CN117824816A - High-pressure-resistant optical fiber hydrophone based on fiber bragg grating structure - Google Patents
High-pressure-resistant optical fiber hydrophone based on fiber bragg grating structure Download PDFInfo
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- CN117824816A CN117824816A CN202311328322.4A CN202311328322A CN117824816A CN 117824816 A CN117824816 A CN 117824816A CN 202311328322 A CN202311328322 A CN 202311328322A CN 117824816 A CN117824816 A CN 117824816A
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 109
- 239000000835 fiber Substances 0.000 title claims abstract description 90
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 8
- 239000010959 steel Substances 0.000 claims abstract description 8
- 239000007787 solid Substances 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 5
- 239000004417 polycarbonate Substances 0.000 claims description 4
- 229920000515 polycarbonate Polymers 0.000 claims description 4
- 238000002310 reflectometry Methods 0.000 claims description 3
- 238000013461 design Methods 0.000 abstract description 5
- 238000004073 vulcanization Methods 0.000 abstract description 4
- 230000003287 optical effect Effects 0.000 description 19
- 230000035945 sensitivity Effects 0.000 description 6
- 230000005236 sound signal Effects 0.000 description 6
- 238000001514 detection method Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 230000007547 defect Effects 0.000 description 3
- 230000007123 defense Effects 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 244000089409 Erythrina poeppigiana Species 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000030808 detection of mechanical stimulus involved in sensory perception of sound Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 230000002706 hydrostatic effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000009931 pascalization Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H3/00—Measuring characteristics of vibrations by using a detector in a fluid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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Abstract
The invention relates to a high-pressure-resistant optical fiber hydrophone based on an optical fiber grating structure, which comprises a cylindrical framework, a first optical fiber grating, a second optical fiber grating, a small-diameter optical fiber, a high-pressure-resistant steel pipe and a vulcanization layer, wherein the cylindrical framework is arranged on the outer side of the cylindrical framework; wherein, the top end of the cylinder skeleton is provided with a plurality of symmetrical U-shaped grooves for placing fiber gratings; the first fiber grating and the second fiber grating are engraved on the optical fiber, the optical fiber after being engraved is wound on the cylindrical skeleton with a certain prestress, and the two fiber gratings are placed in a U-shaped groove specially designed on the end face of the skeleton. The invention can realize the small-size design of the optical fiber hydrophone, has the advantage of high pressure resistance, and improves the overall reliability of the optical fiber hydrophone.
Description
Technical field:
the invention belongs to the technical field of underwater sound sensing and underwater sound measurement, and particularly relates to a high-pressure-resistant optical fiber hydrophone based on an optical fiber grating structure.
The background technology is as follows:
the underwater sound detection technology has important application in the fields of marine defense, marine resource exploration, seismic wave detection and the like. Compared with the traditional piezoelectric hydrophone, the optical fiber hydrophone based on the optical fiber sensing technology has the advantages of large dynamic range, high sensitivity, electromagnetic interference resistance, easiness in large-scale array formation and the like. After being first proposed by Bucaro et al in the American naval laboratory in 1977, the device has developed for nearly half a century, and various application forms such as a shore matrix, a towing matrix, a broadside matrix and the like are formed at present, so that the device has great application value in the fields of national defense and civilian use.
The pressure resistance of the hydrophone is an important item in performance indexes of the hydrophone, and determines the working depth range of the hydrophone. In general, every 1000m increase in water depth, an increase in pressure resistance of 10MPa is required. With the gradual trend of navy of China from offshore to ocean, ocean exploration activities are continuously advanced to deep sea, and the development of army and civil fusion technologies such as deep sea space stations and the like is urgent to develop a high-pressure-resistant hydrophone technology.
The working water depth of the traditional piezoelectric hydrophone is generally not more than 6000m, and the corresponding pressure resistance value is about 60MPa at maximum. For example, standard hydrophones of type 8105 and 8106 developed by danish B & K, working water depth of 1000m; the biggest working depth of hydrophone products of HighTech company in the united states, which can produce multiple types of deep water hydrophones, is 6000m. Because the parameters of the components (mainly the capacitance) constituting the piezoelectric hydrophone change greatly under different hydrostatic pressures, the pressure resistance of the traditional piezoelectric hydrophone is limited to be further improved. Therefore, it is necessary to develop a high pressure resistant hydrophone while presenting certain challenges.
Fiber optic hydrophones have entered the practical application stage and demonstrated their unique advantages. The current optical fiber hydrophone is mainly based on an optical fiber interferometer scheme, and underwater acoustic wave information detected by the hydrophone is restored through demodulation of phase change introduced by acoustic waves. In order to overcome the polarization fading phenomenon and improve the signal-to-noise ratio of interference signals, the mainstream optical fiber hydrophone scheme is a Michelson type interferometer formed by an optical fiber coupler and Faraday rotation mirrors (Faraday rotation mirror, FRM). The scheme has the following defects in the application environment of high hydrostatic pressure: (1) The FRM comprises discrete optical elements, and the pressure resistance value of the FRM is limited, so that the pressure resistance design of the whole optical fiber hydrophone is not facilitated; (2) The fiber Michelson interferometer formed by the fiber coupler and the FRM needs to be carefully considered when the fiber coupler and the FRM are wound, otherwise, larger bending loss is introduced, and the signal to noise ratio of an interference signal output by the fiber hydrophone is affected; (3) The existing optical fiber coupler and FRM have larger sizes, and the volume of an optical fiber hydrophone formed based on the device is difficult to further reduce, so that the high-pressure resistant design of the optical fiber coupler and the FRM is not facilitated.
The invention comprises the following steps:
the invention aims to solve the technical problem of providing the high-pressure resistant optical fiber hydrophone based on the optical fiber grating structure, which can bear high pressure and has the structural characteristics that the volume of the high-pressure resistant optical fiber hydrophone can be reduced as far as possible, so that the picking of underwater acoustic wave signals can be completed within a larger water depth range, and the high-pressure resistant optical fiber hydrophone plays an important role in the fields of ocean defense, ocean resource exploration, ocean environment protection and the like.
The technical scheme of the invention is that the high-pressure resistant optical fiber hydrophone based on the optical fiber grating structure comprises a cylindrical skeleton, a first optical fiber grating (FBG 1), a second optical fiber grating (FBG 2), a small-diameter optical fiber, a high-pressure resistant steel pipe and a vulcanization layer; wherein, the top end of the cylinder skeleton is provided with a plurality of symmetrical U-shaped grooves for placing fiber gratings; the first fiber grating and the second fiber grating are engraved on the optical fiber, the optical fiber after being engraved is wound on the cylindrical skeleton with certain prestress, the two fiber gratings are placed in U-shaped grooves specially designed on the end face of the skeleton, and meanwhile, a section of tail fiber is reserved at each end of the optical fiber, so that the optical fiber hydrophone can be connected with other optical fiber components, the tail fiber of the optical fiber is protected through a loose tube firstly, and then is penetrated into a high-pressure-resistant steel tube for high-pressure protection; the whole structure forms a hydrophone core body, and a vulcanizing layer is added on the outer layer of the whole structure to form protection of the optical fiber, so that the subsequent test and use are convenient; the optical signal is used as a detection signal and is incident to the sensing optical fiber, when the optical signal passes through the first optical fiber grating, a small part of light is reflected back to generate first return light, and most of light continues to propagate forwards through the second optical fiber grating to generate second return light; the first return light and the second return light are overlapped with each other to form an interference light signal; when the optical fiber hydrophone receives the underwater acoustic signal, the cylinder skeleton deforms slightly to cause the optical fiber wound on the cylinder skeleton to deform, so that the phase of the interference optical signal changes and carries the information of the underwater acoustic signal; demodulating the interference optical signal to obtain an underwater sound signal, wherein the phase difference of the interference optical signal is in direct proportion to the underwater sound signal; the demodulation scheme of the interference optical signal can be selected from differential delay heterodyne method, phase generation carrier method, 3×3 demodulation method, etc. Wherein, the cylinder skeleton is made of materials with Young's modulus of 70-105MPa, and the cylinder skeleton is preferably made of polycarbonate.
The U-shaped grooves designed by the invention provide input and output ports of the optical fiber hydrophone, can carry out high-voltage protection on input and output optical fibers, and parameters such as diameter, depth, quantity, distribution angle and the like of the input and output optical fibers need to be optimally matched according to the length of a tail fiber of the optical fiber hydrophone, the type of the optical fibers, the diameter of a stainless steel tube for protection and the like. In addition, the invention uses two fiber gratings to reflect and combine the optical signals, and the optical fiber between the two gratings is wound on the cylinder skeleton to be used as the sensing optical fiber.
2 gratings are engraved on a small-diameter optical fiber to form a Fabry-Perot interferometer to finish the sensing and detection of sound waves, and meanwhile, the Fabry-Perot interferometer has the advantage of high pressure resistance;
the skeleton of the optical fiber hydrophone is manufactured by using a material with lower Young modulus, so that the consideration of the sensitivity and the high pressure resistance of the optical fiber hydrophone is taken into consideration; meanwhile, a plurality of U-shaped grooves are designed at the top end of the cylindrical framework, so that the placement of the grating and the later vulcanization are facilitated, the method can also avoid the grating from being subjected to larger stress, the center wavelength drift is reduced to the greatest extent, and meanwhile, the grating can be protected to a certain extent.
Preferably, the length of the optical fiber between the first optical fiber grating and the second optical fiber grating is 10-50m. The sensitivity of the optical fiber hydrophone is not too low.
Preferably, the lengths of the first and second pigtails are 1-2m. This prevents crosstalk from being formed by multiple reflections between gratings.
Preferably, the cylindrical skeleton is a solid skeleton. The solid cylinder structure is used for improving the overall pressure resistance of the optical fiber hydrophone and avoiding the defects of insufficient pressure resistance and the like caused by structures such as a thin cylinder and the like.
Preferably, the reflectivity between the first fiber grating and the second fiber grating is 5% -10%.
Preferably, a plurality of U-shaped grooves are uniformly distributed on the circumferential surface of the top of the cylindrical skeleton along the circumferential direction.
Further, the optical fiber is a small diameter optical fiber having a diameter of 80. Mu.m.
Compared with the prior art, the invention has the following advantages:
(1) Other additional optical passive devices (such as an optical fiber coupler and a Faraday rotary mirror) are not needed, and the optical fiber coupler has the advantages of simple structure and the like;
(2) Based on the characteristics of the fiber bragg grating, the small-size design of the fiber optic hydrophone can be realized, and the fiber optic hydrophone has the advantage of high pressure resistance;
(3) The polycarbonate solid cylinder is used as a framework of the sensor, so that the sensor has sensitivity and high pressure resistance; the symmetrical multi-U-shaped groove design at the top end facilitates the placement of the grating, protects the grating, facilitates the vulcanization of the optical fiber hydrophone and improves the overall reliability of the optical fiber hydrophone.
Description of the drawings:
fig. 1 is a schematic structural diagram of an embodiment of the invention implementing a high pressure resistant fiber optic hydrophone based on a fiber grating structure.
FIG. 2 is a schematic diagram of a fiber optic grating structure based high pressure resistant fiber optic hydrophone wound grating string.
Fig. 3 is a schematic perspective view of a cylindrical skeleton in a high-pressure resistant fiber hydrophone based on a fiber grating structure.
The specific embodiment is as follows:
the invention is further described in terms of specific embodiments in conjunction with the following drawings:
referring to fig. 1 and 3, there is shown a high pressure resistant optical fiber hydrophone based on an optical fiber grating structure of the present invention, comprising: the optical fiber grating comprises a solid cylinder framework 1, a first optical fiber grating 4, a second optical fiber grating 6, a small-diameter optical fiber 2 and a high-pressure-resistant steel tube 5; wherein, a plurality of symmetrical U-shaped grooves 11 are designed on the peripheral surface of the top of the cylinder framework and are used for placing fiber gratings; the first fiber grating and the second fiber grating are engraved on the optical fiber, the 3dB bandwidth of the grating is set to be 1nm, and the central wavelength is set to be 1550.12nm; the optical fiber after the optical fiber grating is carved is wound on a cylinder framework with certain prestress, two optical fiber gratings are placed in a U-shaped groove 11 designed on the upper part of the framework, and the whole structure forms a hydrophone core body.
In addition, the end part of one end of the optical fiber 2 is arranged at intervals with the first fiber grating 4 to form a first tail fiber 5, the end part of the other end of the optical fiber 2 is arranged at intervals with the second fiber grating 6 to form a second tail fiber 7, the first tail fiber 5 and the second tail fiber 6 protrude out of the cylindrical framework 1 and are arranged in the length direction, a loose tube and a high-pressure resistant steel tube 5 are sequentially sleeved outside the first tail fiber 5 and the second tail fiber 6 from inside to outside, the outer diameter of the high-pressure resistant steel tube is identical to or slightly larger than the diameter of the U-shaped groove 11, and finally, a vulcanized layer 3 is further arranged on the outer surface of the hydrophone core body to form protection of the optical fiber, so that the subsequent test and use are convenient.
In the embodiment, the lengths of the first tail fiber 5 and the second tail fiber 7 are 2m, so that the optical fiber hydrophone can be connected with other optical fiber components; the two tail fibers are protected through loose tubes with the thickness of 0.6mm, and then penetrate into high-pressure-resistant steel tubes with the outer diameter of 2mm for high-pressure protection (the tube wall thickness is 0.3 mm).
As one embodiment, the cylinder skeleton 1 is a solid cylinder skeleton, and the material thereof is Polycarbonate (PC); the solid cylinder structure is used for improving the overall pressure resistance of the optical fiber hydrophone and avoiding the defects of insufficient pressure resistance and the like caused by structures such as a thin cylinder and the like.
A plurality of symmetrical U-shaped grooves on the outer peripheral surface of the solid cylinder framework are uniformly distributed, and the U-shaped grooves provide input and output ports of the optical fiber hydrophone, so that high-voltage resistance protection can be carried out on input and output optical fibers.
As shown in fig. 2, the optical signal is incident to the sensing optical fiber as a detection signal, when the optical signal passes through the first fiber bragg grating 4, 5% of the light is reflected back to generate first return light, and 95% of the light continues to propagate forward through the second fiber bragg grating 6 to generate second return light; the first return light and the second return light are overlapped with each other to form an interference light signal; when the optical fiber hydrophone receives the underwater acoustic signal, the cylindrical framework 1 deforms slightly to cause the optical fiber 2 wound on the cylindrical framework to deform, so that the phase of the interference optical signal changes and carries the information of the underwater acoustic signal; demodulating the interference optical signal to obtain an underwater sound signal, wherein the phase difference of the interference optical signal is in direct proportion to the underwater sound signal; the demodulation scheme of the interference optical signal is that the example selects a differential delay heterodyne method.
The length of the optical fiber 2 between the first optical fiber grating 4 and the second optical fiber grating 5 is 10-50m, so that the sensitivity of the optical fiber hydrophone can be ensured not to be too low.
The reflection and beam combination of the optical signals are carried out by using two fiber gratings, and meanwhile, the optical fiber 2 between the first fiber grating 4 and the second fiber grating 5 is wound on the cylinder framework 1 to serve as a sensing optical fiber.
In the embodiment, the line diameter of the optical fiber is 80 μm, so that the sensitivity of the optical fiber hydrophone is not too low, and the interval between two gratings, namely the length of the sensing optical fiber is 30m; in order to prevent crosstalk formed by multiple reflections between the fiber gratings, the reflectivity between the first fiber grating and the second fiber grating is controlled to be 5%.
The optical signal is used as a detection signal and is incident to the sensing optical fiber, when the optical signal passes through the first optical fiber grating, a small part of light is reflected back to generate first return light, and most of light continues to propagate forwards through the second optical fiber grating to generate second return light; the first return light and the second return light are overlapped with each other to form an interference light signal; when the optical fiber hydrophone receives the underwater acoustic signal, a cylinder skeleton made of a material with a lower Young modulus deforms slightly to cause deformation of an optical fiber wound on the cylinder skeleton, so that the phase of an interference optical signal changes and carries the information of the underwater acoustic signal; demodulating the interference light signal to obtain the underwater sound signal, wherein the phase difference of the interference light signal is in direct proportion to the underwater sound signal.
Claims (8)
1. The utility model provides a high pressure resistant optical fiber hydrophone based on fiber bragg grating structure which characterized in that: the novel hydrophone comprises a cylindrical framework, a first fiber grating, a second fiber grating and optical fibers, wherein a plurality of symmetrical U-shaped grooves are circumferentially distributed on the circumferential surface of the top of the cylindrical framework, the first fiber grating and the second fiber grating are engraved on the optical fibers at intervals, the optical fibers between the first fiber grating and the second fiber grating are wound on the cylindrical framework, the first fiber grating and the second fiber grating are respectively arranged in the two symmetrical U-shaped grooves to form a hydrophone core body, the end part of one end of the optical fibers is arranged at intervals with the first fiber grating to form a first tail fiber, the end part of the other end of the optical fibers is arranged at intervals with the second fiber grating to form a second tail fiber, the first tail fiber and the second tail fiber are arranged in the length direction of the cylindrical framework in a protruding mode, a loose tube and a high-pressure resistant steel tube are sleeved outside the first tail fiber and the second tail fiber are sequentially sleeved outside the first tail fiber and the second tail fiber, a vulcanized layer is further arranged on the outer surface of the core body, and the cylindrical framework is made of materials with Young modulus of 70-105 MPa.
2. The fiber bragg grating structure-based high-pressure resistant fiber optic hydrophone of claim 1, wherein: the length of the optical fiber between the first optical fiber grating and the second optical fiber grating is 10-50m.
3. The fiber bragg grating structure-based high-pressure resistant fiber optic hydrophone of claim 1, wherein: the lengths of the first tail fiber and the second tail fiber are 1-2m.
4. A fiber bragg grating structure-based high-pressure resistant fiber optic hydrophone as recited in claim 3, wherein: the cylinder skeleton is solid skeleton.
5. The fiber bragg grating structure-based high-pressure resistant fiber optic hydrophone of claim 2, wherein: the reflectivity between the first fiber grating and the second fiber grating is 5% -10%.
6. The fiber bragg grating structure-based high-pressure resistant fiber optic hydrophone of claim 1, wherein: the cylinder skeleton is made of polycarbonate.
7. The fiber bragg grating structure-based high-pressure resistant fiber optic hydrophone of claim 1, wherein: a plurality of U-shaped grooves are uniformly distributed on the circumferential surface of the top of the cylinder framework along the circumferential direction.
8. The fiber bragg grating structure-based high-pressure resistant fiber optic hydrophone of claim 1, wherein: the fiber had a wire diameter of 80. Mu.m.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311328322.4A CN117824816A (en) | 2023-10-13 | 2023-10-13 | High-pressure-resistant optical fiber hydrophone based on fiber bragg grating structure |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311328322.4A CN117824816A (en) | 2023-10-13 | 2023-10-13 | High-pressure-resistant optical fiber hydrophone based on fiber bragg grating structure |
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- 2023-10-13 CN CN202311328322.4A patent/CN117824816A/en active Pending
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