CN115931166A - Rapid-response fiber bragg grating ocean temperature and depth sensor and preparation method thereof - Google Patents
Rapid-response fiber bragg grating ocean temperature and depth sensor and preparation method thereof Download PDFInfo
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- CN115931166A CN115931166A CN202211515173.8A CN202211515173A CN115931166A CN 115931166 A CN115931166 A CN 115931166A CN 202211515173 A CN202211515173 A CN 202211515173A CN 115931166 A CN115931166 A CN 115931166A
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Abstract
The invention discloses a fast response fiber grating ocean depth and temperature sensor and a preparation method thereof, belonging to the technical field of fiber sensing, comprising a metal shell and an optical fiber, wherein the metal shell comprises a depth and temperature sensing chamber, a free permeable chamber, a pressure compensation chamber and a temperature compensation chamber from bottom to top in sequence; the structure is designed by adopting metal and optical elements with small sizes, and the finished product is convenient to carry and is suitable for quickly measuring the temperature depth profile data in the ocean range of 0-800 m.
Description
Technical Field
The invention belongs to the technical field of optical fiber sensing, and relates to a fast response fiber bragg grating ocean temperature and depth sensor and a preparation method thereof.
Background
The temperature and depth of seawater are the most basic physical quantities of oceans, and have great significance in the fields of oceanic scientific research, resource development, meteorological prediction, military, national defense and the like. The expendable ocean depth thermometer is low-cost disposable equipment and is an effective means for rapidly measuring temperature and depth data in various countries.
The existing temperature and depth sensors mostly use electrical sensing elements, wherein the response time of a platinum resistor is more than 1s, the response speed of a high-level disposable temperature and depth instrument product can reach 65ms, but the problems of low sensitivity, poor thermal stability and the like still exist. Passive optical devices such as fiber gratings, which have the intrinsic advantages of materials, have received much attention from researchers in various fields. In order to improve the sensitivity of the fiber grating sensor, many researches are carried out to sensitize the optical fiber by means of ion doping, film coating, cantilever beams, diaphragms and the like. In order to improve the response speed of the fiber bragg grating sensor, research is carried out to improve the temperature response speed of the FBG by packaging the FBG into a material sleeve with better heat conductivity, the FBG is transversely placed on an elastic diaphragm, and the sensitivity is improved and the faster pressure response speed is obtained through the deformation of external stress on the FBG.
At present, in many prior art, through processing or designing a special structure for FBGs, although the sensitivity of the temperature and depth sensor is improved, the response speed of the sensor is ignored, in order to meet the requirement of rapid detection of ocean temperature and depth data, the response speed of a single parameter is improved in some researches, but as a sensor for double-parameter detection, if the response speed of two parameter sensors cannot be guaranteed to be close to each other, the drift of temperature data on the depth can be caused, and the precision of the sensor is further reduced.
The patent CN112705843B discloses a diaphragm type cascade structure fiber grating pressure sensor and a manufacturing method thereof, which obtains a temperature and depth sensor with high sensitivity and wide range by cascading diaphragm type pressure sensors with different ranges, but because the structure is difficult to ensure that the response time of the sensors with different levels is the same, and the free fiber grating for temperature sensing can be affected by the water flow of the water inlet and the water outlet, the stability is reduced.
An ocean double-diaphragm fiber grating pressure sensor for a throwing type probe is disclosed in patent CN215374319U, and pressure measuring gratings and temperature compensation gratings are affected by temperature and pressure through the action of double diaphragms on two fiber gratings respectively, so that the pressure measuring gratings and the temperature compensation gratings can be subjected to real-time temperature compensation to improve the pressure measurement accuracy. Although the sensor can perform high-precision measurement on pressure, an empirical formula is required in the ocean temperature measurement part, the pressure response time of the sensor can cause the drift of depth data on temperature during the rapid falling process of the probe, and the optical fibers on the two sides need to be externally repackaged, so that the size of the sensor is large.
In order to solve the technical problems, the invention provides a fast response fiber grating ocean temperature and depth sensor and a preparation method thereof, which have higher temperature and depth sensitivity, can ensure that the response speed of temperature and depth data is fast and matched, and meet the requirement of fast detection of the temperature and depth sensor.
Disclosure of Invention
In view of this, the invention provides a fast response fiber grating ocean temperature and depth sensor and a preparation method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
a fast response fiber bragg grating ocean temperature and depth sensor comprises a metal shell and an optical fiber, wherein the metal shell comprises a temperature and depth sensing cavity, a free permeable cavity, a pressure compensation cavity and a temperature compensation cavity from bottom to top in sequence;
the top metal shell of the temperature depth sensing cavity, the top metal elastic membrane of the free permeable cavity, the top metal shell of the pressure compensation cavity and the top metal shell of the temperature compensation cavity are all provided with central holes, and a primary metal cylinder, a secondary metal cylinder, a tertiary metal cylinder and a quaternary metal cylinder are sequentially welded in the central holes from bottom to top;
the bottom of the temperature and depth sensing cavity is provided with a liquid core metal elastic membrane, a cylindrical liquid tank is arranged inside the center of the liquid core metal elastic membrane, a metal liquid tank is arranged at the center of the liquid core metal elastic membrane, the top and the bottom of the metal liquid tank are both provided with openings, a liquid hole is formed in the center of the top of the cylindrical liquid tank and communicated with the opening at the bottom of the metal liquid tank, gallium indium tin liquid is filled in the cylindrical liquid tank and the metal liquid tank, and a hard piston is arranged in the metal liquid tank and is in surface contact with the gallium indium tin liquid;
one end of the optical fiber is fixed on the hard piston, the other end of the optical fiber sequentially penetrates through the first-stage metal cylinder, the second-stage metal cylinder, the third-stage metal cylinder and the fourth-stage metal cylinder, and finally the tail fiber penetrates out of a tail fiber guiding-out barrel sequentially arranged at the top outside the metal shell;
the top end of the optical fiber provided with the temperature-depth optical fiber grating is fixedly connected with the primary metal cylinder, the two ends of the optical fiber provided with the pressure compensation optical fiber grating are respectively and fixedly connected with the secondary metal cylinder and the tertiary metal cylinder, and the two ends of the optical fiber provided with the temperature compensation optical fiber grating are respectively and fixedly connected with the tertiary metal cylinder and the quaternary metal cylinder;
the part of the optical fiber, which is positioned in the temperature and depth sensing cavity, is provided with a temperature and depth optical fiber grating, the part of the optical fiber, which is positioned in the free water permeable cavity, is a free optical fiber, the part of the optical fiber, which is positioned in the pressure compensation cavity, is provided with a pressure compensation optical fiber grating, and the part of the optical fiber, which is positioned in the temperature compensation cavity, is provided with a temperature compensation optical fiber grating;
the temperature-depth fiber grating and the pressure-compensation fiber grating are in a pre-stretching state, and the temperature-compensation fiber grating is in a free state;
the side wall of the free water permeable cavity is provided with water permeable holes.
Further, the metal shell is in a cylindrical shape with an outer diameter of 12mm, an inner diameter of 7mm and a height of 60mm, the bottom end of the metal shell is open, the metal shell is made of 316 stainless steel, and the bottom of the metal shell is open; the tops of the temperature and depth sensing chamber and the pressure compensation chamber are both metal shells.
Furthermore, the liquid core metal elastic membrane is a brass circular elastic membrane with the diameter of 10mm and the thickness of 2mm, and the radius of the cylindrical liquid groove is 2-3 mm, and the height of the cylindrical liquid groove is 0.2mm.
Further, the above-mentioned hole of permeating water is 4mm wide, 8 mm's square hole.
Furthermore, the metal elastic membrane is a brass circular elastic membrane with the diameter of 10mm and the thickness of 2mm, and is positioned 5mm above the water permeable hole.
Further, the liquid metal tank is a cylindrical tank with an outer diameter of 6mm, an inner diameter of 0.4mm and a height of 12mm, and is made of 316 stainless steel.
Further, the central wavelength of the temperature-depth fiber grating is 1550nm, the effective length is 10mm, the central wavelength of the pressure compensation fiber grating is 1550nm, the effective length is 10mm, the central wavelength of the temperature compensation fiber grating is 1560nm, and the effective length is 3mm.
Further, the liquid core metal elastic membrane is welded with a metal shell on the periphery of the bottom of the temperature and depth sensing cavity in a sealing mode, and the metal elastic membrane is welded with a metal shell on the periphery of the top of the free water permeable cavity in a sealing mode.
Further, the optical fibers are fixedly connected with the first-level metal cylinder, the second-level metal cylinder, the third-level metal cylinder and the fourth-level metal cylinder through epoxy glue.
The invention also provides a preparation method of the quick response fiber grating ocean temperature and depth sensor, which comprises the following steps:
(1) Manufacturing each part according to the size, sequentially enabling one end of an optical fiber to penetrate through a tail fiber leading-out cylinder, a four-level metal cylinder, a temperature compensation chamber, a three-level metal cylinder and a pressure compensation chamber, sleeving a brass circular membrane outside the two-level metal cylinder and sealing and welding the brass circular membrane, translating the temperature compensation fiber grating into the temperature compensation chamber, fixing two ends of the optical fiber provided with the temperature compensation fiber grating with the four-level metal cylinder and the three-level metal cylinder respectively by using epoxy glue, welding the four-level metal cylinder into a central hole in the top end of a metal shell, and welding the three-level metal cylinder into a central hole of the metal shell between the temperature compensation chamber and the pressure compensation chamber to finish the packaging of the temperature compensation fiber grating;
(2) Attaching the periphery of a metal elastic membrane welded with a secondary metal cylinder in a central hole to a metal shell at the bottom end of a pressure compensation chamber, welding the attaching part by using a laser welding machine to form a circular welding spot, applying 2N-2.5N pre-tension to the pressure compensation fiber grating, and fixing two ends of an optical fiber provided with the pressure compensation fiber grating with the secondary metal cylinder and a tertiary metal cylinder respectively by using epoxy glue to finish the packaging of the pressure compensation fiber grating;
(3) Sequentially enabling the optical fiber to penetrate through the free water-permeable cavity, the primary metal cylinder and the temperature-depth sensing cavity, aligning a liquid hole of a cylindrical liquid tank formed in the center of the liquid-core metal elastic membrane with an opening in the bottom of the liquid metal tank, fixedly welding the liquid-core metal elastic membrane and the bottom of the liquid metal tank, filling gallium indium tin liquid, pushing a hard piston with a fine hole in the middle into the liquid metal tank until the hard piston is in contact with the liquid, and fixing the bottom end of the optical fiber provided with the temperature-depth optical fiber grating with the hard piston through epoxy glue;
(4) Attaching a liquid core metal elastic membrane to a metal shell on the periphery of the bottom of a temperature and depth sensing cavity, welding the attaching part by using a laser welding machine to form a circular welding spot, straightening an optical fiber where a temperature and depth optical fiber grating is located and enabling the optical fiber to be located on a central axis where the liquid core metal elastic membrane and a metal liquid tank are located, reserving a deformation distance of 0.2-0.3mm between a primary metal cylinder and the top end of the temperature and depth sensing cavity, fixing the top end of the optical fiber provided with the temperature and depth optical fiber grating and the primary metal cylinder through epoxy glue, applying pre-pressing stress to the temperature and depth optical fiber grating by slowly pushing the primary metal cylinder, and welding and fixing the top metal shell with the temperature and depth sensing cavity to finish the packaging of the temperature and depth optical fiber grating;
(5) And a flexible tube is sleeved on the free optical fiber or a metal-plated outer layer is coated on the free optical fiber, two square holes are formed in two ends of the side wall of the free water-permeable cavity and used for passing in and out seawater, a tail optical fiber guide cylinder is welded to the outer top of the metal shell, the tail optical fiber is protected by a cable, and the whole pressure sensor is assembled.
The invention has the beneficial effects that: the invention provides a fast response fiber grating ocean temperature and depth sensor and a preparation method thereof. The sensor consists of a temperature and depth sensing chamber, a free permeable chamber, a pressure compensation chamber and a temperature compensation chamber, and greatly improves the pressure stress deformation of the bare fiber grating based on the influence of external pressure on a brass diaphragm, and improves the pressure sensitivity; based on the influence of external temperature on heat transfer of gallium indium tin liquid, pressure stress is applied to the temperature-measuring fiber bragg grating, temperature sensing is carried out through the influence of volume change of the liquid on the prestress of the temperature-measuring fiber bragg grating, and the temperature sensitivity of the bare fiber bragg grating is greatly improved; the brass material and the gallium indium tin material are selected to improve the external heat transfer speed and reduce the response speed of temperature sensing, and a certain material specification and size are set, so that the response speed of temperature and pressure is close to the same, and real-time temperature depth compensation can be performed; under the condition of keeping higher temperature and depth sensitivity, the structure can obtain higher response speed compared with the traditional expendable depth thermometer, eliminates the drift of temperature data on depth data compared with the traditional expendable depth thermometer, and improves the precision; the structure is designed by adopting metal and optical elements with small sizes, and the finished product is convenient to carry and is suitable for quickly measuring the temperature depth profile data in the ocean range of 0-800 m.
Drawings
FIG. 1 is a schematic structural diagram of a fast response fiber grating ocean temperature and depth sensor of the present invention.
In the figure: 1-temperature depth sensing chamber, 2-free permeable chamber, 3-pressure compensation chamber, 4-temperature compensation chamber, 5-metal shell, 6-liquid core metal elastic membrane, 7-welding spot, 8-gallium indium tin liquid, 9-hard piston, 10-metal liquid tank, 11-temperature depth fiber grating, 12-free optical fiber, 13-pressure compensation fiber grating, 14-temperature compensation fiber grating, 15-permeable hole, 16-metal elastic membrane, 17-first-level metal cylinder, 18-second-level metal cylinder, 19-third-level metal cylinder, 20-fourth-level metal cylinder, 21-tail fiber leading-out cylinder, 22-tail fiber, 23-optical fiber, 24-cylindrical liquid tank and 25-liquid hole.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
A fast response fiber bragg grating ocean temperature and depth sensor comprises a metal shell 5 and an optical fiber 23, wherein the metal shell 5 sequentially comprises a temperature and depth sensing chamber 1, a free water penetration chamber 2, a pressure compensation chamber 3 and a temperature compensation chamber 4 from bottom to top;
the top metal shell 5 of the temperature and depth sensing chamber 1, the top metal elastic membrane 16 of the free water permeable chamber 2, the top metal shell 5 of the pressure compensation chamber 3 and the top metal shell 5 of the temperature compensation chamber 4 are all provided with central holes, and a primary metal cylinder 17, a secondary metal cylinder 18, a tertiary metal cylinder 19 and a quaternary metal cylinder 20 are sequentially welded in the central holes from bottom to top;
the bottom of the temperature and depth sensing chamber 1 is provided with a liquid core metal elastic membrane 6, a cylindrical liquid groove 24 is formed in the center of the liquid core metal elastic membrane 6, a metal liquid groove 10 is formed in the center of the liquid core metal elastic membrane 6, openings are formed in the top and the bottom of the metal liquid groove 10, a liquid hole 25 is formed in the center of the top of the cylindrical liquid groove 24 and communicated with the opening in the bottom of the metal liquid groove 10, gallium indium tin liquid 8 is filled in the cylindrical liquid groove 24 and the metal liquid groove 10, and a hard piston 9 is arranged in the metal liquid groove 10 and contacts with the surface of the gallium indium tin liquid 8;
one end of the optical fiber 23 is fixed on the hard piston 9, the other end of the optical fiber passes through the first-stage metal cylinder 17, the second-stage metal cylinder 18, the third-stage metal cylinder 19 and the fourth-stage metal cylinder 20 in sequence, and finally the tail fiber 22 passes through a tail fiber leading-out cylinder 21 which is arranged at the top of the metal shell 5 in sequence;
the top end of the optical fiber 23 provided with the temperature-depth optical fiber grating 11 is fixedly connected with the primary metal cylinder 17, the two ends of the optical fiber 23 provided with the pressure compensation optical fiber grating 13 are respectively and fixedly connected with the secondary metal cylinder 18 and the tertiary metal cylinder 19, and the two ends of the optical fiber 23 provided with the temperature compensation optical fiber grating 14 are respectively and fixedly connected with the tertiary metal cylinder 19 and the quaternary metal cylinder 20;
the part of the optical fiber 23, which is positioned in the temperature and depth sensing chamber 1, is provided with a temperature and depth optical fiber grating 11, the part of the optical fiber 23, which is positioned in the free permeable chamber 2, is a free optical fiber 12, the part of the optical fiber 23, which is positioned in the pressure compensation chamber 3, is provided with a pressure compensation optical fiber grating 13, and the part of the optical fiber 23, which is positioned in the temperature compensation chamber 4, is provided with a temperature compensation optical fiber grating 14;
the temperature-depth fiber grating 11 and the pressure compensation fiber grating 13 are in a pre-stretching state, and the temperature compensation fiber grating 14 is in a free state;
the side wall of the free water permeable chamber 2 is provided with water permeable holes 15.
In one embodiment, the metal shell 5 is a cylindrical shape with an outer diameter of 12mm, an inner diameter of 7mm and a height of 60mm, and has an open bottom end, and is made of 316 stainless steel, and the bottom of the metal shell 5 is provided with an opening; the top parts of the temperature and depth sensing chamber 1 and the pressure compensation chamber 3 are both metal shells 5.
In one embodiment, the liquid core metal elastic membrane 6 is a brass circular elastic membrane with a diameter of 10mm and a thickness of 2mm, and the cylindrical liquid tank 24 has a radius of 2-3 mm and a height of 0.2mm.
In one embodiment, the water permeable holes 15 are square holes 4mm wide and 8mm long.
In one embodiment, the metal elastic membrane 16 is a brass circular elastic membrane with a diameter of 10mm and a thickness of 2mm, and is located 5mm above the water permeable holes 15.
In one embodiment, the metal bath 10 is a cylindrical cylinder with an outer diameter of 6mm, an inner diameter of 0.4mm and a height of 12mm, and is made of 316 stainless steel.
In one embodiment, the central wavelength of the temperature-depth fiber grating 11 is 1550nm, the effective length is 10mm, the central wavelength of the pressure-compensation fiber grating 13 is 1550nm, the effective length is 10mm, the central wavelength of the temperature-compensation fiber grating 14 is 1560nm, and the effective length is 3mm.
In one embodiment, the liquid core metal elastic diaphragm 6 is hermetically welded with the metal shell 5 on the periphery of the bottom of the temperature and depth sensing chamber 1, and the metal elastic diaphragm 16 is hermetically welded with the metal shell 5 on the periphery of the top of the free water permeable chamber 2.
In one embodiment, the optical fibers are fixedly connected to the primary metal cylinder 17, the secondary metal cylinder 18, the tertiary metal cylinder 19 and the quaternary metal cylinder 20 by epoxy glue.
The invention relates to a preparation method of a fast response fiber grating ocean temperature and depth sensor, which comprises the following steps:
(1) Manufacturing each part according to the size in the above embodiment, sequentially passing one end of an optical fiber 23 through a tail fiber leading-out cylinder 21, a four-level metal cylinder 20, a temperature compensation chamber 4, a three-level metal cylinder 19 and a pressure compensation chamber 3, sleeving a brass circular membrane outside a two-level metal cylinder 18 and hermetically welding, translating the temperature compensation fiber grating 14 in the temperature compensation chamber 4, fixing two ends of the optical fiber 23 provided with the temperature compensation fiber grating 14 with the four-level metal cylinder 20 and the three-level metal cylinder 19 respectively by using epoxy glue, welding the four-level metal cylinder 20 in a central hole at the top end of a metal shell 5, welding the three-level metal cylinder 19 in a central hole of the metal shell 5 between the temperature compensation chamber 4 and the pressure compensation chamber 3, and finishing the packaging of the temperature compensation fiber grating 14;
(2) The periphery of a metal elastic membrane 16 welded with a secondary metal cylinder 18 in a central hole is attached to a metal shell 5 at the bottom end of a pressure compensation chamber 3, a laser welding machine is used for welding the attachment part to form a circular ring-shaped welding spot 7, 2N-2.5N pre-tension stress is applied to a pressure compensation fiber grating 13, then two ends of an optical fiber 23 provided with the pressure compensation fiber grating 13 are respectively fixed with the secondary metal cylinder 18 and a tertiary metal cylinder 19 by using epoxy glue, and the packaging of the pressure compensation fiber grating 13 is completed;
(3) Sequentially penetrating an optical fiber 23 through a free water-permeable chamber 2, a primary metal cylinder 17 and a temperature and depth sensing chamber 1, aligning a liquid hole 25 of a cylindrical liquid groove 24 formed in the center of a liquid core metal elastic membrane 6 with an opening at the bottom of a metal liquid groove 10, welding and fixing the liquid core metal elastic membrane 6 and the bottom of the metal liquid groove 10, filling gallium indium tin liquid 8, pushing a hard piston 9 with a fine hole in the middle into the metal liquid groove 10 until the hard piston is contacted with the liquid, and fixing the bottom end of the optical fiber 23 provided with a temperature and depth optical fiber grating 11 with the hard piston 9 through epoxy glue;
(4) Attaching a liquid core metal elastic membrane 6 to a metal shell 5 on the periphery of the bottom of a temperature and depth sensing chamber 1, welding the attaching part by using a laser welding machine to form a circular welding spot 7, straightening an optical fiber 23 where a temperature and depth optical fiber grating 11 is located and enabling the optical fiber 23 to be located on a central axis where the liquid core metal elastic membrane 6 and a metal liquid tank 10 are located, reserving a deformation distance of 0.2-0.3mm between a primary metal cylinder 17 and the top end of the temperature and depth sensing chamber 1, fixing the top end of the optical fiber 23 provided with the temperature and depth optical fiber grating 11 and the primary metal cylinder 17 through epoxy glue, applying pre-pressing stress on the temperature and depth optical fiber grating 11 by slowly pushing the primary metal cylinder 17, and welding and fixing the pre-pressing stress and the central hole of the top metal shell 5 of the temperature and depth sensing chamber 1 to finish the packaging of the temperature and depth optical fiber grating 11;
(5) And a flexible pipe is sleeved on the free optical fiber 12 or a metal-plated outer layer is coated on the free optical fiber, two square holes are formed in two ends of the side wall of the free water permeable cavity 2 and used for passing in and out seawater, a tail optical fiber guide cylinder 21 is welded to the outer top of the metal shell 5, and the tail optical fiber 22 is protected by a cable to complete the assembly of the whole pressure sensor.
The invention relates to a quick response fiber grating ocean temperature and depth sensor working principle: the periphery of the liquid core metal elastic membrane 6 is welded with the surface of the metal shell 5, external pressure directly acts on the liquid core metal elastic membrane 6, gallium indium tin liquid 8 filled in the liquid core metal elastic membrane 6 is influenced by external temperature, the pressure prestress of the temperature-depth fiber grating 11 is reduced after the volume is changed and acts on the deformation quantity of the temperature-depth fiber grating 11, so that the temperature-depth fiber grating 11 acts simultaneously with the pressure, and the liquid core metal elastic membrane 6 is made of brass and gallium indium tin liquid 8, so that short heat transfer time can be guaranteed, and ocean pollution cannot be caused. The temperature of the temperature compensation fiber grating 14 can be regarded as the same as the temperature of the pressure compensation chamber 3 and the temperature depth sensing chamber 1 in the falling process of the sensor, and the temperature compensation fiber grating 14 is used for eliminating the influence of the internal temperature of the sensor on the pressure compensation fiber grating 13 and the temperature depth fiber grating 11. The pressure compensation fiber grating 13 directly measures the pressure of the ocean, and the elastic membrane made of the same material and with the same specification is used as the temperature and depth sensing chamber 1, so that the real-time pressure compensation can be ensured.
A cylindrical liquid groove 24 has been seted up in the centre of liquid core metal elastic diaphragm 6, the centre is filled is gallium indium tin liquid 8, metal cistern 10 one end welds in the center of liquid core metal elastic diaphragm 6, the other end is used for placing optic fibre and the stereoplasm piston 9 that is provided with warm and deep fiber grating 11, stereoplasm piston 9 and gallium indium tin liquid 8 direct contact, optic fibre one end that is provided with warm and deep fiber grating 11 is fixed through the epoxy with stereoplasm piston 9, one end is fixed and is exerted pressure prestressing force through epoxy and one-level metal cylinder 17. In the falling process of the sensor, external pressure directly acts on the liquid core metal elastic membrane 6, the metal liquid tank 10 and the hard piston 9 which are connected are displaced downwards by the deformation of the liquid core metal elastic membrane 6 and act on the warm-deep fiber bragg grating 11, gallium indium tin liquid 8 which is subjected to heat transfer through the liquid core metal elastic membrane 6 contracts under the change of the body temperature, due to the fact that the warm-deep fiber bragg grating 11 exerts pressure prestress, under the condition that a liquid column in the cylindrical liquid tank 24 is reduced, the warm-deep fiber bragg grating 11 generates axial strain under the simultaneous action of the temperature and the pressure, and the external temperature and the external depth can be calculated by analyzing the change of the central wavelength of the warm-deep fiber bragg grating 11 and the central wavelength of the temperature compensation fiber bragg grating 14 of the rear-end temperature compensation chamber 4. The liquid core metal elastic membrane 6 is made of brass and gallium indium tin liquid 8, so that short heat transfer time can be ensured, and no pollution is caused to the ocean.
The periphery of a metal elastic membrane 16 with a round hole in the middle is welded with the surface of the metal shell 5, a second-level metal cylinder 18 is sleeved in the metal elastic membrane 16 and welded, one end of a pressure compensation fiber grating 13 is connected with the second-level metal cylinder 18 and fixed by epoxy glue, the other end of the pressure compensation fiber grating is connected and fixed with a third-level metal cylinder 19, a temperature compensation fiber grating 14 is connected and fixed between the third-level metal cylinder 19 and a fourth-level metal cylinder 20, and a rear-end optical fiber 23 is directly led out as a tail fiber 22, due to the fact that the water permeable hole 15 is formed, the metal elastic membrane 16 generates axial stress on the pressure compensation fiber grating 13 under the action of seawater pressure and enables the pressure compensation fiber grating to displace, the temperature compensation fiber grating 14 is in a free state and is used for measuring the temperature in a cavity, wherein the temperature depth sensing cavity 1, the pressure compensation cavity 3 and the temperature compensation cavity 4 are in the same temperature environment, the temperature compensation fiber grating 14 can perform real-time temperature compensation, the metal elastic membrane 16 and the liquid core metal elastic membrane 6 are made of the same material and size, and the pressure of the pressure compensation fiber grating 13 can be used for pressure compensation of the temperature deep fiber grating 11.
The description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A fast response fiber bragg grating ocean temperature and depth sensor is characterized by comprising a metal shell and an optical fiber, wherein the metal shell comprises a temperature and depth sensing chamber, a free permeable chamber, a pressure compensation chamber and a temperature compensation chamber from bottom to top in sequence;
the top metal shell of the temperature depth sensing chamber, the top metal elastic membrane of the free water permeable chamber, the top metal shell of the pressure compensation chamber and the top metal shell of the temperature compensation chamber are all provided with central holes, and a primary metal cylinder, a secondary metal cylinder, a tertiary metal cylinder and a quaternary metal cylinder are sequentially welded in the central holes from bottom to top;
the bottom of the temperature and depth sensing cavity is provided with a liquid core metal elastic membrane, a cylindrical liquid tank is arranged inside the center of the liquid core metal elastic membrane, a metal liquid tank is arranged at the center of the liquid core metal elastic membrane, the top and the bottom of the metal liquid tank are both provided with openings, a liquid hole is formed in the center of the top of the cylindrical liquid tank and communicated with the opening at the bottom of the metal liquid tank, gallium indium tin liquid is filled in the cylindrical liquid tank and the metal liquid tank, and a hard piston is arranged in the metal liquid tank and is in surface contact with the gallium indium tin liquid;
one end of the optical fiber is fixed on the hard piston, the other end of the optical fiber sequentially penetrates through the first-stage metal cylinder, the second-stage metal cylinder, the third-stage metal cylinder and the fourth-stage metal cylinder, and finally the tail fiber penetrates out of a tail fiber guiding-out barrel sequentially arranged at the top outside the metal shell;
the top end of the optical fiber provided with the temperature-depth optical fiber grating is fixedly connected with the primary metal cylinder, the two ends of the optical fiber provided with the pressure compensation optical fiber grating are respectively and fixedly connected with the secondary metal cylinder and the tertiary metal cylinder, and the two ends of the optical fiber provided with the temperature compensation optical fiber grating are respectively and fixedly connected with the tertiary metal cylinder and the quaternary metal cylinder;
the part of the optical fiber, which is positioned in the temperature depth sensing cavity, is provided with a temperature depth optical fiber grating, the part of the optical fiber, which is positioned in the free water permeable cavity, is a free optical fiber, the part of the optical fiber, which is positioned in the pressure compensation cavity, is provided with a pressure compensation optical fiber grating, and the part of the optical fiber, which is positioned in the temperature compensation cavity, is provided with a temperature compensation optical fiber grating;
the temperature-depth fiber grating and the pressure compensation fiber grating are in a pre-stretching state, and the temperature compensation fiber grating is in a free state;
and the side wall of the free water permeable cavity is provided with water permeable holes.
2. The fast response fiber grating ocean temperature and depth sensor according to claim 1, wherein the metal shell is a cylindrical shape with an outer diameter of 12mm, an inner diameter of 7mm and a height of 60mm, and has an open bottom, the metal shell is made of 316 stainless steel, and the bottom of the metal shell is provided with an opening; the tops of the temperature and depth sensing chamber and the pressure compensation chamber are both metal shells.
3. The fast response fiber grating ocean temperature and depth sensor according to claim 1, wherein the liquid core metal elastic diaphragm is a brass circular elastic diaphragm with a diameter of 10mm and a thickness of 2mm, the cylindrical liquid groove has a radius of 2-3 mm and a height of 0.2mm.
4. The fast response fiber grating ocean depth temperature sensor according to claim 1, wherein the water permeable holes are square holes with a width of 4mm and a length of 8 mm.
5. The fast response fiber grating ocean temperature and depth sensor according to claim 1, wherein said metal elastic membrane is a brass circular elastic membrane with a diameter of 10mm and a thickness of 2mm, and is located 5mm above the water permeable hole.
6. The fast response fiber grating ocean temperature and depth sensor according to claim 1, wherein the metal liquid tank is a cylindrical tank with an outer diameter of 6mm, an inner diameter of 0.4mm and a height of 12mm, and is made of 316 stainless steel.
7. The fast response fiber grating ocean temperature depth sensor according to claim 1, wherein the temperature depth fiber grating has a center wavelength of 1550nm and an effective length of 10mm, the pressure compensation fiber grating has a center wavelength of 1550nm and an effective length of 10mm, the temperature compensation fiber grating has a center wavelength of 1560nm and an effective length of 3mm.
8. The fast response fiber bragg grating ocean temperature and depth sensor according to claim 1, wherein the liquid core metal elastic membrane is hermetically welded with a metal shell on the periphery of the bottom of the temperature and depth sensing chamber, and the metal elastic membrane is hermetically welded with a metal shell on the periphery of the top of the free water permeable chamber.
9. The fast response fiber grating ocean temperature and depth sensor according to claim 1, wherein the optical fiber is fixedly connected with the primary metal cylinder, the secondary metal cylinder, the tertiary metal cylinder and the quaternary metal cylinder through epoxy glue.
10. A method for preparing a fast response fiber grating ocean temperature and depth sensor according to any one of claims 1 to 9, comprising the steps of:
(1) Making each component according to the size of any one of claims 2 to 7, sequentially passing one end of the optical fiber through a tail fiber leading-out cylinder, a four-level metal cylinder, a temperature compensation chamber, a three-level metal cylinder and a pressure compensation chamber, sleeving a brass circular membrane outside the two-level metal cylinder and hermetically welding, translating the temperature compensation fiber grating in the temperature compensation chamber, fixing two ends of the optical fiber provided with the temperature compensation fiber grating with the four-level metal cylinder and the three-level metal cylinder respectively by using epoxy glue, welding the four-level metal cylinder in a central hole at the top end of the metal shell, welding the three-level metal cylinder in a central hole of the metal shell between the temperature compensation chamber and the pressure compensation chamber, and completing the packaging of the temperature compensation fiber grating;
(2) Attaching the periphery of a metal elastic membrane welded with a secondary metal cylinder in a central hole to a metal shell at the bottom end of a pressure compensation chamber, welding the attached part by using a laser welding machine to form a circular welding spot, applying 2N-2.5N pre-tension to the pressure compensation fiber grating, and fixing two ends of an optical fiber provided with the pressure compensation fiber grating with the secondary metal cylinder and a tertiary metal cylinder respectively by using epoxy glue to finish the packaging of the pressure compensation fiber grating;
(3) Sequentially penetrating an optical fiber through a free water-permeable cavity, a primary metal cylinder and a temperature depth sensing cavity, aligning a liquid hole of a cylindrical liquid tank formed in the center of a liquid core metal elastic membrane with an opening at the bottom of the metal liquid tank, welding and fixing the liquid core metal elastic membrane and the bottom of the metal liquid tank, filling gallium indium tin liquid, pushing a hard piston with a fine hole in the middle into the metal liquid tank until the hard piston is contacted with the liquid, and fixing the bottom end of the optical fiber provided with the temperature depth optical fiber grating with the hard piston through epoxy glue;
(4) Attaching a liquid core metal elastic membrane to a metal shell on the periphery of the bottom of a temperature and depth sensing cavity, welding the attaching part by using a laser welding machine to form a circular welding spot, straightening an optical fiber where a temperature and depth optical fiber grating is located and enabling the optical fiber to be located on a central axis where the liquid core metal elastic membrane and a metal liquid tank are located, reserving a deformation distance of 0.2-0.3mm between a primary metal cylinder and the top end of the temperature and depth sensing cavity, fixing the top end of the optical fiber provided with the temperature and depth optical fiber grating and the primary metal cylinder through epoxy glue, applying pre-pressing stress to the temperature and depth optical fiber grating by slowly pushing the primary metal cylinder, and welding and fixing the top metal shell with the temperature and depth sensing cavity to finish the packaging of the temperature and depth optical fiber grating;
(5) The free optical fiber is sleeved with a hose or plated with a metal outer layer, two square holes are formed in the two ends of the side wall of the free water permeable cavity and used for entering and exiting seawater, the tail fiber guiding cylinder is welded to the outer top of the metal shell, the tail fiber is protected by a cable, and the whole pressure sensor is assembled.
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| CN116839753A (en) * | 2023-09-01 | 2023-10-03 | 中国电建集团成都勘测设计研究院有限公司 | Temperature depth chain and temperature calibration method |
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| CN116839753A (en) * | 2023-09-01 | 2023-10-03 | 中国电建集团成都勘测设计研究院有限公司 | Temperature depth chain and temperature calibration method |
| CN116839753B (en) * | 2023-09-01 | 2023-11-24 | 中国电建集团成都勘测设计研究院有限公司 | Temperature calibration method of temperature depth chain |
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