Double-interferometer push-pull and common-mode noise differential suppression optical fiber hydrophone

Abstract

The invention is suitable for the technical field of optical fiber sensing, and relates to a double-interferometer push-pull and common-mode noise differential suppression optical fiber hydrophone, which comprises a first thin-wall cylinder, a second thin-wall cylinder, a first optical fiber interferometer and a second optical fiber interferometer, the first thin-wall cylinder is embedded in the second thin-wall cylinder, a first optical fiber winding area and a second optical fiber winding area are arranged on the first thin-wall cylinder, and a third optical fiber winding area and a fourth optical fiber winding area are arranged on the second thin-wall cylinder; the first optical fiber interferometer comprises a first short-arm sensing optical fiber, a first long-arm sensing optical fiber, a first Faraday rotating mirror and a second Faraday rotating mirror, and the second optical fiber interferometer comprises a second short-arm sensing optical fiber, a second long-arm sensing optical fiber, a third Faraday rotating mirror and a fourth Faraday rotating mirror. According to the invention, the dual-push-pull structure is formed by the dual-fiber interferometer, so that temperature drift noise and optical scattering noise caused by the ultra-long sensing fiber are effectively reduced, and common-mode noise formed by light source vibration, transmission optical cable jitter and the like is effectively suppressed.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing, and in particular relates to an optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression. Background Art

[0002] Fiber-optic hydrophone is an underwater acoustic sensor based on optical fiber and optoelectronic technology. It has the characteristics of anti-electromagnetic interference, low signal crosstalk, and easy large-scale array formation. It has received widespread attention at home and abroad and has become an important new technical approach for underwater target detection and underwater acoustic survey equipment.

[0003] Based on the detection principle, fiber optic hydrophones can be categorized as wavelength, intensity, and interferometric types. Interferometric fiber optic hydrophones, with their high sensitivity, ease of array formation, and process-friendly implementation, have become the mainstream technology in the industry. Traditional interferometric fiber optic hydrophones are based on a single-fiber interferometer structure. Under the premise that the hydrophone's skeleton material and structural parameters are determined to ensure hydrostatic pressure resistance, the acoustic pressure phase shift sensitivity is generally improved by extending the length of the interferometer's sensing fiber. However, when the sensing fiber length increases to a certain extent, the increased fiber length increases the fiber optic hydrophone's thermal drift noise and optical scattering noise, raising the system's phase noise floor and resulting in an increase in equivalent noise pressure. Furthermore, transmission cable jitter and light source low-frequency noise are difficult to eliminate in a single-fiber interferometer fiber optic hydrophone. While prior art proposes using pressure-insensitive fiber optic hydrophones with the same parameters to adaptively eliminate transmission cable jitter and system low-frequency noise, pressure-insensitive fiber optic hydrophones cannot achieve absolute co-location detection with the detection hydrophone, resulting in limited suppression capabilities. Patent publication number CN202020809189.X provides an interferometric fiber-optic vector hydrophone with a reference interferometer, comprising a mass, an elastic cylinder, a fiber-optic interferometer, and a housing for housing the mass, elastic cylinder, and fiber-optic interferometer. The fiber-optic hydrophone described in this patent also utilizes a single-fiber interferometer structure, resulting in poor suppression and the same drawbacks as the prior art.

[0004] Therefore, it is urgent to solve the problem of difficult to suppress ultra-long sensing optical fiber and transmission cable jitter and light source low-frequency noise in the traditional fiber optic hydrophone sensitivity enhancement design. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression, so as to solve the problems of using ultra-long sensing optical fibers and the difficulty in suppressing transmission cable jitter and light source low-frequency noise in the traditional fiber optic hydrophone sensitivity enhancement design.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression, comprising:

[0008] A first thin-walled cylinder, a second thin-walled cylinder, a first fiber interferometer and a second fiber interferometer; the first thin-walled cylinder is embedded in the second thin-walled cylinder, and the two form an air cavity; the first thin-walled cylinder is provided with a first fiber winding area and a second fiber winding area, and the second thin-walled cylinder is provided with a third fiber winding area and a fourth fiber winding area; the first fiber interferometer includes a first short-arm sensing fiber, a first long-arm sensing fiber, a first Faraday rotator and a second Faraday rotator; the second fiber interferometer includes a second short-arm sensing fiber, a second long-arm sensing fiber, a third Faraday rotator and a fourth Faraday rotator; the first short-arm sensing fiber is connected to the first Faraday rotator, The first long-arm sensing fiber is connected to the second Faraday rotator, the second short-arm sensing fiber is connected to the third Faraday rotator, and the second long-arm sensing fiber is connected to the fourth Faraday rotator. The first short-arm sensing fiber and the second long-arm sensing fiber are wound in parallel on the first fiber winding area and the second fiber winding area. The first Faraday rotator and the fourth Faraday rotator are fixedly connected to the inner wall of the first thin-walled cylinder. The first long-arm sensing fiber and the second short-arm sensing fiber are wound in parallel on the third fiber winding area and the fourth fiber winding area. The second Faraday rotator and the third Faraday rotator are fixedly connected to the inner wall of the first thin-walled cylinder.

[0009] Furthermore, the first thin-walled cylinder is also provided with a first supporting rib, a second supporting rib and a third supporting rib. The first supporting rib and the third supporting rib are respectively provided at both ends of the first thin-walled cylinder, and the second supporting rib is provided in the middle position of the first thin-walled cylinder.

[0010] Furthermore, the second thin-walled cylinder is also provided with a fourth support rib, a fifth support rib and a sixth support rib. The fourth support rib and the sixth support rib are respectively provided at both ends of the second thin-walled cylinder, and the fifth support rib is provided in the middle position of the second thin-walled cylinder.

[0011] Furthermore, the outer diameters of the first support rib, the second support rib, and the third support rib are the same, and are the same as the inner diameter of the second thin-walled cylinder.

[0012] Furthermore, the second support rib, the third support rib, the fifth support rib and the sixth support rib are all provided with left and right spiral grooves with the same pitch and depth, which are used to cross the support ribs and enter the adjacent optical fiber winding area when winding the optical fiber.

[0013] Furthermore, the first fiber interferometer further includes a first fiber coupler, and the first short-arm sensing fiber and the first long-arm sensing fiber are respectively connected to the first fiber coupler.

[0014] Furthermore, the first fiber interferometer further includes a first optical input pigtail and a first optical output pigtail, and the first optical input pigtail and the first optical output pigtail are respectively connected to the first fiber coupler.

[0015] Furthermore, the second fiber interferometer further includes a second fiber coupler, and the second short-arm sensing fiber and the second long-arm sensing fiber are respectively connected to the second fiber coupler.

[0016] Furthermore, the second fiber interferometer further includes a second optical input pigtail and a second optical output pigtail, and the second optical input pigtail and the second optical output pigtail are respectively connected to the second fiber coupler.

[0017] Furthermore, the optical fiber is wound in two layers.

[0018] Compared with the prior art, the optical fiber hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by the present invention has at least the following beneficial effects:

[0019] Traditional fiber-optic hydrophone sensitivity enhancement designs often use ultra-long sensing optical fibers, and transmission cable jitter and light source low-frequency noise are difficult to suppress. The present invention has a simple structure and convenient operation. It uses dual-fiber interferometers as optical sensors to form a dual push-pull and differential detection structure. Under the influence of an acoustic signal, one of the two sensing fibers of a single fiber interferometer extends and the other shortens, forming a single push-pull structure. The difference between the two deformations is twice the deformation of the single sensing fiber, thereby increasing the relative deformation between the two sensing arms and increasing the sensitivity of the fiber-optic hydrophone. In the present invention, the fibers of the two fiber interferometers deform in opposite directions but of equal magnitude, forming a dual push-pull structure. After differential calculation, the signal amplitude is doubled that of the single fiber interferometer signal. Compared with traditional high-sensitivity single-fiber interferometer hydrophones using extra-long sensing fibers, the length of each fiber interferometer sensing fiber is reduced to half that of traditional single-fiber interferometer hydrophones, while maintaining the same sound pressure sensitivity. This reduces the temperature drift and optical scattering noise caused by the extra-long sensing fiber in single-fiber interferometer hydrophones. Furthermore, the push-pull differential detection method of the dual interferometer structure suppresses transmission cable jitter and low-frequency noise from the light source, thereby reducing the background phase noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the scheme of the present invention, a brief introduction is given below to the figures required for use in the description of the embodiments. Obviously, the figures described below are some embodiments of the present invention. For ordinary technicians in this field, other figures can be obtained based on these figures without paying any creative work.

[0021] Figure 1 A schematic diagram of an assembly of a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of the first thin-walled cylinder structure of a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of the second thin-walled cylinder structure of a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of the completed assembly of a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of the structure of a first fiber optic interferometer of a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by an embodiment of the present invention;

[0026] Figure 6 A schematic structural diagram of a second optical fiber interferometer of an optical fiber hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by an embodiment of the present invention;

[0027] Figure 7 A diagram showing the common-mode noise differential suppression effect of a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by an embodiment of the present invention;

[0028] Figure 8 A diagram showing the signal differential output results of a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression provided by an embodiment of the present invention;

[0029] Reference numerals: 10-first thin-walled cylinder; 101-first optical fiber winding area; 102-second optical fiber winding area; 103-first supporting rib; 104-second supporting rib; 105-third supporting rib; 20-second thin-walled cylinder; 201-third optical fiber winding area; 202-fourth optical fiber winding area; 203-fourth supporting rib; 204-fifth supporting rib; 205-sixth supporting rib; 30-first optical fiber interferometer; 301-first optical fiber input pigtail; 302- First optical fiber output pigtail; 303-first optical fiber coupler; 304-first short-arm sensing optical fiber; 305-first long-arm sensing optical fiber; 306-first Faraday rotator; 307-second Faraday rotator; 40-second optical fiber interferometer; 401-second optical input pigtail; 402-second optical output pigtail; 403-second optical fiber coupler; 404-second short-arm sensing optical fiber; 405-second long-arm sensing optical fiber; 406-third Faraday rotator; 407-fourth Faraday rotator. DETAILED DESCRIPTION

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the present invention pertains; the terms used in the specification herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention; for example, the directions or positions indicated by the terms "length", "width", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the directions or positions shown in the accompanying drawings and are for ease of description only and should not be construed as limiting the present technical solution.

[0031] The terms "including" and "having," as well as any variations thereof, in the specification and claims of the present invention and the accompanying drawings are intended to cover non-exclusive inclusions; the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish between different objects, rather than to describe a specific order. In the specification and claims of the present invention and the accompanying drawings, when an element is referred to as being "fixed to," "mounted on," "disposed on," or "connected to" another element, it may be directly or indirectly located on the other element. For example, when an element is referred to as being "connected to" another element, it may be directly or indirectly connected to the other element.

[0032] Furthermore, references herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0033] The present invention provides a fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression, which is applied to the detection of underwater sound pressure signals. The fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression includes:

[0034] A first thin-walled cylinder, a second thin-walled cylinder, a first fiber optic interferometer and a second fiber optic interferometer; the first thin-walled cylinder is embedded in the second thin-walled cylinder, and the two form an air cavity; the first thin-walled cylinder is provided with a first fiber optic winding area and a second fiber optic winding area, and the second thin-walled cylinder is provided with a third fiber optic winding area and a fourth fiber optic winding area; the first fiber optic interferometer includes a first short-arm sensing fiber, a first long-arm sensing fiber, a first Faraday rotator and a second Faraday rotator; the second fiber optic interferometer includes a second short-arm sensing fiber, a second long-arm sensing fiber, a third Faraday rotator and a fourth Faraday rotator; the first short-arm sensing fiber and the first long-arm sensing fiber are connected to each other; The first and second long-arm sensing optical fibers are connected to the first and second Faraday rotators, the first and second short-arm sensing optical fibers are connected to the third and fourth Faraday rotators, the first and second short-arm sensing optical fibers are wound in parallel on the first and second optical fiber winding areas, the first and fourth Faraday rotators are fixedly connected to the inner wall of the first thin-walled cylinder, the first and second short-arm sensing optical fibers are wound in parallel on the third and fourth optical fiber winding areas, and the second and third Faraday rotators are fixedly connected to the inner wall of the first thin-walled cylinder.

[0035] The present invention adopts a dual-fiber interferometer to form a dual push-pull structure, which effectively reduces the temperature drift noise and optical scattering noise caused by the ultra-long sensing fiber, and effectively suppresses the common-mode noise caused by light source vibration and transmission cable jitter.

[0036] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0037] The present invention provides a fiber optic hydrophone with dual interferometer push-pull and common mode noise differential suppression, which is applied to the detection of underwater sound pressure signals. Figures 1 to 8 In this embodiment, the optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression includes:

[0038] The first thin-walled cylinder 10, the second thin-walled cylinder 20, the first optical fiber interferometer 30 and the second optical fiber interferometer 40, the first thin-walled cylinder 10 and the second thin-walled cylinder 20 can be made of metal or organic polymer, the first thin-walled cylinder 10 includes a first optical fiber winding area 101, a second optical fiber winding area 102, a first supporting rib 103, a second supporting rib 104 and a third supporting rib 105, the second thin-walled cylinder 20 includes a first optical fiber winding area 201, a second optical fiber winding area 202, a first supporting rib 203, a second supporting rib 204 and a third supporting rib 205, the outer diameters of the first supporting rib 103, the second supporting rib 104 and the third supporting rib 105 of the first thin-walled cylinder 10 are equal and the same as the inner diameter of the second thin-walled cylinder 20, the first thin-walled cylinder 10 can be nested into the second thin-walled cylinder 20, The first supporting rib 103, the second supporting rib 104 and the third supporting rib 105 of a thin-walled cylinder 10 are bonded and fixed to the inner wall of the second thin-walled cylinder 20 by structural adhesive, and an air cavity is formed between the first optical fiber winding area 101 of the first thin-walled cylinder 10 and the first optical fiber winding area 201 of the second thin-walled cylinder 20, and between the second optical fiber winding area 102 of the first thin-walled cylinder 10 and the second optical fiber winding area 201 of the second thin-walled cylinder 20. The second supporting rib 104 and the third supporting rib 105 of the first thin-walled cylinder 10 and the second supporting rib 204 and the third supporting rib 205 of the second thin-walled cylinder 20 are all engraved with left and right spiral grooves with the same pitch and depth. When winding the optical fiber, the left and right spiral grooves can be used to cross the supporting ribs to enter the adjacent optical fiber winding area. The bottom of the left and right threaded grooves should be flush with the corresponding optical fiber winding area.

[0039] Furthermore, in this embodiment, the first fiber optic interferometer 30 includes a first optical input pigtail 301, a first optical output pigtail 302, a first optical fiber coupler 303, a first short-arm sensing optical fiber 304, a first long-arm sensing optical fiber 305, a first Faraday rotator 306, and a second Faraday rotator 307. The first optical input pigtail 301 and the first optical output pigtail 302 are respectively connected to one end of the first fiber optic coupler 303, the first short-arm sensing optical fiber 304 and the first long-arm sensing optical fiber 305 are respectively connected to the other end of the first fiber optic coupler 303, the first short-arm sensing optical fiber 304 is connected to the first Faraday rotator 306, the first long-arm sensing optical fiber 305 is connected to the second Faraday rotator 307, and the second optical fiber interferometer 40 The optical fiber interferometer 30 includes a second optical input pigtail 401, a second optical output pigtail 402, a second optical fiber coupler 403, a second short-arm sensing optical fiber 404, a second long-arm sensing optical fiber 405, a third Faraday rotator 406 and a fourth Faraday rotator 407. The second optical input pigtail 401 and the second optical output pigtail 402 are respectively connected to one end of the second optical fiber coupler 403, the second short-arm sensing optical fiber 404 and the second long-arm sensing optical fiber 405 are respectively connected to the other end of the second optical fiber coupler 403, the second short-arm sensing optical fiber 404 is connected to the third Faraday rotator 406, and the second long-arm sensing optical fiber 405 is connected to the fourth Faraday rotator 407. The specifications of the first optical fiber interferometer 30 and the second optical fiber interferometer 40 are completely consistent.

[0040] Specifically, in this embodiment, the optical fiber winding method on the first thin-walled cylinder 10 is as follows: the first short-arm sensing optical fiber 304 of the first optical fiber interferometer 30 and the second long-arm sensing optical fiber 405 of the second optical fiber interferometer 40 are tightly wound in parallel and synchronously on the first optical fiber winding area 101 and the second optical fiber winding area 102 of the first thin-walled cylinder 10. When winding, the winding starts from one end of the first optical fiber coupler 303 and the second end of the optical fiber coupler 403 respectively, and enters from the left-hand thread groove (or right-hand thread groove) of the third supporting rib 105, and the winding of the designed number of turns on the second optical fiber winding area 102 is completed evenly and closely, and the left-hand thread groove (or right-hand thread groove) of the second supporting rib 104 is formed. The optical fiber 102 is wound through the right-hand thread groove (or left-hand thread groove) of the second supporting rib 104 into the first optical fiber winding area 101, and is wound closely until the designed number of turns is completed. Then, starting from the current position, the optical fiber 102 is wound in the reverse direction on the first optical fiber winding area 101. During the winding process, the optical fiber 102 enters the second optical fiber winding area 102 through the right-hand thread groove (or left-hand thread groove) of the second supporting rib 104. After completing the winding of the specified number of turns, the optical fiber 102 is wound out of the second optical fiber winding area 102 through the right-hand thread groove (or left-hand thread groove) of the third supporting rib 105. The first Faraday rotator 306 at the end of the first short-arm sensing optical fiber 304 and the fourth Faraday rotator 407 at the end of the second long-arm sensing optical fiber 405 that are wound out of the second optical fiber winding area 102 are glued and fixed to the inner wall of the first thin-walled cylinder 10.

[0041] Specifically, in this embodiment, the optical fiber winding method on the second thin-walled cylinder 20 is as follows: the first long-arm sensing optical fiber 305 of the first optical fiber interferometer 30 and the second short-arm sensing optical fiber 404 of the second optical fiber interferometer 40 are tightly wound in parallel and synchronously on the first optical fiber winding area 201 and the second optical fiber winding area 202 of the second thin-walled cylinder 20. When winding, the winding starts from one end of the first optical fiber coupler 303 and the second end of the second optical fiber coupler 403 respectively. The optical fiber starts to enter from the left-hand thread groove (or right-hand thread groove) of the sixth supporting rib 205, and the winding of the designed number of turns on the second optical fiber winding area 202 is completed evenly and closely, and is wound by the left-hand thread groove of the fifth supporting rib 204. The optical fiber 202 is wound into the second optical fiber winding area 202 through the right-hand thread groove (or left-hand thread groove) of the fifth support rib 204, and is wound out of the second optical fiber winding area 202 through the right-hand thread groove (or left-hand thread groove) of the sixth support rib 205 after completing the winding of the specified number of turns. The second Faraday rotator 307 at the end of the first long-arm sensing optical fiber 305 and the third Faraday rotator 406 at the end of the second short-arm sensing optical fiber 404 are glued and fixed to the inner wall of the first thin-walled cylinder 10.

[0042] In this embodiment, the number of optical fiber winding areas on the first thin-walled cylinder 10 and the second thin-walled cylinder 20 is two; in other embodiments, if the sensitivity needs to be increased, the number of winding areas can be appropriately increased according to actual conditions.

[0043] In this embodiment, the number of winding layers of the optical fiber is two; in some other embodiments, if the sensitivity needs to be increased, the number of winding layers can be appropriately increased according to actual conditions.

[0044] Furthermore, in this embodiment, the first optical input pigtail 301 of the first optical fiber interferometer 30 and the second optical input pigtail 401 of the second optical fiber interferometer 40 receive laser input, which is divided into two beams by their respective optical fiber couplers, respectively entering the short-arm sensing optical fiber and the long-arm sensing optical fiber of the two optical fiber interferometers, and returning after being reflected by the Faraday rotator at the end of the sensing optical fiber, and converging at the optical fiber coupler to form interference light output. Under the action of the sound pressure signal, the first thin-walled cylinder 10 and the second thin-walled cylinder 20 simultaneously produce opposite radial deformations. Due to the use of a double push-pull structure, under the action of the deformation of the thin-walled cylinder The first short arm sensing fiber 304 of the first fiber interferometer 30 is extended (or shortened), and the first long arm sensing fiber 305 is shortened (or extended) synchronously. The second short arm sensing fiber 404 of the second fiber interferometer 40 is shortened (or extended) synchronously, and the second long arm sensing fiber 405 is extended (or shortened) synchronously. The output interference light of the first fiber interferometer 30 and the second fiber interferometer 40 respectively produces optical phase difference changes with equal amplitude and opposite phase. By performing differential calculation on the optical phase difference signals of the first fiber interferometer 30 and the second fiber interferometer 40, the sound pressure signal can be obtained.

[0045] Compared with the prior art, the fiber optic hydrophone with dual interferometer push-pull and common-mode noise differential suppression described in the above embodiment uses ultra-long sensing fibers, transmission cable jitter, and light source low-frequency noise that are difficult to suppress in traditional fiber optic hydrophone sensitivity enhancement designs. The present invention has a simple structure and convenient operation. It uses a dual-fiber interferometer as an optical sensor to form a dual push-pull and differential detection structure. Under the influence of an acoustic signal, one of the two sensing fibers of a single fiber interferometer extends and the other shortens, forming a single push-pull structure. The difference between the two deformations is twice the deformation of the single sensing fiber, thereby increasing the relative deformation between the two sensing arms and increasing the sensitivity of the fiber-optic hydrophone. The dual-fiber interferometers in the present invention generate fiber deformations of equal magnitude and opposite directions, forming a dual push-pull structure. After differential calculation, the signal amplitude is doubled that of the signal from a single fiber interferometer. Compared with traditional high-sensitivity single-fiber interferometer hydrophones using extra-long sensing fibers, the length of each fiber interferometer is reduced to half that of traditional single-fiber interferometer hydrophones, while maintaining the same sound pressure sensitivity. This reduces the temperature drift and optical scattering noise caused by the extra-long sensing fibers in single-fiber interferometer hydrophones. Furthermore, the push-pull differential detection method of the dual interferometer structure suppresses transmission cable jitter and low-frequency noise from the light source, thereby reducing the background phase noise.

[0046] Obviously, the embodiments described above are only preferred embodiments of the present invention, rather than all embodiments. The preferred embodiments of the present invention are given in the accompanying drawings, but they do not limit the patent scope of the present invention. The present invention can be implemented in many different forms. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Although the present invention has been described in detail with reference to the aforementioned embodiments, for those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned specific embodiments, or to make equivalent replacements for some of the technical features therein. Any equivalent structure made using the contents of the present invention specification and drawings, directly or indirectly used in other related technical fields, is also within the scope of patent protection of the present invention.

Claims

1. A fiber optic hydrophone with dual interferometer push-pull and common mode noise differential suppression, characterized in that: include: a first thin-walled cylinder, a second thin-walled cylinder, a first fiber optic interferometer, and a second fiber optic interferometer; The first thin-walled cylinder is embedded in the second thin-walled cylinder, and the two form an air cavity. The first thin-walled cylinder is provided with a first optical fiber winding area and a second optical fiber winding area, and the second thin-walled cylinder is provided with a third optical fiber winding area and a fourth optical fiber winding area; The first fiber interferometer includes a first short-arm sensing fiber, a first long-arm sensing fiber, a first Faraday rotator, and a second Faraday rotator. The second fiber interferometer includes a second short-arm sensing fiber, a second long-arm sensing fiber, a third Faraday rotator, and a fourth Faraday rotator. The first short-arm sensing fiber is connected to the first Faraday rotator, the first long-arm sensing fiber is connected to the second Faraday rotator, the second short-arm sensing fiber is connected to the third Faraday rotator, and the second long-arm sensing fiber is connected to the fourth Faraday rotator. The first short-arm sensing fiber and the second long-arm sensing fiber are wound in parallel on the first fiber winding area and the second fiber winding area. The first Faraday rotator and the fourth Faraday rotator are fixedly connected to the inner wall of the first thin-walled cylinder. The first long-arm sensing fiber and the second short-arm sensing fiber are wound in parallel on the third fiber winding area and the fourth fiber winding area. The second Faraday rotator and the third Faraday rotator are fixedly connected to the inner wall of the first thin-walled cylinder.

2. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 1, characterized in that: The first thin-walled cylinder is further provided with a first supporting rib, a second supporting rib and a third supporting rib. The first supporting rib and the third supporting rib are respectively provided at both ends of the first thin-walled cylinder, and the second supporting rib is provided in the middle of the first thin-walled cylinder.

3. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 2, characterized in that: The second thin-walled cylinder is further provided with a fourth support rib, a fifth support rib and a sixth support rib. The fourth support rib and the sixth support rib are respectively provided at both ends of the second thin-walled cylinder, and the fifth support rib is provided in the middle of the second thin-walled cylinder.

4. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 3, characterized in that: The outer diameters of the first support rib, the second support rib, and the third support rib are the same, and are the same as the inner diameter of the second thin-walled cylinder.

5. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 4, characterized in that: The second support rib, the third support rib, the fifth support rib and the sixth support rib are all provided with left and right spiral grooves with the same pitch and depth, which are used to cross the support ribs and enter the adjacent optical fiber winding area when winding the optical fiber.

6. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 1, characterized in that: The first fiber interferometer further includes a first fiber coupler, and the first short-arm sensing fiber and the first long-arm sensing fiber are respectively connected to the first fiber coupler.

7. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 6, characterized in that: The first fiber interferometer further includes a first optical input pigtail and a first optical output pigtail, and the first optical input pigtail and the first optical output pigtail are respectively connected to the first fiber coupler.

8. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 1, characterized in that: The second fiber interferometer further includes a second fiber coupler, and the second short-arm sensing fiber and the second long-arm sensing fiber are respectively connected to the second fiber coupler.

9. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 8, characterized in that: The second fiber interferometer further includes a second optical input pigtail and a second optical output pigtail, and the second optical input pigtail and the second optical output pigtail are respectively connected to the second fiber coupler.

10. The optical fiber hydrophone with dual interferometer push-pull and common mode noise differential suppression according to claim 1, characterized in that: The optical fiber is wound in two layers.

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