Wide-range seabed monitoring botda system based on meshed multi-stage remote pumping amplification

Abstract

The present invention belongs to the technical field of measurement and testing. Disclosed is a wide-range seabed monitoring BOTDA system based on meshed multi-stage remote pumping amplification. Seabed monitoring optical fiber cables are laid in a meshed structure, wherein two interleaved optical fiber cables are connected by using seven types of special optical fiber cable interfaces, and shortest path routing and optimal power distribution of remote pumping light can be implemented by means of these optical fiber cable interfaces, such that the distance that the remote pumping light travels to reach a distal end of a sensing optical fiber and the transmission loss thereof are greatly reduced, thereby implementing ultra-long-distance pumping. Some of the optical fiber cable interfaces also include therein passive gain units, which can separately amplify detection light and retrieval pulses of a BOTDA terminal in a targeted manner, such that the constant-gain amplification of the detection light and the constant-power output of the retrieval pulses are implemented, and non-local effects in the BOTDA terminal are suppressed while the signal strength is effectively improved, thereby greatly expanding the area of seabed that can be monitored.

Description

A large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification

[0001] The invention relates to optical fiber sensing technology and discloses a large-scale seabed monitoring BOTDA system based on mesh multi-stage remote pump amplification, belonging to the technical field of measurement and testing. Background Art

[0002] With the rapid development of the marine economy, strengthening marine national defense security, improving marine resource development capabilities, and protecting the marine ecological environment are three mutually reinforcing aspects that are receiving increasing attention. Effective sensing and detection technology is crucial for ensuring marine safety, efficient resource development, real-time monitoring, and other applications, and has become a hot topic of research in the current marine field. Distributed fiber optic sensing uses ordinary single-mode optical fiber as both a sensing medium and a signal transmission medium, enabling real-time measurement of physical quantities along the optical fiber. Compared to traditional marine sensing technologies that use detection equipment such as mobile buoys and towed sensor arrays, distributed fiber optic sensing based on submarine optical cables has obvious advantages in submarine monitoring systems due to its ultra-long-distance sensing and ease of large-scale networking.

[0003] Compared to fiber-optic distributed sensing systems based on Rayleigh scattering, Raman scattering, and spontaneous Brillouin scattering, the Brillouin Optical Time Domain Analyzer (BOTDA) based on stimulated Brillouin scattering offers advantages such as an extremely long sensing range and the ability to simultaneously measure temperature and strain. This makes it crucial for large-scale seafloor monitoring. However, seafloor monitoring systems often employ a grid-like network to achieve wide coverage. This wiring approach requires very long sensing fibers, posing a significant challenge to the sensing range of BOTDA systems. Currently, the main methods for extending the sensing range of BOTDA systems include distributed Raman amplification, remote pump amplification, and pulse coding. Pulse coding technology, however, offers limited range expansion and struggles to meet the requirements of large-scale seafloor monitoring systems. Distributed Raman amplification, however, can introduce issues such as Raman spontaneous emission noise, pump-signal crosstalk, and polarization-dependent gain, reducing the signal-to-noise ratio. Furthermore, even with high-order Raman amplification using high pump power, its effective amplification range is limited. Remote pump amplification can avoid these issues, but conventional remote pump amplification is limited by pump light transmission losses in optical fibers, making it impractical for long-distance remote pump amplification. Without a close proximity to the pump source, the sensing range is also limited. Obviously, a 1480nm pump source cannot be placed on the seafloor, making conventional remote pump amplification architecture incapable of large-scale seafloor monitoring.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to address the technical problems mentioned in the above background and propose a large-scale seabed monitoring BOTDA system based on meshed multi-stage remote pump amplification to achieve the invention purpose of large-scale seabed monitoring.

[0006] The present invention adopts the following technical solutions to achieve the above-mentioned purpose: a large-scale seabed monitoring BOTDA system based on a network multi-stage remote pump amplification, which consists of a BOTDA terminal, L wavelengths of λ A,1 to λ A,L A group of pump sources consisting of L pump sources with wavelength λ B,1 to λ B,L The pump source B consists of a pump source, M sections of horizontal submarine optical cables, N sections of vertical submarine optical cables, (N-2) horizontal branching optical cable interfaces, (M-2) vertical branching optical cable interfaces, (M-2) horizontal dual-gain optical cable interfaces, (N-2) vertical dual-gain optical cable interfaces, one horizontal single-gain optical cable interface, one vertical single-gain optical cable interface, and one bidirectional single-gain optical cable interface. The M sections of horizontal submarine optical cables and the N sections of vertical submarine optical cables are formed by laying a submarine monitoring optical cable and connecting the above seven types of optical cable interfaces. Both N and M are odd numbers greater than or equal to 3.

[0007] The seabed monitoring BOTDA device includes a BOTDA system terminal, a remote pump source group A, and a remote pump source group B. The pump source group A contains L wavelengths of λ A,1 to λ A,L The pump source group B contains L pump sources with wavelength λ B,1 to λ B,L The search pulse and group B pump light generated by the BOTDA system end unit enter the initial end of the monitoring optical cable, and the detection light and group A pump light generated by the BOTDA system end unit enter the terminal end of the monitoring optical cable.

[0008] Furthermore, the submarine monitoring optical cable includes three groups of optical fibers, including group A pump optical fibers, group B pump optical fibers and group F sensing optical fibers. C . Group A pump fiber includes F A,1 to F A,L L optical fibers are used to transmit wavelength λ A,1 to λ A,L The pump light of group B pump fiber includes F B,1 to F B,L L optical fibers are used to transmit wavelength λ B,1 to λ B,L The pump light, sensing fiber F C Used to transmit BOTDA's probe light and retrieval pulses and serve as a sensing medium.

[0009] Furthermore, the submarine monitoring cable is first laid horizontally M times, then vertically N times, and finally returned to its original laying position, forming an M×N grid layout, where both N and M are odd numbers greater than or equal to 3. Fiber optic connectors are used at some grid intersections to connect the internal cables. Each horizontal cable segment is numbered 1, 2, …, i, …, M, and each vertical cable segment is numbered 1, 2, …, j, …, N, starting from the nearest distance to the initial laying position. The grid intersections can be represented by (j, i), and there is no intersection (1, 1). Since the vertical cable is laid starting from the farthest point after the horizontal cables are laid, the first vertical cable segment is actually the last cable laid.

[0010] Furthermore, on the first section of the horizontally laid optical cable, at the grid intersection (j, 1) other than the middle grid intersection ((N+1) / 2, 1), that is, at the grid intersection of the first section of the horizontal optical cable and each section of the longitudinal optical cable except the (N+1) / 2 section of the longitudinal optical cable, a horizontal branching optical cable interface is used to connect the four sections of the upper, lower, left and right optical cables. The optical cable interface includes an optical power splitter and three dense wavelength division multiplexers. The first dense wavelength division multiplexer connects the B group of pump fibers F connected from the left end. B,1 to F B,L The pump light transmitted in the optical fiber is combined together, then divided into two paths by the optical power splitter, and then decomposed by the second dense wavelength division multiplexer and the third dense wavelength division multiplexer respectively before entering the corresponding optical fiber in the right end cable and the upper end cable. C Directly connected, the longitudinal sensing optical fiber F at the upper and lower ends C Directly connected.

[0011] Furthermore, a transverse single-gain optical cable interface is used to connect the optical cables at the grid intersection ((N+1) / 2,1) between the first transverse optical cable and the (N+1) / 2 longitudinal optical cable. The optical cable interface includes an optical power splitter, three dense wavelength division multiplexers, and a single-source gain module. The first dense wavelength division multiplexer connects the B group of pump fibers F B,1 to F B,L The pump light transmitted in the optical fiber is combined and then divided into three paths by the optical power splitter. Two of them are decomposed by the second dense wavelength division multiplexer and the third dense wavelength division multiplexer and then enter the corresponding optical fiber in the right end cable and the upper end cable respectively. The other path is used for the single source gain module in the pump cable interface to amplify the horizontally transmitted Brillouin search pulse and detection light. The longitudinal sensing fiber F at the upper and lower ends of the horizontal single gain cable interface C Directly connected, the lateral sensing optical fiber F at both ends C Connects to a single source gain block.

[0012] Furthermore, on the first longitudinally laid optical cable, at the grid intersection (1, i) other than the middle grid intersection (1, (M+1) / 2), i.e., at the grid intersection of the first longitudinal optical cable and each section of the transverse optical cable except the (M+1) / 2 section of the transverse optical cable, a longitudinal branching optical cable interface is used to connect the four sections of the upper, lower, left, and right optical cables. The optical cable interface includes an optical power splitter and three dense wavelength division multiplexers. The first dense wavelength division multiplexer connects the pump fiber F of group A connected from the lower end. A,1 to F A,L The pump light transmitted in the vertical split cable is combined together, then divided into two paths by the optical power splitter, and then decomposed by the second dense wavelength division multiplexer and the third dense wavelength division multiplexer respectively before entering the corresponding optical fiber in the upper and right ends of the optical cable. C Directly connected, the longitudinal sensing optical fiber F at the upper and lower ends C Directly connected.

[0013] Furthermore, a longitudinal single-gain optical cable interface is used to connect the optical cables at the grid intersection (1, (M+1) / 2) between the first longitudinal optical cable and the (M+1) / 2 transverse optical cable. The longitudinal single-gain optical cable interface includes an optical power splitter, three dense wavelength division multiplexers, and a single-source gain module. The first dense wavelength division multiplexer connects the pump fiber F of group A connected from the lower end. A,1 to F A,L The pump light transmitted in the optical fiber is combined and then divided into three paths by the optical power splitter. Two of them are decomposed by the second dense wavelength division multiplexer and the third dense wavelength division multiplexer and then enter the corresponding optical fiber in the upper and right optical cables respectively. The other path is used for the single source gain module in the pump optical cable interface to amplify the longitudinally transmitted Brillouin search pulse and detection light. The transverse sensing fiber F at the left and right ends of the longitudinal single gain optical cable interface C Directly connected, the longitudinal sensing optical fiber F at the upper and lower ends C Connects to a single source gain block.

[0014] Furthermore, a longitudinal dual-gain optical cable interface is used at the grid intersection (j, (M+1) / 2) of the (M+1) / 2th transverse optical cable and each longitudinal optical cable except the first longitudinal optical cable and the (N+1) / 2th longitudinal optical cable. The longitudinal dual-gain optical cable interface includes an optical power splitter, three dense wavelength division multiplexers, and a dual-source gain module. The first dense wavelength division multiplexer connects the left end of the A group of pump fibers F A,1 to F A,L The pump light transmitted in the middle is combined together and then divided into two paths by the optical power splitter. One path is decomposed by the second dense wavelength division multiplexer and enters the corresponding optical fiber in the right end optical cable, and the other path enters the dual-source gain module inside the optical cable interface to amplify the longitudinally transmitted detection light and retrieval pulse; at the same time, the third dense wavelength division multiplexer amplifies the B group of pump fibers FB,1 to F B,L The pump light transmitted in the longitudinal direction is combined and directly input into the dual-source gain module to amplify the longitudinally transmitted detection light and retrieval pulse. C Directly connected, the longitudinal sensing optical fiber F at the upper and lower ends C Connects to a dual-source gain block.

[0015] Furthermore, a transverse dual-gain optical cable interface is used at the grid intersection ((N+1) / 2,i) of the (N+1) / 2th longitudinal optical cable and each transverse optical cable except the first transverse optical cable and the (M+1) / 2th transverse optical cable. The optical cable interface includes an optical power splitter, three dense wavelength division multiplexers, and a dual-source gain module. The first dense wavelength division multiplexer connects the B group of pump fibers F B,1 to F B,L The pump light transmitted in the middle is combined together and then divided into two paths by the optical power splitter. One path is decomposed by the second dense wavelength division multiplexer and enters the corresponding optical fiber in the upper end optical cable, and the other path enters the dual-source gain module inside the optical cable interface to amplify the horizontally transmitted detection light and retrieval pulse; at the same time, the third dense wavelength division multiplexer amplifies the pump fiber F of group A connected to the left end. A,1 to F A,L The pump light transmitted in the middle is combined and directly input into the dual-source gain module to amplify the transversely transmitted detection light and retrieval pulse. C Directly connected, the lateral sensing optical fiber F at both ends C Connects to a dual-source gain block.

[0016] Furthermore, a bidirectional single-gain optical cable interface is used at the grid intersection ((N+1) / 2, (M+1) / 2) of the (M+1) / 2 segment of the horizontal optical cable and the (N+1) / 2 segment of the longitudinal optical cable. The bidirectional single-gain optical cable interface includes two optical power splitters, four dense wavelength division multiplexers, and two single-source gain modules. The first dense wavelength division multiplexer connects the left end of the A group of pump fibers F A,1 to F A,L The pump light transmitted in the optical fiber is combined together and then divided into two paths by the first optical power splitter. One path is decomposed by the second dense wavelength division multiplexer and enters the corresponding optical fiber in the right end optical cable, and the other path enters the first single source gain module inside the optical cable interface to amplify the transversely transmitted detection light and retrieval pulse; the third dense wavelength division multiplexer connects the B group of pump fibers F B,1 to F B,LThe pump light transmitted in the optical fiber is combined and then divided into two paths by the second optical power splitter. One path is decomposed by the fourth dense wavelength division multiplexer and enters the corresponding optical fiber in the upper end optical cable, and the other path enters the second single source gain module inside the optical cable interface to amplify the longitudinally transmitted detection light and retrieval pulse. C Connected to the second single source gain module, the lateral sensing fiber F at both ends C Connected to the first single-source gain block.

[0017] Furthermore, the single-source gain module consists of an optical power splitter, two circulators, two wavelength division multiplexers, two sections of erbium-doped fiber, and two filters. The search pulse is input from the sensing fiber at one end, passes through the first circulator, and enters the lower amplification branch. The probe light is input from the sensing fiber at the other end, passes through the second circulator, and enters the upper amplification branch. The remote pump light is input from the lower fiber, split into two parts by an optical power splitter, and then enters the two amplification branches. The upper and lower amplification branches are essentially the same: the remote pump light and the BOTDA search pulse / probe light are first combined through a wavelength division multiplexer, then pass through a section of erbium-doped fiber, pass through a filter, and finally pass through a circulator and output from the other sensing fiber. This module can use a single wavelength of remote pump light to specifically amplify the probe light and search pulse of the BOTDA system.

[0018] Furthermore, the dual-source gain module consists of three dense wavelength division multiplexers (DWDMs) and a single-source gain module. The first and second DWDMs separate the pump light groups A and B, respectively. A third DWDM then combines all the pump light into the erbium-doped fiber pump light, which is then fed into the single-source gain module. This module can simultaneously utilize two wavelengths of remote pump light, increasing the available remote pump light power.

[0019] The present invention adopts the above technical solution, which has the following significant beneficial effects compared with the existing technology:

[0020] (1) The present invention proposes a large-scale seabed monitoring BOTDA system based on meshed multi-stage remote pump amplification. The seabed monitoring optical cable is laid into a mesh structure, which solves the problem of limited transmission distance of remote pump light in traditional remote pump amplification BOTDA. It realizes true relay-free meshed multi-stage remote pump amplification, weakens the non-local effect of BOTDA, improves the sensor signal strength and measurement accuracy, and greatly expands the monitorable seabed area.

[0021] (2) The present invention designs seven special optical cable interfaces for connecting two interlaced optical cables. These interfaces enable the shortest path routing and optimal power distribution of pump light around 1480 nm, as well as efficient amplification of the search pulses and probe light in the BOTDA system. Based on these interfaces and the meshed distribution of optical cables, the distance and loss of remote pump light reaching the far end of the sensing fiber are greatly reduced, enabling ultra-long-distance pumping and high-power pulse amplification.

[0022] (3) The present invention designs a single-source gain unit that can perform targeted amplification on the detection light and retrieval pulse of the BOTDA terminal, respectively, to achieve constant gain amplification of the detection light and constant power output of the retrieval pulse, effectively improving the signal strength while suppressing the non-local effect in the BOTDA.

[0023] (4) The present invention designs a dual-source gain unit that can simultaneously utilize two sets of remote pumping lights of different wavelengths to amplify the signal, thereby increasing the pumping light power of the input erbium-doped fiber, reducing the limitation caused by excessive loss of pumping light due to long-distance transmission, further improving the pumping range, and thus expanding the sensing range. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 shows a large-scale seabed monitoring BOTDA system based on meshed multi-stage remote pump amplification with M sections of horizontal optical cables and N sections of longitudinal optical cables.

[0025] Figure 2 shows a large-scale seabed monitoring BOTDA system based on meshed multi-stage remote pump amplification with 5 sections of horizontal optical cables and 5 sections of longitudinal optical cables.

[0026] Figure 3 is a structural diagram of the longitudinal branching optical cable interface.

[0027] FIG4 is a structural diagram of a horizontal split optical cable interface.

[0028] Figure 5 is a structural diagram of a longitudinal single-gain optical cable interface.

[0029] Figure 6 is a structural diagram of a horizontal single-gain optical cable interface.

[0030] Figure 7 is a structural diagram of a longitudinal dual-gain optical cable interface.

[0031] FIG8 is a structural diagram of a transverse dual-gain optical cable interface.

[0032] Figure 9 is a structural diagram of a bidirectional single-gain optical cable interface.

[0033] FIG10 is a structural diagram of a single-wavelength passive gain module.

[0034] FIG11 is a structural diagram of a dual-wavelength passive gain module.

[0035] Explanation of the numbers in the figure: DWDM1~DWDM4, the first to the fourth dense wavelength division multiplexers, WDM1~WDM2, the first to the second wavelength division multiplexers.

[0036] Implementation Method

[0037] The present invention will be further explained below with reference to the accompanying drawings.

[0038] As shown in Figure 1, a large-scale seabed monitoring BOTDA system based on a network multi-stage remote pump amplification consists of a BOTDA terminal, L wavelengths of λ A,1 to λ A,L The pump source group A consists of L pump sources with wavelengths of λ B,1 to λ B,L The pump source consists of a pump source group B, M sections of horizontal submarine optical cables, N sections of vertical submarine optical cables, (N-2) horizontal branching optical cable interfaces, (M-2) vertical branching optical cable interfaces, (M-2) horizontal dual-gain optical cable interfaces, (N-2) vertical dual-gain optical cable interfaces, one horizontal single-gain optical cable interface, one vertical single-gain optical cable interface, and one bidirectional single-gain optical cable interface. The N sections of horizontal submarine optical cables and the M sections of vertical submarine optical cables are formed by connecting a submarine monitoring optical cable after laying, and both N and M are odd numbers greater than or equal to 3. The submarine monitoring optical cable contains three groups of optical fibers, including pump fiber group A, pump fiber group B, and sensing fiber F. C The pump fiber group A includes F A,1 to F A,L L optical fibers are used to transmit wavelength λ A,1 to λ A,L The pump light of pump fiber group B includes F B,1 to F B,L L optical fibers are used to transmit wavelength λ B,1 to λ B,L The pump light, sensing fiber F C It is used to transmit the BOTDA probe light and retrieval pulse and serves as a sensing medium. The retrieval pulse and group B pump light generated by the BOTDA system end unit enter the initial end of the monitoring optical cable, and the probe light and group A pump light generated by the BOTDA system end unit enter the terminal end of the monitoring optical cable.

[0039] The submarine monitoring cable is first laid horizontally M times, then longitudinally N times, before returning to its original location. This creates an M×N grid layout, where both N and M are odd numbers greater than or equal to 3. Fiber optic connectors are used at some grid intersections to connect the cables internally. Each horizontal cable segment is numbered 1, 2, …, i, …, M, from closest to the initial location. Each longitudinal cable segment is numbered 1, 2, …, j, …, N, so the grid intersections can be represented by (j, i), and there is no intersection (1, 1). Since the longitudinal cable is laid starting from the farthest point after the horizontal cables are laid, the first longitudinal cable segment is actually the last cable laid.

[0040] At the grid intersection (j, 1) (j ≠ N+1) / 2) on the first horizontal section of optical cable, a horizontal splitter optical cable interface B is used to connect the four upper, lower, left, and right optical cable segments. At the intersection of the first horizontal section of optical cable and the (N+1) / 2 longitudinal section of optical cable, that is, the middle grid intersection ((N+1) / 2, 1), a horizontal single-gain optical cable interface D is used to connect the optical cables. At the grid intersection (1, i) (i ≠ M+1) / 2) on the first longitudinal section of optical cable, a vertical splitter optical cable interface A is used to connect the four upper, lower, left, and right optical cable segments. At the intersection of the first longitudinal section of optical cable and the (M+1) / 2 transverse section of optical cable, that is, the middle grid intersection (1, (M+1) / 2), a vertical single-gain optical cable interface C is used to connect the optical cables. At the intersection of the (M+1) / 2th transverse and longitudinal optical cables, which is the grid intersection of the middle transverse optical cables (j, (M+1) / 2) (j≠1, (N+1) / 2), use the longitudinal dual-gain optical cable interface E to connect the optical cables. At the intersection of the (N+1) / 2th longitudinal and transverse optical cables, which is the grid intersection of the middle longitudinal optical cables ((N+1) / 2, i) (i≠1, (M+1) / 2), use the transverse dual-gain optical cable interface F to connect the optical cables. At the intersection of the (M+1) / 2th transverse and (N+1) / 2th longitudinal optical cables, which is the grid intersection of the middle longitudinal optical cables ((N+1) / 2, (M+1) / 2), use the bidirectional single-gain optical cable interface G to connect the upper, lower, left, and right optical cables.

[0041] The detection light and retrieval pulse of the BOTDA system are always along the sensing fiber F in the optical cable. C The light propagates in opposite directions and is amplified at each optical cable interface with gain to reduce the loss caused by optical fiber transmission, so that the detection light and retrieval pulse are always kept at a high power, and the measurement accuracy of the system is always maintained at a high level.

[0042] As shown in FIG2 , a large-scale submarine monitoring BOTDA system based on a meshed multi-stage remote pump amplification of this embodiment includes a BOTDA terminal, a pump source A consisting of two pump sources of 1480 nm and 1480.2 nm, a pump source B consisting of two pump sources of 1481 nm and 1481.2 nm, 5 sections of horizontal submarine optical cables, 5 sections of vertical submarine optical cables, 3 horizontal branching optical cable interfaces B1 to B3, 3 vertical branching optical cable interfaces A1 to A3, 3 horizontal dual-gain optical cable interfaces F1 to F3, 3 vertical dual-gain optical cable interfaces E1 to E3, 1 horizontal single-gain optical cable interface D1, 1 vertical single-gain optical cable interface C1, and 1 bidirectional single-gain optical cable interface G1. The 5 sections of horizontal submarine optical cables and the 5 sections of vertical submarine optical cables are formed by connecting a submarine optical cable after being laid. The submarine monitoring optical cable includes 3 groups of optical fibers, including pump optical fiber group A, pump optical fiber group B, and sensing optical fiber F. C The pump fiber group A includes F A,1 to F A,2 The two optical fibers are used to transmit the pump light of 1480nm and 1480.2nm. Pump fiber group B includes F B,1 to F B,2 Two optical fibers are used to transmit pump light at 1481nm and 1481.2nm. Sensing fiber F C It is used to transmit the BOTDA detection light and retrieval pulse and serves as a sensing medium. The 1481nm and 1481.2nm remote pump light enters from the beginning of the optical cable along with the BOTDA retrieval pulse, and the 1480nm and 1480.2nm remote pump light enters from the end of the optical cable along with the BOTDA detection light. The detection light and retrieval pulse of the BOTDA system always follow the sensing fiber F in the optical cable. C The pump lights of group A and group B are split at each optical cable interface and then enter the next optical cable interface or are absorbed by the passive gain module inside the optical cable interface to amplify the sensing signal.

[0043] Figure 3 is a diagram of the longitudinal split optical cable interface structure. The first dense wavelength division multiplexer DWDM1 divides F A,1 to F A,2 The 1480nm and 1480.2nm pump lights transmitted in the vertical splitter are combined together and then split into two paths by the optical power splitter. They are then decomposed by the second dense wavelength division multiplexer DWDM2 and the third dense wavelength division multiplexer DWDM3 and then enter the corresponding optical fibers in the upper and right optical cables. C Directly connected, the longitudinal sensing optical fiber F at the upper and lower ends C Directly connected.

[0044] Figure 4 is a diagram of the structure of the horizontal split optical cable interface. The first dense wavelength division multiplexer DWDM1 divides F B,1 and FB,2 The 1481nm and 1481.2nm pump lights transmitted in the optical fiber are combined together, then divided into two paths by the optical power splitter, and then decomposed by the second dense wavelength division multiplexer DWDM2 and the third dense wavelength division multiplexer DWDM3 respectively before entering the corresponding optical fibers in the right and upper optical cables. C Directly connected, the longitudinal sensing optical fiber F at the upper and lower ends C Directly connected.

[0045] Figure 5 is a diagram of the longitudinal single-gain optical cable interface structure. The first dense wavelength division multiplexer DWDM1 converts F A,1 and F A,2 The 1480nm and 1480.2nm pump lights transmitted in the middle are combined and then divided into three paths by the optical power splitter. Two of them are decomposed by the second dense wavelength division multiplexer DWDM2 and the third dense wavelength division multiplexer DWDM3 and then enter the corresponding optical fibers in the upper and right optical cables respectively. The other path is used for the single-source gain module in the pump cable interface to amplify the longitudinally transmitted Brillouin search pulse and detection light. The transverse sensing fibers F at the left and right ends of the longitudinal single-gain optical cable interface are as follows: C Directly connected, the longitudinal sensing optical fiber F at the upper and lower ends C Connects to a single source gain block.

[0046] Figure 6 is a diagram of the structure of the horizontal single-gain optical cable interface. The first dense wavelength division multiplexer DWDM1 converts F B,1 and F B,2 The 1481nm and 1481.2nm pump lights transmitted in the optical fiber are combined and then divided into three paths by the optical power splitter. Two of them are decomposed by the second dense wavelength division multiplexer DWDM2 and the third dense wavelength division multiplexer DWDM3 and then enter the corresponding optical fibers in the right and upper optical cables respectively. The other path is used for the single-source gain module in the pump cable interface to amplify the horizontally transmitted Brillouin search pulse and detection light. The longitudinal sensing fiber F at the upper and lower ends of the horizontal single-gain optical cable interface C Directly connected, the lateral sensing optical fiber F at both ends C Connects to a single source gain block.

[0047] Figure 7 is a diagram of the longitudinal dual-gain optical cable interface structure. The first dense wavelength division multiplexer DWDM1 connects the left end F A,1 and F A,2 The 1480nm and 1480.2nm pump lights transmitted in the optical fiber are combined together and then divided into two paths by the optical power splitter. One path is decomposed by the second dense wavelength division multiplexer DWDM2 and enters the corresponding optical fiber in the right end optical cable. The other path enters the dual-source gain module inside the optical cable interface to amplify the longitudinally transmitted detection light and retrieval pulse. At the same time, the third dense wavelength division multiplexer DWDM3 amplifies the lower end FB,1 to F B,2 The 1481nm and 1481.2nm pump lights transmitted in the longitudinal direction are combined and directly input into the dual-source gain module to amplify the longitudinally transmitted probe light and retrieval pulse. C Directly connected, the longitudinal sensing optical fiber F at the upper and lower ends C Connects to a dual-source gain block.

[0048] Figure 8 is a diagram of the structure of the horizontal dual-gain optical cable interface. The first dense wavelength division multiplexer DWDM1 connects the lower end F B,1 and F B,2 The 1481nm and 1481.2nm pump lights transmitted in the optical fiber are combined together and then divided into two paths by the optical power splitter. One path is decomposed by the second dense wavelength division multiplexer DWDM2 and enters the corresponding optical fiber in the upper end optical cable. The other path enters the dual-source gain module inside the optical cable interface to amplify the horizontally transmitted detection light and retrieval pulse. At the same time, the third dense wavelength division multiplexer DWDM3 divides the left end F A,1 to F A,2 The 1480nm and 1480.2nm pump lights transmitted in the middle are combined and directly input into the dual-source gain module to amplify the transversely transmitted probe light and retrieval pulse. C Directly connected, the longitudinal sensing optical fibers F at both ends C Connects to a dual-source gain block.

[0049] Figure 9 is a diagram of the bidirectional single-gain optical cable interface structure. The first dense wavelength division multiplexer DWDM1 connects the left end F A,1 to F A,2 The 1480nm and 1480.2nm pump lights transmitted in the optical fiber are combined together and then divided into two paths by the optical power splitter 1. One path is decomposed by the second dense wavelength division multiplexer DWDM2 and enters the corresponding optical fiber in the right end optical cable. The other path enters the single source gain module 1 inside the optical cable interface to amplify the horizontally transmitted detection light and retrieval pulse; the third dense wavelength division multiplexer DWDM3 divides the lower end F B,1 to F B,2 The 1481nm and 1481.2nm pump lights transmitted in the optical fiber are combined together and then divided into two paths by the optical power splitter 2. One path is decomposed by the fourth dense wavelength division multiplexer DWDM4 and enters the corresponding optical fiber in the upper end optical cable. The other path enters the single source gain module 2 inside the optical cable interface to amplify the longitudinally transmitted probe light and retrieval pulse.

[0050] Figure 10 shows the structure of a single-wavelength passive gain module. The search pulse is input from the sensing fiber at one end, passes through circulator 1, and enters the lower amplification branch. The probe light is input from the sensing fiber at the other end, passes through circulator 2, and enters the upper amplification branch. Pump light around 1480 nm is input from the lower fiber, split into two parts by an optical power splitter, and then enters the two amplification branches. The upper and lower amplification branches have essentially the same structure: the 1480 nm pump light and the BOTDA search pulse / probe light are first combined by a wavelength division multiplexer (WDM1) or a wavelength division multiplexer (WDM2). The light then passes through a section of erbium-doped fiber and a filter before being output from the other sensing fiber through a circulator.

[0051] Figure 11 shows the structure of a dual-wavelength passive gain module. First, the first dense wavelength division multiplexer (DWMD1) and the second dense wavelength division multiplexer (DWDM2) demultiplex the pump light at 1480 nm, 1480.2 nm, 1481.0 nm, and 1481.2 nm. These are then combined by a third dense wavelength division multiplexer (DWDM3) to serve as the pump light for the erbium-doped fiber. The remaining structure and steps are identical to those for a single-wavelength passive gain module and are not further described.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A large-scale seabed monitoring BOTDA system based on a network of multi-stage remote pump amplification, characterized in that: include: The monitoring submarine cable is laid into a mesh structure of M sections of transverse optical cables and N sections of longitudinal optical cables interlaced. The transverse optical cable closest to the submarine monitoring BOTDA device is the first section of the transverse optical cable, and the longitudinal optical cable closest to the submarine monitoring BOTDA device is the first section of the longitudinal optical cable. The first section of the transverse optical cable and each section of the longitudinal optical cable except the (N+1) / 2 section of the longitudinal optical cable are connected to a transverse branch optical cable interface at the grid intersection. The first section of the transverse optical cable and the (N+1) / 2 section of the longitudinal optical cable are connected to a transverse single gain optical cable interface at the grid intersection. The first section of the longitudinal optical cable and each section of the transverse optical cable except the (M+1) / 2 section of the transverse optical cable are connected to a longitudinal branch optical cable interface at the grid intersection. A longitudinal single-gain optical cable interface is connected at the grid intersection of the 1st longitudinal optical cable and the (M+1) / 2nd transverse optical cable, a longitudinal dual-gain optical cable interface is connected at the grid intersection of the (M+1) / 2nd transverse optical cable and each longitudinal optical cable except the 1st longitudinal optical cable and the (N+1) / 2nd longitudinal optical cable, a transverse dual-gain optical cable interface is connected at the grid intersection of the (N+1) / 2nd longitudinal optical cable and each transverse optical cable except the 1st transverse optical cable and the (M+1) / 2nd transverse optical cable, a bidirectional single-gain optical cable interface is connected at the grid intersection of the (M+1) / 2nd transverse optical cable and the (N+1) / 2nd longitudinal optical cable, M and N are both odd numbers greater than or equal to 3; and, The seabed monitoring BOTDA device is used to transmit a group B of pumping light and retrieval pulses to the first section of the horizontal optical cable, and to transmit a group A of pumping light and detection light to the first section of the longitudinal optical cable.

2. According to claim 1, a large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification is characterized in that: The seabed monitoring BOTDA device comprises a BOTDA system terminal, a remote pump source group A, and a remote pump source group B, wherein the remote pump source group A comprises L wavelengths of λ A,1 To A,L The pump source of group B remote pumping source contains L wavelengths of λ B,1 To B,L The pump source of the BOTDA system terminal generates a retrieval pulse and a group of pump light B, and the detection light and a group of pump light A generated by the BOTDA system terminal enter the monitoring optical cable initial end, and the monitoring optical cable initial end is the first section of the horizontal optical cable, and the monitoring optical cable terminal is the first section of the longitudinal optical cable; The monitoring optical cable comprises: a group A pump optical fiber for transmitting a group A pump light, a group B pump optical fiber for transmitting a group B pump light, and a sensing optical fiber for transmitting a detection light and a retrieval pulse.

3. According to claim 2, a large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification is characterized in that: The horizontal sensing optical fibers at the left and right ends of the horizontal branch optical cable interface are directly connected, and the vertical sensing optical fibers at the upper and lower ends are directly connected. The horizontal branch optical cable interface includes: A first dense wavelength division multiplexer is used for combining and outputting the pump light transmitted from the B group of pump optical fibers connected from the left end; An optical power splitter, used to split the pump light output by the first dense wavelength division multiplexer into two paths, transmit one path of pump light to the second dense wavelength division multiplexer, and transmit the other path of pump light to the third dense wavelength division multiplexer; A second dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the optical cable at the right end of the grid intersection where the transverse branch optical cable interface is located; and, The third dense wavelength division multiplexer is used for decomposing the received pump light and transmitting it to the optical fiber of the upper end optical cable of the grid intersection where the horizontal branch optical cable interface is located.

4. According to claim 2, a large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification is characterized in that: The longitudinal sensing optical fibers at the upper and lower ends of the transverse single-gain optical cable interface are directly connected, and the transverse single-gain optical cable interface includes: A first dense wavelength division multiplexer is used for combining and outputting the pump light transmitted from the B group of pump optical fibers connected from the left end; An optical power splitter, used to split the pump light output by the first dense wavelength division multiplexer into three paths, transmit the first pump light to the second dense wavelength division multiplexer, transmit the second pump light to the third dense wavelength division multiplexer, and transmit the third pump light to the single-source gain module; A second dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the optical cable at the right end of the grid intersection where the transverse single-gain optical cable interface is located; A third dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the upper end optical cable of the grid intersection where the transverse single gain optical cable interface is located; and, The single-source gain module is used to amplify the transversely transmitted Brillouin retrieval pulse and detection light, and the transverse sensing optical fibers at the left and right ends are connected to the single-source gain module.

5. According to claim 2, a large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification is characterized in that: The transverse sensing optical fibers at the left and right ends of the longitudinal branch optical cable interface are directly connected, and the longitudinal sensing optical fibers at the upper and lower ends are directly connected. The longitudinal branch optical cable interface includes: A first dense wavelength division multiplexer is used for combining and outputting the pump light transmitted from the A group of pump optical fibers connected from the lower end; An optical power splitter, used to split the pump light output by the first dense wavelength division multiplexer into two paths, transmit one path of pump light to the second dense wavelength division multiplexer, and transmit the other path of pump light to the third dense wavelength division multiplexer; A second dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the upper end optical cable of the grid intersection where the longitudinal branch optical cable interface is located; and, The third dense wavelength division multiplexer is used for decomposing the received pump light and transmitting it to the optical fiber of the optical cable at the right end of the grid intersection where the longitudinal branch optical cable interface is located.

6. According to claim 2, a large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification is characterized in that: The transverse sensing optical fibers at the left and right ends of the longitudinal single-gain optical cable interface are directly connected, and the longitudinal single-gain optical cable interface includes: A first dense wavelength division multiplexer is used for combining and outputting the pump light transmitted from the A group of pump optical fibers connected from the lower end; An optical power splitter, used to split the pump light output by the first dense wavelength division multiplexer into three paths, transmit the first pump light to the second dense wavelength division multiplexer, transmit the second pump light to the third dense wavelength division multiplexer, and transmit the third pump light to the single-source gain module; A second dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the upper optical cable of the grid intersection where the longitudinal single-gain optical cable interface is located; A third dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the optical cable at the right end of the grid intersection where the longitudinal single-gain optical cable interface is located; and, The single-source gain module is used to amplify the longitudinally transmitted Brillouin retrieval pulse and detection light, and the longitudinal sensing optical fibers at the upper and lower ends are connected to the single-source gain module.

7. According to claim 2, a large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification is characterized in that: The transverse sensing optical fibers at the left and right ends of the longitudinal dual-gain optical cable interface are directly connected, and the longitudinal dual-gain optical cable interface includes: A first dense wavelength division multiplexer is used for combining and outputting the pump light transmitted from the A group of pump optical fibers connected from the left end; An optical power splitter, used to split the pump light output by the first dense wavelength division multiplexer into two paths, transmit one path of pump light to the second dense wavelength division multiplexer, and transmit the other path of pump light to the dual-source gain module; A second dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the optical cable at the right end of the grid intersection where the longitudinal dual-gain optical cable interface is located; A third dense wavelength division multiplexer is used to combine the pump light transmitted from the B group of pump optical fibers connected from the lower end and output it to the dual-source gain module; and, The dual-source gain module is used to amplify the longitudinally transmitted detection light and retrieval pulse, and the longitudinal sensing optical fibers at the upper and lower ends are connected to the dual-source gain module.

8. According to claim 2, a large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification is characterized in that: The longitudinal sensing optical fibers at the upper and lower ends of the transverse dual-gain optical cable interface are directly connected, and the transverse dual-gain optical cable interface includes: A first dense wavelength division multiplexer, used for combining the pump light transmitted from the B group of pump optical fibers connected from the lower end and outputting the combined pump light to the dual-source gain module; An optical power splitter is used to split the pump light output by the first dense wavelength division multiplexer into two paths, and transmit one pump light to the second A dense wavelength division multiplexer transmits another pump light to a dual-source gain module; A second dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the upper end optical cable of the grid intersection where the transverse dual-gain optical cable interface is located; A third dense wavelength division multiplexer is used to combine the pump light transmitted from the A group of pump optical fibers connected from the left end and output it to the dual-source gain module; and, The dual-source gain module is used to amplify the transversely transmitted detection light and retrieval pulse, and the transverse sensing optical fibers at the left and right ends are connected to the dual-source gain module.

9. According to claim 2, a large-scale seabed monitoring BOTDA system based on network multi-stage remote pump amplification is characterized in that: The bidirectional single-gain optical cable interface comprises: A first dense wavelength division multiplexer is used for combining and outputting the pump light transmitted from the A group of pump optical fibers connected from the left end; A first optical power splitter, used to split the pump light output by the first dense wavelength division multiplexer into two paths, transmit one path of pump light to the second dense wavelength division multiplexer, and transmit the other path of pump light to the first single-source gain module; A second dense wavelength division multiplexer is used to decompose the received pump light and transmit it to the optical fiber of the optical cable at the right end of the grid intersection where the bidirectional single gain optical cable interface is located; A first single-source gain module is used to amplify the transversely transmitted detection light and the search pulse, and the transverse sensing optical fibers at the left and right ends are connected to the first single-source gain module; A third dense wavelength division multiplexer is used for combining and outputting the pump light transmitted from the B group of pump optical fibers connected from the lower end; a second optical power splitter, used to split the pump light output by the third dense wavelength division multiplexer into two paths, transmit one path of pump light to the fourth dense wavelength division multiplexer, and transmit the other path of pump light to the second single-source gain module; and, The second single-source gain module is used to amplify the longitudinally transmitted detection light and retrieval pulse. The longitudinal sensing optical fibers at the upper and lower ends are connected to the second single-source gain module.

10. A large-scale seabed monitoring BOTDA system based on networked multi-stage remote pump amplification according to claim 7 or 8, characterized in that: The dual-source gain module comprises: The first dense wavelength division multiplexer is used to decompose the pump light of group A into pump lights of corresponding wavelengths, The second dense wavelength division multiplexer is used to decompose the B group pump light into pump lights of corresponding wavelengths, a third dense wavelength division multiplexer, used to combine all pump lights decomposed by the first dense wavelength division multiplexer and the second dense wavelength division multiplexer as remote pump light of the single source gain module, and, The single source gain module is used to generate a probe light and a retrieval pulse under the stimulation of the remote pump light generated by the third dense wavelength division multiplexer. The impulse is amplified; The single-source gain module comprises: The optical power splitter is used to split the received remote pump light into two paths, transmit one path of remote pump light to the upper amplification branch, and transmit the other path of remote pump light to the lower amplification branch. The first circulator is used to transmit the search pulse input from the sensing optical fiber at one end to the lower amplification branch, and transmit the detection light received from the upper amplification branch to the sensing optical fiber at the other end, A down-amplification branch consisting of a wavelength division multiplexer, a section of erbium-doped fiber and a filter is used to combine the remote pump light and the search pulse / detection light and transmit them to the second circulator. a second circulator, for transmitting the detection light input from the sensing optical fiber at one end to the upper amplification branch, for transmitting the search pulse received from the lower amplification branch to the sensing optical fiber at the other end, and, An upper amplification branch consisting of a wavelength division multiplexer, a section of erbium-doped optical fiber and a filter is used to combine the remote pump light and the retrieval pulse / detection light and transmit them to the first circulator.

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