A Submarine Optoelectronic Composite Cable Positioning Method Based on Distributed Acoustic Sensing

Abstract

The present invention discloses a method for positioning an undersea optical and electrical composite cable based on distributed acoustic sensing. The method includes: an acoustic transducer emits a swept-frequency acoustic signal; the undersea optical and electrical composite cable is evenly and sequentially divided into optical fiber sensing units, and the swept-frequency acoustic signal is received to generate a backward Rayleigh scattered optical signal; the backward Rayleigh scattered optical signal is transmitted to a distributed acoustic sensing demodulator DAS for demodulation to output a demodulated acoustic signal; the swept-frequency acoustic signal and the demodulated acoustic signal are cross-correlated to obtain the propagation travel time, and the propagation travel time and the position coordinates of the positioning point are formed into a positioning information group; each optical fiber sensing unit obtains the position coordinates through the positioning information group; the positioning position of the undersea optical and electrical composite cable is obtained. The swept-frequency acoustic signal of the present invention is an active sound source, and the positioning is more accurate than that of a passive sound source; using the undersea optical and electrical composite cable as a signal receiver to position itself can quickly and effectively position the undersea optical and electrical composite cable and can perform regular updates of the position.

Description

Technical Field

[0001] The present invention relates to a method for positioning a composite cable, and particularly to a method for positioning an undersea optical and electrical composite cable based on distributed acoustic sensing. Background Art

[0002] The undersea optical and electrical composite cable undertakes tasks such as ocean power transmission and real-time data transmission between underwater fixed relay points and onshore base stations. However, it is often affected by factors such as seawater impact, geological changes, ship anchoring and dragging, which change its original position, greatly increasing the difficulty and cost of maintenance and repair.

[0003] However, there is currently no fast and effective method for positioning an undersea optical and electrical composite cable that can effectively, quickly and accurately perform regular positioning and updating of the position of the undersea optical and electrical composite. Summary of the Invention

[0004] In order to solve the problems existing in the background art, the present invention provides a method for positioning an undersea optical and electrical composite cable based on distributed acoustic sensing.

[0005] The technical solution adopted by the present invention is as follows:

[0006] The method of the present invention includes the following steps:

[0007] Step 1) Control a monitoring ship equipped with an acoustic transducer to sail to M preset positioning points in sequence. For each positioning point, the acoustic transducer actively emits a swept-frequency acoustic signal once to the surrounding area; the emitted swept-frequency acoustic signal is received by the undersea optical and electrical composite cable under the monitoring ship.

[0008] Step 2) Evenly divide the undersea optical and electrical composite cable into N fiber optic sensing units in sequence, that is, regard the undersea optical and electrical composite cable as N fiber optic sensing units connected in sequence, and use the fiber optic sensing unit as an acoustic signal receiver; each fiber optic sensing unit generates a backward Rayleigh scattering optical signal each time it receives the swept-frequency acoustic signal emitted in Step 1).

[0009] The fiber optic sensing unit generates strain deformation under the acoustic wave vibration of the swept-frequency acoustic signal, and the refractive index and length of the fiber optic sensing unit change, thereby generating a backward Rayleigh scattering optical signal. By detecting the phase change of the backward Rayleigh scattering optical signal, the strain measurement of the fiber optic sensing unit is realized.

[0010] Step 3) Each time the generated backward Rayleigh scattering optical signal is transmitted by the corresponding fiber optic sensing unit to a distributed acoustic sensing demodulator DAS electrically connected to the undersea optical and electrical composite cable for demodulation, and after the demodulation is completed, a demodulated acoustic signal is output.

[0011] The acoustic transducer and the distributed acoustic sensing demodulator DAS have a common precise timing calibration.

[0012] Step 4) Use a mobile acquisition device to collect all the swept-frequency acoustic signals, the position coordinates of the positioning points corresponding to the swept-frequency acoustic signals, and the demodulated acoustic signals, and input them into the computer device equipped with a signal analysis module pre-installed at the shore base end through the mobile acquisition device;

[0013] Step 5) For each fiber optic sensing unit in Step 2), the signal analysis module performs cross-correlation processing on each swept-frequency acoustic signal transmitted to the fiber optic sensing unit in the computer device and the demodulated acoustic signal obtained in Step 3) through this swept-frequency acoustic signal to obtain the propagation travel time between the two, and jointly forms a positioning information group with the propagation travel time obtained from this swept-frequency acoustic signal and the position coordinates of the positioning point corresponding to this swept-frequency acoustic signal;

[0014] Step 6) For each fiber optic sensing unit in Step 2), the fiber optic sensing unit receives a total of M swept-frequency acoustic signals transmitted at M positioning points, and each swept-frequency acoustic signal is processed to obtain the positioning information group in Step 5), that is, each fiber optic sensing unit correspondingly obtains M groups of positioning information groups; the signal analysis module processes the M groups of positioning information groups to obtain the position coordinates of a section of fiber optic sensing unit corresponding to the demodulated acoustic signal;

[0015] Step 7) According to the position coordinates of each section of fiber optic sensing unit obtained in Step 6) and the division order of each section of fiber optic sensing unit divided in sequence, obtain the positioning position of the entire submarine hybrid optoelectronic cable.

[0016] In the above-mentioned Step 1), the number of positioning points M≥3.

[0017] In the above-mentioned Step 3), the submarine hybrid optoelectronic cable is laid on the seabed and is electrically connected to the distributed acoustic sensing demodulator DAS at the shore base end.

[0018] In the above-mentioned Step 6), for the M groups of positioning information groups correspondingly obtained for each section of fiber optic sensing unit, the signal analysis module processes the M groups of positioning information groups, and the formula is as follows:

[0019]

[0020]

[0021] Among them, Δd represents the distance difference matrix formed by the position coordinates of the M positioning points and the position coordinates of the i-th section of fiber optic sensing unit corresponding to the demodulated acoustic signal; P S1 、P S2 …P SM respectively represent the position coordinates of the first, second... M-th positioning points; P iRepresents the position coordinates of the i-th fiber optic sensing unit corresponding to the demodulated acoustic signal, where 1 ≤ i ≤ N; ΔT represents the time difference matrix composed of M propagation travel times obtained by processing the M swept-frequency acoustic signals and the demodulated acoustic signal; T1, T2…T M Represents the first, second…M-th propagation travel times obtained by processing the M swept-frequency acoustic signals and the demodulated acoustic signal respectively; C represents the propagation speed of the swept-frequency acoustic signal in seawater;

[0022] The signal analysis module processes the M groups of positioning information groups and the above formula to obtain the position coordinates Pi of the i-th fiber optic sensing unit corresponding to the demodulated acoustic signal i 。

[0023] The beneficial effects of the present invention are:

[0024] By actively exciting the swept-frequency acoustic signal with acoustic transducers at different positions, the present invention has a more accurate positioning than that of passive sound sources; the use of the backward Rayleigh scattering optical signal generated passively by the submarine electro-optical composite cable for joint analysis realizes the accurate positioning of the entire submarine electro-optical composite cable, and can quickly and effectively perform position positioning and regular updates, with the advantages of high positioning accuracy, convenient method use, and saving manpower and material resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Is a schematic diagram of the device for the positioning method of the present invention;

[0026] Figure 2 Is a schematic diagram of the position of a section of fiber optic sensing unit for the positioning of the present invention;

[0027] In the figure: 1. Signal analysis module, 2. Distributed acoustic sensing demodulator DAS, 3. Submarine electro-optical composite cable, 4. Acoustic transducer. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings.

[0029] The steps of the specific embodiment of the present invention are as follows:

[0030] Step 1) Control the monitoring ship equipped with the acoustic transducer 4 to sail to 3 preset positioning points in sequence, namely test points. For each positioning point, the acoustic transducer 4 actively emits a swept-frequency acoustic signal to the surrounding area once, and at the same time obtains the emission time of the swept-frequency acoustic signal; the emitted swept-frequency acoustic signal is received by the submarine electro-optical composite cable 3 under the monitoring ship.

[0031] Step 2) The submarine electro-optical composite cable 3 is evenly divided into N fiber optic sensing units in sequence, that is, the submarine electro-optical composite cable 3 is regarded as N fiber optic sensing units connected in sequence, and the fiber optic sensing units are used as acoustic signal receivers; each fiber optic sensing unit generates a backward Rayleigh scattering optical signal each time it receives the swept-frequency acoustic signal transmitted in Step 1).

[0032] Under the acoustic wave vibration of the swept-frequency acoustic signal, the fiber optic sensing unit generates strain deformation, and the refractive index and length of the fiber optic sensing unit change, thereby generating a backward Rayleigh scattering optical signal. By detecting the phase change of the backward Rayleigh scattering optical signal, the strain of the fiber optic sensing unit is measured.

[0033] Step 3) Each generated backward Rayleigh scattering optical signal is transmitted by the corresponding fiber optic sensing unit to the distributed acoustic sensing demodulator DAS2 electrically connected to the submarine electro-optical composite cable 3 for demodulation, and after demodulation is completed, a demodulated acoustic signal is output; the submarine electro-optical composite cable 3 is laid on the seabed and is electrically connected to the distributed acoustic sensing demodulator DAS2 at the shore base end. The acoustic transducer 4 and the distributed acoustic sensing demodulator DAS2 have a common precise timing calibration, and the device is as Figure 1 shown.

[0034] Step 4) Use a mobile acquisition device to collect all the swept-frequency acoustic signals, the emission time of the transmitted swept-frequency acoustic signals, the position coordinates of the positioning points corresponding to the swept-frequency acoustic signals, and the demodulated acoustic signals, and input them into the computer device equipped with the signal analysis module 1 pre-installed at the shore base end through the mobile acquisition device.

[0035] Step 5) For each fiber optic sensing unit in Step 2), the signal analysis module 1 performs cross-correlation processing on each swept-frequency acoustic signal transmitted to the fiber optic sensing unit in the computer device and the demodulated acoustic signal obtained in Step 3) through the current swept-frequency acoustic signal to obtain the propagation travel time between the two, and combines the propagation travel time obtained from the current swept-frequency acoustic signal, the emission time of the current swept-frequency acoustic signal, and the position coordinates of the positioning point corresponding to the current swept-frequency acoustic signal to form a positioning information group.

[0036] Step 6) For each fiber optic sensing unit in Step 2), the fiber optic sensing unit receives a total of M swept-frequency acoustic signals emitted at M positioning points, and each swept-frequency acoustic signal is processed to obtain the positioning information group in Step 5), that is, each fiber optic sensing unit correspondingly obtains M groups of positioning information groups; the signal analysis module 1 processes the M groups of positioning information groups to obtain the position coordinates of a section of the fiber optic sensing unit corresponding to the demodulated acoustic signal.

[0037] In the above Step 6), for the M groups of positioning information groups correspondingly obtained for each fiber optic sensing unit, the signal analysis module 1 processes them through the M groups of positioning information groups, and the formula is as follows:

[0038]

[0039]

[0040] Among them, Δd represents the distance difference matrix formed by the position coordinates of the positioning points at M and the position coordinates of the i-th fiber optic sensing unit corresponding to the demodulated acoustic signal; P S1 、P S2 …P SM respectively represent the position coordinates of the first, second... M-th positioning points; P i represents the position coordinates of the i-th fiber optic sensing unit corresponding to the demodulated acoustic signal, where 1 ≤ i ≤ N; ΔT represents the time difference matrix formed by the M propagation travel times obtained by processing the M swept-frequency acoustic signals and the demodulated acoustic signal; T1, T2... T M represent the first, second... M-th propagation travel times obtained by processing the M swept-frequency acoustic signals and the demodulated acoustic signal respectively; C represents the propagation speed of the swept-frequency acoustic signal in seawater.

[0041] The signal analysis module 1 processes through M groups of positioning information groups and the above formula to obtain the position coordinates P i of the i-th fiber optic sensing unit corresponding to the demodulated acoustic signal, and the position of a located fiber optic sensing unit is as Figure 2 shown.

[0042] Step 7): According to the position coordinates of each fiber optic sensing unit obtained in step 6) and the division order of each divided fiber optic sensing unit, obtain the positioning position of the entire submarine optical and electrical composite cable 3.

[0043] The innovation of the present invention lies in using the submarine optical and electrical composite cable originally only for transmission. By emitting an active swept-frequency acoustic signal, the submarine optical and electrical composite cable generates strain, that is, deformation, when receiving the swept-frequency acoustic signal, thereby generating a backward Rayleigh scattering optical signal. Furthermore, by jointly processing the backward Rayleigh scattering optical signal and the demodulated acoustic signal, the position of the submarine optical and electrical composite cable itself is located, thus solving the problem that it is difficult to accurately and real-time position the submarine optical and electrical composite cable and regularly update its position.

[0044] The above description is not intended to limit the present technical invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present technical invention shall be included within the protection scope of the present technical invention.

Claims

1. A method for positioning an undersea optical and electrical composite cable based on distributed acoustic sensing, characterized in that: The method comprises the following steps: Step 1) Control the monitoring ship equipped with the acoustic transducer (4) to sail to M preset positioning points in sequence. For each positioning point, the acoustic transducer (4) emits a swept-frequency acoustic signal once to the surrounding; the emitted swept-frequency acoustic signal is received by the undersea optical and electrical composite cable (3) below the monitoring ship; Step 2) Uniformly divide the undersea optical and electrical composite cable (3) into N fiber optic sensing units in sequence. Each fiber optic sensing unit generates a backward Rayleigh scattering optical signal each time it receives the swept-frequency acoustic signal emitted in Step 1); Step 3) Each generated backward Rayleigh scattering optical signal is transmitted by the corresponding fiber optic sensing unit to the distributed acoustic sensing demodulator DAS (2) electrically connected to the undersea optical and electrical composite cable (3) for demodulation. After the demodulation is completed, a demodulated acoustic signal is output; Step 4) Collect all the swept-frequency acoustic signals, the position coordinates of the positioning points, and the demodulated acoustic signals, and input them into the computer device equipped with the signal analysis module (1) pre-equipped at the shore base; Step 5) For each fiber optic sensing unit in Step 2), the signal analysis module (1) performs cross-correlation processing on each swept-frequency acoustic signal transmitted to the fiber optic sensing unit in the computer device and the demodulated acoustic signal obtained in Step 3) through the current swept-frequency acoustic signal to obtain the propagation travel time between the two. The propagation travel time obtained from the current swept-frequency acoustic signal and the position coordinates of the positioning point corresponding to the current swept-frequency acoustic signal jointly form a positioning information group; Step 6) For each fiber optic sensing unit in Step 2), the fiber optic sensing unit receives a total of M swept-frequency acoustic signals emitted at M positioning points. Each swept-frequency acoustic signal is processed to obtain the positioning information group in Step 5), that is, each fiber optic sensing unit correspondingly obtains M groups of positioning information groups; the signal analysis module (1) obtains the position coordinates of a section of fiber optic sensing unit corresponding to the demodulated acoustic signal through processing of the M groups of positioning information groups; Step 7) According to the position coordinates of each section of fiber optic sensing unit obtained in Step 6) and the division sequence of each section of fiber optic sensing unit divided in sequence, obtain the positioning position of the entire undersea optical and electrical composite cable (3).

2. The method for positioning an undersea optical and electrical composite cable based on distributed acoustic sensing according to claim 1, characterized in that: In the said Step 1), the number of positioning points M≥3.

3. The method for positioning an undersea optical and electrical composite cable based on distributed acoustic sensing according to claim 1, characterized in that: In the said Step 3), the undersea optical and electrical composite cable (3) is laid on the seabed and is electrically connected to the distributed acoustic sensing demodulator DAS (2) at the shore base.

4. The method for positioning an undersea optical and electrical composite cable based on distributed acoustic sensing according to claim 1, characterized in that: In the said Step 6), for the M groups of positioning information groups correspondingly obtained for each section of fiber optic sensing unit, the signal analysis module (1) performs processing through the M groups of positioning information groups, and the formula is as follows: Among them, Δd represents the distance difference matrix formed by the position coordinates of the positioning points at M and the position coordinates of the i-th fiber optic sensing unit corresponding to the demodulated acoustic signal; P S1 , P S2 …P SM respectively represent the position coordinates of the first, second… the M-th positioning point; P i represents the position coordinates of the i-th fiber optic sensing unit corresponding to the demodulated acoustic signal, 1≤i≤N; ΔT represents the time difference matrix formed by the M propagation travel times obtained by processing the M swept-frequency acoustic signals and the demodulated acoustic signal; T1, T2…T M represent the first, second… the M-th propagation travel times obtained by processing the M swept-frequency acoustic signals and the demodulated acoustic signal respectively; C represents the propagation speed of the swept-frequency acoustic signal in seawater; The signal analysis module (1) obtains the position coordinates P of the i-th fiber optic sensing unit corresponding to the demodulated acoustic signal through M groups of positioning information groups and the above formula i .

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