CN114114282A

CN114114282A - Unit linear array and full-distributed optical fiber sonar linear array comprising same

Info

Publication number: CN114114282A
Application number: CN202210080041.0A
Authority: CN
Inventors: 严国锋; 王忠新; 张敏行; 饶云江
Original assignee: Zhejiang Lab
Current assignee: Zhejiang Lab
Priority date: 2022-01-24
Filing date: 2022-01-24
Publication date: 2022-03-01

Abstract

The invention discloses a unit linear array and a fully distributed optical fiber sonar linear array containing the same, wherein the unit linear array comprises: a tube body with two sealed ends; a support structure disposed within the tube; the distributed acoustic sensing unit is formed by continuously sensitizing and winding optical fibers on a single elastic body, optical fiber allowance is reserved at two ends, and the two ends are connected with the two ends of the tube body after penetrating through the supporting structure and are not contacted with the side wall of the tube body; and the acoustic impedance matching material is filled in the tube body. The fully distributed optical fiber sonar linear array is formed by sequentially connecting a plurality of the unit linear arrays. The linear array has the characteristics of simple structure without welding points, good consistency, continuously adjustable sensitivity and spatial resolution of the equivalent underwater acoustic sensing unit and the like.

Description

Unit linear array and full-distributed optical fiber sonar linear array comprising same

Technical Field

The application relates to the technical field of optical fiber sonar, in particular to a unit linear array and a fully-distributed optical fiber sonar linear array comprising the same.

Background

The optical fiber hydrophone has the advantages of high sensitivity, seawater corrosion resistance, electric leakage prevention, electromagnetic interference resistance and the like, and is rapidly developed in recent years. Fiber sonar arrays are becoming the focus of research in various countries, and oil-filled and solid-state cabling designs have been proposed in succession. The principle is that point-mode optical fiber hydrophone units are multiplexed and demodulated in a time division, wavelength division, frequency division and other modes, and finally a large-scale array is formed through cabling design. However, the multi-point multiplexing mode has capacity limitation, each unit node in the sensing network also has crosstalk risk, and once the current networking design is completed, the array solidification cannot be adjusted. Different networking modes also have high requirements on each networking unit in the aspects of time delay, working wavelength, consistency and the like.

Publication No. CN106546971A discloses a solid-state towed sonar linear array and an assembly method thereof, and provides a typical towed sonar linear array structure, so that the sonar array formed by discrete underwater acoustic sensing units has relatively complex cabled sensing unit structure, needs precise design and welding of different optical devices, and has high preparation process difficulty and poor reliability. In a specific underwater acoustic sensing application, in order to meet the subsequent array signal processing requirement, time and space synchronization is required between each sensing unit, and the complexity of the system is further increased.

In general, the existing optical fiber sonar linear array has technical challenges and bottleneck limitations in the aspects of optical fiber hydrophone unit performance, large-scale networking and signal synchronization.

Disclosure of Invention

In view of this, an object of the embodiments of the present application is to provide a unit linear array and a fully-distributed optical fiber sonar linear array including the unit linear array, where the unit linear array has the characteristics of simple structure without welding points, good consistency, continuously adjustable sensitivity and spatial resolution of equivalent underwater acoustic sensing units, and the like.

According to a first aspect of the embodiments of the present application, there is provided a unit linear array, including:

a tube body with two sealed ends;

a support structure disposed within the tube;

the distributed acoustic sensing unit is formed by continuously sensitizing and winding optical fibers on a single elastic body, optical fiber allowance is reserved at two ends, and the two ends are connected with the two ends of the tube body after penetrating through the supporting structure and are not contacted with the side wall of the tube body; and

and the acoustic impedance matching material is filled in the tube body.

Further, the body includes:

a PU pipe;

and the two sealing plug cores are respectively and hermetically arranged at two ends of the PU pipe.

Further, the support structure comprises:

the hollow frameworks are placed in the pipe body, every two adjacent hollow frameworks are fixedly connected through a Kevlar rope, and the hollow frameworks at the two ends are fixedly connected with the end part of the pipe body at the end through the Kevlar rope.

Further, the PU pipe and the sealing plug core are sealed through nesting and buckling.

Furthermore, a plurality of the hollow frameworks are arranged in the pipe body at equal intervals.

Furthermore, the Kevlar cord is connected with each hollow framework through a fixing hole on the outer side of each hollow framework and is fixed in the pipe body in a buckling locking mode.

Further, the acoustic impedance matching material is silicone oil or liquid glue.

Further, still include:

and the two ends of the optical fiber of the distributed acoustic sensing unit are respectively connected with the pair of watertight joints.

According to the second aspect of the embodiment of the application, a fully-distributed optical fiber sonar linear array is provided, which is formed by sequentially connecting a plurality of unit linear arrays according to the first aspect.

The technical scheme provided by the embodiment of the application can have the following beneficial effects:

according to the embodiment, the distributed acoustic sensing unit is formed by continuously sensitizing and winding optical fibers on a single elastic body, and the optical fiber margins are reserved at two ends of the distributed acoustic sensing unit.

The distributed acoustic sensing unit is formed by continuously sensitizing and winding optical fibers on a single elastic body, optical fiber margins are reserved at two ends of the distributed acoustic sensing unit, the distributed acoustic sensing unit is formed by one-step winding, any optical device does not need to be welded in the whole process, the process is controllable, the assembly process is simple, the operability is high, and standardized production can be realized; the linear array units are flexibly assembled through the design of mutual connection of the sealing joints, and different linear arrays can be conveniently combined according to the detection aperture requirement.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application.

Fig. 1 is a schematic structural diagram of a unit linear array according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a fully-distributed optical fiber sonar linear array provided in an embodiment of the present invention.

Fig. 3 is an array spatial correlation of a fully-distributed optical fiber hydrophone array provided in an embodiment of the present invention.

Fig. 4 is a frequency response diagram of a fully-distributed optical fiber hydrophone linear array provided in the embodiment of the present invention.

Wherein, 1, sealing the plugging core; 2. a distributed acoustic sensing unit; 3. a Kevlar cord; 4. an empty skeleton; 5. filling glue holes; 6. a silicone oil; 7. a PU pipe; 8. a watertight joint; 9. clamping a hoop; 10. a unit linear array; 11. a watertight jumper wire; 12. and (5) connecting the clamp.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

It is to be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present application. The word "if" as used herein may be interpreted as "at … …" or "when … …" or "in response to a determination", depending on the context.

As shown in fig. 1 and fig. 2, an embodiment of the present application provides a unit linear array 10, which may include: the acoustic impedance matching device comprises a pipe body with two sealed ends, a supporting structure, a distributed acoustic sensing unit and an acoustic impedance matching material.

Two ends of the tube body are sealed to form a closed cavity. Specifically, the body includes: PU pipe 7 and sealed stifled core 1, two sealed stifled core 1 is respectively seal installation in the both ends of PU pipe 7. For sealing the filled acoustic impedance matching material 6 and for leading out the optical fiber on the distributed acoustic sensing unit 2.

The PU pipe 7 and the sealing plugging core 1 are sealed through nesting and buckling. The PU tube 7 in this example had an inner diameter of 39mm and an outer diameter of 45 mm.

The support structure is arranged in the pipe body and mainly plays a role in supporting the distributed acoustic sensing unit 2.

Specifically, the support structure includes: the hollow frameworks 4 are placed in the pipe body, every two adjacent hollow frameworks 4 are fixedly connected through the Kevlar ropes 3, the hollow frameworks 4 at the two ends are fixedly connected with the end part of the pipe body at the end through the Kevlar ropes 3, and therefore a force bearing structure of an integral linear array is formed and is used for bearing axial tension load.

Furthermore, a plurality of the hollow frameworks 4 are arranged in the pipe body at equal intervals, so that the mechanical strength of the linear arrays is guaranteed, meanwhile, the weight and the acoustic coupling loss are reduced, the interval depends on the width of the hollow frameworks 4 and the requirement of the overall rigidity of the linear arrays, the width of the hollow frameworks 44 in the embodiment is 5cm, and the interval is 20 cm.

And a fixing hole for the Kevlar rope 3 to pass through, an oil through hole and a central through hole for the distributed acoustic sensing unit 2 to pass through are formed in the outer side of the hollow framework 4, so that the acoustic unit is supported, and meanwhile, the distributed acoustic sensing unit 2 is prevented from contacting with the inner wall of the PU pipe 7 when the continuous linear array is bent. The hollow frame 4 can be made of alloy and resin materials according to the requirements of linear array mechanical strength and density.

Non-acoustic sensors such as a gyroscope, a pressure vertical meter and the like can also be installed inside the hollow framework 4 for sensing the postures of the linear arrays.

Furthermore, the Kevlar cord 3 is connected with each hollow frame 4 through a fixing hole on the outer side of the hollow frame 4, is fixed on the sealing plug cores 1 at two ends of the PU pipe 7 in a buckling locking mode, bears the tensile force borne by the whole linear array, and prevents the hollow frame 4 and the PU pipe 7 from generating relative displacement.

The Kevlar cord 3 is fastened through a fixing hole at the outer side of each hollow framework 4 and is subjected to glue dispensing treatment, is fixedly connected with each hollow framework 4, is locked with the sealing plug core 1 through a buckle and is subjected to glue dispensing and sealing, and is guaranteed not to be loosened when tension is received. The diameter and the number of the Kevlar 3 are designed according to the stress requirement of the integral linear array, 5-10 times of allowance is reserved, and the Kevlar 3 in the embodiment has the diameter of 4mm and the number of 4.

Distributed acoustic sensing unit 2 is formed by optic fibre continuous sensitization coiling on single elastomer, and the optic fibre surplus is left at both ends for the preparation and the connection of 8 lock pins of watertight joint, realize that whole full distributed optic fibre sonar linear array does not have the melting point, and overall structure is simple reliable. Distributed acoustic sensing unit 2 both ends are passed behind the bearing structure with the both ends of body link to each other, specifically, both ends are passed behind the bearing structure, insert in the sealed stifled core 1 at the both ends of body, but both non-fixed connection, and with the lateral wall of body also does not contact, avoid on stress transmission on the optical cable distributed acoustic sensing unit 2, influence the acoustic wave detection performance.

Sound wave detection realized based on phase sensitive light time domain reflection technology, and sound pressure sensitivity of unit winding length

Can be expressed as:

re：1rad/μPa/m

wherein n is the equivalent refractive index of the optical fiber, P is the sound pressure acting on the linear array, and lambda is the wavelength of the optical signal,

is the displacement change of the elastic body under the action of sound wave, r is the radius of the elastic body,

is the length of the elastomer and L is the length of the wound fiber.

It can be seen that the acoustic sensing unit sensitivity per unit length is related to the length of the wound fiber. Theoretically, the denser the fiber winding on the elastomer, the higher the acoustic sensitivity. Therefore, the underwater acoustic wave detection sensitivity and the spatial resolution can be dynamically adjusted by adopting a complete close winding mode (the optical fiber spacing approaches to 0, and coating layers are arranged closely) and combining the detection optical signal pulse width adjustment and different spacing sampling signal processing methods.

The elastic body is used for enhancing the sensing sensitivity of the optical fiber to sound waves, and materials with proper elastic modulus and Poisson ratio are selected according to different detection frequencies and sensitivity indexes. In the embodiment, the elastomer is made of a TPU material with Young modulus of 304 MPa and Poisson's ratio of 0.3, and the diameter of the elastomer material is 15mm for increasing sound pressure sensitivity and facilitating use. The sensitivity of the acoustic sensing unit with unit length is related to the winding length of the optical fiber, in the embodiment, the winding of the optical fiber adopts 1mm turn pitch, the optical fiber is uniformly and densely wound, and the overall sensitivity can reach-146 dB/rad/mu Pa/m.

The acoustic impedance matching material is filled in the pipe body, specifically, the acoustic impedance matching material is silicone oil 6 or liquid glue, so that the matching of the linear array impedance and the seawater impedance is realized, and the acoustic coupling is facilitated; meanwhile, the density of the filled material is selected and the pressure of filling is controlled, so that the whole density of the linear array can be adjusted, the linear array is close to seawater, and the distribution depth control during towing application is facilitated.

In this example, the PU pipe 7 is filled with silicone oil 6, so as to realize matching of linear array impedance and seawater impedance, and facilitate acoustic coupling; since the silicone oil 6 has a lower density than water, the filling amount of the silicone oil 6 varies at different filling pressures. Therefore, the overall density of the linear array can be adjusted through filling pressure control, so that the linear array is close to seawater, and the distribution depth control during towing application is facilitated. In this example, silicone oil 6 having a density of 0.95 g/cm was used³The filling pressure is 0.4 MPa.

In order to read a linear array signal, an embodiment of the present application provides a unit linear array 10, which further includes: and the two ends of the optical fiber of the distributed acoustic sensing unit 2 are respectively connected with the two watertight joints 8, so that signal output is realized, and interconnection among different linear array units is facilitated.

Specifically, be equipped with watertight joint 8 on sealed stifled core 1, the optical fiber that winds on the acoustics sensing unit closely possesses sensing and main communication function, with watertight joint 8 is connected, realizes interconnection and signal transmission between the different unit array.

Particularly, the watertight joint 8 is not limited to output interconnection of optical fiber signals, and when a non-acoustic sensor is integrated in the hollow framework 4, signals can be output and interconnected through the photoelectric composite joint design of the watertight joint 8.

The embodiment of the application also provides a fully-distributed optical fiber sonar linear array, which is formed by sequentially connecting a plurality of the unit linear arrays 10. Specifically, the fully distributed optical fiber sonar linear array can be formed by connecting and combining a plurality of unit linear arrays 10 through watertight joints 8 and hoops 9 according to the actual requirements on the aperture of the linear array.

As shown in fig. 1 and 2, the steps of assembling and composing the unit linear arrays 10 into the fully distributed optical fiber sonar linear arrays are as follows:

a. the empty frameworks 4 are placed at a set distance of 20cm, fastened with the Kevlar ropes 3 according to the set distance, and fixed by dispensing;

b. the distributed acoustic sensing units 2 penetrate through the central through hole of each hollow framework 4, and two ends of each distributed acoustic sensing unit are fixed on the sealing plug core 1;

c. the root Kevlar rope 3 is locked with the sealing plug cores 1 at the two ends through screws and is subjected to glue dispensing treatment to complete fixed connection;

d. the distributed acoustic sensing unit 2 is reserved with an optical fiber, inserted into the ceramic ferrule in the watertight connector 8 and fixed by dispensing;

e. the assembly of the watertight joint 8 and the sealing plug core 1 is completed;

f. placing the bare array empty skeleton 4, the distributed acoustic sensing units 2, the watertight joints 8 and the sealing and plugging cores 1 into a PU pipe 7, nesting the sealing and plugging cores 1 at two ends with the PU pipe 7, and buckling and sealing through a hoop 9;

g. filling silicone oil 6 into the PU pipe 7 through a glue filling hole 5 on the side surface of the sealing plug core 1, keeping the filling pressure at 0.4 Mpa, and sealing the glue filling hole 5 to form a linear array unit;

h. a plurality of linear array units are connected through a watertight jumper 11 and a connection hoop 12 to form a final fully-distributed optical fiber sonar linear array.

Based on the linear array parameter design in the above embodiment, a linear array signal under the excitation of 200-and 600-Hz chirped sound wave is measured by using a phase sensitive optical time domain technique, and the data of the 430-th sampling channel and 600 sampling channels of the whole linear array are subjected to correlation analysis, the spatial correlation of the array in this embodiment is shown in fig. 3, it can be seen that, except that the channel adjacent to the 430 channel can maintain the correlation of more than 0.9, the correlation coefficients of the rest channels can also be maintained at about 0.8, so that the good array spatial correlation is reflected, and the array signal processing such as subsequent beam synthesis is facilitated. The lake test acoustic frequency response calibration of 50-800Hz is carried out on the linear array of the embodiment, and the mean square error curve of the frequency response of different channels is shown in FIG. 4. It can be seen that the average value of the acoustic sensitivity of the linear array of the embodiment with different frequencies is-146 dB/rad/mu Pa/m, and the upper and lower average fluctuation is about 2dB, so that the linear array shows better response flatness. Meanwhile, the mean square deviation of the frequency responses of different channels is smaller than 1dB, which shows that the linear array has good frequency response consistency at different spatial positions.

The unit linear array 10 and the fully-distributed optical fiber oil-filled sonar linear array adopting the technical scheme have the following remarkable advantages:

1) the fully-distributed optical fiber sonar linear array provided by the invention adopts the design of a distributed acoustic sensing unit 2, and an optical fiber is continuously wound on a single elastic body to form a fully-distributed sensing array. Compared with the traditional linear array scheme of firstly completing preparation of a batch of point type sensing units and then forming an array by networking, the method does not need complex networking light path design and a large number of device connections, and has the characteristics of good consistency, simple structure and high reliability.

2) The fully-distributed optical fiber sonar linear array provided by the invention is filled with silicon oil 6 as an acoustic impedance matching material, and compared with a solid optical cable prepared in an extrusion molding mode, the fully-distributed optical fiber sonar linear array not only can be better matched with seawater impedance and reduce acoustic coupling loss, but also can be used for conveniently adjusting the overall density of linear array units through filling pressure control so as to adapt to arrangement of different towing depths.

3) The fully-distributed optical fiber sonar linear array provided by the invention is based on the phase-sensitive optical time domain reflection sensing principle, is oriented to the design requirement of aperture adjustability, can meet the dynamic adjustment requirements on the detection sensitivity and the spatial resolution of signals of different underwater targets and different frequency bands by a detection optical signal pulse width adjustment and different-interval sampling signal processing method, can realize underwater acoustic sensing with small track pitch and high sensitivity compared with the traditional linear array, and has strong system adaptability and application flexibility.

4) According to the assembling method provided by the invention, the distributed acoustic sensing unit 2 is formed by one-time winding, any optical device is not required to be welded in the whole process, the process is controllable, the assembling process is simple, the operability is strong, and standardized production can be realized; the linear array units are flexibly assembled through the design of mutual connection of the sealing joints, and different linear arrays can be conveniently combined according to the detection aperture requirement.

The embodiments and specific implementation modes of the fully-distributed optical fiber sonar linear array and the assembling method thereof provided by the invention are described above. It is to be understood that the invention is not limited to the precise arrangements and instrumentalities shown, and that various modifications, equivalent alterations, and improvements, which are within the spirit and scope of the invention, are intended to be covered by the appended claims.

Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.

It will be understood that the present application is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims

1. A linear array of elements, comprising:

a tube body with two sealed ends;

a support structure disposed within the tube;

and the acoustic impedance matching material is filled in the tube body.

2. A unitary linear array as claimed in claim 1 wherein said tubular body comprises:

a PU pipe;

3. The linear array of units of claim 1, wherein the support structure comprises:

4. The linear array of elements of claim 2, wherein the PU tube and the sealing plug are sealed by nesting crimping.

5. A linear array of elements as claimed in claim 3, wherein a plurality of said hollow bodies are arranged in said tubular body at equal intervals.

6. The linear array of units of claim 3, wherein the Kevlar cord is connected with each empty skeleton through a fixing hole at the outer side of the empty skeleton and is fixed in the tube body in a buckling and locking manner.

7. A linear array of elements as claimed in claim 1, wherein the acoustic impedance matching material is silicone oil or liquid glue.

8. The linear array of units of claim 1, further comprising:

9. A fully distributed optical fiber sonar linear array, characterized in that, the fully distributed optical fiber sonar linear array is formed by connecting a plurality of unit linear arrays of any one of claims 1-8 in proper order.