CN115014223A - Submarine cable deformation monitoring system based on sensing grating array - Google Patents
Submarine cable deformation monitoring system based on sensing grating array Download PDFInfo
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- CN115014223A CN115014223A CN202210576615.3A CN202210576615A CN115014223A CN 115014223 A CN115014223 A CN 115014223A CN 202210576615 A CN202210576615 A CN 202210576615A CN 115014223 A CN115014223 A CN 115014223A
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- sensing grating
- grating array
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/165—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge by means of a grating deformed by the object
Abstract
The invention discloses a submarine cable deformation monitoring system based on a sensing grating array, which comprises: the monitoring system comprises a flexible carrier and a transmission optical fiber, wherein a plurality of strain sensing grating arrays are arranged on the transmission optical fiber, the transmission optical fiber is embedded into the flexible carrier, the strain sensing grating arrays are arranged along the axial direction of the submarine cable, and the transmission optical fiber is fixed with the submarine cable; the grating demodulator is used for emitting optical signals, acquiring and demodulating the optical signals reflected by the strain sensing grating array and obtaining curvature information of the strain sensing grating array; the monitoring upper computer is used for obtaining the form monitoring information of the submarine cable according to the curvature information. The invention can realize the real-time monitoring of the deformation condition of the submarine cable, realize the remote real-time positioning self-checking function of the submarine cable, and improve the stability and the fault repair capability of the submarine cable.
Description
Technical Field
The invention belongs to the technical field of optical fiber sensing, and particularly relates to a submarine cable deformation monitoring system based on a sensing grating array.
Background
The submarine cable high-precision intelligent health detection technology is a leading-edge hotspot in the field of current international marine intelligent technology and equipment research and development, and is also a technical bottleneck restricting marine resource development and energy information transmission in China. With the rapid rise and the extremely rapid development momentum of the new energy industry in China, a great market is provided for submarine cable products, and meanwhile relatively high requirements are provided for the real-time monitoring capability of submarine cable products. In recent years, with the development of offshore power generation, submarine cables have become the main means of intercontinental communication of the present generation, and are also important routes for information transfer between islands and land, islands and islands. Meanwhile, the submarine optical cable plays a great role in the communication aspects of the military field and the civil field, and particularly has an irreplaceable position in the network communication aspect internationally. Therefore, the development of submarine cable health monitoring technology has great significance for supporting and ensuring the continuous use of submarine cables.
While the submarine cables are widely used, the safety of the submarine cables is becoming a focus of attention. Unlike land-segment cables, submarine cables are exposed to a great deal of risk; moreover, the maintenance difficulty of the submarine cable is higher, and the maintenance of the submarine cable is inseparable from the working environment of the submarine cable. Submarine cables are very prone to faults during operation, and the reasons for faults of submarine cables are mostly closely related to people nowadays, for example: anchor smashes, hooks, etc. cause the failure of the submarine cable. In summary, how to monitor the status of the submarine cable and repair the faulty submarine cable in time becomes a great challenge in the field of optical fiber sensing technology.
Disclosure of Invention
The invention aims to provide a submarine cable deformation monitoring system based on a sensing grating array, so as to solve one or more technical problems in the prior art and provide at least one beneficial choice or creation condition.
The solution of the invention for solving the technical problem is as follows: the submarine cable deformation monitoring system based on the sensing grating array is used for monitoring the form of a submarine cable and comprises: the system comprises a monitoring upper computer, a grating demodulator and a monitoring system, wherein the monitoring upper computer is arranged on a shore base and is connected with the grating demodulator through the internet;
the monitoring system comprises a flexible carrier and a transmission optical fiber, wherein a plurality of strain sensing grating arrays are arranged on the transmission optical fiber, the transmission optical fiber is embedded into the flexible carrier, and the strain sensing grating arrays are arranged along the axial direction of the submarine cable;
the grating demodulator is used for transmitting optical signals, the optical signals are transmitted into the strain sensing grating array through the transmission optical fiber, the optical signals reflected by the strain sensing grating array are obtained and demodulated, and curvature information of the strain sensing grating array is obtained;
and the monitoring upper computer is used for obtaining deformation monitoring information of the submarine cable according to the curvature information.
As a further improvement of the above technical solution, the transmission fiber is further provided with a plurality of temperature sensing grating arrays, the temperature sensing grating arrays are located beside the strain sensing grating arrays, and the temperature sensing grating arrays are used for performing temperature compensation on the strain sensing grating arrays.
As a further improvement of the above technical solution, the grating demodulator is connected to the transmission fiber, and includes a broadband light source and a demodulator, where the broadband light source is configured to emit a light signal into the strain sensing grating array, and the demodulator is configured to acquire and demodulate reflected light reflected by the strain sensing grating array.
As a further improvement of the above technical solution, the central wavelength of the reflected light of the strain sensing grating array satisfies formula (1):
λ＝2n eff ·T (1)
wherein, λ is the central wavelength of the reflected light of the strain sensing grating array, n eff The effective refractive index of the strain sensing grating array is shown, and T is the grating period of the strain sensing grating array;
when the effective refractive index of the strain sensing grating array is unchanged, and when the strain sensing grating array is stretched, the strain sensing grating array approaches to the outer arc of the flexible carrier, the grating period of the strain sensing grating array is increased, and the offset of the central wavelength of the reflected light of the strain sensing grating array is increased.
As a further improvement of the above technical solution, the length of the neutral line of the flexible carrier satisfies formula (2):
L＝R·α (2)
wherein L is the length of the neutral line of the flexible carrier, R is the bending radius of the neutral line of the flexible carrier, and alpha is the bending angle of the neutral line of the flexible carrier;
the curvature of the flexible carrier is in inverse proportion to the bending angle of the neutral line of the flexible carrier, and the curvature of the flexible carrier satisfies formula (3):
wherein q is the curvature of the flexible carrier, L is the length of the neutral line of the flexible carrier, R is the bending radius of the neutral line of the flexible carrier, and alpha is the bending angle of the neutral line of the flexible carrier;
the distances from the strain sensing grating array to the two sides of the flexible carrier are respectively set as a and b (wherein a is<b) When the flexible carrier is bent, the strain sensing grating array is shifted to a position
The grating length of the strain sensing grating array satisfies the following formula (4):
wherein L is FBG The method comprises the steps of representing the grating length of a strain sensing grating array, wherein R is the bending radius of a neutral line of a flexible carrier, a and b are distances from the strain sensing grating array to two sides of the flexible carrier respectively, and alpha is the bending angle of the neutral line of the flexible carrier;
combining the formula (2) and the formula (4) to obtain the grating length variation of the strain sensing grating array; the grating length variation of the strain sensing grating array satisfies the following formula (5):
wherein, Δ L FBG Representing the amount of grating length variation of the strain sensing grating array, L representing the length of the neutral line of the flexible carrier, L FBG The grating length of the strain sensing grating array is represented, and a and b are distances from the strain sensing grating array to two sides of the flexible carrier respectively;
combining the formula (1) and the formula (5), the shift amount of the central wavelength of the reflected light of the strain sensing grating array satisfies the formula (6):
Δλ∝±(a-b) (6)
wherein, Delta lambda represents the offset of the central wavelength of the reflected light of the strain sensing grating array, a and b are the distances from the strain sensing grating array to the two sides of the flexible carrier, respectively, the plus or minus sign in the plus or minus (a-b) represents the plus or minus of the bending direction of the strain sensing grating array, and the bending direction of the strain sensing grating array reflects the bending direction of the submarine cable.
As a further improvement of the above technical solution, the grating demodulator is further configured to set a correspondence between an offset of a center wavelength of reflected light of the strain sensing grating array and curvature information of the strain sensing grating array, and obtain the curvature information of the strain sensing grating array through the offset of the center wavelength of the reflected light of the strain sensing grating array.
As a further improvement of the technical scheme, the transmission optical fiber is fixed with the submarine cable, and the transmission optical fiber and the submarine cable are wrapped by steel wire armored shells.
As a further improvement of the above technical solution, the monitoring upper computer is configured to output a first control signal or a second control signal to the grating demodulator according to a sea surface condition above the submarine cable, where the second control signal is used to turn off the grating demodulator when the sea surface condition is stable, and the first control signal is used to turn on the grating demodulator when the sea surface condition is changed.
The invention has the beneficial effects that: the invention discloses a submarine cable deformation monitoring system based on a sensing grating array, which is provided with a monitoring upper computer, a grating demodulator and a monitoring system, wherein the monitoring system comprises a transmission optical fiber and a flexible carrier, the transmission optical fiber is provided with a plurality of strain sensing grating arrays and a plurality of temperature sensing grating arrays, the transmission optical fiber is embedded into the flexible carrier, the strain sensing grating arrays embedded into the flexible carrier have bi-directionality, and the strain sensing grating arrays are distributed along the axial direction of a submarine cable. The method comprises the steps of obtaining the central wavelength offset of a reflected wave of a strain sensing grating array through the strain sensing grating array, obtaining curvature information of the strain sensing grating array through the central wavelength offset of the reflected wave, and obtaining deformation monitoring information of a submarine cable by a monitoring upper computer according to the curvature information; the invention can realize the real-time monitoring of the deformation condition of the submarine cable, realize the remote real-time positioning self-checking function of the submarine cable, and improve the stability and the fault repairing capability of the submarine cable.
Drawings
In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below. It is clear that the described figures are only some embodiments of the invention, not all embodiments, and that a person skilled in the art can also derive other designs and figures from them without inventive effort.
FIG. 1 is a schematic structural diagram of a submarine cable deformation monitoring system based on a sensing grating array;
FIG. 2 is a schematic distribution diagram of a strain sensing grating array and a temperature sensing grating array of a submarine cable deformation monitoring system based on a sensing grating array;
FIG. 3 is a schematic structural diagram of a transmission optical fiber and an undersea cable of an undersea cable deformation monitoring system based on a sensing grating array;
FIG. 4 is a schematic diagram of the position of the neutral line of the flexible carrier and the offset position of the neutral line in the normal operation of the submarine cable deformation monitoring system based on the sensing grating array;
FIG. 5 is a schematic illustration of the position of the neutral line of a flexible carrier, the offset position of the neutral line when the strain sensing grating array is compressed, for a submarine cable deformation monitoring system based on a sensing grating array;
fig. 6 is a schematic diagram of the position of the neutral line of the flexible carrier and the offset position of the neutral line when the strain sensing grating array of the submarine cable deformation monitoring system based on the sensing grating array is stretched.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of and not restrictive on the broad application.
It is noted that while a division of functional blocks is depicted in the system diagram, and logical order is depicted in the flowchart, in some cases the steps depicted and described may be performed in a different order than the division of blocks in the system or the flowchart. The terms first, second and the like in the description and in the claims, and the drawings described above, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
Referring to fig. 1 to 6, a submarine cable deformation monitoring system based on a sensing grating array is used for monitoring the form of a submarine cable, and comprises: the monitoring system comprises a monitoring upper computer 100, a grating demodulator 200 and a monitoring system 300, wherein the monitoring upper computer 100 is arranged on a shore base and is connected with the optical fiber demodulator 200 through the internet;
the monitoring system 300 comprises a flexible carrier 310 and a transmission fiber 320, wherein the transmission fiber 320 is provided with a plurality of strain sensing grating arrays 321, the transmission fiber 320 is embedded into the flexible carrier 310, and the strain sensing grating arrays 321 are arranged along the axial direction of the submarine cable 400;
the grating demodulator 200 is configured to emit a light signal, acquire and demodulate the light signal reflected by the strain sensing grating array 321, acquire curvature information of the strain sensing grating array 321, and output the curvature information to the monitoring upper computer 100; the optical signal is sent into the strain sensing grating array 321 through the transmission fiber 320;
the grating demodulator 200 is further configured to set a corresponding relationship between an offset of a central wavelength of the reflected light of the strain sensing grating array 321 and curvature information of the strain sensing grating array 321, and obtain the curvature information of the strain sensing grating array 321 through the offset of the central wavelength of the reflected light of the strain sensing grating array 321.
The monitoring upper computer 100 is configured to output a first control signal or a second control signal to the grating demodulator 200 according to a sea surface condition above the submarine cable 400, where the first control signal is used to close the grating demodulator 200 when the sea surface condition is stable, and the second control signal is used to open the grating demodulator 200 when the sea surface condition has a variation;
the monitoring upper computer 100 is further configured to obtain deformation monitoring information of the submarine cable 400 according to the curvature information.
The submarine cable deformation monitoring system provided by the invention has the working characteristic of a normally closed type, and the energy consumption of the whole submarine cable deformation monitoring system can be reduced to the minimum by the normally closed type working characteristic. In addition, the grating demodulator 200 can be started periodically, and the damage condition of the submarine cable 400 or the potential safety hazard can be discovered in time.
The normally closed type working characteristics are represented as follows: when the monitoring upper computer 100 judges that a ship passes above the submarine cable 400 and/or the ship is anchored, a first control signal is output to the grating demodulator 200 to control the grating demodulator 200 to be started; when the monitoring upper computer 100 judges that no ship passes above the submarine cable 400 and/or no ship is anchored, a second control signal is output to the grating demodulator 200 to control the grating demodulator 200 to be closed.
Further, referring to fig. 2, the transmission fiber 320 is further provided with a plurality of temperature sensing grating arrays 322, the temperature sensing grating arrays 322 are located beside the strain sensing grating array 321, and the temperature sensing grating arrays 322 are used for providing temperature compensation for the strain sensing grating array 321.
In this embodiment, the head of the transmission fiber 320 is connected to the grating demodulator 200, and the body of the transmission fiber is divided into a plurality of parallel slits with equal width and equal spacing, wherein one part of the parallel slits is a strain sensing grating array 321, the other part of the parallel slits is a temperature sensing grating array 322, the strain sensing grating array 321 and the temperature sensing grating array 322 are both reflective surfaces, and the reflective surfaces are used for reflecting optical signals conforming to specific wavelengths.
The sensing optical fiber 320 is embedded into the flexible carrier 310, and the strain sensing grating array 321 and the temperature sensing grating array 322 are distributed at different positions of the flexible carrier 310, so that the strain sensing grating array 321 and the temperature sensing grating array 322 both have bi-directionality, wherein the bi-directionality means that the optical path of the strain sensing grating array is reversible.
Since the transmission optical fibers 320 are embedded in the flexible carrier 310, the strain sensing grating array 321 is disposed along the axial direction of the submarine cable 400, the flexible carrier 310 is twisted or deformed along with the distortion or deformation of the submarine cable 400, and the deformation of the flexible carrier 310 is different on two sides of the neutral line 311 of the flexible carrier 310 during the twisting or deformation process, the present invention realizes the discrimination of the bending direction of the submarine cable 400 through this characteristic.
Further, referring to fig. 3, the transmission fiber 320 is fixed on the submarine cable 400 through rubber resin, for convenience of description, the transmission fiber 320 and the submarine cable 400 are regarded as a composite pipe cable, and the operation of the submarine cable 400, the operation of the strain sensing grating array 321, and the operation of the temperature sensing grating array 322 are independent of each other, so that no interference occurs. The composite pipe cable is wrapped by a steel wire armored shell 500, the steel wire armored shell 500 has a waterproof function, and the steel wire armored shell 500 plays a role in protecting the monitoring system 300 and the submarine cable 400; moreover, compared with a copper wire armored shell, the price of the steel wire armored shell 500 is lower, and the manufacturing cost of the monitoring system 300 can be effectively reduced.
Further, the grating demodulator 200 is connected to the transmission fiber 320, and the grating demodulator 200 includes a broadband light source for emitting a broadband light signal to the strain sensing grating array 321 and a demodulator for demodulating the reflected light reflected by the strain sensing grating array 321.
The grating demodulator 200 is used as a broadband light source for sending optical signals and a demodulator for demodulating the reflected light of the strain sensing grating array 321, so that the whole system is simplified, and the grating demodulator 200 and the strain sensing grating array 321 are perfectly attached. The broadband light source emits light signals, the light signals are transmitted into the strain sensing grating arrays 321 through the transmission optical fiber 320, only the light signals with the wavelength meeting the Bragg condition are reflected by the strain sensing grating arrays 321 and the signals with other wavelengths are not reflected by precisely matching the distance between the two strain sensing grating arrays 321, and the demodulator receives and demodulates the light signals with the wavelength meeting the Bragg condition and outputs curvature information of the strain sensing grating arrays 321.
Further, the monitoring upper computer 100 is connected with a 12-volt battery pack, and the 12-volt battery pack is used for supplying power to the monitoring upper computer 100.
Referring to fig. 4 to 6, in this embodiment, the broadband light source sends an optical signal to the strain sensing grating array 321, when the submarine cable 400 is distorted or deformed, the central wavelength of the reflected light of the strain sensing grating array 321 changes due to deformation of the strain sensing grating array 321 disposed at different positions of the submarine cable 400, the grating demodulator 200 obtains curvature information of the submarine cable 400 by analyzing and processing the central wavelength of the reflected light of the strain sensing grating array 321, and outputs the curvature information to the monitoring upper computer 100, and the monitoring upper computer 100 obtains deformation monitoring information of the submarine cable 400 according to the curvature information.
Taking a strain sensing grating array located at any key position of the submarine cable as an example, the following specifically describes the method for obtaining curvature information of the submarine cable by analyzing and processing the central wavelength of reflected light of the strain sensing grating array through a grating demodulator.
After the secondary packaging is performed on the strain sensing grating arrays 321, the secondary packaging means that the transmission optical fiber 320 is embedded into the offset position 312 of the neutral line of the flexible carrier 310, and a plurality of strain sensing grating arrays 321 and a plurality of temperature sensing grating arrays 322 are arranged on the transmission optical fiber 320. As the strain sensing grating array 321 approaches the outer arc of the flexible carrier 310, the strain sensing grating array 321 is stretched; as the strain sensing grating array 321 approaches the inner arc of the flexible carrier 310, the strain sensing grating array 321 is compressed.
The central wavelength of the reflected light of the strain sensing grating array 321 satisfies formula (1):
λ＝2n eff ·T (1)
wherein, λ is the central wavelength of the reflected light of the strain sensing grating array, n eff T is the effective refractive index of the strain sensing grating array, and T is the grating period of the strain sensing grating array.
Specifically, the strain sensing grating array 321 is stretched or compressed to affect the grating period thereof, so that the central wavelength of the reflected light of the strain sensing grating array 321 changes: if the strain sensing grating array 321 is stretched, the strain sensing grating array 321 has a longer grating period, resulting in a shift of the center wavelength of the reflected light of the strain sensing grating array 321 to a longer wavelength; if the strain sensing grating array 321 is compressed, the strain sensing grating array 321 has a shorter grating period, resulting in a shift of the center wavelength of the reflected light of the strain sensing grating array 321 to a shorter wavelength.
According to the above structural characteristics, the strain sensing grating array 321 of the present invention is embedded in the flexible carrier 310, the strain sensing grating array 321 is located at the offset position 312 of the neutral line of the flexible carrier 310, the positive bending of the flexible carrier 310 or the negative bending of the flexible carrier 310 has different effects on the grating period of the strain sensing grating array 321, and when the flexible carrier 310 is bent, the length of the neutral line 311 of the flexible carrier 310 satisfies the formula (2):
L＝R·α (2)
wherein L is the length of the neutral line of the flexible carrier, R is the bending radius of the neutral line of the flexible carrier, and alpha is the bending angle of the neutral line of the flexible carrier;
the curvature of the flexible carrier 310 is in inverse proportion to the bending radius of the neutral line 311 of the flexible carrier, and the curvature of the flexible carrier 310 satisfies the formula (3):
wherein q is the curvature of the flexible carrier.
Since the transmission fiber 320 is embedded in the flexible carrier 310 made of a flexible material, the transmission fiber 320 and the flexible carrier 310 are regarded as the same object to be bent, and as shown in fig. 4, distances from the strain sensing grating array 321 to two ends of the flexible carrier 310 are respectively a and b (where a is a<b) The position where the strain sensing grating array 321 shifts when the flexible carrier 310 is bent is
At the same time
It can also be understood that the distance between the strain sensing grating array 321 and the neutral line 311 of the flexible carrier 310, the grating length of the strain sensing grating array 321 satisfies the formula (4):
wherein L is FBG The grating length of the strain sensing grating array is shown, R is the bending radius of a neutral line of the flexible carrier, and a and b are respectively from the strain sensing grating array to the flexible carrierThe distance between two sides of the flexible carrier, alpha is the bending angle of the neutral line of the flexible carrier;
based on equation (4), equation (4.1) and equation (4.2) can be derived:
equation (4.1) represents the grating length of the strain sensing grating array 321 when the strain sensing grating array 321 is stretched and deflected to near one end of the outer arc of the flexible carrier 310;
equation (4.2) represents the grating length of the strain sensing grating array 321 when the strain sensing grating array 321 is compressed and shifted to near one end of the inner arc of the flexible carrier 310.
The grating length variation of the strain sensing grating array 321 can be derived by combining the length of the neutral line 311 of the flexible carrier and the grating length of the strain sensing grating array 321. Wherein, the grating length variation of the strain sensing grating array 321 satisfies the following formula (5):
wherein, Δ L FBG Showing the grating length variation of the strain sensing grating array, L showing the length of the neutral line of the flexible carrier, L FBG The grating length of the strain sensing grating array is represented, and a and b are distances from the strain sensing grating array to two sides of the flexible carrier respectively;
based on equation (5), equation (5.1) and equation (5.2) can be derived:
equation (5.1) represents the amount of grating length change of the strain sensing grating array 321 as the strain sensing grating array 321 is stretched and deflected to near one end of the outer arc of the flexible carrier 310, at which time the grating length increases;
equation (5.2) represents the amount of grating length change of the strain sensing grating array 321 as the strain sensing grating array 321 is compressed and deflected to near one end of the inner arc of the flexible carrier 310, when the grating length is reduced.
By the grating length variation of the strain sensing grating array 321, it can be known that: the grating period of the strain sensing grating array 321 varies in proportion to the bending angle of the neutral line 311 of the flexible carrier 310.
Based on all the above formulas, the shift amount of the central wavelength of the reflected light of the strain sensing grating array 321 satisfies formula (6):
Δλ∝±(a-b)(6)
wherein, Delta lambda represents the offset of the central wavelength of the reflected light of the strain sensing grating array, a and b are the distances from the strain sensing grating array to the two sides of the flexible carrier respectively, and +/-of +/- (a-b) represents the positive and negative of the bending direction of the strain sensing grating array;
based on the above, referring to fig. 5, fig. 5 shows that the strain sensing grating array 321 is shifted to a position closer to the inner arc of the flexible carrier 310, when the shift amount of the central wavelength of the reflected light of the strain sensing grating array 321 satisfies Δ λ — (a-b), the bending degree of the strain sensing grating array 321 is positive bending, and the strain sensing grating array 321 is compressed because the length of the neutral line 311 of the flexible carrier is greater than the grating length of the strain sensing grating array 321.
Referring to fig. 6, fig. 6 shows that the strain sensing grating array 321 is shifted to a position closer to the outer arc of the flexible carrier 310, when the shift amount of the central wavelength of the reflected light of the strain sensing grating array 321 satisfies Δ λ — (a-b), the bending degree of the strain sensing grating array 321 is negative bending, and the strain sensing grating array 321 is stretched because the length of the neutral line 311 of the flexible carrier is smaller than the grating length of the strain sensing grating array 321.
In summary, the bending direction of the submarine cable 400 can be obtained through the compression or tension of the strain sensing grating array 321.
The curvature calibration of the strain sensing grating array 321 is finished in the previous work, the corresponding relation between the curvature and the offset of the central wavelength of the reflected light of the strain sensing grating array 321 is obtained, and the curvature information is obtained according to the corresponding relation between the curvature and the offset of the central wavelength; meanwhile, temperature information is acquired through the temperature sensing grating array 322 and temperature compensation is performed on the strain sensing grating array 321. In the operation process of the submarine cable deformation monitoring system, the monitoring upper computer 100 acquires curvature information of a plurality of physical points of the submarine cable 400 monitored by the monitoring system 300, the monitoring upper computer 100 performs curve fitting on the submarine cable 400 by using the curvature information, and reconstructs the shape of the submarine cable 400 through a reconstruction algorithm to obtain the two-dimensional form of the submarine cable 400 and position information of the submarine cable 400 with faults.
The submarine cable deformation monitoring system based on the sensing grating array provided by the invention has the following working process:
the monitoring system 300 is directly attached to the submarine cable 400, and the monitoring system 300 monitors the morphology of the critical portions of the submarine cable 400. The strain sensing grating array 321 attached to the submarine cable 400 collects curvature information of each physical point of the submarine cable 400, and transmits the curvature information to the grating demodulator 200 in the form of reflected light through the transmission optical fiber 340; the grating demodulator 200 demodulates the reflected light of the strain sensing grating array 321 to obtain curvature information of each physical point of the submarine cable 400, transmits the curvature information to the monitoring upper computer 100 through the internet, and the monitoring upper computer 100 obtains deformation monitoring information of the submarine cable 400 according to the curvature information.
The invention can realize the real-time monitoring of the deformation condition of the submarine cable 400, realize the remote real-time positioning self-checking function of the submarine cable 400 and improve the stability and the fault repairing capability of the submarine cable 400.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that the present invention is not limited to the details of the embodiments shown and described, but is capable of numerous equivalents and substitutions without departing from the spirit of the invention as set forth in the claims appended hereto.
Claims (8)
1. A submarine cable deformation monitoring system based on sensing grating array is used for monitoring the form of submarine cable, and is characterized by comprising: the monitoring upper computer is arranged on a shore base and is connected with the grating demodulator through the Internet;
the monitoring system comprises a flexible carrier and a transmission optical fiber, wherein a plurality of strain sensing grating arrays are arranged on the transmission optical fiber, the transmission optical fiber is embedded into the flexible carrier, and the strain sensing grating arrays are arranged along the axial direction of the submarine cable;
the grating demodulator is used for transmitting optical signals, the optical signals are transmitted into the strain sensing grating array through the transmission optical fiber, the optical signals reflected by the strain sensing grating array are obtained and demodulated, and curvature information of the strain sensing grating array is obtained;
and the monitoring upper computer is used for obtaining deformation monitoring information of the submarine cable according to the curvature information.
2. The submarine cable deformation monitoring system according to claim 1, wherein the transmission fiber is further provided with a plurality of temperature sensing grating arrays, the temperature sensing grating arrays are located beside the strain sensing grating arrays, and the temperature sensing grating arrays are used for performing temperature compensation on the strain sensing grating arrays.
3. A submarine cable deformation monitoring system according to claim 1, where the grating demodulator is connected to the transmission fiber, and the grating demodulator comprises a broadband light source and a demodulator, the broadband light source is configured to emit a light signal into the strain sensing grating array, and the demodulator is configured to acquire and demodulate the reflected light reflected by the strain sensing grating array.
4. The submarine cable deformation monitoring system based on sensing grating array according to claim 1, wherein the central wavelength of the reflected light of the strain sensing grating array satisfies formula (1):
λ＝2n eff ·T (1)
wherein, λ is the central wavelength of the reflected light of the strain sensing grating array, n eff The effective refractive index of the strain sensing grating array is shown, and T is the grating period of the strain sensing grating array;
when the effective refractive index of the strain sensing grating array is unchanged, and when the strain sensing grating array is stretched, the strain sensing grating array approaches to the outer arc of the flexible carrier, the grating period of the strain sensing grating array is increased, and the offset of the central wavelength of the reflected light of the strain sensing grating array is increased.
5. The submarine cable deformation monitoring system according to claim 4, wherein the length of the neutral line of the flexible carrier satisfies formula (2):
L＝R·α (2)
wherein L is the length of the neutral line of the flexible carrier, R is the bending radius of the neutral line of the flexible carrier, and alpha is the bending angle of the neutral line of the flexible carrier;
the curvature of the flexible carrier is in inverse proportion to the bending angle of the neutral line of the flexible carrier, and the curvature of the flexible carrier satisfies the formula (3):
wherein q is the curvature of the flexible carrier, L is the length of the neutral line of the flexible carrier, R is the bending radius of the neutral line of the flexible carrier, and alpha is the bending angle of the neutral line of the flexible carrier;
the distances from the strain sensing grating array to the two sides of the flexible carrier are respectively set as a and b (wherein a is<) When the flexible carrier is bent, the strain sensing grating array is shifted to a position
The grating length of the strain sensing grating array satisfies the following formula (4):
wherein L is FBG The grating length of the strain sensing grating array is represented, R is the bending radius of a neutral line of the flexible carrier, a and b are respectively the distance from the strain sensing grating array to two sides of the flexible carrier, and alpha is the bending angle of the neutral line of the flexible carrier;
combining the formula (2) and the formula (4) to obtain the grating length variation of the strain sensing grating array; the grating length variation of the strain sensing grating array satisfies the following formula (5):
wherein, Δ L FBG Representing the amount of grating length variation of the strain sensing grating array, L representing the length of the neutral line of the flexible carrier, L FBG The grating length of the strain sensing grating array is represented, and a and b are distances from the strain sensing grating array to two sides of the flexible carrier respectively;
combining the formula (1) and the formula (5), the shift amount of the central wavelength of the reflected light of the strain sensing grating array satisfies the formula (6):
Δλ∝±(a-b) (6)
wherein, Delta lambda represents the offset of the central wavelength of the reflected light of the strain sensing grating array, a and b are the distances from the strain sensing grating array to the two sides of the flexible carrier, respectively, the plus or minus sign in the plus or minus (a-b) represents the plus or minus of the bending direction of the strain sensing grating array, and the bending direction of the strain sensing grating array reflects the bending direction of the submarine cable.
6. The submarine cable deformation monitoring system according to claim 5, wherein the grating demodulator is further configured to set a correspondence between the shift of the central wavelength of the reflected light from the strain sensing grating array and the curvature information of the strain sensing grating array, and obtain the curvature information of the strain sensing grating array according to the shift of the central wavelength of the reflected light from the strain sensing grating array.
7. The submarine cable deformation monitoring system according to claim 1, wherein the transmission optical fiber is fixed to the submarine cable, and the transmission optical fiber and the submarine cable are wrapped by steel wire armored cases.
8. The submarine cable deformation monitoring system according to claim 1, wherein the monitoring host computer is configured to output a first control signal or a second control signal to the grating demodulator according to a sea surface condition above the submarine cable, the first control signal is configured to turn off the grating demodulator when the sea surface condition is stable, and the second control signal is configured to turn on the grating demodulator when the sea surface condition is abnormal.
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