CN117553881A - Optical fiber pressure sensor - Google Patents

Abstract

The invention relates to an optical fiber pressure sensor, which comprises a sensor body and a pressure input assembly for sensing external pressure, wherein the sensor body comprises: a housing, a divider, and a sensing fiber. Through with the fixed setting of sensing optic fibre on the separator, can drive the grating section on the sensing optic fibre and change when the separator slides, external pressure directly applys on pressure input subassembly, and the change that external environment produced is after the filtration buffering of pressure input subassembly, is converted into internal pressure and applys on the separator again, has avoided external pressure directly applys on the separator, has avoided leading to fiber pressure sensor's quick response because of external environment's influence. Compared with the prior art, the optical fiber pressure sensor disclosed by the application can be hardly influenced by the environment in the seawater environment, and the purpose of enabling the optical fiber pressure sensor to be better in stability is achieved.

Description

Optical fiber pressure sensor

Technical Field

The invention relates to the technical field of pressure sensors, in particular to an optical fiber pressure sensor.

Background

The ocean liquid level monitoring is an important measurement work and has important significance in the aspects of knowing ocean environment, evaluating ocean engineering safety, protecting ocean resources, researching earth science and the like. The submarine liquid level monitoring is a technical method for monitoring and measuring the submarine liquid level in real time through various means, and the measurement performance of a submarine pressure sensor directly determines the accuracy of ocean depth positioning, so that the accuracy of tsunami monitoring and early warning is affected.

The optical fiber pressure sensor is a sensor for measuring liquid level by using an optical fiber grating technology, and the optical fiber grating is an optical device, and the reflection of light with specific wavelength can be realized by inscribing a grating structure on an optical fiber. The optical fiber pressure sensor uses this characteristic, and measures the liquid level change by measuring the wavelength change of the reflected light using the optical fiber grating as the pressure sensor. Compared with the traditional pressure sensor, the optical fiber pressure sensor has the advantages of high precision, high stability, interference resistance, safety, flexibility and the like, and can be suitable for higher temperature and pressure and medium environments with stronger corrosiveness.

In the prior art, an optical fiber pressure sensor is provided with a pressed part, seawater is directly contacted with a pressed part, and the pressed part directly causes the optical fiber grating to stretch after being subjected to the pressure brought by the seawater. Because the ocean environment is complicated and the interference is big, the optical fiber pressure sensor can receive factors such as quality of water, temperature of water, surge, atmospheric condition and aerosol when placing in the ocean, consequently sea water is easily receive the interference of above-mentioned factor when directly contacting with pressurized parts, can lead to fiber grating's flexible response too fast from this, and then lead to fiber pressure sensor stability performance relatively poor.

Disclosure of Invention

In order to solve the defect that the stability of the optical fiber pressure sensor is poor due to the fact that the optical fiber pressure sensor is easily affected by the environment in the sea water, the invention provides the optical fiber pressure sensor.

The technical scheme adopted by the invention is that the optical fiber pressure sensor comprises a sensor body and a pressure input assembly for sensing external pressure, wherein the sensor body comprises:

a housing having a receiving cavity formed therein, the receiving cavity having a pressure input port;

the separating piece is in sliding sealing fit with the side wall of the accommodating cavity and forms a closed cavity with the shell;

the sensing optical fiber penetrates through the shell and is respectively and fixedly connected with the end part of the shell and the partition piece in a sealing way, a grating section is arranged on the sensing optical fiber, and the grating section is positioned in the closed cavity;

the pressure input assembly is connected with the pressure input port, so that the external pressure forms internal pressure acting on the partition after being buffered by the pressure input assembly, and the partition is driven to slide.

Preferably, the pressure input assembly is a strain type pressure input assembly capable of elastically deforming under external pressure, and the elastic deformation generated by the strain type pressure input assembly can act on the partition, so that the partition is driven to slide.

Preferably, the strain pressure input assembly comprises an elastic pressure membrane connected with the pressure input port, wherein a sealing space is formed at the other end of the sealed cavity by the elastic pressure membrane, the shell and the partition, and the pressure of the sealing space changes along with the elastic deformation of the elastic pressure membrane, so that the partition is driven to slide.

Preferably, the pressure input port is located at an end of the housing, and the deformation mechanism further includes a mounting structure connected to the pressure input port, the mounting structure being assembled with the elastic pressure membrane and having a deformation space in the mounting structure.

Preferably, the mounting structure has a pressure guide portion along which an external pressure is applied to the elastic pressure diaphragm, the pressure guide portion being disposed opposite to the elastic pressure diaphragm and being located at a center position of the elastic pressure diaphragm.

Preferably, the sealed space is filled with a heat dissipation lubricating medium.

Preferably, a telescopic pipe is arranged in the closed cavity, two ends of the telescopic pipe are fixedly connected with the closed cavity, and the telescopic pipe is covered outside the sensing optical fiber and stretches along with the sensing optical fiber.

Preferably, the inner wall of the shell is provided with a protruding part, the partition piece is a sliding connection block, the protruding part is in sliding sealing fit with the sliding connection block, the transverse edge of the sliding connection block is provided with a limiting protruding block, and when the sliding connection block slides to the limiting position, the limiting protruding block is in butt joint with the protruding part.

Preferably, the shell is provided with a height adjusting block in threaded connection with the inner wall of the shell, the height adjusting block is fixedly connected with the sensing optical fiber, and the sensing optical fiber is in a stretching state or a shrinking state by screwing the height adjusting block.

Preferably, both ends of the shell are fixedly connected with the sensing optical fibers, at least two closed cavities are formed between at least one partition piece and the shell, grating sections are arranged in the closed cavities, and the grating sections are arranged along the telescopic direction of the grating sections.

Compared with the prior art, the invention has the following beneficial effects:

the application discloses optical fiber pressure sensor, including the sensor body and be used for responding to the pressure input subassembly of outside pressure, the sensor body includes: a housing having a receiving cavity formed therein, the receiving cavity having a pressure input port; the separating piece is in sliding sealing fit with the side wall of the accommodating cavity and forms a closed cavity with the shell; the sensing optical fiber penetrates through the shell and is respectively and fixedly connected with the end part of the shell and the partition piece in a sealing way, a grating section is arranged on the sensing optical fiber, and the grating section is positioned in the closed cavity; the pressure input assembly is connected with the pressure input port, so that the external pressure forms internal pressure acting on the partition after being buffered by the pressure input assembly, and the partition is driven to slide. Through with the fixed setting of sensing optic fibre on the separator, can drive the grating section on the sensing optic fibre and change when the separator slides, external pressure directly applys on pressure input subassembly, and the change that external environment produced is after the filtration buffering of pressure input subassembly, is converted into internal pressure and applys on the separator again, has avoided external pressure directly applys on the separator, has avoided leading to fiber pressure sensor's quick response because of external environment's influence. Compared with the prior art, the optical fiber pressure sensor disclosed by the application can be hardly influenced by the environment in the seawater environment, and the purpose of enabling the optical fiber pressure sensor to be better in stability is achieved.

Drawings

The invention is described in detail below with reference to examples and figures, wherein:

FIG. 1 shows a schematic structure of a fiber optic pressure sensor according to an embodiment of the present invention;

FIG. 2 shows a first set of test data for pressure;

FIG. 3 shows a second set of test data for pressure;

FIG. 4 shows a third set of test data for pressure;

FIG. 5 shows a first set of test data for temperature;

FIG. 6 shows a second set of test data for temperature;

fig. 7 shows a third set of test data for temperature.

Reference numerals:

1. an armored optical cable; 2. a gram-type linker; 3. an upper end cap; 4. a first seal ring; 5. a height adjusting block; 6. a first adhesive block; 7. an upper end cylinder; 8. a sensing optical fiber; 9. a telescopic tube; 10. a grating section; 11. the upper end is locked with a screw; 12. an upper locking block; 13. a second seal ring; 14. a sliding connection block; 15. a through hole screw; 16. a plug screw; 17. an intermediate connection; 18. a partition; 19. a third seal ring; 20. expanding the telescopic pipe; 21. a lower end cylinder; 22. expanding the grating section; 23. the lower end is locked with a screw; 24. a lower end locking block; 25. a second adhesive block; 26. a through ring; 27. a fourth seal ring; 28. a lower end cap; 29. installing a lower cover; 30. installing an upper cover; 31. installing a bolt; 32. an elastic pressure membrane; 33. a pressure guide; 34. sealing the cavity; 35. sealing the space; 36. a limit bump; 37. a pressure input port.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings. Examples of embodiments are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements throughout, or elements having like or similar functionality. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.

The invention discloses an optical fiber pressure sensor, please refer to fig. 1, which comprises a sensor body and a pressure input assembly for sensing external pressure, wherein the sensor body comprises:

a housing having a receiving cavity formed therein, the receiving cavity having a pressure input port 37;

a partition 18 in sliding sealing engagement with the side walls of the receiving cavity and forming a closed cavity 34 with the housing;

the sensing optical fiber 8 penetrates through the shell and is respectively and fixedly connected with the end part of the shell and the partition piece 18 in a sealing way, the sensing optical fiber 8 is provided with a grating section 10, and the grating section 10 is positioned in the closed cavity 34;

the pressure input assembly is connected to the pressure input port 37 such that, upon buffering by the pressure input assembly, an internal pressure is developed against the divider 18, which in turn drives the divider 18 into sliding motion.

Through fixedly arranging the sensing optical fiber 8 on the separating piece 18, the grating section 10 on the sensing optical fiber 8 can be driven to change when the separating piece 18 slides, external pressure is directly applied to the pressure input assembly, and the change generated by the external environment is converted into internal pressure to be applied to the separating piece 18 again after being filtered and buffered by the pressure input assembly, so that the external pressure is prevented from being directly applied to the separating piece 18, and the rapid response of the optical fiber pressure sensor caused by the influence of the external environment is prevented. Compared with the prior art, the optical fiber pressure sensor disclosed by the application can be hardly influenced by the environment in the seawater environment, and the purpose of enabling the optical fiber pressure sensor to be better in stability is achieved.

In particular, the filtering and buffering of the external pressure by the pressure input assembly is achieved mainly in two ways. On the one hand, by prolonging the time for external pressure to be transmitted to the separator 18, surge and aerosol factors in sea water tend to exist in local areas, and when such factors occur, the external pressure can be characterized by rapid fluctuation frequency and short acting time, and by arranging a pressure input assembly connected with the external pressure input assembly at the pressure input port 37, the time for external pressure to be transmitted to the separator 18 can be prolonged. In addition, for some disturbance pressures, if the time at which the disturbance pressure occurs is within the transfer time, the disturbance pressure may be filtered. That is, the internal pressure has not yet been applied to the partition 18, and the external disturbing pressure has disappeared at this time, and the internal pressure generated by the disturbing pressure has disappeared together. On the other hand, the sensitivity of the pressure input assembly to external pressure may be adjusted such that the disturbance pressure fluctuating within a certain disturbance range does not change the generated internal pressure of the pressure input assembly, or such that the disturbance pressure fluctuating within a certain disturbance range does change the generated internal pressure of the pressure input assembly but does not cause movement of the partition 18.

In addition, through being equipped with the pressure input subassembly and can increasing the response scope of optic fibre pressure sensor to external pressure, because the tensile scope of measuring optical fiber is certain, consequently can be through adjusting the rate that pressure input subassembly converts external pressure into internal pressure, with great external pressure conversion into less internal pressure, can obtain great pressure measurement scope like this, through setting up like this need not prolong measuring optical fiber's length to make optic fibre pressure sensor's volume littleer.

Wherein, a closed cavity 34 is formed between the separator 18 and the housing, the grating section 10 on the sensing optical fiber 8 is arranged in the closed cavity 34, and the sensing optical fiber 8 is fixedly connected with the end of the housing and the separator 18 respectively, so that when the separator 18 slides in the accommodating cavity, the sensing optical fiber 8 is pulled to change the interval of the grating in the grating section 10, thereby forming an induction signal. The sealed cavity 34 is formed between the separator 18 and the case, and when the separator 18 slides, the pressure in the sealed cavity 34 changes according to the size of the sealed space 35, and when the internal pressure and the pressure exerted on the separator 18 by the pressure in the sealed cavity 34 are balanced with each other, the sliding of the separator 18 is stopped, so that when the internal pressure returns to the initial pressure, the separator 18 can return to the position before sliding.

For the pressure input assembly, the pressure input assembly may be a pressure type pressure input assembly, and the external pressure is converted into the internal pressure acting on the partition 18 through the pressure form, and the specific structure includes a sealing piston, where the sealing piston is in sealing sliding connection with the pressure input port 37 and forms a sealed space with the casing and the partition 18, and the sealing piston can slide under the action of the external pressure, so that the pressure in the sealed space changes, and thus the partition 18 slides.

For the grating section 10, the fiber gratings may be classified into uniform period fiber gratings and non-uniform period fiber gratings, the uniform gratings may be distributed with bragg fiber gratings and long period fiber gratings, and the non-uniform period gratings mainly include chirped fiber gratings, phase-shifted fiber gratings, sampled fiber gratings, and the like. Wherein, the grating section 10 can be one of a bragg fiber grating, a long period fiber grating, a chirped fiber grating, a phase shift fiber grating and a sampling fiber grating, and it should be noted that different fiber gratings need to be selected to perform corresponding signal modulation according to the waveform change characteristics of the fiber gratings, so as to identify the pressure signal of the fiber pressure sensor. Obviously, the user can select other kinds of gratings according to specific use requirements. Preferably, the grating segment 10 is a Fiber Bragg Grating (FBG), which is a fiber bragg diffraction based fiber bragg grating, and has a structure that a part in the middle of an optical fiber has a periodic refractive index change to form a series of reflection gratings with the refractive index periodically changed. The FBG has the structural characteristics of suitability for severe environment, strong electromagnetic interference resistance, high stability, high durability, small size and the like.

The invention is not limited to the location of the pressure input port 37 and the pressure input assembly, it being apparent that the pressure input port 37 may be located on the housing where the enclosed cavity 34 is located, as well as on the end or side of the housing.

In some embodiments, the pressure input assembly is a strain type pressure input assembly that is elastically deformable under external pressure, and the elastic deformation of the strain type pressure input assembly may act on the separator 18, thereby driving the separator 18 to slide.

It should be noted that the elastic deformation of the strain gauge pressure input assembly may act directly or indirectly on the separator 18. The strain gage pressure input assembly directly acts on the spacer 18, i.e., directly contacts the spacer 18, such that the elastic deformation of the strain gage pressure input assembly directly drives the spacer 18 into sliding motion. For example, in other embodiments, the strain-type pressure input assembly includes a balloon having a gas therein, the balloon being fixedly connected directly to the separator 18, the balloon being capable of self-volumetric change with the magnitude of the external pressure, thereby causing the separator 18 to be driven to slide.

Specifically, the strain type pressure input assembly is simple in structure, convenient to install and small in size, and can be suitable for more application scenes, such as special environments like ocean environments.

In some specific embodiments, the strain gauge pressure input assembly includes an elastic pressure diaphragm 32, the elastic pressure diaphragm 32 is connected to a pressure input port 37, the elastic pressure diaphragm 32, the housing, and the partition 18 form a sealed space 35 at the other end of the closed cavity 34, and the pressure of the sealed space 35 changes with the elastic deformation of the elastic pressure diaphragm 32, so that the partition 18 is driven to slide.

Specifically, the strain-type pressure input assembly includes an elastic pressure membrane 32, the elastic pressure membrane 32 can deform under the action of external pressure, a sealed space 35 is formed at the other end of the sealed cavity 34 by the elastic pressure membrane 32, the casing and the separator 18, that is, the sealed space 35 and the sealed cavity 34 are respectively located at two sides of the separator 18, and the elastic pressure membrane 32 can change the size of the sealed space 35 when undergoing elastic deformation, so as to change the pressure inside the sealed space 35, thereby moving the separator 18. The elastic coefficient of the elastic pressure membrane 32 can be set according to the working scene of the optical fiber pressure sensor, and if a larger pressure range needs to be tested, the elastic coefficient of the elastic pressure membrane 32 can be increased for adaptation. Meanwhile, the elastic pressure membrane 32 is low in cost and high in ageing resistance. In addition, the elastic pressure membrane 32 can be made of different elastic materials, and the optical fiber pressure sensor can work in different environments such as acid resistance, alkali resistance and the like through the properties of the different elastic materials.

In some more specific embodiments, the pressure input port 37 is located at an end of the housing, and the deformation mechanism further includes a mounting structure coupled to the pressure input port 37, the mounting structure being assembled with the elastic pressure diaphragm 32 and having a deformation space within the mounting structure.

By providing the mounting structure with the pressure input port 37, the sealing performance of the optical fiber pressure sensor is improved, and the elastic pressure diaphragm 32 is easier to mount. The pressure input port 37 is provided at an end of the housing instead of at a side of the housing in order to make sliding of the partitioning member 18 smoother when the internal pressure acts uniformly on the partitioning member 18. And have deformation space in the mounting structure, make elastic deformation of elastic pressure diaphragm 32 can not be hindered, and be favorable to protecting elastic pressure diaphragm 32.

In some still more specific embodiments, the mounting structure has a pressure guide 33, and the external pressure is applied to the elastic pressure diaphragm 32 along the pressure guide 33, and the pressure guide 33 is disposed opposite to the elastic pressure diaphragm 32 and is located at a center position of the elastic pressure diaphragm 32.

Specifically, the pressure guiding part 33 is arranged opposite to the elastic pressure membrane 32 and is positioned at the center of the elastic pressure membrane 32, and by arranging the pressure guiding part 33, external pressure acts on the elastic pressure membrane 32 after passing through the pressure guiding part 33, so that the deformation of the elastic pressure membrane 32 is more uniform, and the precision of the optical fiber pressure sensor is further improved; meanwhile, the elastic pressure membrane 32 can be further protected, and the influence of certain marine factors is avoided, so that the stability of the optical fiber pressure sensor is higher.

In some more specific embodiments, the sealed space 35 is filled with a heat dissipating lubrication medium.

It should be noted that, by filling the heat dissipation and lubrication medium in the sealed space 35, the optical fiber pressure sensor can obtain a more stable sensing signal, and the heat dissipation and lubrication medium has a relatively high heat conduction capacity, so that the heat generated by sliding the separator 18 can be rapidly transferred to the outside, and meanwhile, the separator 18 can be lubricated, so that the sliding process of the separator 18 is smoother. Preferably, the heat dissipation lubricating medium is silicone oil, and the silicone oil has the effects of eliminating static electricity and preventing oxidation corrosion besides the heat dissipation lubricating effect, so that the corrosion of seawater to the fiber pressure sensor is prevented.

In some embodiments, a telescopic tube 9 is arranged in the closed cavity 34, two ends of the telescopic tube 9 are fixedly connected with the closed cavity 34, and the telescopic tube 9 is covered outside the sensing optical fiber 8 and stretches and contracts along with the sensing optical fiber 8.

The telescopic tube 9 is arranged in the closed cavity 34 and is covered outside the sensing optical fiber 8, and the movement of the partition piece 18 can be buffered by arranging the telescopic tube 9 on the one hand, so that the sensing optical fiber 8 cannot be damaged in an unrecoverable way due to the fact that the partition piece 18 slides too fast; on the other hand, the telescopic tube 9 can protect the sensing optical fiber 8 and prevent other parts from falling down to directly collide with the sensing optical fiber 8.

Preferably, the bellows 9 is a vacuum bellows. The vacuum bellows has the advantage of good flexibility with respect to the bellows, so that vibration and leakage can be reduced, and in addition, the vacuum bellows has a function of withstanding high pressure and high temperature, so that the expansion and contraction of the vacuum bellows and the variation of the grating section 10 are not affected by the pressure variation in the closed cavity 34 and the heat caused by the sliding of the partition 18.

In some embodiments, the inner wall of the housing has a protruding portion, the partition 18 is a sliding connection block, the protruding portion is in sliding sealing fit with the sliding connection block, a limiting bump 36 is arranged at a lateral edge of the sliding connection block, and when the sliding connection block slides to a limiting position, the limiting bump 36 abuts against the protruding portion.

It should be noted that, since the sensing optical fiber 8 can only be elongated to a certain length, exceeding the length will stretch the sensing optical fiber 8, so in order to ensure that the sensing optical fiber 8 will not be stretched due to excessive external pressure during the operation of the optical fiber pressure sensor, a limit structure needs to be provided on the optical fiber pressure sensor. Through selecting for use the sliding connection piece, its area of contact with the inner wall is bigger to make sealed effect better. Preferably, limit bumps 36 are provided at both ends of the sliding connection block, so that the sensing fiber 8 can be limited whether it is elongated or shortened.

In some embodiments, the shell is provided with a height adjusting block 5 in threaded connection with the inner wall of the shell, the height adjusting block 5 is fixedly connected with the sensing optical fiber 8, and the sensing optical fiber 8 is in a stretched state or a contracted state by screwing the height adjusting block 5.

It should be noted that, be equipped with high regulating block 5 on the casing, threaded connection simple structure just easily installs, and high regulating block 5 is used for adjusting the elasticity of sensing optic fibre 8 to let sensing optic fibre 8 be in the initial state that carries out the forced induction. Specifically, if the optical fiber pressure sensor is shorter and shorter along with the increase of the external pressure, the sensing optical fiber 8 can be properly pulled up by the height adjusting block 5, and at this time, the sensing optical fiber 8 can obtain larger length change when the pressure is detected, and vice versa. Therefore, the range of the optical fiber pressure sensor can be increased and the accuracy can be increased by providing the height adjusting block 5.

In some embodiments, two ends of the housing are fixedly connected with the sensing optical fiber 8, at least two closed cavities 34 are formed between the at least one separator 18 and the housing, the grating segments 10 are arranged in the closed cavities 34, and the grating segments 10 are arranged along the telescopic direction of the grating segments 10.

It should be noted that, at least two closed cavities 34 are formed between at least one spacer 18 and the housing, taking one spacer 18 as an example, one spacer 18 can divide the accommodating cavity into two closed cavities 34, the two closed cavities 34 are provided with the grating sections 10 arranged along the extending and retracting directions of the grating sections 10, when the spacer 18 slides, since both ends of the sensing optical fiber 8 are connected with the housing, one of the two grating sections 10 is shortened, the other is lengthened, the distance between the shortening and the lengthening is the same, and the two grating sections 10 are in a push-pull structure. By providing the grating segments 10 in the plurality of closed cavities 34, the influence of factors such as temperature, ultrasonic waves and the like on the grating segments 10 can be eliminated, so that the signal change caused by the extension or shortening of the grating segments 10 can be accurately obtained, and the pressure measurement by the optical fiber pressure sensor is more accurate.

In a particular embodiment, please refer to fig. 1, which is specifically described by the following embodiment: the shell comprises an upper end cover 3, an upper end cylinder 7, a middle connecting piece 17, a lower end cylinder 21 and a lower end cover 28 which are sequentially connected, and the inside of the structure forms a containing cavity together. The partition 18 is arranged on the intermediate connection piece 17 in a sliding sealing fit, wherein the upper end cap 3, the upper end cylinder 7, the intermediate connection piece 17 and the partition 18 form a closed cavity 34, and the partition 18, the lower end cylinder 21, the lower end cap 28 and the intermediate connection piece 17 form a sealed space 35. Here, the sealed space 35 is formed, and a closed cavity similar to the one of the reference numeral 34 is also formed.

A first seal ring 4 is provided between the upper end cap 3 and the upper end tube 7, a second seal ring 13 is provided between the upper end tube 7 and the intermediate connecting member 17, a third seal ring 19 is provided between the intermediate connecting member 17 and the lower end tube 21, and a fourth seal ring 27 is provided between the lower end tube 21 and the lower end cap 28. The optical fiber pressure sensor has better sealing effect by being provided with the first sealing ring 4, the second sealing ring 13, the third sealing ring 19 and the fourth sealing ring 27, and simultaneously, external liquid can be prevented from entering the optical fiber pressure sensor.

The sensing optical fiber 8 penetrates through the optical fiber pressure sensor, and armor is arranged on the sensing optical fiber 8 outside, so that the armored optical cable 1 is formed to protect the sensing optical fiber 8. The upper end cover 3 is provided with a through hole for installing the gram joint 2, and the armored optical cable 1 is arranged through the gram joint 2. The height adjusting block 5, the first bonding block 6 and the telescopic tube 9 which are sequentially connected are arranged in the closed cavity 34, the first bonding block 6 is mainly used for bonding the telescopic tube 9 and the sensing optical fiber 8, the outer edge of the first bonding block 6 is bonded with one end of the telescopic tube 9, the middle pore is used for providing a pore channel for bonding the sensing optical fiber 8, the resin adhesive is used for bonding along the axial direction, and specific parameters can be adjusted according to actual conditions.

The other end of the telescopic pipe 9 is connected with a sliding connecting block 14 through an upper locking block 12, and the upper locking block 12 is fixedly connected with the sliding connecting block 14 through an upper locking screw 11. The upper locking block 12, the slide connection block 14, and the partition 18 are connected in sequence, and can slide together with the partition 18. The sliding connection block 14 is fixedly connected with the partition piece 18 through a through hole screw 15, and the sensing optical fiber 8 penetrates through the through hole screw 15 and is fixedly connected with the through hole screw 15.

The protruding portion is arranged on the middle connecting piece 17, one end of the partition piece 18 is provided with a limiting protruding block 36, and the other end of the partition piece is in butt joint with the middle connecting piece 17 through the sliding connecting block 14 to limit.

The expansion telescopic tube 20, the lower end locking block 24 and the through ring 26 which are sequentially connected are arranged in the sealing space 35, an expansion grating section 22 is arranged in the expansion telescopic tube 20, the expansion telescopic tube 20 is sealed through the second bonding block 25 and fixes the sensing optical fiber 8, the lower end locking block 24 and the lower end cover 28 are fixedly connected through the lower end locking screw 23, the through ring 26 is embedded into the lower end cover 28 and connected with the lower end cover 28, a through hole is arranged on the through ring 26, the through hole can be used for circulation of silicone oil, the silicone oil is arranged in the sealing space 35, and a plug screw 16 is arranged on the intermediate connecting piece 17 and used for preventing the silicone oil from entering the accommodating cavity.

The pressure input port 37 is disposed on the lower end cover 28, the mounting structure includes a mounting upper cover 29, a mounting lower cover 30, a mounting bolt 31 and an elastic pressure membrane 32, the mounting upper cover 29 and the mounting lower cover 30 are fixedly connected through the mounting bolt 31, a deformation space is formed at the connection position, the elastic pressure membrane 32 is disposed in the deformation space and fixedly connected with the mounting lower cover 30, a pressure guide portion 33 is disposed on the mounting lower cover 30, and the pressure guide portion 33 is disposed opposite to the elastic pressure membrane 32.

The armored optical cable 1 is mainly used for protecting tail fibers of the optical fiber pressure sensor and regulating air pressure difference, so that the sensor can work normally and is not influenced by external environment. The optical fiber pressure sensor uses an armored optical cable with the diameter of 3mm for protection.

The gram joint 2 is mainly used for connecting the armored optical cable 1 and an external base, and has the characteristics of dust prevention and water prevention. The fiber optic pressure sensor may use an M8 stainless steel gram joint.

The upper end cover 3 is mainly used for packaging the upper end of the sensor and plays a role in protecting the internal structure of the optical fiber pressure sensor, the outer diameter of the part is phi 70mm, and the material is 316 stainless steel.

The first sealing ring 4, the second sealing ring 13, the third sealing ring 19 and the fourth sealing ring 27 can be fluororubber O-shaped rings.

The height adjusting block 5 is mainly used for adjusting and fixing the telescopic pipe 9, so that the telescopic pipe 9 is stressed to a certain extent, and the part is formed by processing 316 stainless steel.

The telescopic pipe 9 and the expansion telescopic pipe 20 are vacuum corrugated pipes, and the calculation formula of the elastic deformation (namely the length variation) of the vacuum corrugated pipes is as follows:

ΔL＝(F×L)/(E×S)

wherein Δl represents the elastic deformation amount of the vacuum bellows; f represents an external force acting on the bellows; l represents the original length of the bellows; e represents the elastic modulus of the material; s represents the cross-sectional area of the bellows.

The calculation formula of the variation of the section area S of the vacuum bellows after elastic deformation is as follows:

wherein DeltaS is the variation of the cross-sectional area S of the corrugated pipe after elastic deformation; 0.000001337 is the proportionality coefficient between the bellows length variation and the measured value; d is the inner diameter of the corrugated pipe; d is the outer diameter of the bellows.

The grating section 10 is mainly used for converting the deformation of the telescopic pipe 9 into the change of an optical signal; the grating is pre-stretched at about 2nm and then adhered and fixed, the grating can be 1550nm wave band grating, the initial wavelength is 1550.2351, the ambient temperature is 25 ℃, the wavelength after stretching is 1552.2481, and the stretching amount is 2.0130nm.

The grating section 10 is a Bragg grating with Bragg wavelength lambda _B Is determined by the following formula:

λ _Β ＝2n _eff Λ

wherein: n is n _eff An effective refractive index for light propagating within the optical fiber; Λ is the period of the bragg grating. Lambda (lambda) _B Is Λ and n _eff Is a function of (2).

When FBG is not affected by external force field and ambient temperature changes DeltaT, lambda _B Drift occurs, and the relation between the drift amount and the temperature change can be written as

△λ _B ＝λ _B (α+ζ)△T

Wherein: α is the thermal expansion coefficient of the FBG material; ζ is the thermo-optic coefficient of the FBG material; deltaT is the amount of temperature change.

When the ambient temperature is constant, the FBG is acted by an external force field, lambda _B Drift occurs by the following amount

△λ＝λ _B (1-P _e )△ε

Wherein: delta epsilon is the stress variation; p (P) _e ＝n _eff ² [P ₂ -μ(P ₁ +P ₂ )]2, representing the effective elasto-optical coefficient of the FBG material, where P ₁ And P ₂ The elasto-optical coefficient of the FBG material; μ is poisson's ratio of the FBG material.

Lambda when strain and temperature act simultaneously on FBG _B Drift occurs by the following amount

△λ＝λ _B (1-P _e )△ε+λ _B (α+ζ)△T

The intermediate connection member 17 is mainly used for connecting the upper end cylinder 7 with the lower end cylinder 21 and the reciprocating motion passage of the upper and lower bellows, and when the balance of the upper and lower forces is broken, the piston rod makes a linear and repetitive motion within a certain range.

Since the temperature environment of the grating section 10 is the same as that of the expanded grating section 22, namely the drift amount generated by temperature influence is the same, the compressed end grating and the extended end grating can be mutually temperature compensated, and the error caused by temperature change is counteracted.

In addition, for this embodiment, the inventor performs a pressing test on the assembled optical fiber pressure sensor, and one end of the armored optical fiber cable 1 of the optical fiber pressure sensor is connected to the fiber grating demodulator, so that the wavelength value of the sensor is displayed normally. The pressure guiding part 33 is externally connected with a high-pressure hose, the other end of the high-pressure hose is connected with a hand-held pressure pump, the pressure is measured in a gradient of 0.05MPa, the maximum pressure is 0.6MPa, the wavelength value of each gradient is recorded, and three groups of experimental data are shown in fig. 2 to 4.

From the recorded data and the drawn graph, the grating section 10 (the compressed end grating) and the extended grating section 22 (the extended end grating) in the test process have stable change and good linearity, the wavelength change amounts of the two are equal and opposite, the change amount is about 1.512nm/MPa, and the design expectation is met;

the sensor is placed in a constant temperature and humidity box for temperature change test, one end of an armored optical cable 1 of the optical fiber pressure sensor is connected with an optical fiber grating demodulator, the temperature is 5 ℃ as a gradient, the temperature is increased from 5 ℃ to 30 ℃, the wavelength value change of the sensor is recorded, and three groups of experimental data are shown in figures 5 to 7.

From the measured data, the wavelength variation of the grating section 10 (the compressed end grating) and the wavelength variation of the extended grating section 22 (the extended end grating) are equal under the same temperature variation, the variation is about 9 pm/DEG C, and the two are mutually compensated due to the same temperature variation.

In the description of the present specification, the terms "embodiment," "present embodiment," "in one embodiment," and the like, if used, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples; furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In the description of the present specification, the terms "connected," "mounted," "secured," "disposed," "having," and the like are to be construed broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.

In the description of this specification, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The embodiments have been described so as to facilitate a person of ordinary skill in the art in order to understand and apply the present technology, it will be apparent to those skilled in the art that various modifications may be made to these examples and that the general principles described herein may be applied to other embodiments without undue burden. Therefore, the present application is not limited to the above embodiments, and modifications to the following cases should be within the scope of protection of the present application: (1) the technical scheme of the invention is taken as the basis and combined with the new technical scheme implemented by the prior common general knowledge, and the technical effect produced by the new technical scheme is not beyond that of the invention; (2) equivalent replacement of part of the characteristics of the technical scheme of the invention by adopting the known technology produces the technical effect the same as that of the invention; (3) the technical scheme of the invention is taken as a basis for expanding, and the essence of the expanded technical scheme is not beyond the technical scheme of the invention; (4) equivalent transformation made by the content of the specification and the drawings of the invention is directly or indirectly applied to other related technical fields.

Claims (10)

1. An optical fiber pressure sensor comprising a sensor body and a pressure input assembly for sensing an external pressure, the sensor body comprising:

a housing having an accommodating cavity formed therein, the accommodating cavity having a pressure input port;

the partition piece is in sliding sealing fit with the side wall of the accommodating cavity and forms a closed cavity with the shell;

the sensing optical fiber penetrates through the shell and is respectively and fixedly connected with the end part of the shell and the partition piece in a sealing way, and the sensing optical fiber is provided with a grating section which is positioned in the closed cavity;

the pressure input assembly is connected with the pressure input port, so that the external pressure forms internal pressure acting on the partition after being buffered by the pressure input assembly, and the partition is driven to slide.

2. A fiber optic pressure sensor according to claim 1 wherein the pressure input assembly is a strain type pressure input assembly that is elastically deformable under external pressure, the elastic deformation of the strain type pressure input assembly acting on the spacer to cause the spacer to be driven to slide.

3. The optical fiber pressure sensor according to claim 2, wherein the strain pressure input assembly comprises an elastic pressure diaphragm, the elastic pressure diaphragm is connected with the pressure input port, a sealing space is formed by the elastic pressure diaphragm, the shell and the partition piece at the other end of the closed cavity, and the pressure of the sealing space changes along with the elastic deformation of the elastic pressure diaphragm, so that the partition piece is driven to slide.

4. A fiber optic pressure sensor according to claim 3 wherein said pressure input port is located at an end of said housing, said deformation mechanism further comprising a mounting structure connected to said pressure input port, said mounting structure being assembled with said elastic pressure diaphragm and having a deformation space within said mounting structure.

5. The optical fiber pressure sensor according to claim 4, wherein said mounting structure has a pressure guide portion along which an external pressure is applied to said elastic pressure diaphragm, said pressure guide portion being disposed opposite to and at a center position of said elastic pressure diaphragm.

6. A fiber optic pressure sensor according to claim 3 wherein said sealed space is filled with a heat dissipating lubrication medium.

7. The optical fiber pressure sensor according to claim 1, wherein a telescopic tube is arranged in the closed cavity, two ends of the telescopic tube are fixedly connected with the closed cavity, and the telescopic tube is covered outside the sensing optical fiber and stretches and contracts along with the sensing optical fiber.

8. The optical fiber pressure sensor according to claim 1, wherein the inner wall of the housing is provided with a protruding portion, the partition is a sliding connection block, the protruding portion is in sliding sealing fit with the sliding connection block, a limiting protruding portion is arranged at the lateral edge of the sliding connection block, and when the sliding connection block slides to a limiting position, the limiting protruding portion abuts against the protruding portion.

9. The optical fiber pressure sensor according to claim 1, wherein the housing is provided with a height adjusting block in threaded connection with the inner wall of the housing, the height adjusting block is fixedly connected with the sensing optical fiber, and the sensing optical fiber is placed in a stretched state or a contracted state by screwing the height adjusting block.

10. An optical fiber pressure sensor according to any one of claims 1 to 9, wherein two ends of the housing are fixedly connected with the sensing optical fiber, at least two closed cavities are formed between at least one partition and the housing, the grating sections are arranged in a plurality of closed cavities, and the grating sections are arranged along the telescopic direction of the grating sections.