Miniature optical fiber pressure sensor with multistage structure

Abstract

The utility model relates to a miniature optical fiber pressure sensor with a multistage structure, which can ensure the smoothness of an FP cavity end reflecting film and improve the performance and the precision of the sensor, a base part is formed by bonding a plurality of layers of substrates, and an FP cavity and / or an optical fiber mounting part are / is formed by through holes arranged on corresponding substrate layers. Due to the fact that the through holes are through, the problem that the surface is uneven due to a wet etching method or an ion etching method is avoided, the flatness of a reflecting film on the bottom end face of the FP cavity is improved, the light reflecting effect is better, and the measuring precision of the sensor is improved. The end portion of the optical fiber is not in direct contact with the FP cavity, the middle of the optical fiber is separated by the high-light-transmittance substrate, and due to the high flatness of the FP cavity reflecting film, the multimode optical fiber can optimize errors of different optical path differences when receiving multiple beams of reflected signals, and the accuracy of test data is improved. Meanwhile, the three layers of substrates are connected into a whole in a bonding mode, the preparation process is simple, and the obtained base is stable and reliable in structure.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of optical fiber sensor, concretely relates to a multistage structure's miniature optical fiber pressure sensor. BACKGROUND

[0002] With the rapid development of implantable medical devices, optical fiber pressure sensors can be implanted in the human body due to their small size, good biocompatibility, etc., to realize real-time and accurate measurement of physiological parameters such as blood pressure, intracranial pressure, and lung pressure, providing an important basis for disease diagnosis and treatment. Compared with traditional electronic pressure sensors, optical fiber pressure sensors have the advantages of strong anti-electromagnetic interference ability, good chemical stability, high sensitivity, and fast response time, and are suitable for application in complex medical environments such as radio frequency and magnetic resonance.

[0003] In recent years, a considerable number of methods have been applied to the manufacture of optical fiber sensors, such as micro-electro-mechanical systems (MEMS), chemical etching, lasers, and the use of special optical fibers. Optical fiber pressure sensors based on MEMS have attracted great interest due to their small size, which is very suitable for applications with limited space or minimal measurement interference. The MEMS silicon-based process gives optical fiber pressure sensors many advantages and is an important driving force for the development of technology in this field. On the one hand, MEMS can achieve micron or even nanometer-level miniaturization, making the sensor head extremely small and conducive to pressure measurement in narrow spaces; on the other hand, batch manufacturing capability and seamless integration with optical fiber drawing and sawing processes greatly improve manufacturing efficiency and coupling performance. More importantly, silicon and silicon oxide have excellent chemical stability and biocompatibility, outstanding corrosion resistance, and are suitable for harsh environments and in-vivo pressure detection. In 2008, Yixian Ge et al. proposed an optical MEMS pressure sensor based on a mesa-diaphragm structure (Optical MEMS pressure sensor based on a mesa-diaphragm structure, 21746-21752 (2008)). The mechanical model of the platform diaphragm and the signal averaging effect were verified by simulation, showing that the platform diaphragm is superior to the flat diaphragm in parallelism and can reduce the signal averaging effect. However, a too thick platform diaphragm limits the sensor's ability to respond to small pressure changes in a timely manner. Patent US8559770B2 uses hydrofluoric acid to etch the optical fiber to make an FP cavity, but the FP cavity base obtained by this method has a rough surface, causing severe refraction of the optical signal when it is incident. To solve this problem, patent CN110487454B uses a hollow optical fiber (acting as an FP cavity) to bridge the optical fiber and the sensitive pressure diaphragm, which avoids the problem of uneven base surface, but the direct connection of the optical fiber to the FP cavity causes a certain deviation in the reception of the optical signal, affecting the signal loss. Utility model content

[0004] The utility model discloses a multistage structure's miniature optical fiber pressure sensor can ensure the flatness of FP cavity end reflection film, improve sensor performance and precision.

[0005] In order to realize the above-mentioned purpose, the utility model adopts technical scheme, a multistage structure's miniature optical fiber pressure sensor, including base and pressure sensitive diaphragm, wherein pressure sensitive diaphragm is the only structure of optical fiber pressure sensor perception pressure, base is used to and pressure sensitive diaphragm form FP cavity and with optical fiber connection.

[0006] FP cavity, the closed chamber formed between the base and pressure sensitive diaphragm, the light signal of optical fiber enters FP cavity, and multiple reflections are carried out between base reflection surface and pressure sensitive reflection film, and the deflection of pressure sensitive diaphragm caused by pressure is converted into the phase change of FP cavity interference signal through optical interferometer, and the pressure measurement is realized through the phase change of demodulation interference signal.

[0007] Optical fiber, fixed in the optical fiber installation part of base, is used for conducting light signal, and the pressure change of outside makes pressure sensitive diaphragm deformation, changes the length of FP cavity cavity, thereby changes the optical path difference, and through the detection of the light signal that is transmitted back through optical fiber, the size of pressure sensitive diaphragm deformation can be obtained through demodulation.

[0008] The base is bonded by multilayer substrate, the FP cavity and / or optical fiber installation part is formed by the through hole arranged on the corresponding substrate layer, preferably the FP cavity and / or optical fiber installation part are both formed by the through hole. The base is packaged as a whole by bonding technology of multilayer substrate, and the substrate that needs to be provided with a through hole is set as a separate substrate, and the through hole is processed on it. Since the through hole is all through, the problem of uneven surface caused by wet etching or ion etching method is avoided, and the FP cavity end reflection film has high flatness.

[0009] In order to further explicitly the remarkable beneficial effects of the utility model, the specific surface roughness is illustrated. When the traditional wet etching method is adopted, because the etching rate of strong acid or plasma etching is not easy to control, therefore there are differences on the surface of the base, leading to the surface roughness Ra of the base produced in each batch being inconsistent, and under the condition that each condition is well controlled, the surface roughness Ra of the bottom of the FP cavity A is about 100 nm. The scheme adopted in the utility model is that the base 10 is formed by bonding multiple substrates, and the bottom surface of the FP cavity A is composed of the surface of the substrate. Because the single-layer substrate is usually obtained after chemical mechanical polishing when being processed, the surface roughness Ra thereof is very small, for example, the surface roughness Ra of the sapphire substrate wafer can reach 0.3 nm, the surface roughness Ra of the glass substrate wafer can reach 4.11 nm, the surface roughness Ra of the quartz substrate wafer can reach 0.591 nm, and the surface roughness Ra of the single-crystal silicon substrate wafer is less than 0.5 nm. As can be seen from the above three examples, the surface roughness Ra of the substrate wafer in the utility model is much smaller than the surface roughness Ra of the bottom of the FP cavity after reprocessing, and is about several nanometers to several nanometers, therefore the reflection effect on light is better, and the measurement accuracy of the sensor is improved. In the utility model, the problem of etching rate does not need to be considered when the through hole is prepared on the substrate, the manufacturing difficulty of the base is reduced, the three-layer substrate is connected into one body by bonding, the preparation process is simple, and the structure of the obtained base is stable and reliable.

[0010] As a preferred scheme of the utility model, the base comprises a first substrate, a second substrate and a third substrate arranged in sequence from the near to the far from the pressure sensitive diaphragm, the first substrate is provided with a first through hole, and the first through hole, the surface of the second substrate and the pressure sensitive diaphragm jointly enclose an FP cavity. The plane for setting the cavity end reflection film is the surface of the second substrate, the flatness is high, the sensor accuracy is high, meanwhile the consistency of the sensor is high, and the performance of the sensors in the same batch is stable.

[0011] Similarly, the third substrate is provided with a third through hole, and the third through hole and the surface of the second substrate jointly enclose a fiber installation part; the plane in contact with the fiber is the surface of the second substrate, the flatness is high, the deviation generated when the optical signal is received is reduced, and the influence of signal loss is reduced. Preferably, the FP cavity and the fiber installation part are coaxial and arranged at intervals in the axial direction of the fiber, because the fiber and the pressure sensitive diaphragm must be in the same axial direction, the light is output through the front end of the fiber, passes through the base-FP cavity, reaches the sensitive diaphragm, is reflected on the pressure sensitive diaphragm, then passes through the FP cavity and enters the fiber to recycle the optical signal.

[0012] In order to obtain better optical contrast signal, the surface of the second substrate in the FP cavity is provided with a cavity end reflection film. Since the cavity end reflection film is arranged on the surface of the second substrate, and the second substrate is a pure substrate, it is not necessary to make a groove by a wet etching or ion etching method, so that the surface flatness of the second substrate for arranging the cavity end reflection film is higher, thereby improving the performance and accuracy of the sensor. The end of the optical fiber is directly in contact with the surface of the other side of the second substrate, and the flatness of the side surface is also good, which is beneficial to the propagation of the optical signal.

[0013] In order to obtain an optical reflection signal, in order to form interference, the pressure sensitive diaphragm comprises a sensitive layer substrate, and a sensitive layer reflection film is arranged on the surface of the sensitive layer substrate in the FP cavity. The sensitive layer reflection film is arranged in parallel, opposite and spaced apart with the cavity end reflection film, and meanwhile the formation of a resonant cavity on the inner and outer surfaces of the pressure sensitive diaphragm can be avoided.

[0014] The accuracy of the optical fiber pressure sensor in detecting pressure mainly depends on the sensing ability of the pressure sensitive diaphragm to pressure. The deformation of the sensitive pressure layer when subjected to pressure stimulation plays a decisive role in the feedback of pressure. According to the relationship between the physical properties of the material itself and the deformation, the following is described:

[0015] (1)

[0016] In formula (1), is the sensitivity of the sensitive diaphragm, is the pressure received by the sensitive diaphragm, is the Poisson's ratio of the physical properties of the material itself, r is the effective radius of the sensitive diaphragm, E is the Young's modulus of the material itself, and h is the thickness of the sensitive diaphragm, is the radius of any part of the material. As can be seen, when the center point of the sensitive diaphragm, i.e. the part subjected to pressure, at this time, formula (1) can be converted to the following formula:

[0017] (2)

[0018] As can be seen from formula (2), the sensitivity of the optical fiber pressure sensor is related to the effective radius of the diaphragm and the thickness of the sensitive pressure layer, and the sensitivity formula is obtained:

[0019] (3)

[0020] Among them, the sensitivity of the device is proportional to the effective radius of the diaphragm and inversely proportional to the thickness of the diaphragm, that is, the larger the effective radius, the smaller the diaphragm thickness, the higher the sensitivity. Improving the sensitivity can obtain higher measurement accuracy, but the higher the sensitivity, the narrower the measurement range, and the stability is often worse. By selecting a reasonable effective radius and diaphragm thickness, a suitable sensitivity is obtained.

[0021] The sensor in the utility model is a micro sensor, and therefore high requirements are imposed on the selection of substrate material and thickness.

[0022] Further, the sensitive layer substrate is an SOI wafer or a double-polished monocrystalline wafer; preferably, the sensitive layer reflective film is composed of two layers of first reflective film and second reflective film; preferably, the first reflective film and the second reflective film are selected from one or two kinds of mixtures of Au, Ag, Pt, Ti, Cr, Al, Pt, Ta2O5 and Al2O3; preferably, the thickness of the pressure-sensitive diaphragm is 3-100 um. The second reflective film is preferably a reflective film with high emissivity, and the first reflective film is preferably a reflective film with high adhesion, thereby improving the stability of the combination of the second reflective film and the sensitive layer substrate.

[0023] The second substrate is one of glass, quartz and sapphire, and the thickness is 20 um-200 um; the cavity end reflective film is composed of two layers of third reflective film and fourth reflective film; preferably, the third reflective film and the fourth reflective film are selected from one or two kinds of mixtures of Au, Ag, Pt, Ti, Cr, Al, Pt, Ta2O5 and Al2O3. The fourth reflective film is preferably a reflective film with high reflectivity, and the third reflective film is preferably a reflective film with high adhesion, thereby improving the stability of the combination of the fourth reflective film and the second substrate.

[0024] Further, the first substrate is one of sapphire, monocrystalline silicon, glass and quartz, and preferably, the thickness is 10 um-200 um; preferably, the first through hole diameter is 20 um-300 um.

[0025] The third substrate is one of silicon wafer, glass, quartz and sapphire, and preferably, the thickness is 20 um-200 um; preferably, the third through hole diameter is 100 um-300 um.

[0026] An object of the utility model is to provide a preparation method of a multi-stage structure micro optical fiber pressure sensor which can ensure the flatness of the FP cavity end reflective film and improve the performance and precision of the sensor.

[0027] Compared with the prior art, the above scheme has at least the following beneficial effects:

[0028] 1. The FP cavity bottom surface has high flatness, so that the reflective film thereon has high flatness, has small light refraction loss and has high sensor precision.

[0029] 2. The plane in contact with the optical fiber is the surface of the second substrate, has high flatness, reduces the deviation of the optical signal during reception and reduces the influence of signal loss.

[0030] 3. The ends of the optical fiber do not directly contact the FP cavity, but are separated by a high-transmittance substrate. When receiving multiple reflected signals, the multimode optical fiber can optimize the error of different optical path differences and improve the accuracy of test data.

[0031] 4. Fabricating vias on the substrate eliminates the need to consider corrosion rates, reducing the difficulty of substrate manufacturing;

[0032] 5. The three-layer substrate is connected into one piece by bonding, which is a simple fabrication process and results in a stable and reliable substrate structure;

[0033] 6. Both the end cavity reflective film and the sensitive layer reflective film have a double-layer structure, with one layer being a highly adhesive reflective film and the other being a highly reflective film, thus ensuring that the reflective film adheres firmly and stably to the substrate. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a fiber optic pressure sensor;

[0035] Figure 2 for Figure 1 A schematic diagram of the structure after removing the optical fiber;

[0036] Figure 3 This is a schematic diagram of the base structure;

[0037] Figure 4 This is a schematic diagram of the structure of a pressure-sensitive diaphragm;

[0038] Figure 5 This is a schematic diagram of the structure of the first substrate;

[0039] Figure 6 This is a schematic diagram of the structure of the second substrate;

[0040] Figure 7 This is a schematic diagram of the third substrate.

[0041] Figure 8 This is the data from Example 2 showing how the fiber optic pressure sensor maintains stability under different pressures. Detailed Implementation

[0042] The following is in conjunction with the appendix Figures 1-8 The present invention will be described in detail through specific embodiments. It should be noted that the selection of fill lines for each component in the accompanying drawings is only to distinguish the components and does not represent the materials; moreover, the proportions between the structural layers do not represent the actual structural proportions of the product, and the materials and dimensions should be based on the written description. Example 1

[0043] A first substrate 11 of quartz material with a thickness of 80um is placed in a solution for cleaning, a layer of photoresist is spin-coated on the first substrate 11, and then a specific pattern is left on the first substrate 11 by exposure and development techniques. The surface of the sapphire is etched to form a region with a diameter of 50um by using the NLD dry process, and then the sapphire substrate is further etched by HF acid until the first through hole 111 is formed. A third substrate 13 of sapphire material with a thickness of 100um is cleaned, and an array pattern with a diameter of 150um is prepared on the third substrate 13 by using the photolithography process, and the exposed pattern is completely penetrated to form the third through hole 131 by using the sandblasting process. After the first substrate 11, the second substrate 12 and the third substrate 13 are stacked from top to bottom, the bonding process is performed to obtain a multi-level structure base 10, and the base 10 is arranged with the first substrate 11 upwards, and a layer of reflective film Al is first evaporated in the upper FP cavity A by using the evaporation process, and then a layer of reflective film Ag is evaporated.

[0044] The sensitive layer substrate 21 of SOI wafer material is subjected to cleaning and activation treatment to remove surface impurities and organic contaminants and improve surface affinity, and photoresist is uniformly coated on the sensitive layer substrate 21 by using the spin coating method, and the required micro-nano structure pattern is formed on the wafer substrate. A layer of 4nm Al is deposited on the patterned sensitive layer substrate 21 as a reflective layer by physical vapor deposition method, and then a 50nm Au reflective film is grown on the substrate by using the thermal evaporation deposition method, and the sensitive layer substrate 21 sample with the grown metal mirror layer is immersed in a selected photoresist remover solution for soaking, ultrasonic treatment and drying.

[0045] The surfaces of the base 10 and the sensitive layer substrate 21 are subjected to chemical mechanical polishing and cleaning to remove surface contaminants and chemical contamination layers and improve surface affinity. The two pre-bonded substrates are assembled into the upper and lower electrode plates of an anodic bonding system, and under the conditions of applying a certain pressure, temperature and high voltage, the high electric field will cause the two substrate surfaces to lose ions, forming a long-range coulomb attraction to firmly bond the two substrates together. After detection, the top monocrystalline silicon layer of the sensitive layer substrate 21 is separated from the through hole base, and then the top silicon film is subjected to CMP or polishing to remove surface damage and adjust the film thickness to 5nm.

[0046] The bonded whole large chip is placed on the worktable of the ultraviolet laser cutting system, and the large chip is cut by using a high-energy ultraviolet laser beam to divide it into a single small sensor chip. A multimode optical fiber 30 with a proper length is prepared, one end of the optical fiber 30 is inserted into a quartz tube with a proper inner diameter, and the other end of the small sensor chip with a through hole is fixed on the assembly platform. The quartz tube with the optical fiber 30 inserted is slowly inserted into the optical fiber mounting portion B on the base 10, so that the end face of the optical fiber can be accurately aligned with the functional area on the surface of the base 10. When the optical fiber 30 and the base 10 reach the ideal alignment position, UV curing ultraviolet glue is dropped in the cavity of the optical fiber mounting portion B and exposed and cured. The cured ultraviolet glue firmly fixes the position and angle of the quartz tube and the optical fiber 30 on the base 10. Example 2

[0047] A first substrate 11 of sapphire material with a thickness of 140 um is placed in a solution for cleaning. A layer of photoresist is spin-coated on the first substrate 11, and then a specific pattern is left on the first substrate 11 by exposure and development technology. The surface of the sapphire is etched to form a region with a diameter of 100 um by using NLD dry process, and then the sapphire substrate is completely etched through to form a first through hole 111 by using HF acid. A third substrate 13 of glass material with a thickness of 160 um is cleaned, and an array pattern with a diameter of 180 um is prepared on the third substrate 13 by using photolithography process. The exposed pattern is completely etched through to form a third through hole 131 by using sandblasting process. After the first substrate 11, the second substrate 12 and the third substrate 13 are stacked from top to bottom, a bonding process is performed to obtain a multi-level structure base 10. The first substrate 11 of the base 10 is arranged upwards, and a layer of reflective film Al is first evaporated in the upper FP cavity A by using evaporation process, and then a layer of reflective film Ag is evaporated.

[0048] The sensitive layer substrate 21 of SOI wafer material is subjected to cleaning and activation treatment to remove surface impurities and organic contaminants and improve surface affinity. Photoresist is uniformly coated on the sensitive layer substrate 21 by spin coating, and a required micro-nano structure pattern is formed on the wafer substrate. A 10 nm Ti layer is deposited on the patterned sensitive layer substrate 21 as a reflective layer by physical vapor deposition method, and a 120 nm Au reflective film is grown on the substrate by thermal evaporation deposition method. The sensitive layer substrate 21 sample with the grown metal mirror layer is immersed in a selected photoresist remover solution, ultrasonic treated and dried.

[0049] The base 10 and the surface of the sensitive layer substrate 21 are chemically mechanically polished, cleaned, and surface contaminants and chemical contamination layers are removed to improve the surface affinity. The pre-bonded two substrates are assembled into the upper and lower electrode plates of the anodic bonding system, and under the conditions of applying a certain pressure, temperature, and high voltage, the high electric field will make the two substrate surfaces ionize and form a long-range Coulomb attraction to firmly bond the two substrates together. After passing the detection, the top monocrystalline silicon layer of the sensitive layer substrate 21 is separated from the through-hole base, and then the top silicon film is polished by CMP or grinding to remove surface damage and adjust the film thickness to 20 nm.

[0050] The bonded whole large chip is placed on the workbench of the ultraviolet laser cutting system, and the large chip is cut into a single small sensor chip by using a high-energy ultraviolet laser beam. A multi-mode optical fiber 30 with appropriate length is prepared, one end of which is inserted into a quartz tube with appropriate inner diameter, and the other end of which is fixed on the assembly platform with a small sensor chip with a through hole. The quartz tube with the optical fiber 30 inserted is slowly inserted into the optical fiber mounting part B on the base 10, so that the end face of the optical fiber can be accurately aligned with the functional area on the surface of the base 10. When the optical fiber 30 and the base 10 reach the ideal alignment position, UV curing ultraviolet glue is dropped in the cavity of the optical fiber mounting part B and exposed and cured. The cured ultraviolet glue firmly fixes the position and angle of the quartz tube and the optical fiber 30 on the base 10. Example 3

[0051] A first substrate 11 of monocrystalline silicon material with a thickness of 180 um is placed in a solution for cleaning, and a layer of photoresist is spin-coated on the first substrate 11. Then, a specific pattern is left on the first substrate 11 by exposure and development technology. First, the NLD dry process is used to etch a region with a diameter of 80 um on the sapphire surface, and then HF acid is used for further etching until the sapphire substrate is completely penetrated to form a first through hole 111. A third substrate 13 of glass material with a thickness of 200 um is cleaned, and a pattern with a diameter of 150 um is prepared on the third substrate 13 by photolithography process. The exposed pattern is completely penetrated to form a third through hole 131 by sandblasting process. After stacking the first substrate 11, the second substrate 12, and the third substrate 13 from top to bottom, the bonding process is performed to obtain a multi-level structure base 10. The first substrate 11 of the base 10 is arranged upwards, and a layer of reflective film Pt is first evaporated in the upper FP cavity A by evaporation process, and then a layer of reflective film Ag is evaporated.

[0052] The sensitive layer substrate 21 of the double-throw single crystal wafer material is subjected to cleaning and activation treatment to remove surface impurities and organic contaminants and improve surface affinity, and a photoresist is uniformly coated on the sensitive layer substrate 21 by using a spin coating method, and a required micro-nano structure pattern is formed on the wafer substrate. A layer of 18nm Ti is deposited on the patterned sensitive layer substrate 21 as a sticky reflective layer by a physical vapor deposition method, and a 100nm Au reflective film is grown on the substrate by using a thermal evaporation deposition method, and the sensitive layer substrate 21 sample with the grown metal mirror layer is immersed in a selected photoresist remover solution for soaking, ultrasonic treatment and drying.

[0053] The base 10 and the surface of the sensitive layer substrate 21 are subjected to chemical mechanical polishing and cleaning to remove surface contaminants and chemical contamination layers and improve surface affinity. The two substrates are assembled into the upper and lower electrode plates of an anodic bonding system, and under the condition of applying a certain pressure, temperature and high voltage, the high electric field will remove ions from the surfaces of the two substrates to form a long-range coulomb attraction to firmly bond the two substrates together. After detection, the top single crystal silicon layer of the sensitive layer substrate 21 is separated from the through-hole base, and then the top silicon film is subjected to CMP or polishing to remove surface damage and adjust the film thickness to 60nm.

[0054] The bonded whole chip is placed on the workbench of an ultraviolet laser cutting system, and the chip is cut by using a high-energy ultraviolet laser beam to divide it into a single small sensor chip. A multimode optical fiber 30 with appropriate length is prepared, one end of the optical fiber is inserted into a quartz tube with appropriate inner diameter, and the other end of the small sensor chip with a through hole is fixed on the assembly platform. The quartz tube with the optical fiber 30 inserted is slowly inserted into the optical fiber mounting portion B on the base 10, so that the end face of the optical fiber can be accurately aligned with the functional area on the surface of the base 10. When the optical fiber 30 and the base 10 reach the ideal alignment position, UV curing ultraviolet glue is dropped in the cavity of the optical fiber mounting portion B and is exposed and cured. The cured ultraviolet glue firmly fixes the position and angle of the quartz tube and the optical fiber 30 on the base 10.

[0055] The optical fiber pressure sensor in the utility model, the base is bonded by multilayer substrate, the FP cavity A and the optical fiber mounting portion B are formed by the through hole on the corresponding substrate layer, the base is packaged as a whole by the multilayer substrate through the bonding technology, the substrate which needs to set the through hole is set as a single substrate, and the through hole is processed on it, since the through hole is all through, there is no problem of uneven surface caused by wet etching or ion etching method, the FP cavity A end face reflective film has high flatness. The end of the optical fiber 30 does not directly contact with the FP cavity A, and there is a substrate in the middle, the FP cavity A surface has good flatness, the multimode optical fiber can optimize the error of different optical path difference when receiving multiple reflection signals, and the accuracy of test data is improved.

[0056] In summary, this multi-level structure of micro optical fiber pressure sensor has the advantages of stable structure, high flatness reflective film and optimized optical path difference error, and is suitable for pressure monitoring and measurement requirements in various fields, such as industrial automation, medical equipment and aerospace, etc.

[0057] The optical fiber pressure sensor in the utility model has a range of 0-1500mm Hg, Figure 8 To maintain stable test data of the optical fiber pressure sensor under different pressures, we can see that the optical fiber pressure sensor can ensure its measurement stability within a relatively wide pressure range of 0-200mm Hg. The normal blood pressure range of human body is 90-140mm Hg, which is within the pressure range of the optical fiber pressure sensor, so this multi-level structure of micro optical fiber pressure sensor is suitable for blood pressure measurement and has high measurement accuracy. At the same time, the stable time lasts for several minutes at each pressure value, and the optical fiber pressure sensor has good stability. It should be noted that the optical fiber pressure sensor is a micro optical fiber pressure sensor with a diameter of only a few hundred microns. The accuracy of the optical fiber pressure sensor can reach ±0.1%Fs, the resolution is ±0.01%Fs, and the working temperature is 0-100℃. It can be said that the measurement accuracy of the micro optical fiber pressure sensor in the utility model is very high, and it is especially suitable for measuring blood pressure in interventional medical devices, such as interventional ventricular assist devices, etc.

[0058] Those skilled in the art should understand that the above is only some specific embodiments of the utility model, not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications and improvements that do not exceed the scope of the claims should be considered as the protection scope of the utility model.

Claims

1. A multi-level micro fiber optic pressure sensor, comprising a base (10) and a pressure-sensitive diaphragm (20). FP cavity (A) is a closed chamber formed between the base (10) and the pressure-sensitive diaphragm (20); An optical fiber (30) is fixed inside the optical fiber mounting part (B) of the base (10) and is used to transmit optical signals; Its features are: The base (10) is composed of multilayer substrate bonding, and the FP cavity (A) and the optical fiber mounting part (B) are composed of through holes provided on the corresponding substrate layers; The base (10) includes a first substrate (11), a second substrate (12) and a third substrate (13) arranged sequentially from near to far from the pressure-sensitive diaphragm (20). The first substrate (11) has a first through hole (111). The first through hole (111), the surface of the second substrate (12) and the pressure-sensitive diaphragm (20) together form an FP cavity (A). The surface of the second substrate (12) in the FP cavity (A) is provided with a cavity end reflective film (14). The pressure-sensitive diaphragm (20) includes a sensitive layer substrate (21). The surface of the sensitive layer substrate (21) located in the FP cavity (A) is provided with a sensitive layer reflective film (22). The sensitive layer reflective film (22) and the cavity end reflective film (14) are arranged in parallel, opposite and spaced apart.

2. The multi-stage micro fiber optic pressure sensor according to claim 1, characterized in that: A third through hole (131) is provided on the third substrate (13). The third through hole (131) and the surface of the second substrate (12) together form the optical fiber mounting part (B). The FP cavity (A) and the optical fiber mounting part (B) are arranged coaxially and spaced apart in the axial direction of the optical fiber (30).

3. The multi-stage micro fiber optic pressure sensor according to claim 1, characterized in that: The sensitive layer substrate (21) is an SOI wafer or a double-polished single wafer, and the sensitive layer reflective film (22) is composed of two layers: a first reflective film (221) and a second reflective film (222).

4. The multi-stage micro fiber optic pressure sensor according to claim 3, characterized in that: The first reflective film (221) and the second reflective film (222) are selected from one of Au, Ag, Ti, Cr, Al, Pt, Ta2O5, and Al2O3; the pressure-sensitive membrane (20) has a thickness of 3um-100um.

5. The multi-stage micro fiber optic pressure sensor according to claim 1, characterized in that: The second substrate (12) is selected from glass, quartz and sapphire, with a thickness of 20um-200um. The cavity end reflective film (14) is composed of two layers: a third reflective film (141) and a fourth reflective film (142).

6. The multi-stage micro fiber optic pressure sensor according to claim 5, characterized in that: The third reflective film (141) and the fourth reflective film (142) are selected from one of Au, Ag, Ti, Cr, Al, Pt, Ta2O5, and Al2O3.

7. The multi-stage micro fiber optic pressure sensor according to claim 1, characterized in that: The first substrate (11) is selected from sapphire, single crystal silicon, glass, and quartz, with a thickness of 10um-200um; the first through hole (111) has a diameter of 20um-300um.

8. The multi-stage micro fiber optic pressure sensor according to claim 1, characterized in that: The third substrate (13) is selected from silicon wafer, glass, quartz, and sapphire, with a thickness of 20um-200um and a diameter of 100um-300um for the third via (131).

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