Wavelength modulation type optical differential pressure transmitter based on MEMS technology and F-P cavity principle

Abstract

The invention belongs to the technical field of optical sensing, and particularly relates to a wavelength modulation type optical differential pressure transmitter based on an MEMS manufacturing process and an optical fiber F-P cavity principle. Comprising a differential pressure sensor and a full spectrum analyzer which are connected and combined together through an optical fiber cable in a split mode. The optical differential pressure transmitter has the beneficial effects that (1) the optical differential pressure transmitter manufactured on the basis of an optical fiber micro electro mechanical system (MEMS) micromachining technology realizes chip manufacturing of an optical fiber MEMS sensor, is simple in structure, high in packaging integration level and miniaturized in appearance size, and has the advantages of being small in size, light in weight, soft, variable in appearance and the like; and (2) the optical differential pressure transmitter provided by the invention adopts an optical fiber F-P flat plate interference mechanism and a film-island sensitive structure, has excellent linearity and high resolution, has a huge linear dynamic range, and realizes ultra-high-precision measurement.

Description

Technical Field

[0001] The invention belongs to the technical field of optical sensing, and in particular relates to a wavelength modulated optical differential pressure transmitter based on a MEMS manufacturing process and an optical fiber FP cavity principle. Background Art

[0002] Differential pressure transmitters based on traditional measurement principles generally adopt silicon piezoresistive, capacitive, diffused silicon or single crystal silicon principle technologies. In actual applications, they have the following technical problems: bulky appearance and structure, large installation stress and welding stress, significant influence of electromagnetic interference, temperature and static pressure on the accuracy and long-term stability of differential pressure sensor measurement, large noise interference on analog output, limited transmission distance, small temperature range, susceptibility to humidity and chemical corrosion, complex installation and maintenance, both measurement and signal transmission are susceptible to electromagnetic interference, poor radiation resistance, poor accuracy of micro differential pressure transmitters, large measurement errors, poor stability and susceptibility to the surrounding environment.

[0003] There are the following inherent disadvantages in practical applications:

[0004] Poor anti-electromagnetic interference ability: Traditional transmitters (such as silicon piezoresistive and capacitive) are easily affected by the surrounding electromagnetic interference, especially when there are high-power rotating equipment or long-distance transmission, the electromagnetic interference is more obvious, resulting in unstable signals and inaccurate measurement results.

[0005] Bulky structure: These transmitters are usually bulky in design, complex to install and take up a lot of space. Stress is easily generated during the installation process, which will affect the long-term stability and measurement accuracy of the sensor.

[0006] Significant temperature influence: Traditional measurement principle pressure transmitters are very sensitive to temperature changes and are prone to drift under different temperature conditions. Complex temperature compensation measures are required to ensure measurement accuracy. Temperature has a significant impact on the aging of differential pressure transmitters, affecting their service life.

[0007] Significant influence of static pressure: Changes in static pressure have a significant impact on the measurement accuracy of traditional sensors, often leading to large measurement errors and a large calibration workload. In addition, the system static pressure has different effects on different meters, which are not batch- and repeatable.

[0008] Large noise interference: Traditional pressure transmitters with analog output are susceptible to noise interference, and errors may occur during signal transmission, especially over long distances.

[0009] Limited transmission distance: Traditional electrical analog signals have limited transmission distance. Signal attenuation and noise interference are serious problems during long-distance transmission, and they cannot effectively resist the impact of severe weather such as lightning strikes outdoors.

[0010] Small temperature range: Traditional sensors have unstable performance in extreme temperature environments, which limits their application in high or low temperature environments.

[0011] Susceptible to humidity and chemical corrosion: Traditional sensor materials and designs make them susceptible to environmental humidity and chemical corrosion, which reduces service life and reliability.

[0012] Complex installation and maintenance: The installation and maintenance process of traditional pressure transmitters is cumbersome, time-consuming and costly.

[0013] Poor radiation resistance: Traditional pressure transmitters have poor resistance to radiation environments, and some materials cannot withstand long-term radiation exposure, resulting in loss of performance or reduced sealing performance, and cannot meet the technical and functional requirements in nuclear power accident environments.

[0014] Poor stability of micro differential pressure transmitter: Micro differential pressure transmitter based on traditional measurement principle is easily affected by changes in external environment, has poor measurement stability, low measurement accuracy and large display error.

[0015] These shortcomings limit the application of traditional differential pressure transmitters in certain harsh environments. In contrast, traditional fiber optic pressure sensors also have different shortcomings such as low sensitivity, slow response speed, and poor micro differential pressure measurement capabilities. For example, the microbend structure period of the fiber grating sensor has strict requirements, so the mechanical design is quite complicated. In addition, the acceleration effect will also deteriorate its performance: For example, the intensity modulated fiber optic pressure sensor has high requirements for the flatness of the fiber end face. When the distance between the fiber end faces increases, the coupling efficiency will decrease exponentially. Therefore, the processing accuracy requirements are high, and the primary dynamic range is relatively small, which is not suitable for occasions with large pressure changes. Summary of the invention

[0016] The purpose of the present invention is to provide a wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle. The transmitter adopts a split structure design, uses a passive pressure chip based on the optical fiber FP cavity interference principle made by MEMS technology, and uses a digital wavelength demodulation method and an intelligent logic algorithm to realize the differential pressure measurement of the measured medium, thereby solving the inherent shortcomings of differential pressure transmitters based on traditional measurement principles and traditional optical fiber differential pressure transmitters.

[0017] The present invention is implemented as follows: it includes a differential pressure sensor and a full spectrum analyzer, which are connected and combined together in a split manner through optical fiber cables; 3 or 6 pressure measurement chips are arranged in the pressure sampling cavity of the instrument pressure lead pipe, and an optical fiber temperature chip is set at the same measurement plane to perform real-time temperature compensation on the pressure measurement signal to eliminate the influence of temperature on the measured medium, forming a differential pressure sensing core body with three-channel redundant measurement and instant temperature compensation of temperature and pressure integration, the differential pressure sensing core body adopts a dual absolute pressure sensing chip measurement method, which is respectively installed on the positive and negative pressure sides of the differential pressure sensor to measure the actual pressure and temperature of the measured medium on the positive and negative pressure sides, the differential pressure sensor encodes the measured pressure optical signal and temperature optical signal and transmits them to the full spectrum analyzer through an optical fiber connector, an optical fiber cable and an optical fiber penetration, and the full spectrum analyzer demodulates and temperature compensates the pressure measurement values ​​on the positive and negative pressure sides respectively.

[0018] The differential pressure sensor comprises a pressure taking structure, a positive pressure side pressure taking cavity and a negative pressure side pressure taking cavity with the same structure, a positive pressure side differential pressure sensing core and a negative pressure side differential pressure sensing core with the same structure, a core fixed connection structure, an optical fiber winding chamber, a plug-in seal and an optical fiber transfer connector; wherein, the pressure taking structure is respectively provided with a positive pressure side pressure taking cavity and a negative pressure side pressure taking cavity, the positive pressure side differential pressure sensing core and the negative pressure side differential pressure sensing core are installed in the core fixed connection structure, and are respectively welded to the positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity by glass melting, the optical fiber pigtail on the sensing core is sent into the optical fiber winding chamber through the core fixed connection structure, the optical fiber pigtail of excess length is wound in the chamber and welded to the optical fiber transfer connector, and the optical fiber winding chamber is sealed by the plug-in seal.

[0019] The pressure taking structure, the positive pressure side differential pressure sensing core, the negative pressure side differential pressure sensing core, the core fixing connection structure and the optical fiber coil chamber are assembled by bolts and nuts and fastened together by crimping and sealing to form a differential pressure sensor.

[0020] The differential pressure sensor measures the optical signal obtained by the differential pressure sensing core in the positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity, and connects it to the optical fiber transfer connector and the optical fiber cable through the optical fiber pigtail. The optical fiber cable transmits the optical signal to the full spectrum analyzer through the optical interface for demodulation calculation and display output, thus forming a complete differential pressure transmitter measurement circuit.

[0021] The positive pressure side differential pressure sensing core and the negative pressure side differential pressure sensing core of the differential pressure sensor are both MEMS optical fiber absolute pressure sensing cores. The medium pressures of the upstream and downstream pressure taking ports are measured respectively through the positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity on the pressure taking structure. The measured optical signal is connected to the optical fiber cable through the optical fiber transfer connector on the differential pressure sensor. The optical fiber cable sends the optical signal to the full spectrum analyzer through the optical interface module. The full spectrum analyzer provides a standard light wave signal to the differential pressure sensor. At the same time, the wavelength demodulation calculation of the optical fiber measurement signal fed back by the differential pressure sensor is performed and the differential pressure value of the measured medium is calculated through a specific fitting algorithm and logical operation.

[0022] The positive pressure side pressure taking cavity is communicated with the positive pressure side differential pressure sensing core, and the negative pressure side pressure taking cavity is communicated with the negative pressure side differential pressure sensing core; the positive pressure side differential pressure sensing core and the negative pressure side differential pressure sensing core have the same structure; the positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity have the same structure, both of which are standard threaded interfaces, which are used to connect the measured medium and measure the absolute pressure of the positive and negative pressure sides of the measured medium in real time. The positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity are not communicated with each other, thereby realizing the isolation of the positive and negative pressure sides.

[0023] The differential pressure sensing core is divided into a differential pressure sensing core without static pressure and a differential pressure sensing core with static pressure.

[0024] The static-pressure-free differential pressure sensing core is composed of three absolute pressure chip modules and one temperature chip module, and is used to sense pressure signals and temperature signals; the differential pressure sensing core is a cylindrical structure, and three MEMS optical fiber absolute pressure chip modules and one optical fiber temperature chip module are welded and packaged in a stainless steel differential pressure sensing core by glass melting, wherein the optical fiber temperature chip module is installed in the center of the differential pressure sensing core, and the three MEMS optical fiber absolute pressure chip modules are symmetrically distributed around the optical fiber temperature chip module in the core, and are arranged at an angle of 120°.

[0025] The static pressure differential pressure sensing core is composed of 6 absolute pressure chip modules and 1 temperature chip module, which is used to sense pressure signals and temperature signals. The differential pressure sensing core is a cylindrical structure, wherein the 6 absolute pressure chip modules are respectively composed of 3 large static pressure range absolute pressure chips and 3 small range absolute pressure chips. 6 MEMS fiber optic absolute pressure chip modules and 1 fiber optic temperature chip module are welded and packaged in a stainless steel differential pressure sensing core by glass melting. The fiber optic temperature chip module is installed in the center of the differential pressure sensing core. The 6 MEMS fiber optic absolute pressure chip modules are symmetrically distributed around the fiber optic temperature chip module in the core and arranged at an angle of 60°.

[0026] The MEMS fiber absolute pressure chip module comprises a fiber pigtail and a chip packaging module. The chip packaging module adopts two silicon wafer planes manufactured by MEMS technology, namely, a first silicon wafer plane and a second silicon wafer plane to form a FP vacuum interference cavity chip. The standard light signal is sent to the interference cavity formed by the first silicon wafer plane and the second silicon wafer plane through the fiber pigtail for multiple refractions. The light wave refraction signals representing different pressures are transmitted through the fiber pigtail to complete the light wave measurement function.

[0027] The full spectrum analyzer is used to provide standard light waves, light wave signal demodulation, data processing and intelligent calculation. The internal circuit of the analyzer converts the sensed optical signal into a digital signal, and performs photoelectric data conversion and specific logic calculation according to the redundant intelligent diagnosis logic of the differential pressure transmitter without static pressure and the redundant intelligent diagnosis logic of the differential pressure transmitter with static pressure, outputs differential pressure data, and transmits the 4~20mA signal or digital signal or in the form of a communication protocol through the communication module and interface.

[0028] The overall appearance of the full spectrum analyzer is a rectangular parallelepiped, in which the side that generates input and output interfaces with the outside world contains an optical interface, a communication interface and a power interface, and the other sides are all smooth surfaces. The structural shell is the supporting component of the analyzer, and the upper shell cover and the shell bottom plate together constitute the protective shell of the analyzer. The integrated power module, acquisition module and light source module are installed in the analyzer in sequence, in which the power interface is installed on the power module, the communication interface is installed on the acquisition module, and the optical interface is installed on the light source module.

[0029] The optical fiber cable comprises an integrated MPO connector, a transmission optical cable and a single-core connector; the integrated MPO connector is connected to the single-core connector via the transmission optical cable, wherein the integrated MPO connector of the optical fiber cable is inserted into the optical interface of the full spectrum analyzer, and the single-core connector is connected to the optical fiber transfer connector on the differential pressure sensor, so as to transmit the optical signal of the sensor to the full spectrum analyzer, and together form a differential pressure transmitter measurement system.

[0030] One end of the fiber feedthrough is connected to the single-core connector of the fiber optic cable and then connected to the full spectrum demodulator, while the other end of the fiber optic feedthrough is connected to the fiber optic transfer connector of the gauge pressure sensor through the fiber optic cable.

[0031] The optical fiber feedthrough comprises a stainless steel tube, a boss, a copper tube and a pressure test port. The boss is mounted on both ends of the stainless steel tube by welding. A through hole is opened in the middle of the boss as a pressure test port. Multiple copper tubes are inserted in the axial position of the boss. Optical fibers are installed in the copper tubes for connecting to optical fiber cables.

[0032] The beneficial effects of the present invention are as follows: (1) The optical differential pressure transmitter manufactured by the present invention based on the optical fiber micro-electromechanical system (MEMS) micromachining technology realizes the chip-based production of optical fiber MEMS sensors, has a simple structure, high packaging integration, miniaturized external dimensions, and has the advantages of small size, light weight, softness, and variable appearance; (2) The optical differential pressure transmitter proposed by the present invention adopts the optical fiber FP flat plate interference mechanism and membrane-island sensitive structure, has excellent linearity, high resolution, and a huge linear dynamic range to achieve ultra-high precision measurement; (3) The MEMS optical differential pressure transmitter manufactured by the present invention based on the optical fiber FP flat plate interference principle has good temperature resistance and the upper limit of the operating temperature can reach 400 to 600 degrees Celsius; (4) The optical differential pressure transmitter proposed by the present invention The differential pressure transmitter has the advantages of non-conductivity, little effect on the measured medium, and high sensitivity; (5) The optical differential pressure transmitter proposed in the present invention has the advantages of zero drift, good stability, good repeatability, etc., which greatly improves the long-term stability and calibration-free cycle of the differential pressure transmitter; (6) The differential pressure transmitter based on the optical measurement principle proposed in the present invention realizes the MEMS chip production of optical interferometer, that is, the "passive sensorization" of precision optical measuring instruments. Both the sensor and the optical fiber cable are passive devices, which are completely resistant to interference from static electricity, electromagnetic and radio frequency sources, and have the advantage of anti-electronic interference; (7) The optical differential pressure transmitter proposed in the present invention has a tiny sensor chip, and a single sensor core can realize multi-chip redundant backup and multi-range combination. The differential pressure sensing core of the positive and negative pressure sides adopts 3 or 6 absolute pressure chip modules in redundant arrangement, and 1 temperature chip module is set for each side, which innovatively forms a redundant measurement scheme of temperature and pressure integration, and can timely and accurately eliminate the temperature influence of the measuring medium through temperature compensation measures. The redundant setting of the absolute pressure chip improves the reliability and accuracy of the measurement, and greatly improves the stability and reliability of the differential pressure transmitter measurement; (8) The optical differential pressure transmitter proposed in the present invention adopts a passive sensor and a wavelength demodulation device arranged separately, and the measured passive optical fiber signal can be isolated for long-distance transmission, which is easier to use and maintain, and easy to realize the PHM expansion function; (9 ) The optical differential pressure transmitter proposed in the present invention has a firm sensor core installation method, strong adaptability to harsh environments such as chemical substances, good corrosion resistance, and a service life of more than 25 years; (10) The present invention innovatively proposes a solution of using high-precision dual absolute pressure chips to measure differential pressure, which effectively solves the application limitations of fiber optic technology in the field of differential pressure measurement; (11) The present invention innovatively proposes a collaborative solution that combines large-range chip pressure range positioning with small-range chip precise measurement, which effectively solves the problem of optical sensors measuring micro-differential pressure under high static pressure conditions; (12) The present invention proposes a unique absolute pressure chip structure layout method and position arrangement method.The absolute pressure and temperature chips use the same pressure-sensing surface and measure downward, which effectively avoids the influence of medium precipitation on the pressure-sensing surface; (13) The present invention innovatively proposes design ideas and application examples such as chip redundancy design, logic algorithm, and intelligent diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a composition diagram of the wavelength modulated optical differential pressure transmitter based on the MEMS process and FP cavity principle provided by the present invention;

[0034] Figure 2 Schematic diagram of differential pressure sensor

[0035] Figure 3 It is a schematic diagram of a differential pressure sensing core without static pressure;

[0036] Figure 4 It is a schematic diagram of a static pressure differential pressure sensor core;

[0037] Figure 5 This is a schematic diagram of the interferometry principle of the enamel-platinum cavity;

[0038] Figure 6 Make chip and package schematics for MEMS process;

[0039] Figure 7 This is the appearance diagram of the full spectrum analyzer;

[0040] Figure 8 This is the exploded diagram of the full spectrum analyzer;

[0041] Fig. 9 It is a redundant intelligent diagnosis logic diagram for differential pressure transmitter without static pressure;

[0042] Fig.10 It is a redundant intelligent diagnosis logic diagram for static pressure and differential pressure transmitters;

[0043] Fig.11 This is a schematic diagram of the optical cable and connector;

[0044] Fig.12 is a schematic diagram of an optical fiber feed-through;

[0045] Fig.13 This is a schematic diagram of the local box;

[0046] Fig.14 This is a diagram of the composition of the differential pressure transmitter measurement system for conventional industrial application scenarios;

[0047] Fig.15 This is the composition diagram of the differential pressure transmitter measurement system for application scenarios in the nuclear island of a nuclear power plant;

[0048] Fig.16 for Figure 3 AA section view;

[0049] Fig.17 for Figure 4 AA section view;

[0050] Fig.18 This is a side view of the full spectrum analyzer.

[0051] In the figure: 1 differential pressure sensor, 2 full spectrum analyzer, 10 assembly bolts and nuts, 11 pressure taking structure, 12 positive pressure side pressure taking cavity, 13 negative pressure side pressure taking cavity, 14 positive pressure side differential pressure sensing core, 15 negative pressure side differential pressure sensing core, 16 core body fixed connection structure, 17 optical fiber coil chamber, 18 plug seal, 19 optical fiber transfer connector, 20 analyzer structure housing, 21 optical interface, 21 communication interface, 23 power supply interface, 24 housing cover, 25 power supply module, 26 acquisition module, 27 light source module, 28 housing bottom plate, 30 static free Differential pressure sensor core, 31 absolute pressure chip module, 32 temperature chip module, 40 static pressure differential pressure sensor core, 41 absolute pressure chip module, 42 temperature chip module, 50 optical fiber pigtail, 51 first silicon wafer plane, 52 second silicon wafer plane, 53 bonding solder, 60 chip packaging module, 61F-P cavity chip, 62 optical fiber and chip bonding structure, 70 optical fiber cable, 71 integrated MPO connector, 72 transmission optical cable, 73 single-core connector, 80 optical fiber feed-through, 81 stainless steel tube, 82 boss, 83 copper tube, 84 pressure test port. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] The wavelength modulated optical differential pressure transmitter provided by the present invention is based on the MEMS manufacturing process and the fiber FP interferometer cavity principle. By using the MEMS micro-nano processing technology to prepare a micron-level FP cavity fiber structure chip, the rapid detection and response of the pressure of the measured medium is realized. At the same time, in principle, the above-mentioned shortcomings of the traditional measurement principle differential pressure transmitter, fiber grating and intensity modulation fiber pressure transmitter are avoided. Compared with the traditional electrical detection pressure transmitter and the traditional fiber optic pressure transmitter, the differential pressure transmitter of the present invention, as a new type of sensing and measuring means, mainly solves the main problems and technical requirements such as anti-electromagnetic interference ability, humidity tolerance, chemical corrosion resistance, volume, life, stability, multiplexing (such as wavelength division multiplexing and time division multiplexing), wide temperature range operation, and easy long-distance signal transmission. It is not only intrinsically safe and explosion-proof, anti-electromagnetic interference, and compact, but also has significant technical advantages in micro differential pressure measurement, high and low temperature resistance, and high stability and reliability.

[0054] The optical differential pressure transmitter of the present invention has a wide measurement range, high accuracy, and little influence of static pressure. The minimum range of the transmitter can reach 500Pa, and the maximum range can reach 30MPa; the basic accuracy can achieve ±0.05%FS; the normal working temperature range of the optical differential pressure transmitter (differential pressure measurement system) can reach -40℃ to 85℃, the normal working temperature of the sensor body can reach 180℃, and the extreme temperature can reach 400℃~600℃; the maximum system static pressure that the differential pressure transmitter can withstand can reach 20MPa, which effectively solves the influence of the static pressure of the measurement system on the measurement accuracy and stability of the differential pressure transmitter.

[0055] The optical differential pressure transmitter provided in the present invention is divided into two types: a differential pressure transmitter without static pressure and a differential pressure transmitter with static pressure.

[0056] like Figure 1 As shown, the wavelength modulated optical differential pressure transmitter based on the MEMS manufacturing process and the FP cavity principle provided by the present invention adopts a split design of a MEMS optical differential pressure sensor 1 and a full spectrum analyzer 2. The optical differential pressure transmitter includes main components such as a differential pressure sensor 1, a full spectrum analyzer 2, and an optical fiber cable 70. The differential pressure sensor 1 and the full spectrum analyzer 2 are connected by the optical fiber cable 70 to form an optical differential pressure transmitter, and the configuration length and arrangement path of the optical fiber cable 70 are different according to different application scenarios and installation locations.

[0057] The present invention adopts MEMS micromachining technology to design and manufacture a high-precision FP interferometric optical MEMS pressure measurement chip, and adopts 3 or 6 redundant pressure measurement chips to be arranged in the pressure sampling cavity of the instrument pressure lead pipe according to specific rules, and an optical fiber temperature chip is set at the same measurement plane to perform real-time temperature compensation on the pressure measurement signal to eliminate the influence of temperature on the measured medium, forming a differential pressure sensing core with three-channel redundant measurement and instant temperature compensation of temperature and pressure integration. The differential pressure sensing core adopts a dual absolute pressure sensing chip measurement method, which is installed on the positive and negative pressure sides of the differential pressure sensor respectively to measure the actual pressure and temperature of the measured medium on the positive and negative pressure sides. The differential pressure sensor encodes the measured pressure optical signal and temperature optical signal and transmits them to the full spectrum analyzer through optical fiber connectors, optical fiber cables and optical fiber penetration parts. The full spectrum analyzer demodulates and temperature compensates the pressure measurement values ​​on the positive and negative pressure sides respectively, realizes holographic spectrum and high-precision digital demodulation, and calculates the differential pressure value through a specific fitting algorithm to realize on-site display of the differential pressure signal and multi-mode remote output.

[0058] like Figure 1As shown, the optical signals measured by the positive pressure side pressure taking cavity 12 and the negative pressure side pressure taking cavity 13 on the pressure taking structure 11 of the differential pressure sensor 1 are sent to the optical fiber transfer connector 19 through the optical fiber pigtail in the optical fiber winding chamber 17, and connected to the optical fiber cable 70. The optical fiber cable 70 transmits the optical signal to the full spectrum analyzer 2 through the optical interface 21, performs demodulation calculation and logical operation, obtains the differential pressure value of the measured medium and outputs it for display, thus forming a complete differential pressure transmitter measurement circuit.

[0059] like Figure 1 As shown, the differential pressure sensing core 14 on the positive pressure side and the differential pressure sensing core 15 on the negative pressure side of the differential pressure sensor 1 are both MEMS optical fiber absolute pressure sensing cores. The medium pressures of the upstream and downstream pressure ports are measured respectively through the positive pressure side pressure taking cavity 12 and the negative pressure side pressure taking cavity 13 on the pressure taking structure 11; the measured optical signal is connected to the optical fiber cable 70 through the optical fiber transfer connector 19 on the differential pressure sensor, and the optical fiber cable 70 sends the optical signal to the full spectrum analyzer 2 through the optical interface module. The full spectrum analyzer 2 provides a standard light wave signal, and calculates the differential pressure value of the measured medium by wavelength demodulating the optical fiber measurement signal fed back by the differential pressure sensor and using a specific fitting algorithm. The differential pressure sensor 1 and the full spectrum analyzer 2 together constitute an optical differential pressure transmitter, and the optical fiber cable 70, the local box or the optical fiber feedthrough 80 of corresponding length are configured according to different application scenarios to form a complete differential pressure measurement system.

[0060] like Figure 2 As shown, the differential pressure sensor 1 includes bolts and nuts 10 used to assemble the sensor, a pressure-taking structure 11, a positive pressure side pressure-taking cavity 12 and a negative pressure side pressure-taking cavity 13 of the same structure, a positive pressure side differential pressure sensing core 14 and a negative pressure side differential pressure sensing core 15 of the same structure, a core fixed connection structure 16, an optical fiber coil chamber 17, a plug-in seal 18 and an optical fiber transfer connector 19; wherein, the pressure-taking structure 11 is a stainless steel flange casting, and the pressure-taking structure is respectively provided with a positive pressure side pressure-taking cavity 12 and a negative pressure side pressure-taking cavity 13, which are integrally formed during the casting of the structure. The positive pressure side differential pressure sensing core 14 and the negative pressure side differential pressure sensing core 15 are installed in the core fixed connection structure 16, and are respectively welded to the positive pressure side pressure-taking cavity 12 and the negative pressure side pressure-taking cavity 13 by glass melting. The optical fiber pigtail on the differential pressure sensing core is fed into the optical fiber coiling chamber 17 through the core fixed connection structure 16. The excess length of the optical fiber pigtail is coiled in the chamber and welded to the optical fiber transfer connector 19, and the optical fiber coiling chamber is sealed by the plug-in seal 18. Finally, the pressure taking structure 11, the positive pressure side differential pressure sensing core 14, the negative pressure side differential pressure sensing core 15, the core fixed connection structure 16 and the optical fiber coiling chamber 17 are assembled by assembling bolts and nuts 10 and fastened together by crimping and sealing to form a differential pressure sensor 1.

[0061] Among them, the positive pressure side pressure taking cavity 12 is connected with the positive pressure side differential pressure sensing core 14, and the negative pressure side pressure taking cavity 13 is connected with the negative pressure side differential pressure sensing core 15. The positive pressure side differential pressure sensing core 14 and the negative pressure side differential pressure sensing core 15 have exactly the same structure and shape; the positive pressure side pressure taking cavity 12 and the negative pressure side pressure taking cavity 13 also have exactly the same structure and shape, and both are standard threaded interfaces, which are used to connect the measured medium and measure the pressure of the positive and negative pressure sides of the measured medium in real time. The positive pressure side pressure taking cavity 12 and the negative pressure side pressure taking cavity 13 are not connected to each other, so as to achieve the isolation of the positive and negative pressure sides.

[0062] The optical differential pressure sensor 1 uses two MEMS optical fiber absolute pressure sensing cores with exactly the same structure, shape and size to achieve differential pressure measurement of the measured medium. The positive pressure side differential pressure sensing core 14 and the negative pressure side differential pressure sensing core 15 are both used to measure the real-time absolute pressure of the system pressure point. The differential pressure sensor core is divided into a non-static pressure differential pressure sensing core (such as Figure 3 as shown) and with a static pressure differential pressure sensing core (as shown Figure 4 The differential pressure sensor core is composed of different numbers of optical fiber absolute pressure chips and optical fiber temperature chips arranged on the same plane according to certain arrangement rules, and the measuring pressure sensing surface is facing downward.

[0063] like Figure 3 and 16 As shown, the non-static pressure differential pressure sensing core 30 includes two forms: a positive pressure side differential pressure sensing core 14 and a negative pressure side differential pressure sensing core 15. The non-static pressure differential pressure sensing core 30 is composed of three absolute pressure chip modules 31 and one temperature chip module 32, which are used to sense pressure signals and temperature signals; the differential pressure sensing core 30 is a cylindrical structure, made of stainless steel, and three MEMS optical fiber absolute pressure chip modules 31 and one optical fiber temperature chip module 32 are welded and packaged in the stainless steel differential pressure sensing core by glass melting. The optical fiber temperature chip module 32 is installed in the center of the differential pressure sensing core 30, and the three MEMS optical fiber absolute pressure chip modules 31 are symmetrically distributed around the optical fiber temperature chip module 32 in the core, and are arranged at an angle of 120°.

[0064] like Figure 4 and 17As shown, there is a static pressure differential pressure sensing core 40, which is composed of 6 absolute pressure chip modules 41 and 1 temperature chip module 42, and is used to sense pressure signals and temperature signals. The differential pressure sensing core 40 is a cylindrical structure made of stainless steel, in which the 6 absolute pressure chip modules 41 are respectively composed of 3 large static pressure range absolute pressure chips and 3 small range absolute pressure measurement chips, and are arranged according to a specific arrangement strategy. The 6 MEMS fiber optic absolute pressure chip modules 41 and the 1 fiber optic temperature chip module 42 are welded and packaged in the stainless steel differential pressure sensing core by glass melting. The fiber optic temperature chip module 32 is installed in the center of the pressure sensing core 40, and the 6 MEMS fiber optic absolute pressure chip modules 41 are symmetrically distributed around the fiber optic temperature chip module 42 in the core, and are arranged at an angle of 60°.

[0065] like Figure 5 and 6 As shown, the MEMS fiber absolute pressure chip module is based on the enamel platinum cavity interference principle (such as Figure 5 As shown in the figure), the chip is made by MEMS technology and automatically packaged (as shown in the figure). Figure 6 As shown); the MEMS fiber absolute pressure chip module includes a fiber pigtail 50 and a chip packaging module 60. The MEMS fiber chip is based on the enamel platinum cavity interference principle. The chip packaging module 60 uses two silicon wafer planes made by MEMS technology, namely, the first silicon wafer plane 51 and the second silicon wafer plane 52 to form a FP vacuum interference cavity chip 61. The standard light signal is sent to the interference cavity formed by the first silicon wafer plane 51 and the second silicon wafer plane 52 through the fiber pigtail 50, and after multiple refractions, the light wave refraction signals representing different pressures are transmitted through the fiber pigtail 50 to complete the light wave measurement function. Figure 6 The middle chip packaging module 60 adopts an automatic packaging process, and uses glass bonding solder 53 to weld and fix the optical fiber pigtail 50 to the FP interference cavity chip 61 through a bonding structure 62, thereby forming a minimized absolute pressure chip packaging module.

[0066] like Figure 7 , 8 As shown in FIG. 18 , the full spectrum analyzer 2 is used to provide functions such as standard light wave, light wave signal demodulation, data processing and intelligent operation. The internal circuit of the full spectrum analyzer 2 converts the sensed optical signal into a digital signal, and respectively according to the redundant intelligent diagnosis logic of the non-static pressure differential pressure transmitter (such as Fig. 9 as shown) and static pressure differential pressure transmitters with redundant intelligent diagnostic logic (such as Fig.10 The device performs photoelectric data conversion and logic operation, outputs differential pressure data, and transmits 4~20mA signal or digital signal in the form of communication protocol through the communication module and interface.

[0067] like Figure 7 and 18As shown, the overall appearance of the full spectrum analyzer 2 is a rectangular parallelepiped, wherein one side of the surface that generates input and output interfaces with the outside world contains an optical interface 21, a communication interface 22 and a power interface 23, and the other sides are all smooth surfaces.

[0068] like Figure 8 As shown, the structural housing 20 is the supporting component of the analyzer, the upper housing cover plate 24 and the housing bottom plate 28 together constitute the protective housing of the analyzer, and the inside of the analyzer is sequentially installed with a power module 25, an acquisition module 26 and a light source module 27. The power interface 23 is installed on the power module 25, the communication interface 22 is installed on the acquisition module 26, and the optical interface 21 is installed on the light source module. These interfaces, internal modules and the housing together constitute a complete full spectrum analyzer 2.

[0069] Fig. 9 and Fig.10 The figure shows the redundant intelligent diagnostic logic of the differential pressure transmitter. Different intelligent operation logic modules are selected according to whether there is static pressure in the system under different measurement environments.

[0070] like Fig.11 As shown, the optical fiber cable 70 includes an integrated MPO connector 71, a transmission optical cable 72 and a single-core connector 73; the integrated MPO connector 71 is connected to the single-core connector 73 through the transmission optical cable 72. The integrated MPO connector 71 of the optical fiber cable 70 is inserted into the optical interface 21 of the full spectrum analyzer, and the single-core connector 73 is connected to the optical fiber transfer connector 19 on the differential pressure sensor 1, so as to transmit the optical signal of the sensor to the full spectrum analyzer, and together form a differential pressure transmitter measurement system. When the differential pressure transmitter is installed and applied in the nuclear island, the single-core connector 73 needs to be connected to one end of the optical fiber feedthrough 80, and the other end of the optical fiber feedthrough 80 is connected to the optical fiber transfer connector 19 of the differential pressure sensor 1 through the optical fiber cable 70, and together form a nuclear island differential pressure transmitter measurement system.

[0071] like Fig.12 As shown, the optical fiber feed-through 80 comprises a stainless steel tube 81, a boss 82, a copper tube 83 and a pressure test port 84. The boss 82 is mounted on both ends of the stainless steel tube 81 by welding, and a through hole is opened in the middle of the boss 82 as the pressure test port 84. A plurality of copper tubes 83 are inserted into the boss 82 at its axial position, and optical fibers are installed in the copper tubes 83 for connecting with the optical fiber cable 70. Fig.11 70 and medium optical cables and connectors Fig.12The optical fiber feedthrough 80 is used for signal transmission communication, and is selected and combined according to different application scenarios to meet the needs of transmitter signal transmission in different application scenarios. When the differential pressure sensor is installed in the nuclear island, the optical fiber feedthrough 80 is used for the interconnection of optical fiber signals inside and outside the nuclear island, connecting the optical signal of the differential pressure sensor in the nuclear island to the full spectrum analyzer outside the nuclear island, and forming a nuclear island differential pressure transmitter measurement system.

[0072] Fig.13 It is an on-site box, mainly used to install the analyzer and related accessories, and plays a protective role.

[0073] The optical differential pressure transmitter (differential pressure measurement system) described in the present invention is based on the MEMS fiber FP cavity pressure sensor technology. The overall design adopts a split approach, and the development adopts a technical solution of separating the MEMS optical differential pressure sensor and the full spectrum analyzer host. The optical differential pressure sensor adopts the wavelength modulation type dual absolute pressure sensor chip measurement principle implementation solution. The MEMS optical differential pressure sensor is equipped with a MEMS fiber absolute pressure chip and a fiber temperature chip on the positive and negative pressure sides, respectively, to measure the actual pressure and temperature of the medium at the measured point. The pressure optical signal and temperature optical signal measured by the differential pressure sensor are connected to the full spectrum analyzer by means of optical fiber connectors, optical cables and optical fiber penetrations. The absolute pressure measurement values ​​on the positive and negative pressure sides are demodulated and temperature compensated by the full spectrum analyzer, and the differential pressure value is calculated by a specific fitting algorithm to achieve differential pressure measurement.

[0074] like Figure 2 The differential pressure sensor in the present invention realizes fast dynamic response and high-resolution and high-precision measurement of gas or fluid pressure, and has the advantages of high sensitivity, high temperature resistance, corrosion resistance, and electromagnetic interference resistance. MEMS optical differential pressure sensing cores are divided into two types: differential pressure sensing cores without static pressure and differential pressure sensing cores with static pressure. The differential pressure sensing cores on the positive and negative pressure sides of the optical differential pressure sensor are MEMS optical fiber absolute pressure cores with the same configuration. The positive and negative pressure side differential pressure sensing cores respectively use 3 (without static pressure) or 6 (with static pressure) absolute pressure chip modules and 1 temperature chip module, which are arranged according to specific rules. The temperature chip module in the differential pressure sensing core is placed in the center of the pressure chip module, which is used to perform real-time temperature compensation and correction on each absolute pressure chip module in each temperature zone; the absolute pressure chip module is arranged according to specific sensor chip layout rules ( Figure 3 and Figure 4 ), symmetrically distributed in the same area and the same plane, with the pressure-sensitive surface of the measuring chip facing downward, and multiple chips measure the pressure at the same location. This installation arrangement can avoid the influence of medium precipitation crystals on the pressure-sensing effect, while ensuring the consistency and real-time performance of the redundant chip measurement data.

[0075] The absolute pressure chip modules on the positive and negative pressure sides are arranged redundantly, and the static pressure differential pressure transmitter measures the three absolute pressure measurement signals on the positive and negative pressure sides respectively. Fig. 9 The redundant intelligent diagnosis logic algorithm is used to select and judge; if there is a static pressure differential pressure transmitter, the 6 absolute pressure measurement signals on the positive and negative pressure sides are respectively Fig.10 The redundant intelligent diagnosis logic algorithm is used to select and judge, and the temperature signal is used to perform temperature compensation and calculation correction on the absolute pressure measurement signal in each temperature range, thereby improving the accuracy of pressure measurement. The absolute pressure chip module and the temperature chip module are packaged in a glass melting method. Figure 3 and Figure 4 The differential pressure sensing core is shown.

[0076] The MEMS optical non-static pressure differential pressure sensing core ( Figure 3 and 16 ) has 3 absolute pressure chip modules and 1 temperature chip module built in. The 3 absolute pressure chip modules adopt redundant design to measure the actual pressure of the measured medium, and at the same time, the temperature chip module performs temperature effect compensation in real time. The 6 measured pressure optical signals and 2 temperature optical signals are connected through the optical fiber cable connector ( Fig.11 ) or optical cables and optical fiber penetrations ( Fig.12 ) method to connect the optical signal measured by the differential pressure sensor to the full spectrum analyzer, and the pressure value of each chip is obtained by algorithm fitting and compensation calculation based on the two physical quantities of pressure and temperature. Fig. 9 The redundant intelligent diagnosis logic algorithm in the system selects the optimal pressure value to output as the absolute pressure value on the positive pressure side and the negative pressure side, thereby calculating the measured differential pressure value and realizing differential pressure measurement.

[0077] The MEMS optical static pressure differential pressure sensor core ( Figure 4 and 17 ) are designed with 6 built-in absolute pressure chip modules (3 small-range chips and 3 large-range chips) and 1 temperature chip module. The large-range chip has a pressure range indication function and is used to determine the FSR cycle of the small-range chip. The large-range chip uses 3 absolute pressure chip modules for redundant design, and uses the temperature chip module to compensate for temperature effects in real time to obtain the current absolute pressure value and determine the pressure measurement range; at the same time, the FSR cycle of the 3 small-range chips is obtained, and the small-range chip has more than 5 times the overpressure capacity. The accuracy of each chip is designed to meet the accuracy requirements of 0.01%. The measured pressure optical signal and temperature optical signal are transmitted through the fiber optic cable connector ( Fig.11 ) or optical cables and optical fiber penetrations ( Fig.12 ) to connect the differential pressure sensor optical signal to the full spectrum analyzer. The pressure measurement values ​​of each large-range chip and small-range chip are obtained by algorithm fitting and compensation calculation of the two physical quantities of pressure and temperature, and then Fig.10 The redundant intelligent diagnosis logic algorithm in the system selects the optimal high-precision pressure value to output as a single-side absolute pressure value, and uses the positive and negative side absolute pressures to obtain the differential pressure value.

[0078] The absolute pressure chip module in the present invention ( Figure 6 ) is packaged by a chip and optical fiber to complete the measurement and transmission of pressure optical signals. Absolute pressure chip uses Figure 5 The Fabry-Perot (FP) interferometer principle described in the paper converts the measured pressure change into the change in the length of the FP pressure sensitive cavity inside the chip. Figure 5 ) consists of two parallel planes with a certain reflectivity. The light beam is reflected multiple times between them to form multi-beam interference. Under the action of pressure, the FP cavity length changes accordingly, so that the incident light is modulated. By demodulating the light wave output signal containing pressure information, the corresponding pressure value can be obtained. The pressure chip is based on the cutting-edge technology of micro-electromechanical systems (MEMS) and micro-machining preparation technology. The double reflective surface is formed by depositing a high-reflective film on the original polished surface of the SOI silicon wafer. Figure 6 After the silicon-glass anodic bonding manufacturing process and the packaging method are fixed, an absolute pressure chip module with very high FP optical interference cavity interference fineness can be obtained.

[0079] The full spectrum analyzer in the present invention ( Figure 7 , 8 and 18) are used to complete the collection, analysis, demodulation, calculation, logical judgment and output display of the optical signal of the pressure sensor. The analyzer uses wavelength signal demodulation and analysis to transmit standard light wave signals and detect optical fiber pressure signals to improve pressure resolution and measurement accuracy. The analyzer transmits standard light signals to the chip FP interferometer cavity, converts the change in the physical quantity (pressure P) into a change in the optical signal through the optical fiber absolute pressure chip, and uses wavelength signal demodulation technology to convert the change in light into a digital signal that can be recognized by the computer, and gives precise calibration, thereby realizing the detection and display of the measured physical quantity.

[0080] The full spectrum analyzer performs temperature compensation and logic analysis on the signal data of the two groups of absolute pressure chips on the positive and negative pressure sides respectively according to the redundant pressure chip demodulation algorithm and temperature compensation algorithm, obtains the pressure value of each group of chips, and then performs specific selection logic algorithms to obtain the optimal actual measured absolute pressure value. Finally, the measured pressure value on the negative pressure side is subtracted from the actual measured absolute pressure value on the positive pressure side to obtain the differential pressure value, so that the final differential pressure result is transmitted through analog signals, digital signals, or specific bus protocols, etc., to complete the complete function of the differential pressure transmitter.

[0081] When demodulating the differential pressure sensor signal without static pressure requirements, the pressure values ​​of the two groups of absolute pressure chips on the positive and negative pressure sides are temperature compensated according to the three-redundant pressure chip demodulation algorithm and temperature compensation algorithm to obtain the pressure values ​​of each group of three absolute pressure chips. Fig. 9 The differential pressure value is obtained by the redundant intelligent diagnostic logic algorithm, and the final differential pressure result is transmitted through analog signals or digital signals, completing the complete function of the differential pressure transmitter.

[0082] When demodulating the differential pressure sensing signal with static pressure requirements, the large-range chip that matches the static pressure is used to realize the static pressure indication, and the small-range pressure chip with high overpressure is used to realize the accurate measurement of the required range pressure. Fig.10 According to the redundant intelligent diagnosis logic rules in the sensor, the positive and negative pressure side differential pressure sensor cores obtain absolute pressure measurement values ​​through two sets of absolute pressure chips respectively, and then use a specific temperature compensation algorithm and a multi-sensor chip redundant algorithm to obtain the differential pressure value, so that the final differential pressure result is transmitted through analog signals or digital signals, and finally the differential pressure measurement is realized.

[0083] The full spectrum analyzer in the present invention ( Figure 8 ), mainly including light source driving part, signal acquisition part, FPGA data processing demodulation analysis and diagnosis part and data protocol distribution part and other hardware and software equipment, used to complete the acquisition, analysis, calculation, parameter setting, data storage, logic judgment, online diagnosis and fault alarm and other related functions of the pressure sensor light signal. At the same time, the analyzer provides human-machine interface access function, and exchanges data with the client device through 4~20mA analog signal or RJ45 Ethernet interface, so as to realize the debugging, calibration, detection, parameter setting, data storage, logic judgment, online diagnosis and fault alarm and other related functions of the transmitter equipment. For the solution of the signal of the differential pressure sensor without static pressure, the Fig. 9 The transmitter redundancy intelligent diagnosis logic algorithm is realized in the embodiment of FIG. 1 ; for the solution of the static pressure differential pressure sensor signal, the Fig.10 Implementation of transmitter redundancy intelligent diagnosis logic algorithm in .

[0084] The full spectrum analyzer in the present invention also involves software configuration, which mainly includes:

[0085] (1) Full spectrum analyzer module FPGA solution software: completes the acquisition and demodulation of sensor signals;

[0086] (2) Full spectrum analyzer module core chip embedded software: complete various algorithms, software functions, diagnostic alarms and information processing functions;

[0087] (3) Host computer human-machine interface software: completes the processing of the human-machine interaction function of the full spectrum analyzer module.

[0088] The optical fiber cable and connector described in the present invention ( Fig.11 ), mainly used for signal transmission or signal connection / transfer of differential pressure transmitters. The optical cables used by industrial-grade and nuclear-grade transmitters are all stranded optical cable structures. Ordinary industrial-grade optical cables include main cable outer sheath, central reinforcement, sub-unit sheath, Kevlar reinforcement and spiral steel pipe, etc. Nuclear-grade optical cables include sub-unit sheath, aramid, non-woven fabric, central reinforcement and main cable outer sheath. At the same time, the optical fibers used in optical cables are also divided into ordinary industrial-grade optical fibers and nuclear-grade optical fibers. The core and cladding of industrial-grade optical fibers are germanium-doped quartz core and quartz cladding, and the optical fiber coating is acrylic resin; the core and cladding of nuclear-grade optical fibers use pure quartz core and pure quartz cladding, and the optical fiber coating is polyimide. The optical cable connector adopts the connector method of main cable to branch cable, which is enhanced in the way of connectors. Such as Fig.11 As shown, the optical cable branch jumper for cable-type or panel-type installation is a quick-connect connector that can easily connect 12-core or 24-core optical cables, improving the efficiency and accuracy of multi-channel optical cable connections.

[0089] The optical fiber feedthrough of the present invention ( Fig.12 ), is a component of the transmitter used in the nuclear island building of a nuclear power plant. In the nuclear island building, the measured optical signal is transmitted to the outside of the control area. The feedthrough needs to meet the penetration of multi-channel 12-core or 24-core optical cables and meet the certification standards for nuclear-grade penetrations. The optical cable uses penetrations to pass through the isolation area. The basic structure is as follows Fig.12 The optical fiber sealing module includes an optical fiber with connectors at both ends, sealing components placed at both ends of the feed-through tube, and a welding tube section.

[0090] The on-site box in the present invention ( Fig.13 ) is a low-voltage device, distributed in various corners of the nuclear island, conventional island and BOP plant, and is responsible for the safe operation of safety-level or non-safety-level optical fiber signals and demodulator equipment. Analyzers and power supplies and other equipment are installed in the local box, and the local cabinet and the components in the cabinet are designed and configured differently according to the different use environments.

[0091] The optical differential pressure transmitter in the present invention is divided into two configuration modes: a conventional industrial-grade differential pressure transmitter and a differential pressure transmitter in a nuclear island building of a nuclear power plant according to the requirements of different application scenarios.

[0092] according to Fig.14 The optical differential pressure transmitter used in industrial environments shown in the figure includes differential pressure sensor, full spectrum analyzer, optical fiber cable, local cabinet and other components. The connection relationship and cross-linking diagram of each component are shown in Fig.14As shown in the figure, the bidirectional arrow connecting line indicates the connection relationship between the two related components. The differential pressure sensor measures the signal, and the sensor optical signal is sent to the full spectrum analyzer in the local cabinet through the optical fiber connector and the optical cable. After the full spectrum analyzer demodulates the optical signal, it transmits the result to the terminal signal receiving device in the form of 4mA~20mA analog signal or digital signal.

[0093] according to Fig.15 The optical differential pressure transmitter used in the nuclear island plant environment of a nuclear power plant shown in FIG. includes a differential pressure sensor, a full spectrum analyzer, optical fiber cables, optical fiber penetrations, local cabinets, and other components. The connection relationship and cross-linking diagram of each component are shown in FIG. Fig.15 As shown in the figure, the bidirectional arrow connecting line indicates the connection relationship between the two related components. The signal measured by the differential pressure sensor is sent to the optical fiber penetration piece through the optical fiber connector and optical cable. The sensor optical signal is connected to the full spectrum analyzer in the local cabinet outside the island through the penetration piece. After the full spectrum analyzer demodulates the optical signal, the result is transmitted to the terminal signal receiving device in the form of 4mA~20mA analog signal or digital signal.

[0094] The difference between the two configuration methods for different application scenarios in the present invention is mainly that: for the optical differential pressure transmitter in the nuclear island building of a nuclear power plant, the measurement signal of the differential pressure sensor needs to be transmitted through Fig.11 Fiber optic cables delivered to Fig.12 The optical fiber feedthrough is sent to the full spectrum analyzer outside the nuclear island through the feedthrough. For conventional industrial use environments, there is no need to use an optical fiber feedthrough. The differential pressure sensor signal is directly sent through the feedthrough. Fig.11 The optical fiber cable can be sent to the full spectrum analyzer in the local cabinet.

Claims

1. Wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle, characterized by: The differential pressure sensor and the full spectrum analyzer are connected and combined in a split manner through optical fiber cables. Three or six pressure measurement chips are arranged in the pressure sampling cavity of the instrument pressure pipe, and an optical fiber temperature chip is arranged at the same measurement plane to perform real-time temperature compensation on the pressure measurement signal to eliminate the influence of temperature on the measured medium, forming a differential pressure sensing core with integrated temperature and pressure three-channel redundant measurement and instant temperature compensation. The differential pressure sensing core adopts a dual absolute pressure sensing chip measurement method and is respectively installed on the positive and negative pressure sides of the differential pressure sensor to measure the actual pressure and temperature of the measured medium on the positive and negative pressure sides. The differential pressure sensor encodes the measured pressure optical signal and temperature optical signal and transmits them to the full spectrum analyzer through optical fiber connectors, optical fiber cables and optical fiber penetrations. The full spectrum analyzer demodulates and temperature compensates the pressure measurement values ​​on the positive and negative pressure sides respectively.

2. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 1, characterized in that: The differential pressure sensor comprises a pressure taking structure, a positive pressure side pressure taking cavity and a negative pressure side pressure taking cavity with the same structure, a positive pressure side differential pressure sensing core and a negative pressure side differential pressure sensing core with the same structure, a core fixed connection structure, an optical fiber winding chamber, a plug-in seal and an optical fiber transfer connector; wherein, the pressure taking structure is respectively provided with a positive pressure side pressure taking cavity and a negative pressure side pressure taking cavity, the positive pressure side differential pressure sensing core and the negative pressure side differential pressure sensing core are installed in the core fixed connection structure, and are respectively welded to the positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity by glass melting, the optical fiber pigtail on the sensing core is sent into the optical fiber winding chamber through the core fixed connection structure, the optical fiber pigtail of excess length is wound in the chamber and welded to the optical fiber transfer connector, and the optical fiber winding chamber is sealed by the plug-in seal.

3. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 2, characterized in that: The pressure taking structure, the positive pressure side differential pressure sensing core, the negative pressure side differential pressure sensing core, the core fixing connection structure and the optical fiber coil chamber are assembled by bolts and nuts and fastened together by crimping and sealing to form a differential pressure sensor.

4. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 2, characterized in that: The differential pressure sensor measures the optical signal obtained by the differential pressure sensing core in the positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity, and connects it to the optical fiber transfer connector and the optical fiber cable through the optical fiber pigtail. The optical fiber cable transmits the optical signal to the full spectrum analyzer through the optical interface for demodulation calculation and display output, thus forming a complete differential pressure transmitter measurement circuit.

5. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 2, characterized in that: The positive pressure side differential pressure sensing core and the negative pressure side differential pressure sensing core of the differential pressure sensor are both MEMS optical fiber absolute pressure sensing cores. The medium pressures of the upstream and downstream pressure taking ports are measured respectively through the positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity on the pressure taking structure. The measured optical signal is connected to the optical fiber cable through the optical fiber transfer connector on the differential pressure sensor. The optical fiber cable sends the optical signal to the full spectrum analyzer through the optical interface module. The full spectrum analyzer provides a standard light wave signal to the differential pressure sensor. At the same time, the wavelength demodulation calculation of the optical fiber measurement signal fed back by the differential pressure sensor is performed and the differential pressure value of the measured medium is calculated through a specific fitting algorithm and logical operation.

6. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 2, characterized in that: The positive pressure side pressure taking cavity is communicated with the positive pressure side differential pressure sensing core, and the negative pressure side pressure taking cavity is communicated with the negative pressure side differential pressure sensing core; the positive pressure side differential pressure sensing core and the negative pressure side differential pressure sensing core have the same structure; the positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity have the same structure, both of which are standard threaded interfaces, which are used to connect the measured medium and measure the absolute pressure of the positive and negative pressure sides of the measured medium in real time. The positive pressure side pressure taking cavity and the negative pressure side pressure taking cavity are not communicated with each other, thereby realizing the isolation of the positive and negative pressure sides.

7. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 2, characterized in that: The differential pressure sensing core is divided into a differential pressure sensing core without static pressure and a differential pressure sensing core with static pressure.

8. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 2, characterized in that: The static-pressure-free differential pressure sensing core is composed of three absolute pressure chip modules and one temperature chip module, and is used to sense pressure signals and temperature signals; the differential pressure sensing core is a cylindrical structure, and three MEMS optical fiber absolute pressure chip modules and one optical fiber temperature chip module are welded and packaged in a stainless steel differential pressure sensing core by glass melting, wherein the optical fiber temperature chip module is installed in the center of the differential pressure sensing core, and the three MEMS optical fiber absolute pressure chip modules are symmetrically distributed around the optical fiber temperature chip module in the core, and are arranged at an angle of 120°.

9. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 2, characterized in that: The static pressure differential pressure sensing core is composed of 6 absolute pressure chip modules and 1 temperature chip module, which is used to sense pressure signals and temperature signals. The differential pressure sensing core is a cylindrical structure, wherein the 6 absolute pressure chip modules are respectively composed of 3 large static pressure range absolute pressure chips and 3 small range absolute pressure chips. 6 MEMS fiber optic absolute pressure chip modules and 1 fiber optic temperature chip module are welded and packaged in a stainless steel differential pressure sensing core by glass melting. The fiber optic temperature chip module is installed in the center of the differential pressure sensing core. The 6 MEMS fiber optic absolute pressure chip modules are symmetrically distributed around the fiber optic temperature chip module in the core and arranged at an angle of 60°.

10. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 9, characterized in that: The MEMS fiber absolute pressure chip module comprises a fiber pigtail and a chip packaging module. The chip packaging module adopts two silicon wafer planes manufactured by MEMS technology, namely, a first silicon wafer plane and a second silicon wafer plane to form a FP vacuum interference cavity chip. The standard light signal is sent to the interference cavity formed by the first silicon wafer plane and the second silicon wafer plane through the fiber pigtail for multiple refractions. The light wave refraction signals representing different pressures are transmitted through the fiber pigtail to complete the light wave measurement function.

11. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 1, characterized in that: The full spectrum analyzer is used to provide standard light waves, light wave signal demodulation, data processing and intelligent calculation. The internal circuit of the analyzer converts the sensed optical signal into a digital signal, and performs photoelectric data conversion and specific logic calculation according to the redundant intelligent diagnosis logic of the differential pressure transmitter without static pressure and the redundant intelligent diagnosis logic of the differential pressure transmitter with static pressure, outputs differential pressure data, and transmits the 4~20mA signal or digital signal or in the form of a communication protocol through the communication module and interface.

12. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 11, characterized in that: The overall appearance of the full spectrum analyzer is a rectangular parallelepiped, in which the side that generates input and output interfaces with the outside world contains an optical interface, a communication interface and a power interface, and the other sides are all smooth surfaces. The structural shell is the supporting component of the analyzer, and the upper shell cover and the shell bottom plate together constitute the protective shell of the analyzer. The integrated power module, acquisition module and light source module are installed in the analyzer in sequence, in which the power interface is installed on the power module, the communication interface is installed on the acquisition module, and the optical interface is installed on the light source module.

13. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 1, characterized in that: The optical fiber cable comprises an integrated MPO connector, a transmission optical cable and a single-core connector; the integrated MPO connector is connected to the single-core connector via the transmission optical cable, wherein the integrated MPO connector of the optical fiber cable is inserted into the optical interface of the full spectrum analyzer, and the single-core connector is connected to the optical fiber transfer connector on the differential pressure sensor, so as to transmit the optical signal of the sensor to the full spectrum analyzer, and together form a differential pressure transmitter measurement system.

14. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 13, characterized in that: One end of the fiber optic feedthrough is connected to the single-core connector of the fiber optic cable and then connected to the full-spectrum demodulator. At the same time, the other end of the fiber optic feedthrough is connected to the fiber optic transfer connector of the gauge pressure sensor through the fiber optic cable, acting as a bridge connecting the inside and outside of the nuclear island.

15. The wavelength modulated optical differential pressure transmitter based on MEMS technology and FP cavity principle as claimed in claim 13, characterized in that: The optical fiber feedthrough comprises a stainless steel tube, a boss, a copper tube and a pressure test port. The boss is mounted on both ends of the stainless steel tube by welding. A through hole is opened in the middle of the boss as a pressure test port. Multiple copper tubes are inserted in the axial position of the boss. Optical fibers are installed in the copper tubes for connecting to optical fiber cables.

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