A temperature and depth dual-parameter sensor based on reflective OMC and its demodulation method

Abstract

This invention discloses a temperature and depth dual-parameter sensor based on a reflective OMC and its demodulation method. The temperature and depth dual-parameter sensor includes: a reflective OMC temperature sensor, a pressure-isolated protective shell, a reflective OMC pressure sensor, a pressure-encapsulated shell, a metal-encapsulated shell, an optical switch, a demodulator, and a computer. The overall structure is simple and easy to deploy; the sensor is easy to manufacture, has strong reusability, and is convenient to place. The designed metal-encapsulated shell not only improves the service life of the reflective OMC sensor but also enhances its pressure resistance. Since OMC sensors often suffer from cross-decoupling and large demodulation errors, the pressure-isolated protective shell ensures that the reflective OMC temperature sensor responds to only a single parameter, avoiding cross-sensitivity and reducing demodulation errors. Furthermore, this invention innovatively uses a demodulation method combining machine learning and sensitivity fitting, further reducing sensor demodulation errors and improving demodulation accuracy.

Description

Technical Field

[0001] This invention relates to the field of marine environmental monitoring equipment and fiber optic sensing technology, and more specifically to a high-sensitivity, high-precision temperature-depth dual-parameter sensor based on reflective OMC and a demodulation method. Background Technology

[0002] Currently, temperature and depth-pressure parameters are fundamental to obtaining parameters such as ocean sound velocity, current velocity, density, and heat content. Accurate measurement of ocean temperature and depth-pressure is crucial for ocean monitoring. Temperature-depth sensors, as basic equipment for ocean exploration, occupy an important position in marine economy, marine ecology, and marine military fields. Traditional XBT and TD sensors used for ocean temperature-depth detection mostly utilize electrical measurement elements. While electrical sensors are relatively mature, they suffer from low sensitivity and slow response time. Compared to electrical sensors, fiber optic marine environmental monitoring sensors overcome the disadvantages of traditional sensors, such as high cost, low measurement accuracy, and crosstalk between multiple parameters. They also offer advantages such as ease of deployment, the ability of a single sensor model to simultaneously sense multiple parameters, and the capacity to utilize various multiplexing technologies to deploy sensors on a large scale to form distributed marine environmental monitoring arrays. Therefore, fiber optic marine environmental monitoring sensors are receiving increasing attention.

[0003] In the field of fiber optic sensing, based on differences in sensing carriers and sensing mechanisms, fiber optic sensors mainly include fiber interferometer type, fiber surface plasmon resonance effect type, and Fabry-Borro type, etc. However, these types of sensors all suffer from problems such as short application life, difficulty in fabrication, and poor stability. Compared with other fiber optic sensors, micro / nano fiber (OMC) has advantages such as strong corrosion resistance, strong electromagnetic interference resistance, and fast response speed. Moreover, the strong optical field confinement capability and large evanescent field characteristics of OMC give it high sensitivity characteristics. Therefore, more and more researchers and engineers are conducting research on it.

[0004] Sensors based on OMC have been used in research on parameters such as temperature, salinity, depth, micro-stress, liquid refractive index, and magnetic field (e.g., Chinese patent "Marine Multi-parameter Integrated Monitoring System and Method Based on Micro-Nano Fiber Optic Semi-Coupled", patent number: ZL201811056286.X). Furthermore, the requirements for sensor accuracy and sensitivity are constantly increasing, and sensor structures are trending towards miniaturization.

[0005] Therefore, how to achieve high response speed, high sensitivity, high stability, and high precision in the measurement of both temperature and depth of seawater has become an urgent problem for professionals in the field. Summary of the Invention

[0006] In view of this, the present invention provides a temperature and depth dual-parameter sensor based on reflective OMC and a demodulation method, which solves the problems of insufficient accuracy and low sensitivity of current optical sensors, as well as the error amplification caused by the sensitivity matrix method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a temperature and depth dual-parameter sensor based on reflective OMC, comprising: a reflective OMC temperature sensor, a pressure-isolated protective shell, a reflective OMC pressure sensor, a pressure-encapsulated shell, a metal-encapsulated shell, an optical switch, a demodulator, and a computer;

[0009] The pressure-isolated protective shell encapsulates the reflective OMC temperature sensor inside, forming a temperature sensor; the pressure-encapsulated shell encapsulates the reflective OMC pressure sensor inside, forming a pressure sensor.

[0010] The temperature sensor and the pressure sensor are arranged in parallel inside the metal enclosure.

[0011] Both the reflective OMC temperature sensor and the reflective OMC pressure sensor include four ports, a tapered transition area, and a waist area; the four ports are port1, port2, port3, and port4; and port2, port3, and port4 are all encapsulated by metal tubes.

[0012] The port1 of each of the reflective OMC temperature sensor and the reflective OMC pressure sensor is connected to the two output ports of the optical switch; the input port of the optical switch is connected to one end of the demodulator; and the other end of the demodulator is connected to the computer.

[0013] Furthermore, the pressure isolation protective shell includes: a square groove, a support shell, a protective shell body, a cylindrical protective cylinder, and a base;

[0014] The square slot has a groove inside, and each end of the groove has an opening for placing and fixing a reflective OMC temperature sensor; the square slot is installed on the protective shell body;

[0015] The support shell is semi-cylindrical in shape, covers the square groove, and is fixed to the main body of the protective shell;

[0016] The protective shell body has a cylindrical symmetrical structure, with a fiber outlet hole and a rubber ring on the cylindrical head; the base is installed on one end of the cylindrical head of the protective shell body; the cylindrical protective tube surrounds the protective shell body and is fixed to the protective shell body together with the base.

[0017] Furthermore, the pressure-sealing housing includes: a square groove, a pressure-protecting housing body, and an upper shell;

[0018] The square groove has a recess inside, and each end of the recess has an opening for placing and fixing a reflective OMC pressure sensor; the square groove is installed on the pressure protection shell body, and the upper shell covers the square groove; the top of the upper shell has a square hole; the head of the pressure protection shell body has a fiber outlet.

[0019] Furthermore, the metal enclosure includes: a water inlet cover, an enclosure body, and a top cover; wherein the enclosure body houses the temperature sensor and the pressure sensor arranged in parallel.

[0020] The encapsulation body is cylindrical in shape and has a water inlet hole on the side;

[0021] The water inlet cover is a hemispherical metal cover with holes, which is sealed at the tail of the encapsulation body; the top cover is sealed at the head of the encapsulation body; the top cover is composed of arc-shaped columns, a ceiling and a cylindrical tube; multiple arc-shaped columns are arranged in a ring, with their two ends connected to the ceiling and the cylindrical tube respectively; the gap between any adjacent arc-shaped columns forms a cable channel; the ceiling has rope holes.

[0022] Furthermore, the optical switch is a 1:2 coupler with one input terminal and two output terminals, which splits the input optical signal into two output signals.

[0023] Furthermore, the fabrication process of the reflective OMC temperature sensor and the reflective OMC pressure sensor includes:

[0024] S1: A single-mode optical fiber is bent and folded in half to form a SAGNAC ring. The SAGNAC ring port is fixed with glue. Then, the cladding of the two optical fibers at the glue-fixed part of the SAGNAC ring is removed and fused and tapered to form a micro-nano fiber coupler SAGNAC ring.

[0025] S2: The fabricated micro-nano fiber optic coupler SAGNAC ring is then encapsulated in a square groove and coated with polydimethylsiloxane to enhance the temperature sensitivity of the sensor, thereby forming an OMC-SAGNAC ring structure.

[0026] S3: Cut the ring structure to obtain a four-port OMC. Port 3 is polished with a grinder, and after polishing, the end face is silvered with silver plating solution to form a silver reflector. Ports 2 and 4 are treated with refractive index matching liquid to eliminate end face reflection. Port 1 of the two sensors is connected to the output port of the optical switch. After processing, ports 2, 3 and 4 are encapsulated in a metal tube.

[0027] This invention also provides a demodulation method for a temperature and depth dual-parameter sensor based on a reflective OMC, comprising the following steps:

[0028] S1. First, the temperature sensor and pressure sensor are placed in a water tank filled with seawater for temperature calibration. The computer calculates the temperature sensitivity S of the pressure sensor by determining the wavelength-temperature relationship. T The pressure sensor was placed in a pressure tank for pressure calibration experiments, and the pressure sensitivity S of the pressure sensor was calculated. P At the same time, the original wavelength λ0 and the original ambient temperature T0 of the environment where the pressure sensor is located are measured.

[0029] S2. After the two sensors are packaged and cascaded and placed in a metal package, temperature and pressure experiments are conducted. A large number of reflection spectrum sample data of temperature and depth dual-parameter sensor under different temperature and pressure environments are obtained in multiple experiments.

[0030] S3. Match the temperature data recorded in the time domain with the real-time spectral data to obtain a large amount of spectral data of the reflective temperature sensor at different temperatures; use the large sample of collected spectral data to construct a dataset, divide it into training set and test set according to a preset ratio, and establish a machine learning model for training and testing; after the model is established, the temperature at the sensor location is obtained by inputting the wavelength value of the valley in the spectrum of the reflective OMC temperature sensor.

[0031] S4. Obtain the temperature T measured by the reflective temperature sensor through the PSO-SVR algorithm, and substitute it into the formula, where Δλ=λ-λ0, ΔT=T-T0, ΔP=P-P0, and P0 is the atmospheric pressure.

[0032] Δλ=S p ΔP+S T ΔT

[0033] The automatic peak-finding algorithm in the dynamic range spectrum of the pressure sensor calculates the wavelength value λ of the trough in the spectrum at this moment, and substitutes it into the above formula to obtain the pressure P of the environment at this moment.

[0034] As can be seen from the above technical solutions, compared with existing technologies:

[0035] 1. The packaging structure of this invention solves the cross-decoupling problem of multi-parameter measurement in OMC type sensors, and improves the accuracy of sensor measurement data.

[0036] 2. The encapsulation shell designed in this invention not only improves the service life of the reflective OMC sensor, but also effectively enhances the measurement stability of the sensor.

[0037] 3. The method of measuring temperature and pressure separately using a dual OMC structure cascade in this invention not only avoids cross-decoupling, but also achieves high sensitivity sensing for stable temperature and pressure. The combination of direct solution and machine learning demodulation methods further reduces errors and improves accuracy. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the overall connection of a temperature and depth dual-parameter sensor based on a reflective OMC.

[0040] Figure 2 This is a schematic diagram of the demodulation principle of a temperature and depth dual-parameter sensor based on a reflective OMC.

[0041] Figure 3 This is a structural diagram of a reflective OMC sensor.

[0042] Figure 4 This is an exploded structural diagram of the pressure isolation protective shell 2.

[0043] Figure 5 This is a structural diagram of square groove 2-1.

[0044] Figure 6 This is a structural diagram of the main body of the protective shell, 2-3.

[0045] Figure 7 This is a structural diagram of the pressure-sealed housing 4.

[0046] Figure 8 This is a structural diagram of the metal encapsulation shell 5.

[0047] Figure 9 The flowchart is for the PSO-SVR algorithm. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0049] Example 1:

[0050] Reference Figure 1 , Figure 2 As shown, an embodiment of the present invention discloses a device comprising: a reflective OMC temperature sensor 1, a pressure isolation protective shell 2, a reflective OMC pressure sensor 3, a pressure encapsulation shell 4 and a metal encapsulation shell 5, an optical switch 6, a demodulator 7 and a computer 8.

[0051] The specific structure of the temperature-depth dual-parameter sensor refers to: a temperature sensor made of a reflective OMC temperature sensor 1 encapsulated in a pressure-isolated protective shell 2, and a pressure sensor made of a reflective OMC pressure sensor 3 encapsulated in a pressure-encapsulated shell 4.

[0052] Temperature and pressure sensors are arranged in parallel inside the metal enclosure 5; (refer to...) Figure 3 As shown, both the reflective OMC temperature sensor 1 and the reflective OMC pressure sensor 3 include four ports, a tapered transition region 1-1, and a waist region 1-2. The four ports are port1, port2, port3, and port4. Ports 2, 3, and 4 are all encapsulated in metal tubes. The reflective OMC sensor is first constructed by structurally controllable fused tapering of a single-mode optical fiber using a fiber tapering system to create a micro / nano fiber coupler SAGNAC (OMC-SAGNAC) ring structure. Subsequently, the OMC-SAGNAC ring is cut to form a four-port micro / nano device. Port1 is connected to the optical switch 6, port3 is silver-plated using silver plating solution, and ports 2 and 4 are treated with refractive index matching solution to eliminate fiber end-face reflection. After processing, ports 2, 3, and 4 are encapsulated in metal tubes.

[0053] like Figure 2 As shown, port 1 of both the reflective OMC temperature sensor 1 and the reflective OMC pressure sensor 3 is connected to the two output ports of the optical switch 6; the input port of the optical switch 6 is connected to one end of the demodulator 7; and the other end of the demodulator 7 is connected to the computer 8.

[0054] In its implementation, the optical switch 6 employs a 1:2 coupler to split an optical signal into two outputs. It is typically constructed from optical fibers or waveguides, designed so that the input optical signal is divided into two output signals, with the intensity of the output signal proportional to the intensity of the input signal. The 1:2 coupler is used to distribute the optical signal to different channels or sensors to achieve data transmission or detection functions.

[0055] The demodulator 7 outputs a control signal to the sensor and converts the sensor's output optical signal into an electrical signal, which is then sent to the signal demodulation computer 8. The computer 8 can demodulate the spectral data transmitted by the sensor in real time and calculate the real-time temperature and pressure of the sensor's environment to ensure timely and accurate monitoring of environmental changes.

[0056] The sensing principles of reflective OMC temperature sensor 1 and reflective OMC pressure sensor 3 are as follows:

[0057] According to the local coupled-mode theory, the total coupling in an OMC is the superposition of its local couplings. The entire coupling region of an OMC includes a weakly coupled region in the tapered transition zone, a strongly coupled region, and a strongly coupled region in the uniform waist zone. The degree of fusion between two fibers in an OMC can be represented by D = d / r, where d is the distance between the two fiber cores and r is the radius of one of the tapered regions.

[0058] When D>=2, it is defined as weak coupling, and the weak coupling coefficient is expressed by the following formula:

[0059]

[0060] z(x) = x / 2

[0061] Where k is a constant, U ∞ =2.405, representing the cutoff frequency of the higher-order modes, r representing the radius of the cone region, z representing the length of one of the cone regions, x representing the length of the melt-drawn cone, and V WC Let n be the normalized frequency of the cone region, n3 be the refractive index of the seawater environment, and n2 be the refractive index around the waist region of the OMC, which is in most cases either air or seawater. Unlike parallel waveguide couplers, in an axially varying coupler structure, the transverse dimension of the interacting fiber varies along its length. Therefore, the coupling coefficient also varies with z, which can be expressed as C(z). The function C(z) depends on the longitudinal shape of the cone region and the dimensions and refractive index distribution of the coupler cross-section. Therefore, the power distribution between the coupler output ports depends on the effective length of the interaction (waist region length) and the effective coupling coefficient C.

[0062] When D < 2, it is defined as strong coupling, and the strong coupling coefficient C SC It can be expressed by the following formula:

[0063]

[0064] Where a is a constant, representing the radius of the uniform waist region, V SC The normalized frequency of the uniform waist region. Light with intensity P0 enters from input port 2, reaches the uniform waist region 1-2 for coupling, and then propagates to the through arm port 4. The light intensity of this light is:

[0065]

[0066] Where l represents the waist length; then the light is reflected back to the uniform waist 1-2 by the mirror for secondary coupling and returns to the output light intensity P1' of port 1:

[0067]

[0068] Furthermore, by using a demodulator to monitor port1 and training the machine with the full-spectrum wavelength-intensity information using the PSO-SVR algorithm, simultaneous measurement of seawater temperature and pressure can be achieved.

[0069] Reference Figure 4 As shown, the pressure isolation protective shell 2 includes a square groove 2-1, a support shell 2-2, a protective shell body 2-3, a cylindrical protective cylinder 2-4, and a base 2-5. (Refer to...) Figure 5 As shown, the square slot 2-1 contains a recess 2-1-1, with an opening 2-1-2 at each end for housing and fixing the reflective OMC 1, i.e., for housing the reflective micro / nano optical fiber. The square slot 2-1 is mounted on the protective housing body 2-3. The support shell 2-2 is semi-cylindrical and is fixed to the protective housing body 2-3 with screws, completely covering the square slot 2-1 to prevent the reflective OMC temperature sensor 1 encapsulated in the square slot 2-1 from being affected by excessive pressure. (Refer to...) Figure 6 As shown, the protective shell body 2-3 has a cylindrical symmetrical structure. The cylindrical head has a fiber outlet hole 2-3-3 and a rubber ring 2-6, which can connect to the cylindrical protective cylinder 2-4 to ensure overall sealing. The protective shell body has a large groove 2-3-1 and a threaded hole 2-3-2, used to accommodate the square slot and fix the support shell, respectively. The head of the protective shell body has a fiber outlet 2-3-3, through which ports 1 and 2 of the reflective OMC temperature sensor 1 pass. The cylindrical protective cylinder 2-4 and the base 2-5 have rubber rings 2-6 at their openings. After the protective shell body is placed inside the cylindrical protective cylinder and the base is connected to the cylindrical protective cylinder, the rubber rings 2-6 ensure that the entire temperature sensor is sealed.

[0070] Reference Figure 7 As shown, the pressure encapsulation housing 4 comprises a square groove 2-1, a pressure protection housing body 4-1, and an upper shell 4-2. The pressure protection housing body has a large groove 4-1-1 and a threaded hole 4-1-3, which are used to fix the square groove 4-1 and the upper shell 4-2. The pressure protection housing body 4-1 has a fiber outlet 4-1-2 at its head. The top of the upper shell 4-2 has a square hole 4-2-1, which is used to allow seawater to enter and contact the reflective OMC pressure sensor.

[0071] Reference Figure 8As shown, the metal enclosure 5 includes a water inlet cover 5-1, an enclosure body 5-2, and a top cover 5-3. Its main function is to house and integrate the cascaded reflective OMC temperature sensor 1 and reflective OMC pressure sensor 3 into a single sensor structure. The water inlet cover is a hemispherical metal cover with a water inlet hole 5-1-1, allowing water pressure to act on the base and drive the force transmission rod to move. The enclosure body 5-2 is cylindrical with a water inlet hole 5-2-1 on the side, and two sensors can be placed in the middle of the cylinder. The top cover 5-3 is composed of four arc-shaped pillars 5-3-1 connected to the ceiling 5-3-2 and the cylindrical tube 5-3-3. The arc-shaped pillars 5-3-1 reduce the head weight, allowing the sensor to free fall in the water; the gaps between any adjacent arc-shaped pillars form a cable channel. The cylindrical tube 5-3-3 has threads for threaded connection with the enclosure body 5-2. The ceiling panel 5-3-2 has a circular rope hole 5-3-2-1 in the middle, which can be used to connect cables.

[0072] Furthermore, the fabrication method of the reflective OMC temperature sensor 1 and the reflective OMC pressure sensor 3 is as follows:

[0073] S1: A single-mode optical fiber is bent and folded in half to form a SAGNAC ring. The SAGNAC ring port is fixed with glue. Then, the cladding of the two optical fibers at the glue-fixed part of the SAGNAC ring is removed and fused tapered to form a micro-nano fiber coupler SAGNAC ring.

[0074] S2: The fabricated micro / nano fiber optic coupler SAGNAC ring is then encapsulated in a square groove and coated with polydimethylsiloxane (PDMS) to enhance the sensor's temperature sensitivity, thereby forming an OMC-SAGNAC ring structure.

[0075] S3: Cut the ring structure to obtain a four-port OMC. Port 3 is polished with a grinder. After polishing, the end face is silvered with silver plating solution to form a silver reflector. Ports 2 and 4 are treated with refractive index matching liquid to eliminate end face reflection. Port 1 of the two sensors is connected to the output port of optical switch 6. After processing, ports 2, 3 and 4 are encapsulated in a metal tube.

[0076] Then, the reflective OMC temperature sensor 1, made by this method, is externally encapsulated with a pressure-isolated protective shell 2; the reflective OMC pressure sensor 3, made by this method, is externally encapsulated with a pressure-encapsulated shell 4; and then the two are cascaded and encapsulated in a metal encapsulation shell 5.

[0077] In this embodiment, there are only two sensors: a reflective OMC temperature sensor and a pressure sensor. They are then cascaded and housed in a large metal enclosure 5. The temperature sensor measures temperature, and the pressure sensor measures pressure. However, since both sensors have the same structure, they will respond to both temperature and pressure, which leads to cross-decoupling. Therefore, a pressure-isolated protective shell and a pressure-encapsulated shell, along with a demodulation method, are designed to solve this problem.

[0078] This invention utilizes a reflective OMC structure and proposes a high-sensitivity, high-precision temperature-depth dual-parameter sensor based on reflective OMC. The overall structure is simple and easy to deploy; the sensor is easy to manufacture, has strong reusability, and is convenient to place. A special metal encapsulation shell is also designed, which not only improves the service life of the reflective OMC sensor but also enhances its pressure resistance. Since OMC sensors often suffer from cross-decoupling and large demodulation errors, the pressure-isolated protective shell designed in this invention ensures that the reflective OMC temperature sensor responds to only a single parameter, avoiding cross-sensitivity and reducing demodulation errors.

[0079] Example 2:

[0080] A demodulation method for a temperature and depth dual-parameter sensor based on a reflective OMC includes the following steps:

[0081] S1. First, the temperature sensor and pressure sensor are placed in a water tank filled with seawater for temperature calibration. The computer calculates the temperature sensitivity S of the pressure sensor by determining the wavelength-temperature relationship. T The pressure sensor was placed in a pressure tank for pressure calibration experiments, and the pressure sensitivity S of the pressure sensor was calculated. P At the same time, the original wavelength λ0 and the original ambient temperature T0 of the environment where the pressure sensor is located are measured.

[0082] S2. After the two sensors are packaged and cascaded and placed in a metal enclosure, temperature and pressure experiments are conducted. A large number of reflection spectrum sample data of the temperature-depth dual-parameter sensor under different temperature and pressure environments are obtained in multiple experiments.

[0083] S3. The temperature data recorded by TD was matched with the real-time spectral data to obtain a large amount of spectral data of the reflective temperature sensor at different temperatures. For example, a large sample of the collected spectral data was used to construct a dataset with 122 samples in the dataset, ranging from 3℃ to 40℃. All data were different. About 80% (97) of these samples were randomly put into the training set, and the remaining 20% ​​(25) of the samples were put into the test set to verify the demodulation results of the machine learning method. After the verification was completed and the model was established, the temperature at the location of the sensor could be known by inputting the wavelength value of the valley in the spectrum of the reflective OMC temperature sensor.

[0084] S4, see reference Figure 9 As shown, the temperature T measured by the reflective temperature sensor is obtained through the PSO-SVR algorithm. Substituting this into the formula, where Δλ=λ-λ0, ΔT=T-T0, ΔP=P-P0, and P0 is the atmospheric pressure.

[0085] Δλ=S p ΔP+S T ΔT

[0086] The wavelength value λ of the trough in the spectrum at this moment is calculated by the automatic peak finding algorithm in the dynamic range spectrum of the pressure sensor. Substituting this value into the above formula, the pressure P of the environment at this moment can be obtained.

[0087] To address the ill-conditioned matrix error introduced by traditional sensitivity matrix demodulation methods, this invention innovatively employs a demodulation method combining machine learning and sensitivity fitting, further reducing sensor demodulation error and improving demodulation accuracy.

[0088] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0089] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A temperature and depth dual-parameter sensor based on reflective OMC, characterized in that, include: Reflective OMC temperature sensor (1), pressure isolation protective housing (2), reflective OMC pressure sensor (3), pressure encapsulation housing (4), metal encapsulation housing (5), optical switch (6), demodulator (7), and computer (8); Among them, the pressure isolation protective shell (2) encapsulates the reflective OMC temperature sensor (1) inside to form a temperature sensor; the pressure encapsulation shell (4) encapsulates the reflective OMC pressure sensor (3) inside to form a pressure sensor. The temperature sensor and the pressure sensor are arranged in parallel inside the metal encapsulation housing (5); The reflective OMC temperature sensor (1) and the reflective OMC pressure sensor (3) both include four ports, a conical transition area (1-1), and a waist area (1-2); the four ports are port1, port2, port3, and port4; the ports2, port3, and port4 are all encapsulated by metal tubes. The port1 of each of the reflective OMC temperature sensor (1) and the reflective OMC pressure sensor (3) is connected to the two output ports of the optical switch (6); the input port of the optical switch (6) is connected to one end of the demodulator (7); and the other end of the demodulator (7) is connected to the computer (8). The pressure isolation protective shell (2) includes: a square groove (2-1), a support shell (2-2), a protective shell body (2-3), a cylindrical protective cylinder (2-4), and a base (2-5); The square groove (2-1) has a recess (2-1-1) inside, and each end of the recess has an opening (2-1-2) for placing and fixing the reflective OMC temperature sensor (1); the square groove (2-1) is installed on the protective shell body (2-3); The support shell (2-2) is semi-cylindrical in shape, covering the square groove (2-1) and fixed to the protective shell body (2-3); The protective shell body (2-3) has a cylindrical symmetrical structure, with a fiber outlet hole (2-3-3) and a rubber ring (2-6) on the cylindrical head; the base (2-5) is installed on one end of the cylindrical head of the protective shell body (2-3); the cylindrical protective tube (2-4) surrounds the protective shell body (2-3) and is fixed to the protective shell body (2-3) together with the base (2-5); The pressure-sealed outer shell (4) includes: a square groove (2-1), a pressure-protected shell body (4-1), and an upper shell (4-2); The square groove (2-1) has a recess (2-1-1) inside, and each end of the recess has an opening (2-1-2) for placing and fixing a reflective OMC pressure sensor (3); the square groove (2-1) is installed on the pressure protection shell body (4-1), and the upper shell (4-2) covers the square groove (2-1); the top of the upper shell (4-2) has a square hole (4-2-1); the head of the pressure protection shell body is provided with a fiber outlet (4-1-2); The metal encapsulation shell (5) includes: a water inlet cover (5-1), an encapsulation body (5-2), and a top cover (5-3); wherein, the encapsulation body (5-2) accommodates the temperature sensor and the pressure sensor arranged in parallel; The encapsulation body (5-2) is cylindrical in shape and has a water inlet hole (5-2-1) on the side; The water inlet cover is a perforated hemispherical metal cover that seals the tail of the encapsulation body (5-2); the top cover (5-3) seals the head of the encapsulation body (5-2); the top cover (5-3) is composed of an arc-shaped column (5-3-1), a ceiling (5-3-2), and a cylindrical tube (5-3-3); multiple arc-shaped columns (5-3-1) are arranged in a ring, with their two ends connected to the ceiling (5-3-2) and the cylindrical tube (5-3-3) respectively; the gaps between any adjacent arc-shaped columns form cable channels; the ceiling (5-3-2) has rope holes.

2. The temperature and depth dual-parameter sensor based on reflective OMC according to claim 1, characterized in that, The optical switch (6) is a 1:2 coupler with one input terminal and two output terminals, which splits the input optical signal into two output signals.

3. A temperature and depth dual-parameter sensor based on reflective OMC according to claim 1, characterized in that, The fabrication process of the reflective OMC temperature sensor (1) and the reflective OMC pressure sensor (3) includes: S1: A single-mode optical fiber is bent and folded in half to form a SAGNAC ring. The SAGNAC ring port is fixed with glue. Then, the cladding of the two optical fibers at the glue-fixed part of the SAGNAC ring is removed and fused and tapered to form a micro-nano fiber coupler SAGNAC ring. S2: The fabricated micro-nano fiber optic coupler SAGNAC ring is then encapsulated in a square groove and coated with polydimethylsiloxane to enhance the temperature sensitivity of the sensor, thereby forming an OMC-SAGNAC ring structure. S3: Cut the ring structure to obtain a four-port OMC. Port 3 is polished with a grinder, and after polishing, the end face is silvered with silver plating solution to form a silver reflector. Ports 2 and 4 are treated with refractive index matching liquid to eliminate end face reflection. Port 1 of the two sensors is connected to the output port of the optical switch. After processing, ports 2, 3 and 4 are encapsulated in a metal tube.

4. A demodulation method for a temperature and depth dual-parameter sensor based on a reflective OMC, characterized in that, The temperature and depth dual-parameter sensor based on a reflective OMC as described in any one of claims 1-3 includes the following steps: S1. First, the temperature sensor and pressure sensor are placed in a water tank filled with seawater for temperature calibration experiments; then, for the pressure sensor, a computer is used to calculate the wavelength-temperature relationship to determine the temperature sensitivity S of the pressure sensor. T The pressure sensor was placed in a pressure tank for pressure calibration experiments, and the pressure sensitivity S of the pressure sensor was calculated. P At the same time, the original wavelength λ0 and the original ambient temperature T0 of the environment where the pressure sensor is located are measured. S2. After the two sensors are packaged and cascaded and placed in a metal package, temperature and pressure experiments are conducted. A large number of reflection spectrum sample data of temperature and depth dual-parameter sensor under different temperature and pressure environments are obtained in multiple experiments. S3. Match the temperature data recorded in the time domain with the real-time spectral data to obtain a large amount of spectral data of the reflective temperature sensor at different temperatures; use the large sample of collected spectral data to construct a dataset, divide it into training set and test set according to a preset ratio, and establish a machine learning model for training and testing; after the model is established, the temperature at the sensor location is obtained by inputting the wavelength value of the valley in the spectrum of the reflective OMC temperature sensor. S4. Obtain the temperature T measured by the reflective temperature sensor through the PSO-SVR algorithm, and substitute it into the formula, where Δλ=λ-λ0, ΔT=T-T0, ΔP=P-P0, and P0 is the atmospheric pressure. Δλ=S p ΔP+S T ΔT The automatic peak-finding algorithm in the dynamic range spectrum of the pressure sensor calculates the wavelength value λ of the trough in the spectrum at this moment, and substitutes it into the above formula to obtain the pressure P of the environment at this moment.

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