then, the vacuum tube is evacuated, and then the vacuum tube is fused and sealed, and then the sensing arm A and the sensing arm B are connected to the optical fiber coupling splitter, and then the optical fiber coupling splitter is connected to the optical fiber cable; Finally, a portion of the optical fiber cable, the optical fiber coupling splitter, the sensing arm A, the sensing arm B, the sealing sleeve, and the vacuum tube are fixed on the sensor base.

9. An ocean temperature sensor, characterized in that: The invention comprises a wide-spectrum light source, a spectrum demodulator, a fiber optic circulator and a sensor probe, wherein the sensor probe is a sensor probe based on a differential vernier effect as claimed in any one of claims 1 to 6; the wide-spectrum light source is connected to a first port of the fiber optic circulator, the spectrum demodulator is connected to a third port of the fiber optic circulator, and the fiber optic cable in the sensor probe is connected to a second port of the fiber optic circulator.

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