Seabed optical cable for earthquake early warning

Abstract

A submarine optical cable for earthquake early warning belongs to the technical field of optical fiber sensing. Comprising an outer sheath and a cable core, the cable core comprises a central optical unit, an armored steel wire layer and sensing optical fiber units, the armored steel wire layer and the sensing optical fiber units are twisted outside the optical unit, the sensing optical fiber units are symmetrically distributed in the armored steel wire layer in pairs, and a wrapping tape layer is arranged outside the cable core. The optical cable is reasonable in design structure, can be used in the field of earthquake monitoring, has the characteristics of high sensitivity, high stability, water resistance and the like, can better adapt to the seabed environment, and provides a more accurate and reliable technical means for earthquake early warning.

Description

Technical Field

[0001] The utility model relates to a submarine optical cable for earthquake early warning, belonging to the technical field of optical fiber sensing. Background Art

[0002] A fiber-optic hydrophone is a device that uses fiber-optic sensing technology to detect and transmit underwater acoustic signals. It can transmit underwater sound wave signals through optical fibers and convert them into electrical signals for analysis and processing, providing a new idea for submarine earthquake research and tsunami warning.

[0003] Fiber optic hydrophones are classified into intensity type, polarization type, phase interference type, etc. according to their principle. Among them, phase interference type fiber optic hydrophones have become the main object of research and development due to their advantages of high precision, good stability, small size, and easy large-scale array formation. In pursuit of miniaturization and high precision, higher performance requirements are placed on the submarine optical cable connected to the fiber optic hydrophone. However, the existing submarine optical cable structure is too complex, with a thick outer diameter and poor mechanical reliability, and cannot be quickly connected to the fiber optic hydrophone. Utility Model Content

[0004] The purpose of the utility model is to provide a submarine optical cable for earthquake early warning with a simple structure, good mechanical reliability and convenient for quick connection to optical fiber hydrophones in view of the above-mentioned deficiencies in the prior art.

[0005] The technical solution of the utility model is as follows: a submarine optical cable for earthquake early warning, comprising an outer sheath and a cable core, characterized in that the cable core comprises a central optical unit, and an armored steel wire layer and a sensing optical fiber unit twisted outside the optical unit, the sensing optical fiber units are paired and symmetrically distributed in the armored steel wire layer, and a wrapping tape layer is provided outside the cable core.

[0006] With the above solution, the entire submarine optical cable adopts a central tube structure (the optical unit is located in the center), which meets the communication transmission requirements, has a simple structure, reduces unnecessary complicated processes during installation, has good anti-extrusion performance, strong tensile performance, and can effectively prevent the optical fiber from being damaged by the external environment.

[0007] Part of the armored steel wires in the armored steel wire layer are replaced by sensing optical fiber units, which are used to connect the sensor optical fibers in the fiber-optic hydrophone. Without destroying the performance of the armored structure, the optical cable sensing optical fiber is given a new function. The sensing optical fiber unit is located inside the armored steel wire layer, which is convenient for external stripping. During the assembly process, there is no need to cut the central tube, only the outer sheath needs to be cut, and the sensing optical fiber unit can be quickly connected to the fiber-optic hydrophone, which can reduce the assembly time of the hydrophone, reduce the time and difficulty of the assembly process, and improve construction efficiency.

[0008] Furthermore, the outer sheath is black HDPE, which has high hardness and tensile strength, good wear resistance and chemical corrosion resistance, and strong impact resistance.

[0009] Furthermore, the optical unit includes a stainless steel tube, an optical fiber and a fiber paste placed in the stainless steel tube, and a layer of HDPE inner sheath is extruded on the outside of the optical unit. Preferably, the optical unit is a standard central tube structure with a circular cross-section, and includes 8 fiber pairs (16 cores) of G.652D optical fiber, thixotropic hydrogen-absorbing fiber paste, and a 304 stainless steel tube; the optical fiber is used for optical signal transmission to achieve communication functions; the fiber paste is filled in the gap between each core optical fiber, and plays the role of optical fiber buffering, longitudinal water blocking and hydrogen absorption; the stainless steel tube is formed by laser welding the steel strip and reducing the diameter to form a seamless steel tube, which plays the role of protecting the optical fiber, resisting pressure, and radial water blocking.

[0010] Furthermore, the armored steel wires in the armored steel wire layer are galvanized steel wires, 8 in total, and their structural design complies with the requirements of GB / T 24202-2009 standard, with a tensile strength of ≥1400Mpa, and have good strength and corrosion resistance.

[0011] Furthermore, the sensing optical fiber unit includes a stainless steel tube, a sensing optical fiber and fiber paste placed in the stainless steel tube, and a layer of HDPE inner sheath is extruded on the outside of the sensing optical fiber unit.

[0012] The sensing optical fiber in the sensing optical fiber unit is used for earthquake monitoring and early warning, with a total of 2 cores (i.e. 2 groups, two armored steel wires are replaced by two sensing optical fiber units). Preferably, the mode field diameter of the sensing optical fiber is only 5.9μm, the cladding diameter is only 80μm, and the coating diameter is 165μm (optional sensing optical fiber model: CS1060-80-14 / 165, manufacturer: Changfei Optical Fiber and Cable Co., Ltd.), with the advantages of low macrobending loss and high mechanical strength.

[0013] Furthermore, in the armored steel wire layer, the gaps between the armored steel wires and the gaps between the armored steel wires and the sensing optical fiber unit are filled with a water-blocking adhesive structure. The water-blocking adhesive has strong waterproof performance and good adhesion, and can fill the gaps between the armored steel wires and between the armored steel wires and the sensing optical fiber unit, play a longitudinal water-blocking role, have strong water-blocking performance, and achieve a good sealing effect.

[0014] On this basis, a wrapping tape layer is formed on the cable core. The wrapping tape is made of hot-melt self-adhesive wrapping tape, which has high strength and excellent wrapping performance, corrosion resistance, bonding performance and material safety performance. It can improve the service life and reliability of the optical cable and reduce the probability of failure.

[0015] Furthermore, the inner sheath is white HDPE, which has good toughness and cold resistance, long service life and high cost performance.

[0016] Furthermore, the outer diameter of the sensing optical fiber unit is consistent with the outer diameter of the armored steel wire in the armored steel wire layer, ensuring the roundness of the cable core. In addition, the stainless steel tube in the sensing optical fiber unit can not only meet the requirements of the sensing optical fiber, but also cooperate with the armored steel wire to ensure the mechanical strength of the optical unit; the setting of the HDPE inner sheath of the sensing optical fiber unit can not only effectively protect the sensing optical fiber unit, but also strengthen the tightness between it and the armored steel wire.

[0017] Furthermore, the sensing optical fiber unit is provided with two groups, and the HDPE inner sheaths of the two groups of sensing optical fiber units are of different colors. Optical fiber sensing generally consists of two optical fibers, one as a transmitting optical fiber and the other as a receiving optical fiber. Two different colors of HDPE are used as the inner sheaths of the sensing optical fiber unit, red is used to connect the transmitting optical fiber, and blue is used to connect the receiving optical fiber.

[0018] The beneficial effects of the utility model are:

[0019] 1. Safety performance: 8-fiber pair G.652D optical fiber is used to meet the communication transmission requirements. Two sensing optical fibers are placed in the sensing optical fiber unit and separated from the central communication optical fiber to meet the connection of the hydrophone. The two are independent of each other to avoid damage to other communication optical fibers due to cutting the central tube, thereby improving the safety factor.

[0020] 2. Anti-bending performance: The sensing optical fiber used has the advantage of low macrobending loss compared to other similar sensing optical fibers. The phase interference type optical fiber hydrophone detects the changes in the interference fringes of light waves in the sensing arm and the reference arm by a photodetector, and then extracts the sound pressure signal through a signal processor. Its key component is the optical fiber ring wound by the sensing optical fiber. At the same time, based on the pursuit of miniaturization, the size of this optical fiber ring is generally small. Using the sensing optical fiber in this application, the wound optical fiber ring with a small bending diameter can still maintain low loss, providing performance and reliability guarantees for large hydrophone array networking.

[0021] 3. Tensile performance: Under the same bending radius, the tensile stress of the sensing optical fiber with a cladding diameter of only 80μm is lower than that of other optical fibers; at the same time, the 80μm sensing optical fiber meets the screening of ≥175kpsi, has high tensile and anti-aging strength, and has better mechanical protection performance.

[0022] 4. Timeliness: The two sensing optical fibers in the armored steel wire layer are located in separate stainless steel tubes, which are used to connect the sensor optical fibers in the fiber-optic hydrophone. Keeping the sensing optical fibers in separate tubes eliminates the need to cut the center tube during the assembly of the hydrophone, only the outer sheath needs to be cut, which can reduce the assembly time of the hydrophone and greatly improve efficiency.

[0023] 5. Comprehensiveness: Based on the principle of light polarization, the sensor cable "transforms" the transoceanic communication cable into a seismograph. It does not require additional instruments and does not involve communication privacy. It protects national security and communication privacy while reducing production costs.

[0024] The utility model has a reasonable design structure, and the optical cable can be used in the field of earthquake monitoring, especially for monitoring submarine earthquakes and tsunamis. Due to the use of technical means such as sensing optical fiber and sealing structure, this product has the characteristics of high sensitivity, high stability, and waterproofness, and can better adapt to the submarine environment, providing a more accurate and reliable technical means for earthquake early warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural block diagram of the utility model;

[0026] Figure 2 This is a schematic diagram of the internal structure of the light unit in the utility model;

[0027] Figure 3 This is a schematic diagram of the internal structure of the sensing optical fiber unit in the utility model;

[0028] In the figure: 1. optical fiber; 2. fiber paste; 3. stainless steel tube; 4. HDPE inner sheath; 5. armored steel wire layer; 6. water-blocking glue; 7. wrapping tape layer; 8. HDPE outer sheath; 9. sensing optical fiber; 10. fiber paste; 11. stainless steel tube; 12. HDPE inner sheath. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the present application, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0030] Reference Figure 1 A sensing submarine optical cable for earthquake early warning, the optical cable structure includes: an optical unit, an inner sheath 4, an armored steel wire layer 5, a sensing optical fiber unit, a water-blocking glue 6, a hot-melt self-adhesive wrapping tape layer 7, and an outer sheath 8.

[0031] The optical unit is composed of an optical fiber 1, a fiber gel 2 and a stainless steel tube 3, and a layer of HDPE inner sheath 4 is extruded outside the optical unit. Figure 2 The optical unit consists of 8 fiber pairs of G.652D optical fibers, thixotropic hydrogen-absorbing fiber paste and 304 stainless steel tubes, which are used for optical signal transmission to realize communication functions.

[0032] refer to Figure 3The sensing optical fiber unit is composed of a single-core sensing optical fiber 9, a fiber gel 10, and a 304 stainless steel tube 11, which is used for earthquake monitoring and early warning. A layer of HDPE inner sheath 12 is extruded outside the sensing optical fiber unit. In one embodiment of the utility model, a layer of galvanized steel wire (a total of 8 wires) is armored outside the inner sheath of the central optical unit, and two of the steel wires are replaced by two sensing optical fiber units. In one embodiment of the utility model, the mode field diameter of the sensing optical fiber is only 5.9μm, the cladding diameter is only 80μm, and the coating diameter is 165μm (sensing optical fiber model: CS1060-80-14 / 165, manufacturer: Changfei Optical Fiber and Cable Co., Ltd.).

[0033] The optical unit of the utility model is extruded with an HDPE inner sheath and a layer of galvanized steel wire for armoring, so as to ensure the mechanical properties of the optical unit. The structural design of the galvanized steel wire meets the requirements of the GB / T 24202-2009 standard. The sensing optical fiber unit has low macrobending loss and high mechanical strength, so as to meet the networking requirements of the hydrophone array in earthquake early warning.

[0034] The utility model has a reasonable design structure. The ocean communication optical cable is "converted" into a seismograph, and all-weather earthquake and tsunami monitoring is achieved by only recording the polarization state of the optical fiber. No additional instruments are required, and the normal communication of the optical fiber is not affected. On the basis of reducing costs, network communication and earthquake and tsunami warnings are achieved at the same time.

Claims

1. A submarine optical cable for earthquake early warning, comprising an outer sheath and a cable core, characterized in that: The cable core comprises a central optical unit, an armored steel wire layer and a sensing optical fiber unit twisted outside the optical unit, the sensing optical fiber units are arranged in pairs and symmetrically in the armored steel wire layer, and a wrapping tape layer is arranged outside the cable core.

2. The submarine optical cable for earthquake early warning according to claim 1 is characterized in that: The optical unit comprises a stainless steel tube, an optical fiber and fiber paste placed in the stainless steel tube, and a layer of HDPE inner sheath is extruded outside the optical unit.

3. The submarine optical cable for earthquake early warning according to claim 1 is characterized in that: In the armored steel wire layer, the gaps between the armored steel wires and the gaps between the armored steel wires and the sensing optical fiber units are all filled with a water-blocking glue structure.

4. The submarine optical cable for earthquake early warning according to claim 1 is characterized in that: The sensing optical fiber unit comprises a stainless steel tube, a sensing optical fiber and fiber paste placed in the stainless steel tube, and a layer of HDPE inner sheath is extruded on the outside of the sensing optical fiber unit.

5. The submarine optical cable for earthquake early warning according to claim 4 is characterized in that: The outer diameter of the sensing optical fiber unit is consistent with the outer diameter of the armored steel wire in the armored steel wire layer.

6. The submarine optical cable for earthquake early warning according to claim 4 or 5, characterized in that: The sensing optical fiber units are provided with two groups, and the HDPE inner sheaths of the two groups of sensing optical fiber units are of different colors.

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