CN113295260A - Optical fiber hydrophone based on push-pull structure - Google Patents
Optical fiber hydrophone based on push-pull structure Download PDFInfo
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- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
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Abstract
The invention provides an optical fiber hydrophone based on a push-pull structure, which comprises a narrow-line-width laser, an optical fiber isolator, an optical fiber circulator, an optical attenuator, a photoelectric detector and a signal processing and displaying module which are connected in sequence, wherein one output port of the optical fiber circulator is connected with an optical fiber hydrophone sensing probe, and the other output port of the optical fiber circulator is connected with the optical attenuator; the optical fiber hydrophone sensing probe comprises an inner thin-wall elastic cylinder, an outer thin-wall elastic cylinder, an upper end cover, a lower end cover and a cover plate; when the inner thin-wall elastic cylinder wound around the inner optical fiber ring is nested in the outer thin-wall elastic cylinder wound around the outer optical fiber ring, an air cavity is formed between the two thin-wall elastic cylinders; one end of the inner optical fiber ring is connected with the second Faraday rotator mirror, and the other end of the inner optical fiber ring is connected with the first input end of the coupler; one end of the outer optical fiber ring is connected with the first Faraday rotator mirror, and the other end of the outer optical fiber ring is connected with the second input end of the coupler; the output end of the coupler is connected with the optical fiber circulator.
Description
Technical Field
The invention belongs to the field of optical fiber sensing and underwater acoustic signal detection, and particularly relates to a double-sensitivity low-noise interference type optical fiber hydrophone based on a push-pull structure.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The sound wave is the only energy form capable of being propagated in a long distance in the ocean, the transmission distance of the low-frequency sound wave can even reach thousands of kilometers, and the main technical means for detecting, identifying and analyzing underwater targets still detects underwater sound signals at present. Compared with the traditional piezoelectric hydrophone, the optical fiber hydrophone has the advantages of high sensitivity, no electromagnetic interference, large dynamic range, easiness in multiplexing and the like, gradually replaces the position of the traditional piezoelectric hydrophone, and becomes the mainstream underwater acoustic signal detection technology at present. The technical scheme of the optical fiber hydrophone mainly comprises an optical fiber grating type, an optical fiber laser type, an optical fiber Fabry-Perot type and an optical fiber interference type, wherein the interference type optical fiber hydrophone is the most mature in technology and the most widely applied, and is the mainstream optical fiber hydrophone type at present. In recent years, optical fiber interferometric hydrophones with various structures have been invented to improve the performance of optical fiber hydrophones to meet the needs of different backgrounds.
Chinese patent: CN 111256807B discloses a small-sized interference optical fiber hydrophone based on a folded air cavity, which includes four thin-wall hollow cylinders capable of being nested and installed and an optical fiber interferometer, although the sensitivity is improved, the structure is compact, the manufacturing process is complex, and the interferometer is not fixed, which may affect the stability of the detection result.
Chinese patent: CN 112649839A discloses a push-pull type optical fiber hydrophone, which uses metal parts and elastic bodies as sensitive elements to form a push-pull type structure, but because the performance difference of the two sensitive elements is larger, the sensitivity is improved less, and the structure is mainly used for solving the problem of unreliable water leakage of the optical fiber hydrophone under the seabed long-term working environment.
Disclosure of Invention
The invention aims to solve the problems and provides an optical fiber hydrophone based on a push-pull structure.
According to some embodiments, the invention adopts the following technical scheme:
an optical fiber hydrophone based on a push-pull structure comprises a narrow-linewidth laser, an optical fiber isolator, an optical fiber circulator, an optical attenuator, a photoelectric detector and a signal processing and displaying module which are connected in sequence, wherein one output port of the optical fiber circulator is connected with an optical fiber hydrophone sensing probe, and the other output port of the optical fiber circulator is connected with the optical attenuator;
the optical fiber hydrophone sensing probe comprises an inner thin-wall elastic cylinder, an outer thin-wall elastic cylinder, an upper end cover, a lower end cover and a cover plate; when the inner thin-wall elastic cylinder wound around the inner optical fiber ring is nested in the outer thin-wall elastic cylinder wound around the outer optical fiber ring, an air cavity is formed between the two thin-wall elastic cylinders; one end of the inner optical fiber ring is connected with the second Faraday rotator mirror, and the other end of the inner optical fiber ring is connected with the first input end of the coupler; one end of the outer optical fiber ring is connected with the first Faraday rotator mirror, and the other end of the outer optical fiber ring is connected with the second input end of the coupler; the output end of the coupler is connected with the optical fiber circulator; after the upper end cover and the lower end cover enclose the inner thin-wall elastic cylinder and the outer thin-wall elastic cylinder into a structure with two open ends, the lower port is sealed through the cover plate, and only the upper port is kept open.
Furthermore, a groove is formed between the lower end cover and the cover plate and used for placing the coupler.
Furthermore, the cover plate and the lower end cover are provided with optical fiber through holes, the tail optical fiber of the outer optical fiber ring and the tail optical fiber of the inner optical fiber ring penetrate through the optical fiber through holes on the lower end cover and then are connected to the two input ends of the coupler, and the optical fiber at the output end of the coupler extends to the outside through the optical fiber through holes on the cover plate.
Furthermore, the inner thin-wall elastic tube wound on the inner optical fiber ring and the outer thin-wall elastic tube wound on the outer optical fiber ring are both provided with optical fiber protective layers.
Furthermore, the upper end cover is in a hollow ring shape in the middle, the diameter of the hollow ring in the middle is the same as the inner diameter of the inner thin-wall elastic cylinder, one surface of the upper end cover is flat, the other surface of the upper end cover is provided with an annular boss, the inner diameter of the annular boss is the same as the outer diameter of the inner thin-wall elastic cylinder, and the outer diameter of the annular boss is the same as the inner diameter of the outer thin-wall elastic cylinder.
Further, the gap between the two thin-wall elastic cylinders is constant and equal to the width of the annular boss of the upper end cover.
Furthermore, the lower end cover is in a ring shape with a hollow middle, the diameter of the hollow middle circle is the same as the inner diameter of the inner thin-wall elastic cylinder, one side of the lower end cover is provided with an annular boss, the inner diameter of the annular boss is the same as the outer diameter of the inner thin-wall elastic cylinder, the outer diameter of the annular boss is the same as the inner diameter of the outer thin-wall elastic cylinder, and the other side of the lower end cover is provided with a groove, so that the coupler is sealed and fixed in the groove.
Furthermore, an inner optical fiber ring on the inner thin-wall elastic cylinder and an outer optical fiber ring on the outer thin-wall elastic cylinder form a push-pull structure.
Furthermore, the optical fiber isolator only allows unidirectional transmission of light and is used for isolating interference signals returned from the hydrophone sensing probe so as not to influence the laser.
Further, the optical attenuator is used for adjusting the optical power of the detected interference signal.
When the fiber hydrophone sensing probe is used, the fiber hydrophone sensing probe is placed in water, the inner wall of the inner thin-wall elastic cylinder is in contact with the water and is filled with the water, and air is arranged outside the inner thin-wall elastic cylinder. The elastic outer wall of the outer thin wall is contacted with water and is filled with water, and air is filled in the elastic cylinder of the outer thin wall. When dynamic underwater sound pressure signals are applied to the inner wall of the inner thin-wall elastic cylinder and the outer wall of the outer thin-wall elastic cylinder, the inner wall of the inner thin-wall elastic cylinder is subjected to radially outward dynamic underwater sound pressure, and the outer wall of the inner thin-wall elastic cylinder is not subjected to stress, so that the inner thin-wall elastic cylinder is radially outward expanded under the action of expansion strain, the radius is increased, the circumference is increased, and the inner optical fiber ring wound on the inner thin-wall elastic cylinder is dynamically lengthened. On the contrary, the outer wall of the outer thin-wall elastic cylinder is subjected to dynamic underwater sound pressure in the radial direction, and the inner wall is not subjected to force, so that the outer thin-wall elastic cylinder contracts inwards under the action of compressive strain, the circumference length is shortened due to the fact that the radius is reduced, and the outer optical fiber ring wound on the outer thin-wall elastic cylinder is also dynamically shortened. The deformation directions of the optical fibers in the inner optical fiber ring and the outer optical fiber ring are opposite, and correspondingly generated phase changes are also opposite, so that a push-pull type structure is formed. The total phase change can be obtained by subtracting the phase changes in the two optical fiber rings, and the total phase change can be twice of the phase change in the inner optical fiber ring/the outer optical fiber ring by selecting the proper lengths of the inner optical fiber ring and the outer optical fiber ring, so that the sensitivity of the acoustic signal response of the optical fiber hydrophone is doubled.
Compared with the prior art, the invention has the beneficial effects that:
the optical fiber hydrophone sensing probe adopts a push-pull structure, wherein the inner thin-wall elastic tube and the outer thin-wall elastic tube are made of the same material, the lengths of the inner optical fiber ring and the outer optical fiber ring are selected and matched, and the sensitivity of the optical fiber hydrophone sensing probe is improved and is twice of that of the optical fiber hydrophone with the same type of single sensing arm structure.
The inner optical fiber ring on the inner thin-wall elastic cylinder and the outer optical fiber ring on the outer thin-wall elastic cylinder are both used as sensing arms of the interferometer and are in the same temperature and environmental noise when applied, so that the influence of temperature change and environmental noise on the optical fiber hydrophone is eliminated, the common mode rejection effect of the noise is improved, the noise of the optical fiber hydrophone is reduced, and the ultra-low frequency underwater acoustic signal can be detected. In addition, the device is suitable for a deep sea environment, and hydrostatic pressure balance is achieved because the two sensing arms sense the same hydrostatic pressure.
The 1x2 coupler is fixed in the lower end cover of the optical fiber hydrophone sensing probe, so that the influence of fluctuation generated by environmental influence on the non-sensing optical fiber near the coupler on the output signal of the optical fiber hydrophone is reduced, the stability of the hydrophone is improved, and the noise of the optical fiber hydrophone is reduced.
The Faraday rotation mirror is used as a light signal reflection element in the two sensing arms, so that the influence of optical fiber jitter on the visibility of interference signal fringes is reduced, and the polarization fading phenomenon existing in an interferometer sensor is improved.
The optical fiber hydrophone is simple in principle and structure design, few in required optical devices, simple in manufacturing process, easy to realize, low in cost, flexible in design and convenient to apply.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
Fig. 1 is a structural diagram of a push-pull structure-based optical fiber hydrophone of the present invention;
wherein: 1. the optical fiber ring optical fiber laser comprises a narrow linewidth laser, 2, an optical fiber isolator, 3, an optical fiber circulator, 4, an outer thin-wall elastic cylinder, 5, an outer optical fiber ring, 6, a first Faraday rotator mirror, 7, an inner thin-wall elastic cylinder, 8, an inner optical fiber ring, 9, a second Faraday rotator mirror, 10, a lower end cover, 11, an upper end cover, 12, an air cavity, 13, an optical fiber protective layer, 14, an optical fiber through hole, 15, a 1x2 coupler, 16, a cover plate, 17, an optical attenuator, 18, a photoelectric detector, 19 and a signal processing and display module.
The specific implementation mode is as follows:
the invention is further described with reference to the following figures and examples.
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
In the present invention, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only terms of relationships determined for convenience of describing structural relationships of the parts or elements of the present invention, and are not intended to refer to any parts or elements of the present invention, and are not to be construed as limiting the present invention.
In the present invention, terms such as "fixedly connected", "connected", and the like are to be understood in a broad sense, and mean either a fixed connection or an integrally connected or detachable connection; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be determined according to specific situations by persons skilled in the relevant scientific or technical field, and are not to be construed as limiting the present invention.
Example one
The embodiment provides a fiber optic hydrophone based on a push-pull structure.
An optical fiber hydrophone based on a push-pull structure comprises a narrow-linewidth laser, an optical fiber isolator, an optical fiber circulator, an optical attenuator, a photoelectric detector and a signal processing and displaying module which are connected in sequence, wherein one output port of the optical fiber circulator is connected with an optical fiber hydrophone sensing probe, and the other output port of the optical fiber circulator is connected with the optical attenuator;
the optical fiber hydrophone sensing probe comprises an inner thin-wall elastic cylinder, an outer thin-wall elastic cylinder, an upper end cover, a lower end cover and a cover plate; when the inner thin-wall elastic cylinder wound around the inner optical fiber ring is nested in the outer thin-wall elastic cylinder wound around the outer optical fiber ring, an air cavity is formed between the two thin-wall elastic cylinders; one end of the inner optical fiber ring is connected with the second Faraday rotator mirror, and the other end of the inner optical fiber ring is connected with the first input end of the coupler; one end of the outer optical fiber ring is connected with the first Faraday rotator mirror, and the other end of the outer optical fiber ring is connected with the second input end of the coupler; the output end of the coupler is connected with the optical fiber circulator; after the upper end cover and the lower end cover enclose the inner thin-wall elastic cylinder and the outer thin-wall elastic cylinder into a structure with two open ends, the lower port is sealed through the cover plate, and only the upper port is kept open.
Specifically, a fiber optic hydrophone based on a push-pull structure includes: the optical fiber ring-shaped optical fiber laser comprises a narrow-linewidth laser 1, an optical fiber isolator 2, an optical fiber circulator 3, an outer thin-wall elastic cylinder 4, an outer optical fiber ring 5, a first Faraday rotator mirror 6, an inner thin-wall elastic cylinder 7, an inner optical fiber ring 8, a second Faraday rotator mirror 9, a lower end cover 10, an upper end cover 11, an air cavity 12, an optical fiber protective layer 13, an optical fiber through hole 14, a 1x2 coupler 15, a cover plate 16, an optical attenuator 17, a photoelectric detector 18 and a signal processing and display module 19.
The input of the optical fiber isolator 2 is connected to the optical output port of the narrow linewidth laser 1, the output of the optical fiber isolator 2 is connected to the input of the optical fiber circulator 3, one output of the optical fiber circulator 3 is connected to the optical fiber hydrophone sensing probe, the other output port of the optical fiber circulator 3, which returns, is connected to any one end of the optical attenuator 17, the other end of the optical attenuator 17 is connected to the photoelectric detector 18, and the photoelectric detector 18 is finally connected to the signal processing and display module 19; the fiber isolator 2 allows only unidirectional transmission of light for isolating the interference signals returning from the hydrophone sensing probe so as not to affect the laser. The optical attenuator 17 is used to adjust the optical power of the detected interference signal. The central wavelength of the narrow linewidth laser 1 may be selected from 1550nm, 1310nm, etc.
The upper end cover 11 is in a hollow ring shape in the middle, the diameter of the hollow ring in the middle is the same as the inner diameter of the inner thin-wall elastic cylinder 7, one surface of the upper end cover 11 is flat, an annular boss is arranged on the other surface of the upper end cover, the inner diameter of the annular boss is the same as the outer diameter of the inner thin-wall elastic cylinder 7, the outer diameter of the annular boss is the same as the inner diameter of the outer thin-wall elastic cylinder 4, after the inner thin-wall elastic cylinder 7 is nested in the outer thin-wall elastic cylinder 4, an air cavity 12 is formed between the two thin-wall elastic cylinders, and the gap between the two thin-wall elastic cylinders is constantly equal to the width of the annular boss of the upper end cover.
The lower end cover 10 is in a hollow ring shape, the diameter of the hollow ring is the same as the inner diameter of the inner thin-wall elastic tube 7, one side of the lower end cover 10 is provided with an annular boss, the inner diameter of the annular boss is the same as the outer diameter of the inner thin-wall elastic tube 7, the outer diameter of the annular boss is the same as the inner diameter of the outer thin-wall elastic tube 4, and the other side of the lower end cover is provided with a groove, so that the 1x2 coupler 15 can be hermetically fixed in the groove, the response stability of the optical fiber hydrophone is improved, and the noise of.
One end of the outer optical fiber ring 5 and one end of the inner optical fiber ring 8 are respectively connected with the first Faraday rotator mirror 6 and the second Faraday rotator mirror 9, and the other ends are respectively connected with two input ends of the 1x2 coupler 15.
The optical fiber winding scheme is as follows: the outer optical fiber ring 5 and the inner optical fiber ring 8 which are pre-coated with the adhesive are uniformly and tightly arranged and wound on the outer thin-wall elastic cylinder 4 and the inner thin-wall elastic cylinder 7 from one end of the first Faraday rotator mirror 6 and one end of the second Faraday rotator mirror 9 respectively to serve as two sensing arms of the optical fiber hydrophone sensing probe.
The optical fiber protective layers 13 are uniformly and equally coated on the outer optical fiber ring 5 and the inner optical fiber ring 8 respectively, and the thickness of the optical fiber protective layers is less than 1mm so as to protect optical fibers from mechanical external force, high-pressure environment, acid-base corrosion and mildew; the acoustic impedance of the optical fiber protective layer material is matched with the acoustic impedance of the transmission medium water, so that the acoustic energy loss is small, and the acoustic transmission rubber, the epoxy resin, the polyurethane and the like can be selected.
After the winding of the two sensing arm optical fiber rings of the optical fiber hydrophone is completed, the inner thin-wall elastic tube 7 and the outer thin-wall elastic tube 4 are embedded into the outer thin-wall elastic tube 4 according to the radius, the inner thin-wall elastic tube 7 and the outer thin-wall elastic tube 4 are coaxial, two ends of the inner thin-wall elastic tube 7 and two ends of the outer thin-wall elastic tube 4 are fixed on one surfaces, provided with bosses, of the upper end cover 11 and the lower end cover 10 by using sealing water-proof sealant, a gap between the two elastic tubes is kept to be constantly equal to the width of the annular bosses, a sealed air cavity 12 is formed between the two elastic tubes, an inner optical fiber ring 8 on the inner thin-wall elastic tube 7 and an outer optical fiber ring 5 on the outer thin-wall elastic tube 4 form a push-pull structure, opposite deformation is generated on the same sound pressure, and the detection sensitivity is improved.
The cover plate 16 is fixed on the lower end cover 10 in a sealing mode through sealing waterproof glue, optical fiber through holes 14 are formed in the cover plate 16 and the lower end cover 10, the tail fibers of the outer optical fiber ring 5 and the tail fibers of the inner optical fiber ring 8 penetrate through the optical fiber through holes 14 in the lower end cover and then are connected to two input ends of the 1x2 coupler 15, and the optical fibers at the output end of the 1x2 coupler 15 extend to the outside through the optical fiber through holes 14 in the cover plate.
In one or more embodiments, the 1x2 coupler 15 is fixed in the groove of the bottom end cap 10 by glue seal, so that the coupler is not changed in vibration state when being disturbed by the outside and is still in a static state, thereby reducing the influence of optical fiber disturbance on the hydrophone, improving the stability of the hydrophone response and reducing the noise of the optical fiber hydrophone.
In one or more embodiments, the inner thin-walled elastomeric cylinder 7 and the outer thin-walled elastomeric cylinder 4 are different in size but the same material and therefore have the same physical property parameters, and the sensitivity of the hydrophone can be improved by selecting a material with a relatively low modulus of elasticity.
As one or more embodiments, the inner optical fiber ring 8 and the outer optical fiber ring 5 are made of the same material and have different lengths, and the lengths of the inner optical fiber ring 8 and the outer optical fiber ring 5 are selected to be suitable, so that the phase variation amounts in the two optical fiber rings are equal, and the double-sensitivity effect is achieved.
As one or more embodiments, the signal processing and display module may employ a CPU and a display.
The working principle is as follows: laser emitted by a narrow-linewidth laser 1 enters an optical fiber circulator 3 after passing through an optical fiber isolator 2, light emitted from the optical fiber circulator 3 is sent to a hydrophone sensing probe, the laser enters a 1x2 coupler 15 and is divided into two paths, the two paths of laser respectively enter an outer optical fiber ring 5 and an inner optical fiber ring 8, then the two paths of laser are respectively reflected by a first Faraday rotator 6 and a second Faraday rotator 9 at the other ends of the outer optical fiber ring 5 and the inner optical fiber ring 8, the two paths of reflected light enter the same 1x2 coupler 15 after passing through the outer optical fiber ring 5 and the inner optical fiber ring 8 again, the two paths of light generate interference, an interference signal output from an output end of the 1x2 coupler 15 enters an optical attenuator 17 after being output from another output end of the optical fiber circulator 3, the interference signal enters a photoelectric detector 18 after the light intensity of the optical attenuator 17 is adjusted, the photoelectric detector 18 converts the interference light signal into an electric signal, the electrical signal is sent to the signal processing and display module 19, and finally the external sound pressure signal to be detected is demodulated and displayed in the signal processing and display module 19.
When the optical fiber hydrophone sensing probe is used, the optical fiber hydrophone sensing probe is placed in water, the inner wall of the inner thin-wall elastic cylinder 7 is in contact with the water and is filled with the water, and air is arranged outside the inner thin-wall elastic cylinder 7. The outer wall of the outer thin-wall elastic tube 4 is contacted with water and is filled with water, and the inside of the outer thin-wall elastic tube 4 is air. When a dynamic underwater sound pressure signal is applied to the inner wall of the inner thin-wall elastic cylinder 7 and the outer wall of the outer thin-wall elastic cylinder 4, the inner wall of the inner thin-wall elastic cylinder 7 is subjected to radially outward dynamic underwater sound pressure, and the outer wall is not subjected to force, so that the inner thin-wall elastic cylinder 7 is radially outwardly expanded under the action of expansion strain, the radius is increased, the circumference is increased, and the inner optical fiber ring 8 wound on the inner thin-wall elastic cylinder is dynamically lengthened. On the contrary, the outer wall of the outer thin-walled elastic tube 4 is subjected to dynamic underwater sound pressure radially inward, while the inner wall is not subjected to force, so that the outer thin-walled elastic tube 4 is contracted inward by compressive strain, the circumference becomes short due to the decrease in radius, and the outer optical fiber ring 5 wound therearound is also dynamically shortened. The deformation directions of the optical fibers in the inner optical fiber ring 8 and the outer optical fiber ring 5 are opposite, and the correspondingly generated phase changes are also opposite, so that a push-pull type structure is formed. The phase changes in the two optical fiber rings are subtracted to obtain the total phase change, and the total phase change is twice of the phase change in the inner optical fiber ring 8/the outer optical fiber ring 5, so that the sensitivity of the acoustic signal response of the optical fiber hydrophone is doubled. When the inner thin-wall elastic tube 7, the inner optical fiber ring 8, the outer thin-wall elastic tube 4 and the outer optical fiber ring 5 are in the same temperature and environmental noise when in use, the influence of temperature change and environmental noise on the optical fiber hydrophone is eliminated, the common mode rejection of the noise is improved, the noise of the optical fiber hydrophone is reduced, and therefore the ultra-low frequency underwater acoustic signal can be detected. Meanwhile, two sensing arms of the optical fiber hydrophone sense the same hydrostatic pressure in water, so that hydrostatic pressure balance is achieved, and the optical fiber hydrophone is suitable for being applied to deep sea environments. In addition, the non-sensing optical fiber parts of the two interference arms near the 1x2 coupler 15 are fixed in the lower end cover 10, so that the disturbance of the optical fiber is reduced, the response stability of the optical fiber hydrophone is improved, and the noise of the optical fiber hydrophone is reduced. Compared with other push-pull optical fiber hydrophones, the device has the advantages of simple design on principle structure, less required optical devices, uncomplicated design of the hydrophone sensing probe, effective reduction of the manufacturing process and cost of the optical fiber hydrophone, low cost, easiness in realization, stability, flexibility in application and the like.
One or more of the above embodiments have the following advantages:
in the embodiment, the inner and outer thin-wall elastic cylinders are used as sensitive elements, and the underwater sound pressure enables the inner and outer thin-wall elastic cylinders to deform, so that the lengths of the inner and outer optical fiber rings wound on the inner and outer thin-wall elastic cylinders are changed, and therefore underwater sound pressure signals are detected. The thin-wall elastic cylinder is much more sensitive as a sensitive element than the optical fiber ring directly as a sensitive element.
The inner and outer thin-walled elastic cylinders adopted in the embodiment are made of the same material, and the length of the inner and outer optical fiber rings wound on the inner and outer thin-walled elastic cylinders is properly selected, so that the light phase variation quantity in the final inner and outer optical fiber rings is equal in magnitude and out of phase in direction, and the double sensitivity effect is generated.
The 1x2 coupler adopted in this embodiment is fixed in the lower end cover, so that the coupler can not change in vibration state when being disturbed by the outside world and still stays in a static state, thereby reducing the influence of optical fiber disturbance on the hydrophone, improving the response stability of the hydrophone, reducing the noise of the optical fiber hydrophone and being beneficial to realizing the effect of low noise.
In the embodiment, the Faraday rotator mirror is used as the light signal reflecting elements in the two sensing arms, so that the influence of optical fiber jitter on the visibility of interference signal fringes is reduced, and the polarization fading phenomenon existing in an interferometer sensor is improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (10)
1. An optical fiber hydrophone based on a push-pull structure is characterized by comprising a narrow-line-width laser, an optical fiber isolator, an optical fiber circulator, an optical attenuator, a photoelectric detector and a signal processing and displaying module which are sequentially connected, wherein one output port of the optical fiber circulator is connected with an optical fiber hydrophone sensing probe, and the other output port of the optical fiber circulator is connected with the optical attenuator;
the optical fiber hydrophone sensing probe comprises an inner thin-wall elastic cylinder, an outer thin-wall elastic cylinder, an upper end cover, a lower end cover and a cover plate; when the inner thin-wall elastic cylinder wound around the inner optical fiber ring is nested in the outer thin-wall elastic cylinder wound around the outer optical fiber ring, an air cavity is formed between the two thin-wall elastic cylinders; one end of the inner optical fiber ring is connected with the second Faraday rotator mirror, and the other end of the inner optical fiber ring is connected with the first input end of the coupler; one end of the outer optical fiber ring is connected with the first Faraday rotator mirror, and the other end of the outer optical fiber ring is connected with the second input end of the coupler; the output end of the coupler is connected with the optical fiber circulator; after the upper end cover and the lower end cover enclose the inner thin-wall elastic cylinder and the outer thin-wall elastic cylinder into a structure with two open ends, the lower port is sealed through the cover plate, and only the upper port is kept open.
2. The push-pull structure based optical fiber hydrophone of claim 1, wherein a groove is provided between the lower end cap and the cover plate for receiving a coupler.
3. The optical fiber hydrophone based on the push-pull structure as claimed in claim 1, wherein the cover plate and the lower end cap are provided with optical fiber through holes, the pigtails of the outer optical fiber loop and the pigtails of the inner optical fiber loop are connected to the two input ends of the coupler after passing through the optical fiber through holes on the lower end cap, and the optical fibers at the output end of the coupler extend to the outside through the optical fiber through holes on the cover plate.
4. The optical fiber hydrophone based on the push-pull structure of claim 1, wherein the inner thin-walled elastic tube wound around the inner optical fiber ring and the outer thin-walled elastic tube wound around the outer optical fiber ring are both provided with optical fiber protective layers.
5. The optical fiber hydrophone based on the push-pull structure as claimed in claim 1, wherein the upper end cover is in a shape of a circular ring with a hollow middle part, the diameter of the hollow middle part is the same as the inner diameter of the inner thin-wall elastic cylinder, one surface of the upper end cover is flat, the other surface of the upper end cover is provided with an annular boss, the inner diameter of the annular boss is the same as the outer diameter of the inner thin-wall elastic cylinder, and the outer diameter of the annular boss is the same as the inner diameter of the outer thin-wall elastic cylinder.
6. The push-pull structure based fiber optic hydrophone of claim 5, wherein the gap between the two thin-walled elastomeric cylinders is constant equal to the width of the annular boss of the upper end cap.
7. The optical fiber hydrophone based on the push-pull structure as claimed in claim 1, wherein the lower end cap is in a ring shape with a hollow middle, the diameter of the hollow middle circle is the same as the inner diameter of the inner thin-wall elastic cylinder, one surface of the lower end cap is provided with an annular boss, the inner diameter of the annular boss is the same as the outer diameter of the inner thin-wall elastic cylinder, the outer diameter of the annular boss is the same as the inner diameter of the outer thin-wall elastic cylinder, and the other surface of the lower end cap is provided with a groove, so that the coupler is hermetically fixed in the groove.
8. The push-pull structure-based optical fiber hydrophone according to claim 1, wherein the inner optical fiber ring on the inner thin-walled elastic cylinder and the outer optical fiber ring on the outer thin-walled elastic cylinder form a push-pull structure.
9. The push-pull structure based fiber optic hydrophone of claim 1, wherein the fiber optic isolator allows only unidirectional transmission of light for isolating interference signals returned from the hydrophone sensing probe so as not to affect the laser.
10. The push-pull configuration based fiber optic hydrophone of claim 1, wherein the optical attenuator is configured to adjust an optical power of the detected interference signal.
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