Optical fiber hydrophone adjusting method

Abstract

The embodiment of the invention discloses an optical fiber hydrophone adjusting method. An optical fiber hydrophone comprises a shell, a sensitive coil and a spring, the sensitive coil and the spring are arranged in the shell, two ends of the spring are fixed on two opposite inner walls of the shell, and the sensitive coil is arranged in the spring and surrounded by the spring; the sensitive coil comprises an elastomer and a sensitive optical fiber wound on the surface of the elastomer; the elastomer is fixedly connected with the shell; the spring is fixedly connected with the middle area of the elastic body. The length of the sensitive optical fiber is not changed under the action of the acceleration, so that the sensitivity of the optical fiber hydrophone to the acceleration is reduced, and the effect of sound signal measurement is prevented from being influenced under the action of the acceleration.

Description

Technical Field

[0001] The invention relates to the field of optical fiber sensing technology, and in particular to an optical fiber hydrophone adjustment method. Background Art

[0002] Fiber optic hydrophone technology is a new type of hydrophone technology that uses fiber optic technology to achieve high-sensitivity underwater acoustic sensing. Due to its advantages of high detection accuracy, large dynamic range, underwater passiveness, and easy large-scale array formation, it plays an increasingly important role in the fields of ocean observation and underwater detection. The application of fiber optic hydrophones, especially in towed arrays and vertical arrays, places strict requirements on its own acceleration sensitivity, which needs to be as low as possible. It is related to whether the fiber optic hydrophone array can effectively suppress the vibration noise interference caused by array jitter, ocean eddies, etc.

[0003] The mechanism by which the fiber-optic hydrophone is sensitive to acceleration is that the elastic structure used as the hydroacoustic sensor and the sensitive optical fiber coil wound on it produce corresponding deformation under the action of acceleration, causing the length of the sensitive optical fiber to change, which will affect the measurement of the sound signal. There are usually two ways to reduce the acceleration sensitivity of the fiber-optic hydrophone: one is to reduce the acceleration sensitivity through the design of the sensitive coil itself, and the second is to add a corresponding vibration isolation structure to the sensor to reduce the vibration of the sensitive coil.

[0004] Figure 1 This is a schematic diagram of the structure of a mandrel-type interferometric fiber optic hydrophone. In the actual production of fiber optic hydrophones, their acceleration sensitivity is usually -10dB to -30dB rad / g, and the theoretical insensitivity to acceleration cannot be achieved. The reasons are as follows: the machining of the elastomer and the winding of the sensitive coil cannot achieve the perfect symmetry in the theoretical design, resulting in the deformation of the upper and lower parts of the hydrophone not being strictly conjugated under the action of acceleration. Figure 2 It is a schematic diagram of the structure of a fiber optic hydrophone using spring vibration isolation. Comparing the acceleration sensitivity test data before and after vibration isolation, the introduction of the spring can indeed achieve a better vibration isolation effect, but its desensitization effect is limited. Summary of the invention

[0005] The present invention provides a method for adjusting a fiber optic hydrophone, in which the length of the sensitive optical fiber does not change under the action of acceleration, thereby reducing the sensitivity of the fiber optic hydrophone to acceleration and avoiding the effect of acceleration affecting the measurement of sound signals.

[0006] According to one aspect of the present invention, there is provided a fiber optic hydrophone, comprising:

[0007] housing, sensitive coil and spring;

[0008] The sensitive coil and the spring are both arranged in the housing, the two ends of the spring are fixed on two opposite inner walls of the housing, and the sensitive coil is arranged in the spring and surrounded by the spring;

[0009] The sensitive coil comprises an elastic body and a sensitive optical fiber wound on the surface of the elastic body; the elastic body is fixedly connected to the shell; and the spring is fixedly connected to the middle area of ​​the elastic body.

[0010] Optionally, two ends of the spring are respectively fixed to the first surface and the second surface of the shell, and the first surface of the shell is further provided with a rigid bracket, which is fixedly connected to the shell;

[0011] The rigid bracket penetrates into the elastic body to fix the elastic body.

[0012] Optionally, the elastomer includes a first end, a first winding portion, a middle portion, a second winding portion, and a second end portion which are connected in sequence along a direction from the first surface to the second surface, the sensitive optical fiber is wound on the first winding portion and the second winding portion, and dimensions of the first end, the middle portion, and the second winding portion along a direction parallel to the first surface are greater than dimensions of the first winding portion and the second winding portion along a direction parallel to the first surface, and the middle portion is fixedly connected to the spring.

[0013] Optionally, the first winding portion and the first end portion are symmetrical with respect to the middle portion and the second winding portion and the second end portion.

[0014] Optionally, the fiber optic hydrophone further includes a fiber optic reflector, a fiber optic coupler and a transition fiber;

[0015] The fiber reflector and the fiber coupler are connected to the sensitive fiber through transition fiber;

[0016] The optical fiber reflector, the optical fiber coupler and the transition optical fiber are fixed on a rigid bracket.

[0017] Optionally, the spring is fixedly connected to the elastic body by means of screws or an adhesive layer;

[0018] The spring is rigidly fixed to the housing by screws.

[0019] Optionally, the material of the elastomer includes metal, nylon or polysulfone.

[0020] According to another aspect of the present invention, a method for adjusting a fiber optic hydrophone is provided, which is applied to the fiber optic hydrophone according to any embodiment of the present invention, and the method for adjusting comprises:

[0021] Fix the fiber optic hydrophone on the vibration table and measure its acceleration sensitivity. If the acceleration sensitivity exceeds the index value, increase or decrease the length of the sensitive coil until the acceleration sensitivity of the fiber optic hydrophone is less than or equal to the index value.

[0022] Optionally, if the acceleration sensitivity exceeds the index value, increasing or decreasing the length of the sensitive coil until the acceleration sensitivity of the fiber optic hydrophone is less than or equal to the index value, including:

[0023] If the acceleration sensitivity value exceeds the index value, part of the transition optical fiber connected to the sensitive coil wound on the second winding part is wound onto the second winding part to increase the length of the sensitive coil, or part of the sensitive coil on the second winding part is loosened to convert it into a transition optical fiber.

[0024] Optionally, after winding a portion of the transition optical fiber connected to the sensitive coil wound by the second winding portion into the second winding portion to increase the length of the sensitive coil, if the acceleration sensitivity shows a decreasing trend, continue to wind the portion of the transition optical fiber into the second winding portion to increase the length of the sensitive coil until the acceleration sensitivity of the optical fiber hydrophone is less than or equal to the index value;

[0025] After loosening part of the sensitive coil on the second winding part and converting it into a transition optical fiber, if the acceleration sensitivity shows a decreasing trend, continue to loosen part of the sensitive coil on the second winding part and convert it into a transition optical fiber until the acceleration sensitivity of the optical fiber hydrophone is less than or equal to the index value.

[0026] The fiber optic hydrophone provided in the embodiment of the present invention includes a housing, a sensitive coil and a spring; the sensitive coil and the spring are both arranged in the housing, the two ends of the spring are fixed on two opposite inner walls of the housing, and the sensitive coil is arranged in the spring and surrounded by the spring; so that the spring can buffer external impact, reduce the vibration of the entire elastomer, and achieve a good vibration isolation effect. The sensitive coil includes an elastomer and a sensitive optical fiber wound on the surface of the elastomer; the elastomer is fixedly connected to the housing; and the spring is fixedly connected to the middle area of ​​the elastomer. By fixing the elastomer to the housing and the spring to the middle area of ​​the elastomer, the sensitive coil is divided into two symmetrical parts, forming a push-pull effect. Under the action of vibration (acceleration), the vibration will be transmitted to the elastomer through the shell, and the upper and lower parts of the elastomer will undergo opposite deformations. The sensitive optical fiber wrapped on the surface of the elastomer will also undergo opposite deformations, with the upper part deforming in compression and the lower part deforming in tension. Since the middle part of the sensitive coil is fixedly connected to the spring, and the spring is fixedly connected to the middle area of ​​the elastomer, under the action of the spring, the deformation amounts of the upper and lower parts of the sensitive coil are strictly conjugated, so that the length of the sensitive optical fiber will not change under the action of acceleration, thereby reducing the sensitivity of the fiber-optic hydrophone to acceleration and avoiding the effect of affecting the measurement of sound signals under the action of acceleration.

[0027] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 It is a schematic diagram of the structure of a mandrel-type interference fiber optic hydrophone.

[0030] Figure 2 It is a schematic diagram of the structure of a fiber optic hydrophone using spring vibration isolation.

[0031] Figure 3 It is a structural schematic diagram of a fiber optic hydrophone provided by an embodiment of the present invention.

[0032] Figure 4 It is a schematic structural diagram of another fiber optic hydrophone provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] An embodiment of the present invention provides a fiber optic hydrophone. Figure 3 Schematic diagram of the structure of a fiber optic hydrophone provided by an embodiment of the present invention. Figure 3 , fiber optic hydrophone, including:

[0036] Housing 10, sensitive coil 20 and spring 30;

[0037] The sensitive coil 20 and the spring 30 are both arranged in the housing 10, and the two ends of the spring 30 are fixed on two opposite inner walls of the housing 10. The sensitive coil 20 is arranged in the spring 30 and surrounded by the spring 30;

[0038] The sensitive coil 20 includes an elastic body 21 and a sensitive optical fiber 22 wound on the surface of the elastic body 21 ; the elastic body 21 is fixedly connected to the housing 10 ; and the spring 30 is fixedly connected to the middle area of ​​the elastic body 21 .

[0039] The housing 10 is the main support and protection structure of the fiber optic hydrophone. The sensitive coil 20 adopts a mandrel structure. The spring 30 adopts a damping spring, and the two ends of the spring 30 are fixed on the two opposite inner walls of the housing 10. The spring 30 is fixedly connected to the middle area of ​​the elastic body 21. The setting of the spring 30 can buffer external impact and achieve a good vibration isolation effect. The elastic body 21 is used to detect sound waves or pressure changes in water.

[0040] Specifically, the fiber optic hydrophone is in a static state, and the housing 10, the sensitive coil 20 (including the elastomer 21 and the sensitive optical fiber 22) and the spring 30 remain in their original state. The sensitive optical fiber 22 maintains a certain tension and shape on the elastomer 21. Under the action of the hydroacoustic signal, the elastomer 21 undergoes corresponding deformation, driving the optical fiber arm to deform, forming a sound pressure sensitive characteristic. When external vibration (acceleration) acts on the fiber optic hydrophone, the vibration will act on the housing 10. Since the elastomer 21 is fixedly connected to the housing 10, and the spring 30 is fixedly connected to the middle area of ​​the housing 10 and the elastomer 21, the spring 30 can have a good shock absorption effect, and the sensitive coil 20 is divided into two symmetrical parts, the vibration is transmitted to the elastomer 21, and under the action of the vibration, the upper and lower parts of the elastomer 21 will undergo opposite deformations, that is, a push-pull effect is formed. This deformation will cause the sensitive optical fiber 22 wrapped around the surface of the elastomer 21 to stretch or compress accordingly. In fact, the upper part is deformed and compressed, and the lower part is deformed and stretched. Since the middle part of the sensitive coil 20 is fixedly connected to the spring 30, that is, the spring 30 is fixedly connected to the middle area of ​​the elastic body 21, under the action of the spring 30, the deformation amounts of the upper and lower parts of the sensitive coil 20 are strictly conjugated, and the length changes of the upper and lower parts of the sensitive optical fiber 22 are offset, and the length of the sensitive optical fiber 22 will not change.

[0041] The fiber optic hydrophone provided by the embodiment of the present invention includes a housing 10, a sensitive coil 20 and a spring 30; the sensitive coil 20 and the spring 30 are both arranged in the housing 10, and the two ends of the spring 30 are fixed on two opposite inner walls of the housing 10, and the sensitive coil 20 is arranged in the spring 30 and surrounded by the spring 30; so that the spring 30 can buffer the external impact, reduce the vibration of the entire elastic body 21, and play a good vibration isolation effect. The sensitive coil 20 includes an elastomer 21 and a sensitive optical fiber 22 wound on the surface of the elastomer 21; the elastomer 21 is fixedly connected to the housing 10; and the spring 30 is fixedly connected to the middle area of ​​the elastomer 21. By fixing the elastomer 21 to the housing 10 and the spring 30 to the middle area 23 of the elastomer, the sensitive coil 20 is divided into two symmetrical parts, forming a push-pull effect. Under the action of vibration (acceleration), the vibration will be transmitted to the elastomer 21 through the shell 10, and the upper and lower parts of the elastomer 21 will undergo opposite deformations. The sensitive optical fiber 22 wrapped on the surface of the elastomer 21 will also undergo opposite deformations, with the upper part deforming in compression and the lower part deforming in tension. Since the middle part of the sensitive coil 20 is fixedly connected to the spring 30, and the spring 30 is fixedly connected to the middle area of ​​the elastomer 21, under the action of the spring 30, the deformation amounts of the upper and lower parts of the sensitive coil 20 are strictly conjugated, so that the length of the sensitive optical fiber 22 will not change under the action of acceleration, thereby reducing the sensitivity of the fiber optic hydrophone to acceleration and avoiding the effect of affecting the measurement of sound signals under the action of acceleration.

[0042] Optionally, two ends of the spring 30 are respectively fixed to the first surface and the second surface of the housing 10, and the first surface of the housing 10 is further provided with a rigid bracket 40, and the rigid bracket 40 is fixedly connected to the housing 10;

[0043] The rigid bracket 40 penetrates into the elastic body 21 to fix the elastic body 21 .

[0044] Specifically, the two ends of the spring 30 are respectively fixedly connected to the first surface and the second surface of the housing 10 by screws, and the first surface of the housing 10 is also provided with a rigid bracket 40. The rigid bracket 40 is fixedly connected to the first surface of the housing 10 by screws, and penetrates into the elastic body 21 to fix the elastic body 21. The elastic body 21 is fixed to the housing 10 more stably, the deformation of the elastic body 21 under the action of acceleration is reduced, and the acceleration sensitivity of the optical fiber hydrophone is further reduced.

[0045] Optionally, the elastomer 21 includes a first end 211, a first winding portion 212, a middle portion 213, a second winding portion 214 and a second end 215 which are connected in sequence along a direction from the first surface to the second surface. The sensitive optical fiber 22 is wound on the first winding portion 212 and the second winding portion 214. The dimensions of the first end 211, the middle portion 213 and the second winding portion 214 along a direction parallel to the first surface are larger than the dimensions of the first winding portion 212 and the second winding portion 214 along a direction parallel to the first surface. The middle portion 213 is fixedly connected to the spring 30.

[0046] Specifically, the sensitive optical fiber 22 is wound on the first winding part 212 and the second winding part 214, so that the optical fiber can more effectively sense the sound wave changes in the water. When there is a sound wave signal propagating underwater, the sound wave signal will act on the elastic body 21, especially the sensitive optical fiber 22 on the first winding part 212 and the second winding part 214. The deformation of the elastic body 21 caused by the sound wave signal will be captured by the sensitive optical fiber 22 and converted into a change in the optical signal in the optical fiber. The converted optical signal is transmitted to the signal processing system through the optical fiber for demodulation and analysis, so as to extract the sound wave information in the water. The dimensions of each part of the elastic body 21 are reasonably designed, especially the dimensions of the first end 211, the middle part 213 and the second winding part 214 along the direction parallel to the first surface are larger than the dimensions of the first winding part 212 and the second winding part 214 along the direction parallel to the first surface, which can better fix the sensitive coil 20, prevent the sensitive coil 20 from detaching from the elastic body 21, and prevent the length of the sensitive optical fiber 22 from changing significantly, thereby reducing the acceleration sensitivity of the optical fiber hydrophone.

[0047] Optionally, the first winding portion 212 and the first end portion 211 are symmetrical to the second winding portion 214 and the second end portion 215 relative to the middle portion 213 .

[0048] Specifically, the first winding portion 212 and the first end portion 211 are symmetrically designed relative to the middle portion 213 and the second winding portion 214 and the second end portion 215, so that the sensitive optical fiber 22 on the first winding portion 212 and the second winding portion 214 can receive the sound wave signal more evenly. The symmetrical structure can balance the force of the optical fiber hydrophone in all directions and reduce the structural instability factors caused by external interference.

[0049] Figure 4 FIG. 1 is a schematic diagram of the structure of another optical fiber hydrophone provided by an embodiment of the present invention. Figure 3 and Figure 4 , the fiber optic hydrophone further includes a fiber optic reflector 50, a fiber optic coupler 60 and a transition optical fiber 70;

[0050] The fiber reflector 50 and the fiber coupler 60 are both connected to the sensitive optical fiber 22 via a transition optical fiber 70;

[0051] The fiber reflector 50 , the fiber coupler 60 and the transition optical fiber 70 are fixed on the rigid support 40 .

[0052] Among them, the main function of the fiber optic reflector 50 is to reflect the optical signal. In the fiber optic hydrophone, the fiber optic reflector 50 is used to connect with one end of the sensitive coil 20 to form an optical closed loop. When the optical signal is emitted from the light source and enters the sensitive coil 20 through the fiber optic coupler 60, part of the optical signal will be reflected back to the sensitive coil 20 at the fiber optic reflector 50, interfering with the original optical signal. This interference effect is crucial to the sensitivity and working performance of the fiber optic hydrophone, because it can enhance the change of the optical signal, so as to respond to the acceleration stimulus more accurately. The fiber optic coupler 60 is responsible for effectively introducing and leading the optical signal into and out of the fiber optic hydrophone. The fiber optic coupler 60 acts as a bridge, connecting the light source, the fiber optic hydrophone and the photoelectric converter. Specifically, the fiber optic coupler 60 couples the optical signal from the light source into the sensitive coil 20, and at the same time couples the optical signal returned from the sensitive coil 20 into the photoelectric converter for subsequent signal processing and measurement. The performance of the fiber optic coupler 60 directly affects the transmission efficiency of the optical signal and the sensitivity of the fiber optic hydrophone. The transition fiber 70 connects the sensitive fiber 22 with the fiber reflector 50 and the fiber coupler 60, so that the optical signal can be efficiently transmitted between the optical fiber devices. Since the physical positions of different optical fiber devices may be different, the transition fiber can be used to compensate for these length differences to ensure that the optical signal can correctly reach the target optical fiber device.

[0053] Specifically, the fiber optic reflector 50 and the fiber optic coupler 60 are connected to the sensitive optical fiber 22 through the transition optical fiber 70; the fiber optic devices such as the fiber optic reflector 50, the fiber optic coupler 60 and the transition optical fiber 70 are fixed to the rigid bracket 40 by gluing, screwing, etc., thereby avoiding the structural unevenness caused by the fiber optic devices to the sensitive coil 20.

[0054] Optionally, the spring 30 is fixedly connected to the elastic body 21 by screws or an adhesive layer;

[0055] The spring 30 is rigidly fixed to the housing 10 by screws.

[0056] Specifically, the spring 30 is fixedly connected to the elastic body 21 by screws or an adhesive layer, and can withstand large external forces and vibrations, thereby ensuring the overall structural stability of the fiber optic hydrophone. The spring 30 is rigidly fixed to the housing 10 by screws. The design of screw connection makes it easy to disassemble and replace the various components of the fiber optic hydrophone. When a component fails or needs maintenance, it can be easily removed and repaired or replaced, reducing maintenance costs and time.

[0057] Optionally, the material of the elastic body 21 includes metal, nylon or polysulfone.

[0058] Specifically, the material of the elastomer 21 includes metal, nylon or polysulfone. Metal has high strength and rigidity, can withstand large stress and deformation, and ensure the stability and reliability of the fiber optic hydrophone in complex underwater environments. Metal has good thermal conductivity, which helps to dissipate heat quickly and avoid performance fluctuations caused by temperature changes. Some metals (such as stainless steel) have strong corrosion resistance and can be used for a long time in harsh environments such as the ocean without damage. Nylon material has low density and light weight, but has high strength, and is suitable for use in fiber optic hydrophone designs that need to reduce weight. Nylon has good wear resistance and can resist friction and wear in underwater environments, extending the service life of fiber optic hydrophones. Nylon is easy to process and shape, and can easily produce elastomer shapes that meet design requirements. Polysulfone material has high thermal stability, can maintain stable performance at high temperatures, and is suitable for use in high temperature environments such as deep sea. Polysulfone has good stability to a variety of chemical substances and can resist erosion by corrosive substances such as acids and alkalis. Polysulfone has high strength and toughness, can withstand certain external forces and vibrations, and ensures the stable performance of fiber optic hydrophones.

[0059] According to another aspect of the present invention, a method for adjusting a fiber optic hydrophone is provided, which is applied to the fiber optic hydrophone according to any embodiment of the present invention, and the method for adjusting comprises:

[0060] Fix the fiber optic hydrophone on the vibration table and measure its acceleration sensitivity. If the acceleration sensitivity exceeds the index value, increase or decrease the length of the sensitive coil until the acceleration sensitivity of the fiber optic hydrophone is less than or equal to the index value.

[0061] Among them, acceleration sensitivity is an important indicator to measure the response ability of fiber optic hydrophone to acceleration changes. The acceleration sensitivity of fiber optic hydrophone is defined as the change of optical signal under unit acceleration.

[0062] Specifically, the fiber optic hydrophone is fixed on a vibration table, and the vibration table is started to vibrate within the required frequency range, thereby applying acceleration stimulation to the fiber optic hydrophone. While applying the acceleration stimulation, the optical signal test system is used to measure the change of the output optical signal of the fiber optic hydrophone. According to the change of the output optical signal and the known acceleration stimulation value, the acceleration sensitivity of the fiber optic hydrophone is calculated. Exemplarily, if the calculated acceleration sensitivity exceeds the index value of -40dB rad / g, the 5cm transition optical fiber connected to the upper half of the sensitive coil is precisely wound around the upper half of the elastic body to make it a part of the sensitive coil. Its acceleration sensitivity is measured again until the acceleration sensitivity of the fiber optic hydrophone is less than or equal to the index value of -40dB rad / g.

[0063] Optionally, if the acceleration sensitivity value exceeds the index value, part of the transition optical fiber connected to the sensitive coil wound by the second winding part is wound onto the second winding part to increase the length of the sensitive coil, or part of the sensitive coil on the second winding part is loosened to convert it into a transition optical fiber.

[0064] Specifically, the part of the second winding part that was originally connected as the transition optical fiber can be wound onto the second winding part, thereby increasing the length of the sensitive coil; or part of the sensitive coil on the second winding part can be loosened to transform it into a transition optical fiber, thereby reducing the length of the sensitive coil. The acceleration sensitivity of the fiber optic hydrophone can be fine-tuned to achieve its index value. The principle is that by adjusting the length of the sensitive optical fiber tightly wound on the elastic body, the difference in the length change of the upper half of the sensitive coil and the lower half of the sensitive coil during the vibration process can be regularly adjusted to make it tend to zero. After the adjustment is completed, the transition optical fiber is wound on a rigid bracket and fixed with soft glue to improve its stability.

[0065] Optionally, after the portion of the transition optical fiber connected to the sensitive coil wound by the second winding part is wound around the second winding part to increase the length of the sensitive coil, if the acceleration sensitivity shows a decreasing trend, continue to wind the portion of the transition optical fiber around the second winding part to increase the length of the sensitive coil until the acceleration sensitivity of the fiber optic hydrophone is less than or equal to the index value.

[0066] Specifically, after the portion of the transition optical fiber connected to the sensitive coil wound by the second winding part is wound around the second winding part to increase the length of the sensitive coil, its acceleration sensitivity continues to be measured; if the acceleration sensitivity shows a decreasing trend, the portion of the transition optical fiber continues to be wound around the second winding part to increase the length of the sensitive coil, and its acceleration sensitivity is measured again until the acceleration sensitivity of the optical fiber hydrophone is less than or equal to the index value of -40dB rad / g.

[0067] Optionally, after loosening part of the sensitive coils on the second winding portion and converting them into transition optical fibers, if the acceleration sensitivity shows a decreasing trend, continue to loosen part of the sensitive coils on the second winding portion and convert them into transition optical fibers until the acceleration sensitivity of the optical fiber hydrophone is less than or equal to the index value.

[0068] Specifically, loosen some of the sensitive coils on the second winding part, convert them into transition optical fibers, and continue to measure their acceleration sensitivity. If the acceleration sensitivity shows a decreasing trend, continue to loosen some of the sensitive coils on the second winding part and convert them into transition optical fibers. This method is repeated with a step length of 2 cm of transition optical fiber until the acceleration sensitivity is reduced to below the index value of -40 dB rad / g.

[0069] The technical solution of the embodiment of the present invention is to obtain the acceleration stimulus value of the fiber optic hydrophone by fixing the fiber optic hydrophone on a vibration table. While applying the acceleration stimulus, the output optical signal change of the fiber optic hydrophone is measured using an optical signal test system. According to the change of the output optical signal and the known acceleration stimulus value, the acceleration sensitivity of the fiber optic hydrophone is calculated. If the calculated acceleration sensitivity exceeds the index value of -40dB rad / g, the part of the transition optical fiber connected to the sensitive coil wound by the second winding part is wound to the second winding part to increase the length of the sensitive coil, or the part of the sensitive coil on the second winding part is loosened to convert it into a transition optical fiber. After the part of the transition optical fiber connected to the sensitive coil wound by the second winding part is wound to the second winding part to increase the length of the sensitive coil, continue to measure its acceleration sensitivity. If the acceleration sensitivity shows a decreasing trend, continue to wind the part of the transition optical fiber to the second winding part to increase the length of the sensitive coil, and measure its acceleration sensitivity again until the acceleration sensitivity of the fiber optic hydrophone is less than or equal to the index value of -40dB rad / g. When part of the sensitive coil on the second winding part is loosened and converted into a transition optical fiber, its acceleration sensitivity is measured. If the acceleration sensitivity shows a decreasing trend, part of the sensitive coil on the second winding part is further loosened and converted into a transition optical fiber, and its acceleration sensitivity is measured again until the acceleration sensitivity decreases to below the index value of -40dB rad / g. By tightly winding a small section of transition optical fiber on an elastic body to become a sensitive optical fiber, or loosening a small section of sensitive optical fiber to become a transition optical fiber, the acceleration sensitivity of the optical fiber hydrophone can be flexibly and controllably adjusted, effectively reducing the acceleration sensitivity of the optical fiber hydrophone, and solving the batch consistency problem of the optical fiber hydrophone during the manufacturing process.

[0070] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0071] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fiber optic hydrophone, characterized in that: include: housing, sensitive coil and spring; The sensitive coil and the spring are both arranged in the shell, the two ends of the spring are fixed on two opposite inner walls of the shell, and the sensitive coil is arranged in the spring and surrounded by the spring; The sensitive coil comprises an elastic body and a sensitive optical fiber wound on the surface of the elastic body; the elastic body is fixedly connected to the shell; and the spring is fixedly connected to the middle area of ​​the elastic body.

2. The optical fiber hydrophone according to claim 1, characterized in that: The two ends of the spring are respectively fixed to the first surface and the second surface of the shell, and the first surface of the shell is also provided with a rigid bracket, and the rigid bracket is fixedly connected to the shell; The rigid bracket penetrates into the elastic body to fix the elastic body.

3. The optical fiber hydrophone according to claim 1, characterized in that: The elastic body includes a first end portion, a first winding portion, a middle portion, a second winding portion, and a second end portion which are sequentially connected along a direction from the first surface to the second surface. The sensitive optical fiber is wound on the first winding portion and the second winding portion. The dimensions of the first end portion, the middle portion, and the second winding portion along a direction parallel to the first surface are greater than the dimensions of the first winding portion and the second winding portion along a direction parallel to the first surface. The middle portion is fixedly connected to the spring.

4. The optical fiber hydrophone according to claim 3, characterized in that: The first winding portion and the first end portion are symmetrical to the second winding portion and the second end portion with respect to the middle portion.

5. The optical fiber hydrophone according to claim 2, characterized in that: The fiber optic hydrophone also includes a fiber optic reflector, a fiber optic coupler and a transition fiber; The fiber reflector and the fiber coupler are both connected to the sensitive optical fiber via a transition optical fiber; The optical fiber reflector, the optical fiber coupler and the transition optical fiber are fixed on the rigid bracket.

6. The optical fiber hydrophone according to claim 1, characterized in that: The spring is fixedly connected to the elastic body via screws or an adhesive layer; The spring is rigidly fixed to the housing via screws.

7. The optical fiber hydrophone according to claim 1, characterized in that: The material of the elastic body includes metal, nylon or polysulfone.

8. A method for adjusting a fiber optic hydrophone, characterized in that: Applied to the optical fiber hydrophone according to any one of claims 1 to 7, the adjustment method comprises: Fix the fiber optic hydrophone on the vibration table and measure its acceleration sensitivity. If the acceleration sensitivity exceeds the index value, increase or decrease the length of the sensitive coil until the acceleration sensitivity of the fiber optic hydrophone is less than or equal to the index value.

9. The method for adjusting the optical fiber hydrophone according to claim 8, characterized in that: If the acceleration sensitivity exceeds the index value, increase or decrease the length of the sensitive coil until the acceleration sensitivity of the fiber optic hydrophone is less than or equal to the index value, including: If the acceleration sensitivity value exceeds the index value, part of the transition optical fiber connected to the sensitive coil wound on the second winding part is wound onto the second winding part to increase the length of the sensitive coil, or part of the sensitive coil on the second winding part is loosened to convert it into a transition optical fiber.

10. The method for adjusting the optical fiber hydrophone according to claim 9, characterized in that: After winding a portion of the transition optical fiber connected to the sensitive coil wound by the second winding part into the second winding part to increase the length of the sensitive coil, if the acceleration sensitivity shows a decreasing trend, continue to wind the portion of the transition optical fiber into the second winding part to increase the length of the sensitive coil until the acceleration sensitivity of the optical fiber hydrophone is less than or equal to the index value; After loosening part of the sensitive coil on the second winding part and converting it into a transition optical fiber, if the acceleration sensitivity shows a decreasing trend, continue to loosen part of the sensitive coil on the second winding part and convert it into a transition optical fiber until the acceleration sensitivity of the optical fiber hydrophone is less than or equal to the index value.

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