Water-land integrated micro-disturbance sensing optical cable

Abstract

The application discloses a water-land integrated micro-disturbance sensing optical cable, which comprises a ground-listening optical cable, water-listening sensing elements, weak reflectivity gratings, a sheath and a cable core. The water-listening sensing elements are sleeved on the cable core at intervals, the ground-listening optical cable passes through the water-listening sensing elements and is fixed on the cable core in the axial direction, the weak reflectivity gratings are arranged at one end of the water-listening sensing elements, and the sheath is wrapped on the outermost layer. The water-land integrated micro-disturbance sensing optical cable combines the vibration measurement function with the underwater acoustic measurement function, forms an integrated sensing optical cable structure, and can realize the sensing of signals of various frequency bands such as extremely low frequency, low frequency, medium frequency, high frequency and ultrahigh frequency by using one optical cable, is suitable for independent or synchronous monitoring of water-body and land vibration signals and underwater acoustic signals, and can also be used for distributed sensing of strain and temperature. The micro-disturbance sensing optical cable has rich measurement parameters, a wide frequency band, high sensitivity, strong anti-interference capability, and has a very high cost performance and a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical fiber sensing and underwater target monitoring, and specifically relates to a water-land integrated micro-disturbance sensing optical cable. BACKGROUND

[0002] With the development of optical fiber technology and optical fiber communication technology, optical fiber sensing technology as a new type of sensing technology has been gradually widely applied in the measurement and monitoring of physical quantities such as temperature, strain, electric field, magnetic field, etc. The distributed optical fiber micro-disturbance sensing system utilizes the characteristics of the changes in intensity, phase, frequency, polarization state, etc. of the light wave generated by the light signal in the measured optical fiber under the influence of external micro-disturbance to monitor and locate vibration information. Distributed optical fiber micro-disturbance sensing utilizes optical cable as a sensor, intelligently analyzes and pattern recognizes the signal characteristics of micro-disturbance events through digital signal processing, and improves the event monitoring accuracy.

[0003] The distributed optical fiber micro-disturbance sensing technology has two application scenarios. One is to monitor underwater vibration signals such as marine biological activities, ship navigation, etc. underwater acoustic signals, which are generally realized by a hydrophone. The types of hydrophones mainly include piezoelectric hydrophones and optical fiber hydrophones. The piezoelectric hydrophone belongs to a traditional hydrophone, which is limited by the electric sensing characteristics of the piezoelectric underwater acoustic sensor. The optical fiber hydrophone has advantages such as anti-electromagnetic interference and corrosion resistance, and has a broad application space. There are various types of optical fiber hydrophones, which can be divided into intensity type, polarization type and phase interference type according to the sensing principle. The intensity type and polarization type hydrophones have low demodulation sensitivity and are not suitable for array, so there are fewer research and application cases. The phase interference type hydrophone is based on the principle of an optical interferometer and can be divided into various physical structures, such as optical fiber hydrophones based on Mach-Zehnder, Michelson, Fabry-Perot and Sagnac fiber interferometers and hydrophones based on fiber grating reflection. Among them, the first four are mainly probe structure hydrophones, which have weak multiplexing and cannot be large-scale arrayed, while the optical fiber grating hydrophone can be large-scale arrayed, but its sensitivity can be further improved through structure sensitization and material sensitization.

[0004] The other application scenario of the distributed optical fiber micro-disturbance sensing technology is to monitor underwater vibrations such as submarine earthquakes and plate movements and various vibration signals on land such as traffic activities and pipeline leaks, etc. Such signals are monitored by a ground listening optical cable. A general underground communication optical cable can also serve as a ground listening optical cable. It is usually buried underground and its laying methods include direct burial, pipeline laying and tunnel laying, etc. Compared with the traditional overhead optical cable, the ground listening optical cable is not easily affected by bad weather and other external factors, and has higher safety and reliability. However, since it is mainly used for communication, the structure of the optical cable is difficult to adapt to the monitoring of various types of micro-disturbance signals, and cannot well meet the monitoring requirements of strong durability, multiple parameters and high sensitivity in terms of fiber core types, laying methods and mechanical strength, etc. SUMMARY

[0005] The present application aims at the deficiencies of the prior art, and provides a water-land integrated micro-disturbance sensing optical cable, which is a multi-core and high mechanical strength multifunctional sensing optical cable, and realizes water-land integrated monitoring of various micro-disturbance signals through a core shaft type fiber grating hydrophone linear array.

[0006] To achieve the above-mentioned application purposes, the water-land integrated micro-disturbance sensing optical cable comprises a ground listening optical cable, a hydrophone sensing element, a sheath and a cable core.

[0007] Further, the ground listening optical cable comprises loose-jacketed multimode optical fibers, loose-jacketed single-mode optical fibers and tight-jacketed single-mode optical fibers.

[0008] Further, the core shaft comprises an elastic sensitizing layer, an air layer and a rigid shaft, and the weak grating array optical fiber is tightly and single-layered wound on the outer wall of the core shaft.

[0009] Further, the hydrophone sensing element is a hollow structure, and further comprises a fixing device.

[0010] Further, the weak grating array fiber (201) includes a first part and a second part, the first part of the weak grating array fiber (201) is wound on a mandrel, and the second part of the weak grating array fiber is fixed to the outer wall of the cable core in the axial direction.

[0011] Another improvement, the weak grating array fiber is fused with the loose sleeve single-mode optical fiber at both ends of the hydrophone sensing element, and the signal is transmitted by using the geophone cable.

[0012] Further, the cable core is composed of a steel strand and a hard plastic layer, the hard plastic layer wraps the steel strand, and the geophone cable and the weak grating array fiber are fixed on the hard plastic layer.

[0013] Further, the sheath is made of waterproof and sound-transmitting high polymer material, and is wrapped outside the geophone cable and the hydrophone sensing element.

[0014] The water-land integrated micro-disturbance sensing optical cable disclosed in the application combines the vibration measurement function and the underwater acoustic measurement function to form an integrated sensing optical cable structure, but the combination is not a simple connection of the optical fiber hydrophone and the geophone cable, but a new type of optical cable structure and material type, which can meet the miniaturization and light weight requirements of the sensor by controlling the structure size, can realize sensing of various signals of different frequency bands such as extremely low frequency, low frequency, medium frequency, high frequency and ultrahigh frequency by using one optical cable, is suitable for independent or synchronous monitoring of water body and land vibration signals and underwater acoustic signals, and can also be used for distributed sensing of strain and temperature. The micro-disturbance sensing optical cable has the advantages of rich measurement parameters, wide frequency band, high sensitivity, strong anti-interference ability, good economy, high cost performance and wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a structure schematic view of a water-land integrated micro-disturbance sensing optical cable in an embodiment of the application;

[0016] Figure 2 is a transverse sectional view of a geophone cable in an embodiment of the application;

[0017] Figure 3 is a combination structure of a hydrophone sensing element and a cable core in an embodiment of the application;

[0018] Figure 4 is a transverse sectional view of a hydrophone sensing element in an embodiment of the application.

[0019] Wherein: 1 - ground listening optical cable, 101 - loose multi-mode optical fiber, 102 - loose single-mode optical fiber, 103 - tight single-mode optical fiber, 2 - hydrophone sensing element, 201 - weak light grating array optical fiber, 202 - elastic sensitive layer, 203 - air layer, 204 - rigid shaft, 205 - fixing device, 3 - weak reflectivity grating, 4 - sheath, 5 - cable core, 501 - steel strand, 502 - hard plastic layer. DETAILED DESCRIPTION

[0020] The water-land integrated micro-disturbance sensing optical cable provided by the present application will be described in detail below with reference to the drawings. In the description of the present application, it should be understood that the terms "left side", "right side", "upper part", "lower part", "bottom" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and "A", "B", "C" and the like do not represent the importance of the parts, and therefore cannot be understood as limiting the present application. The specific dimensions used in the present embodiment are only for the purpose of illustrating the technical solutions and do not limit the protection scope of the present application.

[0021] As shown in Figure 1 , the embodiment of the present application provides a water-land integrated micro-disturbance sensing optical cable, which comprises a ground listening optical cable 1, a hydrophone sensing element 2, a sheath 4 and a cable core 5. A plurality of hydrophone sensing elements 2 are sleeved on the cable core 5 at a certain distance, and the ground listening optical cable 1 passes through the hydrophone sensing element 2 and is fixed on the cable core 5 in the axial direction. A weak reflectivity grating 3 is arranged at one end of the hydrophone sensing element 2. The hydrophone sensing element 2 comprises a mandrel and a weak light grating array optical fiber 201, a first part of the weak light grating array optical fiber 201 is wound around the mandrel, and a second part (a part exceeding the length of the hydrophone sensing element 2) of the weak light grating array optical fiber 201 is fixed on the cable core 5; a weak reflectivity grating 3 is inscribed on the weak light grating array optical fiber 201 at a certain interval; the weak reflectivity grating 3 is arranged outside one end of the hydrophone sensing element 2; and the weak reflectivity grating 3 is always in a stress-free state.

[0022] The sheath 4 is wrapped on the outermost layer, specifically, the sheath 4 is made of waterproof and sound-transmitting high polymer material, which ensures accurate perception of underwater acoustic signals, and the sheath is wrapped outside the ground listening optical cable 1 and the hydrophone sensing element 2. Typical high polymer sheath material 4 includes polycarbonate, polystyrene, polystyrene sulfonic acid, etc.

[0023] As shown in Figure 2As shown, the geoacoustic cable 1 includes loose-tube multimode optical fiber 101, loose-tube single-mode optical fiber 102 and tight-tube single-mode optical fiber 103 for sensing strain, temperature and vibration signals. The loose-tube multimode optical fiber 101, the loose-tube single-mode optical fiber 102 and the tight-tube single-mode optical fiber 103 are fixed axially at certain intervals on the outer wall of the cable core 5 and run through the entire sensing optical cable. Preferably, the sensing optical fibers constituting the geoacoustic cable 1 are fixed symmetrically and at equal intervals on the outer wall of the cable core 5. As shown in Figure 3 As shown, the cable core 5 is composed of a steel strand 501 and a hard plastic layer 502, the hard plastic layer 502 wrapping the steel strand 501 and the optical fibers being fixed on the hard plastic layer 502. The hard plastic layer 502 is formed by wrapping a layer of hard plastic material on the outer surface of a steel strand of a certain diameter, and the outer surface is smooth and flat. Typically, polyamide, high-density polystyrene, polytetrafluoroethylene and the like can be used. The steel strand can ensure that the optical cable has sufficient mechanical strength. The steel strand should have good corrosion resistance.

[0024] As shown in Figure 3 and 4 The core shaft of the hydroacoustic sensing element 2 includes an elastic sensitizing layer 202, an air layer 203 and a rigid shaft 204, and the hydroacoustic sensing element 2 further includes a fixing device 205. The weak grating array optical fiber 201 is tightly and in a single layer wound on the outer wall of the core shaft. The rigid shaft 204 is made of a rigid material such as stainless steel, copper, aluminum and the like, and the two ends of the rigid shaft 204 are protruding, providing support for the elastic sensitizing layer 202 and forming an air cavity between the rigid shaft 204 and the elastic sensitizing layer 202 to serve as the air layer 203. The elastic sensitizing layer 202 is made of a material with low elastic modulus and Poisson's ratio, and the two ends of the elastic sensitizing layer 202 are protruding to improve the sound pressure sensitivity.

[0025] The geoacoustic cable 1 passes through the central through hole of the hydroacoustic sensing element 2 in sequence, and the fixing device 205 fixes the hydroacoustic sensing element 2 on the geoacoustic cable 1 at a certain interval to form a hydrophone linear array with different frequency bands. The hydrophone linear array can be located at both ends, in the middle or at any section of the sensing optical cable, or can be distributed throughout the sensing optical cable.

[0026] The weak grating array fiber 201 is a complete fiber, a first part of the weak grating array fiber 201 is wound on the mandrel, and a second part (a part exceeding the length of the hydrophone sensing element 2) of the weak grating array fiber 201 is fixed on the cable core 5. The scheme has the advantages of less fusion points, low optical loss, high signal-to-noise ratio, no need to consider the protection of the fusion points, high degree of automation in processing and manufacturing, and easy formation of a large-scale hydrophone linear array. However, the scheme needs to write the weak reflectivity grating 3 at the corresponding position according to the length of the fiber wound on the mandrel and the length of the second part fixed on the cable core 5 (i.e. the spacing of the hydrophone sensing element 2), to form a complete weak grating array fiber 201, which causes the processing and manufacturing process of the weak grating array fiber 201 and the perturbation sensing optical cable to be relatively complex. Alternatively, the first part of the weak grating array fiber 201 is wound on the hydrophone sensing element 2, the weak reflectivity grating 3 is arranged outside one end of the hydrophone sensing element 2, and the weak grating array fiber 201 is fused with the loose-tube single-mode optical fiber 102 of the hydrophone cable 1, that is, the weak grating array fiber 201 wound on each hydrophone sensing element 2 is fused with the loose-tube single-mode optical fiber 102 of the hydrophone cable 1. The loose-tube single-mode optical fiber 102 of the hydrophone cable 1 is reserved a certain length of redundancy at a certain interval when fixed to the cable core 5, to offset the length loss in the fusion process. The alternative scheme has the advantage of simple processing and manufacturing process, but has the problems of more fusion points, large line loss, and low signal-to-noise ratio of the hydrophone linear array.

[0027] Based on the description of the preferred embodiments of the present application, it should be clear that the present application defined by the appended claims is not limited to the specific details described above, and many obvious modifications of the present application can be made without departing from the spirit or scope of the present application.

Claims

1. A terrestrial and marine micro-disturbance sensing optical cable, characterized in that: The invention comprises a geoacoustic optical cable (1), a hydroacoustic sensor element (2), a sheath (4) and a cable core (5); a plurality of the hydroacoustic sensor elements (2) are sleeved on the cable core (5) at a certain interval, the geoacoustic optical cable (1) passes through the hydroacoustic sensor element (2) and is fixed to the cable core (5) in the axial direction; the sheath (4) is wrapped in the outermost layer; the hydroacoustic sensor element (2) comprises a core shaft and a weak grating array optical fiber (201), and weak reflectivity gratings (3) are engraved on the weak grating array optical fiber (201) at a certain interval; the weak reflectivity grating (3) is arranged on the outside of one end of the hydroacoustic sensor element (2); the weak reflectivity grating (3) is always in a stress-free state; the weak grating array optical fiber (201) comprises a first part and a second part, the first part of the weak grating array optical fiber (201) is wound on the core shaft, and the second part of the weak grating array optical fiber (201) is fixed to the outer wall of the cable core (5) in the axial direction.

2. The amphibious micro-disturbance sensing optical cable according to claim 1, characterized in that: The geoacoustic optical cable (1) comprises a loose-tube multimode optical fiber (101), a loose-tube single-mode optical fiber (102) and a tight-tube single-mode optical fiber (103); the loose-tube multimode optical fiber (101), the loose-tube single-mode optical fiber (102) and the tight-tube single-mode optical fiber (103) are axially fixed to the outer wall of the cable core (5) at certain intervals and run through the entire sensing optical cable; the sensing optical fibers constituting the geoacoustic optical cable (1) are symmetrically and evenly fixed to the outer wall of the cable core (5).

3. The amphibious micro-disturbance sensing optical cable according to claim 2, characterized in that: The core shaft comprises an elastic sensitizing layer (202), an air layer (203) and a rigid shaft (204); the weak grating array optical fiber (201) is tightly and single-layeredly wound around the outer wall of the core shaft; the rigid shaft (204) is made of a rigid material, with both ends raised, providing support for the elastic sensitizing layer (202) while forming an air cavity between the rigid shaft (204) and the elastic sensitizing layer (202) to serve as the air layer (203); the elastic sensitizing layer (202) is made of a material with a low elastic modulus and Poisson's ratio, with both ends raised.

4. The amphibious micro-disturbance sensing optical cable according to claim 3, characterized in that: The hydrophone sensing element (2) is a hollow structure, and the hydrophone sensing element (2) further includes a fixing device (205); the geophone optical cable (1) sequentially passes through the central through hole of the hydrophone sensing element (2), and the fixing device (205) fixes the hydrophone sensing element (2) on the geophone optical cable (1) at a certain interval, thereby forming a hydrophone linear array with different frequency bands.

5. The amphibious micro-disturbance sensing optical cable according to claim 3, characterized in that: The weak grating array optical fiber (201) is fused with the loose sleeve single-mode optical fiber (102) at both ends of the hydrophone sensing element (2), and the signal is transmitted using the hydrophone optical cable (1).

6. The amphibious micro-disturbance sensing optical cable according to claim 4 or 5, characterized in that: The cable core (5) is composed of a steel strand (501) and a hard plastic layer (502), the hard plastic layer (502) wraps the steel strand (501), and the ground-based optical cable (1) and the weak grating array optical fiber (201) are fixed on the hard plastic layer (502).

7. The amphibious micro-disturbance sensing optical cable according to claim 1, characterized in that: The sheath (4) is made of a waterproof and sound-permeable polymer material and is wrapped around the geophone optical cable (1) and the hydrophone sensor element (2).

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