Gradient scattering enhanced optical fiber and design method thereof

Abstract

The invention provides a gradient scattering enhanced optical fiber and a design method thereof. The gradient scattering enhanced optical fiber comprises a first enhanced optical fiber, a second enhanced optical fiber and a third enhanced optical fiber, detection pulse signals sent by the plurality of lasers enter the first enhanced optical fiber through the first WDM device; a detection pulse signal transmitted by the first enhanced optical fiber and a first type of amplification signal sent by the first optical fiber amplifier enter a second enhanced optical fiber through a second WDM (Wavelength Division Multiplexer); a detection pulse signal transmitted by the second enhanced optical fiber and a second type of amplification signal sent by the second optical fiber amplifier enter a third enhanced optical fiber through a third WDM (Wavelength Division Multiplexer); the gradient scattering enhanced optical fiber comprises a plurality of optical fiber units, and target scattering rates of different optical fiber units are different or the same; the optical fiber unit determines a signal reflection power based on a reception power of the probe pulse signal and a target scattering rate of the optical fiber unit, and transmits the scattered light signal based on the signal reflection power. According to the scheme, the detection distance of distributed sound wave detection can be remarkably increased.

Description

Technical Field

[0001] This application relates to the field of optical fiber technology, and particularly to a gradient scattering enhanced optical fiber and its design method. Background Art

[0002] Distributed Acoustic Sensing (DAS) technology is a technology that uses an optical fiber as a sensing element to realize continuous distributed measurement of environmental parameters along the optical fiber path. The principle of DAS technology is that by using the interaction between photons and intrinsic lattice defects in the optical fiber, a laser sends pulsed laser light to the optical fiber, and the lattice defects in the optical fiber will scatter some light back to the demodulator, and the backscattered Rayleigh scattering is used to infer the longitudinal strain change over time every few meters along the optical fiber. DAS technology can perform real-time monitoring of the strain distributed along the optical fiber over the entire length of the optical fiber, and obtain the spatial distribution state of the measured quantity and the information changing over time. DAS technology has the characteristics of high signal-to-noise ratio and high stability, and can achieve long-distance, high-resolution, distributed real-time online acoustic wave detection capabilities. Therefore, DAS technology is widely used.

[0003] When implementing distributed acoustic wave detection using DAS technology, if the detection distance is long, it will bring large transmission losses, and the signal power at the end of the optical fiber is weak, resulting in inevitable large noise and low sensitivity of the signal at the end of the optical fiber, and it cannot achieve high signal-to-noise ratio detection for the entire link, reducing reliability. Summary of the Invention

[0004] This application provides a gradient scattering enhanced optical fiber, which includes a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber; wherein, the detection pulse signals sent by multiple lasers enter the first enhanced optical fiber through a first Wavelength Division Multiplexing (WDM) device; the detection pulse signals transmitted by the first enhanced optical fiber and the first type of amplification signals sent by a first optical fiber amplifier enter the second enhanced optical fiber through a second WDM device; the detection pulse signals transmitted by the second enhanced optical fiber and the second type of amplification signals sent by a second optical fiber amplifier enter the third enhanced optical fiber through a third WDM device;

[0005] Wherein, the gradient scattering enhanced optical fiber includes multiple optical fiber units, and a target scattering rate of each optical fiber unit is configured at the position where each optical fiber unit is located, and the target scattering rates of different optical fiber units are different or the same;

[0006] For each optical fiber unit, when the optical fiber unit receives a detection pulse signal, it determines the signal reflection power based on the received power of the detection pulse signal and the target scattering rate of the optical fiber unit, and sends the scattered light signal corresponding to the detection pulse signal to the distributed acoustic wave detection host based on the signal reflection power.

[0007] The present application provides a design method for a gradient scattering enhanced optical fiber. The gradient scattering enhanced optical fiber includes a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber. Among them, the detection pulse signals sent by multiple lasers enter the first enhanced optical fiber through a first wavelength division multiplexing (WDM) device; the detection pulse signals transmitted by the first enhanced optical fiber and the first type of amplified signals sent by a first optical fiber amplifier enter the second enhanced optical fiber through a second WDM device; the detection pulse signals transmitted by the second enhanced optical fiber and the second type of amplified signals sent by a second optical fiber amplifier enter the third enhanced optical fiber through a third WDM device.

[0008] Among them, the gradient scattering enhanced optical fiber includes multiple optical fiber units, and the method includes:

[0009] For each optical fiber unit, based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between this optical fiber unit and the starting position of the gradient scattering enhanced optical fiber, determine the target scattering rate of this optical fiber unit. Among them, the first power gain factor is used to control the emission power of the laser when sending the detection pulse signal, the second power gain factor is used to control the emission power of the first optical fiber amplifier when sending the first type of amplified signal, and the third power gain factor is used to control the emission power of the second optical fiber amplifier when sending the second type of amplified signal.

[0010] Configure the target scattering rate for each optical fiber unit. The target scattering rates of different optical fiber units may be different or the same. Among them, when an optical fiber unit receives a detection pulse signal, based on the received power of the detection pulse signal and the target scattering rate of this optical fiber unit, determine the signal reflection power, and send the scattered optical signal corresponding to the detection pulse signal to the distributed acoustic wave detection host based on the signal reflection power.

[0011] The present application provides a design device for a gradient scattering enhanced optical fiber. The gradient scattering enhanced optical fiber includes a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber. Among them, the detection pulse signals sent by multiple lasers enter the first enhanced optical fiber through a first wavelength division multiplexing (WDM) device; the detection pulse signals transmitted by the first enhanced optical fiber and the first type of amplified signals sent by a first optical fiber amplifier enter the second enhanced optical fiber through a second WDM device; the detection pulse signals transmitted by the second enhanced optical fiber and the second type of amplified signals sent by a second optical fiber amplifier enter the third enhanced optical fiber through a third WDM device.

[0012] Among them, the gradient scattering enhanced optical fiber includes multiple optical fiber units, and the device includes:

[0013] A determination module, configured to determine, for each optical fiber unit, a target scattering rate of the optical fiber unit based on a first power gain factor of the laser, a second power gain factor of the first optical fiber amplifier, a third power gain factor of the second optical fiber amplifier, and a distance between the optical fiber unit and a starting position of the gradient scattering enhanced optical fiber; wherein the first power gain factor is used to control the transmission power of the laser when sending the detection pulse signal, the second power gain factor is used to control the transmission power of the first optical fiber amplifier when sending the first type of amplified signal, and the third power gain factor is used to control the transmission power of the second optical fiber amplifier when sending the second type of amplified signal;

[0014] A configuration module, configured to configure the target scattering rate of each optical fiber unit, and the target scattering rates of different optical fiber units may be different or the same; wherein when an optical fiber unit receives a detection pulse signal, it determines a signal reflection power based on the received power of the detection pulse signal and the target scattering rate of the optical fiber unit, and sends a scattered light signal corresponding to the detection pulse signal to the distributed acoustic wave detection host based on the signal reflection power.

[0015] The present application provides a computer program product, the computer program product includes a computer program, and when the computer program is executed by a processor, the design method of the gradient scattering enhanced optical fiber as described above is implemented.

[0016] The present application provides an electronic device, including: a processor and a machine-readable storage medium, the machine-readable storage medium stores machine-executable instructions that can be executed by the processor; wherein, the processor is used to execute the machine-executable instructions to implement the design method of the gradient scattering enhanced optical fiber as described above.

[0017] The present application provides a machine-readable storage medium, the machine-readable storage medium stores machine-executable instructions that can be executed by a processor; wherein, the processor is used to execute the machine-executable instructions to implement the design method of the gradient scattering enhanced optical fiber in the above example.

[0018] As can be seen from the above technical solutions, in the embodiments of the present application, a new type of optical fiber (i.e., gradient scattering enhanced optical fiber) is designed. The gradient scattering enhanced optical fiber includes a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber. The first enhanced optical fiber enhances the signal with the detection pulse signals sent by multiple lasers. The second enhanced optical fiber enhances the signal with the first type of amplified signal sent by the first optical fiber amplifier. The third enhanced optical fiber is enhanced with the second type of amplified signal sent by the second optical fiber amplifier. In this way, multiple distance detections for distributed acoustic wave detection can be achieved. Even when the detection distance is long, transmission loss can be reduced, the signal power at the fiber tail section is strong, the noise of the signal at the fiber tail section is reduced, the sensitivity of the signal at the fiber tail section is improved, high signal-to-noise ratio detection for the entire link is achieved, and reliability is improved. Multiple lasers can be used to form a multi-wavelength optical fiber to increase the incident optical power. The first optical fiber amplifier is used to increase the optical power in the middle section (the power of the second enhanced optical fiber), and the second optical fiber amplifier is used to increase the optical power at the tail section (the power of the third enhanced optical fiber). The problem of uneven signal power between the proximal and distal ends of the link can be solved, and the detection distance of distributed acoustic wave detection can be significantly increased. The link power distribution is obtained by various amplification methods, and the scattering rate distribution of the gradient scattering enhanced optical fiber is designed and optimized according to the link power distribution to achieve ultra-long distance and high-quality distributed acoustic wave detection for the entire link. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of a gradient scattering enhanced optical fiber in an embodiment of the present application;

[0020] Figure 2 is a flowchart of a design method for a gradient scattering enhanced optical fiber in an embodiment of the present application;

[0021] Figure 3 is a schematic structural diagram of a distributed acoustic wave detection system in an embodiment of the present application;

[0022] Figure 4 is a schematic diagram of suppressing MI non-linearity in an embodiment of the present application;

[0023] Figure 5 is a schematic flow diagram of a design method for a gradient scattering enhanced optical fiber in an embodiment of the present application;

[0024] Figure 6A is a schematic diagram of a link power distribution in an embodiment of the present application;

[0025] Figure 6B is a schematic diagram of a link scattering enhancement intensity distribution in an embodiment of the present application;

[0026] Figure 6C is a schematic diagram of the backscattering power distribution of the entire optical fiber link in an embodiment of the present application;

[0027] Figure 7 It is a flowchart of a design method for a gradient scattering enhanced optical fiber in an embodiment of the present application;

[0028] Figure 8 It is a structural diagram of a design device for a gradient scattering enhanced optical fiber in an embodiment of the present application;

[0029] Figure 9 It is a hardware structural diagram of an electronic device in an embodiment of the present application. Specific embodiments

[0030] In an embodiment of the present application, a gradient scattering enhanced optical fiber is proposed. Refer to Figure 1 As shown, it is a schematic structural diagram of the gradient scattering enhanced optical fiber. The gradient scattering enhanced optical fiber may include a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber. For example, the first enhanced optical fiber may be a front-segment enhanced optical fiber, the second enhanced optical fiber may be a middle-segment enhanced optical fiber, and the third enhanced optical fiber may be a tail-segment enhanced optical fiber.

[0031] Exemplarily, the detection pulse signals sent by multiple lasers enter the first enhanced optical fiber after passing through the first WDM (Wavelength Division Multiplexing) multiplexer, and the detection pulse signals are transmitted in the first enhanced optical fiber. The detection pulse signals transmitted by the first enhanced optical fiber and the first type of amplification signal sent by the first optical fiber amplifier enter the second enhanced optical fiber through the second WDM multiplexer. The first type of amplification signal is used to enhance the detection pulse signals. In this way, the enhanced detection pulse signals can be transmitted in the second enhanced optical fiber. The detection pulse signals transmitted by the second enhanced optical fiber and the second type of amplification signal sent by the second optical fiber amplifier enter the third enhanced optical fiber through the third WDM multiplexer. The second type of amplification signal is used to enhance the detection pulse signals. In this way, the enhanced detection pulse signals can be transmitted in the third enhanced optical fiber.

[0032] Exemplarily, the gradient scattering enhanced optical fiber may include multiple optical fiber units. The target scattering rate of each optical fiber unit is configured at the position where each optical fiber unit is located. The target scattering rates of different optical fiber units may be different or the same. For each optical fiber unit, when the optical fiber unit receives a detection pulse signal, it determines the signal reflection power based on the received power of the detection pulse signal and the target scattering rate of the optical fiber unit, and sends the scattered light signal corresponding to the detection pulse signal to the distributed acoustic wave detection host based on the signal reflection power.

[0033] Exemplarily, for each optical fiber unit, the target scattering rate of the optical fiber unit is determined based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between the optical fiber unit and the starting position of the gradient scattering enhancement optical fiber. For example, for the first power gain factor, the second power gain factor, and the third power gain factor, the first power gain factor is used to control the emission power of the laser when sending a detection pulse signal, the second power gain factor is used to control the emission power of the first optical fiber amplifier when sending a first type of amplified signal, and the third power gain factor is used to control the emission power of the second optical fiber amplifier when sending a second type of amplified signal.

[0034] Exemplarily, the process of determining the target scattering rate of each optical fiber unit may include, but is not limited to: determining the optical fiber power distribution of the optical fiber unit based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between the optical fiber unit and the starting position of the gradient scattering enhancement optical fiber; obtaining a plurality of scattering rate sets, and for each scattering rate set, the scattering rate set includes the candidate scattering rate of each optical fiber unit, and the candidate scattering rate is any scattering rate supported by the optical fiber unit; selecting a target scattering rate set from the plurality of scattering rate sets based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rate of each optical fiber unit in each scattering rate set; and determining the target scattering rate of each optical fiber unit based on the target scattering rate set.

[0035] Exemplarily, determining the optical fiber power distribution of the optical fiber unit based on the first power gain factor, the second power gain factor, the third power gain factor, and the distance between the optical fiber unit and the starting position of the gradient scattering enhancement optical fiber may include, but is not limited to: determining the optical fiber power distribution of the optical fiber unit by using the following formula: P(L) represents the optical fiber power distribution of the optical fiber unit; H R (l) represents the third power gain factor, H EDFA (l) represents the second power gain factor, E p represents the first power gain factor, P in represents the initial power value, α represents the configured optical fiber loss factor, and l represents the distance between the optical fiber unit and the starting position of the gradient scattering enhancement optical fiber.

[0036] Exemplarily, based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit within each set of scattering rates, selecting a target set of scattering rates from multiple sets of scattering rates may include, but is not limited to: sequentially traversing each set of scattering rates from multiple sets of scattering rates; for the currently traversed set of scattering rates, determining the reference power value of each optical fiber unit based on the candidate scattering rate of each optical fiber unit within this set of scattering rates and the optical fiber power distribution of each optical fiber unit; wherein, the reference power value is the product value of the candidate scattering rate of the optical fiber unit and the optical fiber power distribution of the optical fiber unit; selecting the minimum reference power value and the maximum reference power value from the reference power values of each optical fiber unit; if it is determined that this set of scattering rates meets the preset conditions based on the minimum reference power value and the maximum reference power value, then select this set of scattering rates as the target set of scattering rates; if it is determined that this set of scattering rates does not meet the preset conditions based on the minimum reference power value and the maximum reference power value, then traverse the next set of scattering rates from multiple sets of scattering rates.

[0037] If the difference between the maximum reference power value and the minimum reference power value is less than the first power value and the minimum reference power value is greater than the second power value, then the set of scattering rates meets the preset conditions; if the difference between the maximum reference power value and the minimum reference power value is not less than the first power value, and / or, the minimum reference power value is not greater than the second power value, then the set of scattering rates does not meet the preset conditions; the first power value is the difference between the configured upper limit value of the scattered optical power and the configured lower limit value of the scattered optical power, and the second power value is the lower limit value of the scattered optical power.

[0038] Exemplarily, based on the first power gain factor, the following formula can be used to determine the transmission power P of the laser when sending a detection pulse signal in-e : P in-e = E p ·P in ; based on the second power gain factor, the following formula can be used to determine the transmission power P(L1) of the first optical fiber amplifier when sending the first type of amplified signal: Based on the third power gain factor, the following formula can be used to determine the transmission power P(L2) of the second optical fiber amplifier when sending the second type of amplified signal: E p represents the first power gain factor, P in represents the initial power value, H EDFA (l) represents the second power gain factor, H R (l) represents the third power gain factor, α represents the optical fiber loss factor, and l represents the distance between the optical fiber unit and the starting position of the gradient scattering enhancement optical fiber.

[0039] Exemplarily, the multiple lasers include at least two single-frequency lasers. The at least two single-frequency lasers correspond to different wavelengths, and detection pulse signals of different wavelengths are sent through the at least two single-frequency lasers; the first optical fiber amplifier includes a remote-pumped erbium-doped optical fiber amplifier. The pumping structure of the remote-pumped erbium-doped optical fiber amplifier is co-pumping or by-pass pumping, and the pumping direction of the remote-pumped erbium-doped optical fiber amplifier is forward pumping, backward pumping or bidirectional pumping; when the remote-pumped erbium-doped optical fiber amplifier sends the first type of amplified signal, the wavelength of the first type of amplified signal is different from the wavelength of the detection pulse signal; the second optical fiber amplifier includes a Raman distributed optical fiber amplifier. The pumping structure of the Raman distributed optical fiber amplifier is co-pumping or by-pass pumping, and the pumping direction of the Raman distributed optical fiber amplifier is forward pumping, backward pumping or bidirectional pumping; when the Raman distributed optical fiber amplifier sends the second type of amplified signal, the wavelength of the second type of amplified signal is different from the wavelength of the detection pulse signal.

[0040] As can be seen from the above technical solutions, in the embodiments of the present application, a new type of optical fiber (i.e., gradient scattering enhanced optical fiber) is designed. The gradient scattering enhanced optical fiber includes a first enhanced optical fiber, a second enhanced optical fiber and a third enhanced optical fiber. The first enhanced optical fiber enhances the signal by the detection pulse signals sent by multiple lasers. The second enhanced optical fiber enhances the signal by the first type of amplified signal sent by the first optical fiber amplifier. The third enhanced optical fiber is enhanced by the second type of amplified signal sent by the second optical fiber amplifier. In this way, multiple-distance detection of distributed acoustic wave detection can be realized. Even when the detection distance is long, transmission loss can be reduced, the signal power at the optical fiber tail section is strong, the noise of the signal at the optical fiber tail section is reduced, the sensitivity of the signal at the optical fiber tail section is improved, and high signal-to-noise ratio detection of the entire link is achieved, improving reliability. Multiple lasers can be used to form a multi-wavelength optical fiber to increase the incident optical power. The first optical fiber amplifier is used to increase the optical power in the middle section (the power of the second enhanced optical fiber), and the second optical fiber amplifier is used to increase the optical power at the tail section (the power of the third enhanced optical fiber). The problem of uneven signal power between the proximal end and the distal end of the link can be solved, and the detection distance of distributed acoustic wave detection can be significantly increased. The link power distribution is obtained by multiple amplification methods, and the scattering rate distribution of the gradient scattering enhanced optical fiber is designed and optimized according to the link power distribution, realizing ultra-long-distance high-quality distributed acoustic wave detection of the entire link.

[0041] Based on the same technical concept as the above gradient scattering enhanced optical fiber, in the embodiments of the present application, a design method of a gradient scattering enhanced optical fiber is proposed. The gradient scattering enhanced optical fiber includes a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber. Among them, the detection pulse signals sent by multiple lasers enter the first enhanced optical fiber through a first WDM device. The detection pulse signals transmitted by the first enhanced optical fiber and the first type of amplified signals sent by the first optical fiber amplifier enter the second enhanced optical fiber through a second WDM device. The detection pulse signals transmitted by the second enhanced optical fiber and the second type of amplified signals sent by the second optical fiber amplifier enter the third enhanced optical fiber through a third WDM device. Refer to Figure 2 As shown in

[0042] Step 201: For each optical fiber unit, based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between this optical fiber unit and the starting position of the gradient scattering enhanced optical fiber, determine the target scattering rate of this optical fiber unit.

[0043] Exemplarily, the first power gain factor is used to control the emission power of the laser when sending detection pulse signals, the second power gain factor is used to control the emission power of the first optical fiber amplifier when sending the first type of amplified signals, and the third power gain factor is used to control the emission power of the second optical fiber amplifier when sending the second type of amplified signals. Among them, the gradient scattering enhanced optical fiber can include multiple optical fiber units.

[0044] Step 202: Configure the target scattering rate for each optical fiber unit, and the target scattering rates of different optical fiber units can be different or the same. Exemplarily, when an optical fiber unit receives a detection pulse signal, based on the received power of the detection pulse signal and the target scattering rate of this optical fiber unit, determine the signal reflection power, and send the scattered optical signal corresponding to the detection pulse signal to the distributed acoustic wave detection host based on the signal reflection power.

[0045] Exemplarily, determining the target scattering rate of this optical fiber unit can include, but is not limited to: based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between this optical fiber unit and the starting position of the gradient scattering enhanced optical fiber, determine the optical fiber power distribution of this optical fiber unit; obtain multiple scattering rate sets, for each scattering rate set, the scattering rate set can include the candidate scattering rates of each optical fiber unit, and the candidate scattering rate is any scattering rate supported by this optical fiber unit; based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit in each scattering rate set, select the target scattering rate set from multiple scattering rate sets; determine the target scattering rate of each optical fiber unit based on the target scattering rate set.

[0046] Exemplarily, based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit within each set of scattering rates, selecting a target set of scattering rates from multiple sets of scattering rates may include, but is not limited to: sequentially traversing each set of scattering rates from the multiple sets of scattering rates; for the currently traversed set of scattering rates, determining a reference power value for each optical fiber unit based on the candidate scattering rate of each optical fiber unit within the set of scattering rates and the optical fiber power distribution of each optical fiber unit; wherein the reference power value is the product value of the candidate scattering rate of the optical fiber unit and the optical fiber power distribution of the optical fiber unit; selecting the minimum reference power value and the maximum reference power value from the reference power values of each optical fiber unit; if it is determined that the set of scattering rates satisfies a preset condition based on the minimum reference power value and the maximum reference power value, then selecting the set of scattering rates as the target set of scattering rates; if it is determined that the set of scattering rates does not satisfy the preset condition based on the minimum reference power value and the maximum reference power value, then traversing the next set of scattering rates from the multiple sets of scattering rates.

[0047] If the difference between the maximum reference power value and the minimum reference power value is less than a first power value and the minimum reference power value is greater than a second power value, the set of scattering rates satisfies the preset condition; if the difference between the maximum reference power value and the minimum reference power value is not less than the first power value, and / or, the minimum reference power value is not greater than the second power value, the set of scattering rates does not satisfy the preset condition; the first power value is the difference between the configured upper limit value of the scattered optical power and the configured lower limit value of the scattered optical power, and the second power value is the lower limit value of the scattered optical power.

[0048] As can be seen from the above technical solutions, in the embodiments of the present application, a novel optical fiber (i.e., a gradient scattering enhanced optical fiber) is designed. The gradient scattering enhanced optical fiber includes a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber. The first enhanced optical fiber enhances the signal by the detection pulse signals sent by multiple lasers. The second enhanced optical fiber enhances the signal by the first type of amplified signal sent by the first optical fiber amplifier. The third enhanced optical fiber is enhanced by the second type of amplified signal sent by the second optical fiber amplifier. In this way, multiple distance detections of distributed acoustic wave detection can be achieved. Even if the detection distance is long, transmission loss can be reduced, the signal power at the end of the optical fiber is strong, the noise of the signal at the end of the optical fiber is reduced, the sensitivity of the signal at the end of the optical fiber is improved, and high signal-to-noise ratio detection of the entire link is achieved, improving reliability. Multiple lasers can be used to form a multi-wavelength optical fiber to increase the incident optical power. The first optical fiber amplifier is used to increase the optical power in the middle section (the power of the second enhanced optical fiber), and the second optical fiber amplifier is used to increase the optical power at the end section (the power of the third enhanced optical fiber). The problem of uneven signal power between the proximal end and the distal end of the link can be solved, and the detection distance of distributed acoustic wave detection can be significantly increased. The link power distribution is obtained by various amplification methods, and the scattering rate distribution of the gradient scattering enhanced optical fiber is designed and optimized according to the link power distribution to achieve ultra-long distance and high-quality distributed acoustic wave detection of the entire link.

[0049] The above technical solutions of the embodiments of the present application will be described below in combination with specific application scenarios.

[0050] DAS technology uses optical fiber as a sensing element to achieve continuous distributed measurement of environmental parameters along the optical fiber path. When using DAS technology to achieve distributed acoustic wave detection, if the detection distance is long, it will bring large transmission losses, and the signal power at the end of the optical fiber is weak, resulting in inevitable large noise and low sensitivity of the signal at the end of the optical fiber, and high signal-to-noise ratio detection of the entire link cannot be achieved.

[0051] To obtain a longer detection distance, a higher-power Rayleigh scattering signal is required. One way is to inject a detection pulse with a higher peak power, that is, to send a detection pulse with a higher peak power. However, a detection pulse with a high peak power will cause nonlinear effects such as modulation instability (MI) and stimulated Brillouin scattering (SBS), which limit the further improvement of the detection distance and cannot obtain a longer detection distance. For example, the threshold of the MI nonlinear effect is low. When the power is high, gain sidebands will be generated on both sides, amplifying the spontaneous emission noise within the gain bandwidth, causing serious power loss and detection light fluctuations. Moreover, the MI nonlinearity will gradually accumulate with light transmission, which is the main factor limiting the peak power of the detection pulse.

[0052] In view of the above findings, a gradient scattering enhanced optical fiber and its design method are proposed in the embodiments of the present application, which can achieve long-distance distributed acoustic wave detection with high detection optical power and high signal-to-noise ratio throughout the link, provide multiple distance extensions for distributed acoustic wave detection, and solve the problem of limited detection distance caused by low peak power of the detection optical pulse and poor signal-to-noise ratio throughout the link. The gradient scattering enhanced optical fiber and its design method will be described below.

[0053] See Figure 3 As shown, it is a schematic structural diagram of a distributed acoustic wave detection system. The distributed acoustic wave detection system may include a distributed acoustic wave detection host, a gradient scattering enhanced optical fiber, multiple lasers, a first optical fiber amplifier, a second optical fiber amplifier, and multiple WDM devices. The gradient scattering enhanced optical fiber (GDSEF) may include a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber. The first enhanced optical fiber may be a front-segment enhanced optical fiber, the second enhanced optical fiber is a middle-segment enhanced optical fiber, and the third enhanced optical fiber is a tail-segment enhanced optical fiber.

[0054] First, for the first enhanced optical fiber, in order to achieve signal enhancement of the first enhanced optical fiber, detection pulse signals (which can also be referred to as detection pulses or pulsed lasers) can be sent by multiple lasers. The detection pulse signals sent by the multiple lasers enter the first enhanced optical fiber after passing through the first WDM device. The detection pulse signals are transmitted in the first enhanced optical fiber. In this way, the signal transmitted in the first enhanced optical fiber is the wavelength-division multiplexed signal of multiple detection pulse signals, thereby enhancing the detection pulse signals transmitted in the first enhanced optical fiber.

[0055] The multiple lasers can include at least two single-frequency lasers. The at least two single-frequency lasers correspond to different wavelengths, so as to send detection pulse signals of different wavelengths through the at least two single-frequency lasers. For the convenience of description, two single-frequency lasers are taken as an example for illustration. Of course, the number of single-frequency lasers can be more.

[0056] The two single-frequency lasers can be respectively denoted as laser 1 and laser 2. The wavelength of laser 1 can be λ1, that is, a detection pulse signal with wavelength λ1 is sent through laser 1. The wavelength of laser 2 can be λ2, that is, a detection pulse signal with wavelength λ2 is sent through laser 2. The detection pulse signal with wavelength λ1 and the detection pulse signal with wavelength λ2 are combined by the first WDM device and simultaneously injected into the first enhanced optical fiber.

[0057] Exemplarily, in the process of distributed acoustic wave detection, in order to obtain a longer detection distance, Rayleigh scattering signals with higher power are required. One way is to inject detection pulses with higher peak power. However, detection pulses with high peak power will cause modulation instability (MI), which limits the further improvement of the detection distance.

[0058] In view of the above discovery, in this embodiment, multiple lasers with different wavelengths are used to send detection pulse signals of different wavelengths through the multiple lasers, thereby suppressing the MI nonlinearity. See Figure 4 As shown, it is a schematic diagram for suppressing MI nonlinearity. In Figure 4 laser 1 and laser 2 are taken as an example for illustration.

[0059] For example, when the peak power of the incident light exceeds the MI threshold, the MI nonlinear effect will generate symmetric double-sideband gain on both sides of the detection light frequency. The gain bandwidth is related to the peak power, such as 50 - 200 GHz. Therefore, the amplified spontaneous emission (ASE) noise within the gain bandwidth will be amplified and quickly consume the detection light power.

[0060] On this basis, in this embodiment, in order to increase the peak power of the incident light and suppress the MI nonlinear effect, multiple single-frequency lasers are used to form a multi-wavelength light source, and the multi-wavelength light source is used as the incident light source of the distributed acoustic wave detection system. Taking laser 1 and laser 2 as an example, from Figure 4It can be seen that if the optical powers of two lasers are increased, symmetric gain sidebands g(λ1) and g(λ2) are generated on both sides of their respective frequencies.

[0061] Since the wavelengths of the two lasers are different (i.e., it is not necessary to configure the wavelengths of the two lasers to be the same), by adjusting the wavelengths of the two lasers, they can be located at the wavelengths corresponding to the peak gain within the MI gain bandwidth generated by the other laser. For example, for Laser 1, the lower sideband of its MI gain amplifies the ASE noise, but the upper sideband amplifies Laser 2. Since Laser 2 has a higher power relative to the ASE noise, the energy lost by Laser 1 will be transferred to Laser 2 rather than amplifying the ASE noise. Similarly, for Laser 2, the lower sideband of its MI gain amplifies the ASE noise, but the upper sideband amplifies Laser 1. Since Laser 1 has a higher power relative to the ASE noise, the energy lost by Laser 2 will be transferred to Laser 1 rather than amplifying the ASE noise. In summary, a dual-wavelength light source (a dual-wavelength light source composed of two single-frequency lasers) can promote the energy transfer between the two lasers, thereby significantly suppressing the MI nonlinear effect.

[0062] In summary, it can be seen that the MI nonlinear effect can be suppressed by using a multi-wavelength light source. The multi-wavelength light source is at least two single-frequency lasers with different wavelengths, and the wavelengths of the single-frequency lasers are at the wavelengths corresponding to the peak gain within the MI nonlinear gain bandwidth of adjacent single-frequency lasers. See Figure 4 as shown.

[0063] For this reason, in this embodiment, in order to enhance the signal of the first enhanced optical fiber, probe pulse signals can be sent by multiple lasers, and the wavelengths of the multiple lasers are different. Since multiple lasers with different wavelengths are used, the power of the lasers can be increased, that is, the lasers can send probe pulse signals with higher power without causing modulation instability (MI), and increasing the power can enhance the signal.

[0064] In a possible implementation, in order to enhance the detection pulse signal transmitted by the first enhanced optical fiber, a third optical fiber amplifier and a fourth WDM device (the third optical fiber amplifier and the fourth WDM device are optional) can also be deployed. The third optical fiber amplifier can send a third type of amplified signal, which is used to enhance the detection pulse signal. The third type of amplified signal can be a continuous signal, not a pulse signal. Based on this, the detection pulse signal transmitted by the first enhanced optical fiber and the third type of amplified signal sent by the third optical fiber amplifier enter the first enhanced optical fiber through the fourth WDM device. What is transmitted in the first enhanced optical fiber is the signal after wavelength division multiplexing of the detection pulse signal and the third type of amplified signal, so as to enhance the detection pulse signal based on the third type of amplified signal, and make the enhanced detection pulse signal transmit in the first enhanced optical fiber.

[0065] Exemplarily, the third optical fiber amplifier can include, but is not limited to, a Raman distributed optical fiber amplifier. Taking the Raman distributed optical fiber amplifier as an example, the pumping structure of the Raman distributed optical fiber amplifier can be co-path pumping or by-pass pumping, and the pumping direction of the Raman distributed optical fiber amplifier can be forward pumping, backward pumping, or bi-directional pumping. When the Raman distributed optical fiber amplifier sends the third type of amplified signal, the wavelength of the third type of amplified signal can be different from the wavelength of the detection pulse signal, or the wavelengths can also be the same.

[0066] For example, the Raman distributed optical fiber amplifier can include a pump source with a wavelength of 1455 nm (the value is only an example), that is, the Raman distributed optical fiber amplifier uses a laser with a wavelength of 1455 nm as the pump source. In this way, the pump source can send a third type of amplified signal with a wavelength of 1455 nm.

[0067] For example, the Raman distributed optical fiber amplifier can be located at the starting end or the ending end of the gradient scattering enhanced optical fiber. In Figure 3 this case, taking it as an example of being located at the starting end of the gradient scattering enhanced optical fiber.

[0068] By deploying the Raman distributed optical fiber amplifier, and having the Raman distributed optical fiber amplifier send the third type of amplified signal, it is possible to improve the signal-to-noise ratio of the signal in the first enhanced optical fiber and amplify the signal at the proximal end.

[0069] Second, for the second enhanced optical fiber, in order to achieve signal enhancement of the second enhanced optical fiber, that is, to enhance the detection pulse signal transmitted by the second enhanced optical fiber, a first optical fiber amplifier and a second WDM device can be deployed. The first optical fiber amplifier can send a first type of amplified signal, which is used to enhance the detection pulse signal. The first type of amplified signal can be a continuous signal, rather than a pulse signal.

[0070] Based on this, the detected pulse signal transmitted by the first enhanced optical fiber and the first type of amplified signal sent by the first optical fiber amplifier enter the second enhanced optical fiber through the second WDM device. What is transmitted in the second enhanced optical fiber is the signal after wavelength division multiplexing of the detected pulse signal and the first type of amplified signal. Thus, the detected pulse signal is enhanced based on the first type of amplified signal, and the enhanced detected pulse signal is transmitted in the second enhanced optical fiber.

[0071] Exemplarily, there is no limitation on the lengths of the first enhanced optical fiber, the second enhanced optical fiber, and the third enhanced optical fiber in this embodiment, and they can be configured according to experience. For example, the first WDM device, the second WDM device, and the third WDM device can be deployed according to actual needs. The optical fiber between the first WDM device and the second WDM device is called the first enhanced optical fiber, the optical fiber between the second WDM device and the third WDM device is called the second enhanced optical fiber, and the optical fiber after the third WDM device is called the third enhanced optical fiber.

[0072] Exemplarily, the first optical fiber amplifier can include, but is not limited to, a remotely pumped erbium-doped fiber amplifier (remotely pumped EDFA). Taking the remotely pumped erbium-doped fiber amplifier as an example, the pumping structure of the remotely pumped erbium-doped fiber amplifier can be co-pumping or by-pass pumping, and the pumping direction of the remotely pumped erbium-doped fiber amplifier can be forward pumping, backward pumping, or bidirectional pumping. When the remotely pumped erbium-doped fiber amplifier sends the first type of amplified signal, the wavelength of the first type of amplified signal can be different from the wavelength of the detected pulse signal, or the wavelengths can also be the same.

[0073] The remotely pumped erbium-doped fiber amplifier includes a pump source and an erbium-doped fiber. The wavelength of the pump source can be 980 nm or 1480 nm, that is, the remotely pumped erbium-doped fiber amplifier uses a laser with a wavelength of 980 nm or 1480 nm as the pump source. In this way, the pump source can send the first type of amplified signal with a wavelength of 980 nm or 1480 nm.

[0074] For example, the remotely pumped erbium-doped fiber amplifier can be located at the starting end or the ending end of the gradient scattering enhanced optical fiber. In Figure 3 it, taking the case of being located at the starting end of the gradient scattering enhanced optical fiber as an example.

[0075] By deploying the remotely pumped erbium-doped fiber amplifier to send the first type of amplified signal, the signal-to-noise ratio of the signal in the second enhanced optical fiber can be improved, and the signal in the middle section can be amplified.

[0076] For example, when the detection pulse signal is transmitted over 100 km, the optical fiber will introduce a power difference of 40 dB. At this time, the power is relatively weak, causing the detection pulse signal to be submerged in noise. Thus, the second WDM device can be placed at the 100 km position of the optical fiber. The first type of amplified signal sent by the remote pump erbium-doped fiber amplifier enters the second WDM device, thereby amplifying the weak detection pulse signal to extend the detection distance. It should be noted that the position of the second WDM device can be changed according to the detection requirements, and there is no limitation in this regard.

[0077] Third, for the third enhanced optical fiber, in order to achieve signal enhancement of the third enhanced optical fiber, that is, to enhance the detection pulse signal transmitted by the third enhanced optical fiber, a second fiber amplifier and a third WDM device can be deployed. The second fiber amplifier can send a second type of amplified signal, and the second type of amplified signal is used to enhance the detection pulse signal. The second type of amplified signal can be a continuous signal rather than a pulse signal.

[0078] Based on this, the detection pulse signal transmitted by the second enhanced optical fiber and the second type of amplified signal sent by the second fiber amplifier enter the third enhanced optical fiber through the third WDM device. What is transmitted in the third enhanced optical fiber is the wavelength-division multiplexed signal of the detection pulse signal and the second type of amplified signal. Thus, the detection pulse signal is enhanced based on the second type of amplified signal, and the enhanced detection pulse signal is transmitted in the third enhanced optical fiber.

[0079] Exemplarily, the second fiber amplifier can include, but is not limited to, a Raman distributed fiber amplifier. Taking the Raman distributed fiber amplifier as an example, the pumping structure of the Raman distributed fiber amplifier can be in-line pumping or bypass pumping, and the pumping direction of the Raman distributed fiber amplifier can be forward pumping, backward pumping, or bidirectional pumping. When the Raman distributed fiber amplifier sends the second type of amplified signal, the wavelength of the second type of amplified signal can be different from the wavelength of the detection pulse signal, or the wavelengths can also be the same.

[0080] For example, the Raman distributed fiber amplifier can include a pump source with a wavelength of 1455 nm (the value is just an example), that is, the Raman distributed fiber amplifier uses a laser with a wavelength of 1455 nm as the pump source. In this way, the pump source can send a second type of amplified signal with a wavelength of 1455 nm.

[0081] For example, the Raman distributed fiber amplifier can be located at the starting end or the ending end of the gradient scattering enhanced optical fiber. In Figure 3 it, taking the case of being located at the ending end of the gradient scattering enhanced optical fiber as an example.

[0082] By deploying the Raman distributed fiber amplifier and having the Raman distributed fiber amplifier send the second type of amplified signal, the signal-to-noise ratio of the signal in the third enhanced optical fiber can be improved, and the signal at the far end can be amplified.

[0083] For example, in the process of long-distance distributed acoustic wave detection, the quality of the distal signal is limited by the low backscattering power and affected by optical noise, resulting in a poor signal-to-noise ratio. Moreover, the large power difference between the proximal and distal ends can also introduce noise. Based on this, in this embodiment, a Raman distributed fiber amplifier is used to amplify the signal in the tail section. The second type of amplified signal sent by the Raman distributed fiber amplifier enters the third WDM device, so as to amplify the weak detection pulse signal and extend the detection distance.

[0084] Fourth, the gradient scattering enhanced fiber may include multiple fiber units, that is, the first enhanced fiber includes multiple fiber units, the second enhanced fiber includes multiple fiber units, and the third enhanced fiber includes multiple fiber units. For example, one fiber unit corresponds to every 100 m. When designing the gradient scattering enhanced fiber, it is necessary to determine the target scattering rate of each fiber unit and configure the target scattering rate of the fiber unit at the position where the fiber unit is located. For example, the same target scattering rate can be configured for all fiber units, or the target scattering rate can be configured separately for each fiber unit. In this embodiment, the case of configuring the target scattering rate separately for each fiber unit is taken as an example for description. When configuring the target scattering rate separately for each fiber unit, the target scattering rates of different fiber units may be different, or the target scattering rates of different fiber units may also be the same.

[0085] In order to configure the target scattering rate separately for each fiber unit, it is necessary to determine the target scattering rate of each fiber unit. Based on this, an embodiment of the present application proposes a design method for a gradient scattering enhanced fiber. Refer to Figure 5 As shown, it is a schematic flow chart of the design method. The method may include the following steps:

[0086] Step 501: For each fiber unit, based on the first power gain factor of the laser, the second power gain factor of the first fiber amplifier, the third power gain factor of the second fiber amplifier, and the distance between the fiber unit and the starting position of the gradient scattering enhanced fiber, determine the fiber power distribution of the fiber unit.

[0087] Exemplarily, the fiber power distribution of the fiber unit can be determined by the following formula (1):

[0088]

[0089] In formula (1), P(L) represents the fiber power distribution of the fiber unit, that is, the fiber power distribution of the Lth fiber unit. H R(l) represents the third power gain factor of the second fiber optic amplifier. The third power gain factor can be a pre-configured gain factor or a gain factor after dynamic adjustment. The dynamic adjustment process is described in the subsequent embodiments, that is, the third power gain factor is a known value. H EDFA (l) represents the second power gain factor of the first fiber optic amplifier. The second power gain factor can be a pre-configured gain factor or a gain factor after dynamic adjustment, that is, the second power gain factor is a known value. E p Represents the first power gain factor of the laser. The first power gain factor can be a pre-configured gain factor or a gain factor after dynamic adjustment, that is, the first power gain factor is a known value. P in Represents the initial power value, such as the power value configured by the upper-layer application. Assume that the upper-layer application configures the laser to send a detection pulse signal with power value A, then the initial power value is power value A. However, when the laser actually sends the detection pulse signal, it does not use power value A, but needs to adjust power value A using the first power gain factor to obtain power value B. The laser sends the detection pulse signal with power value B, and power value B is the actual power value of the detection pulse signal.

[0090] In formula (1), α represents the configured fiber loss factor, and this fiber loss factor can be configured according to experience. l represents the distance between this fiber unit and the starting position of the gradient scattering enhanced fiber. For example, when designing the gradient scattering enhanced fiber, the position of each fiber unit is known, and this position is used to represent the distance between the fiber unit and the starting position of the gradient scattering enhanced fiber. Based on this, for each fiber unit, the distance between this fiber unit and the starting position of the gradient scattering enhanced fiber can be obtained. In formula (1), L and l can be the length of the fiber unit and variables of the transmission distance along with the fiber unit.

[0091] In summary, for each fiber unit, the first power gain factor of the laser, the second power gain factor of the first fiber optic amplifier, the third power gain factor of the second fiber optic amplifier, the initial power value, the fiber loss factor, and the distance between the fiber unit and the starting position of the gradient scattering enhanced fiber are known. In this way, through formula (1), the fiber power distribution of this fiber unit can be calculated.

[0092] Exemplarily, for the first power gain factor, the first power gain factor is used to control the transmission power of the laser when sending the detection pulse signal. For example, the following formula (2) can be used to determine the transmission power P of the laser when sending the detection pulse signal in-e , so that when the laser (such as each laser among multiple lasers) sends the detection pulse signal, it uses P in-e to send the detection pulse signal.

[0093] Pin-e = E p ·P in Formula (2)

[0094] In Formula (2), E p represents the first power gain factor of the laser, and P in represents the initial power value (i.e., the optical power before incidence). Thus, the initial power value can be adjusted based on the first power gain factor to obtain the actual power value P in-e of the detection pulse signal. P in-e represents the incident power after gain. In addition, since a multi-wavelength light source can be used to suppress the nonlinear effects caused by modulation instability (MI), the optical power incident on the optical fiber can be increased, that is, the initial power value P in can be increased.

[0095] Exemplarily, for the second power gain factor, the second power gain factor is used to control the transmission power of the first fiber amplifier when transmitting the first type of amplified signal. For example, the following formula (3) can be used to determine the transmission power P(L1) of the first fiber amplifier when transmitting the first type of amplified signal. Thus, when the first fiber amplifier transmits the first type of amplified signal, it transmits the first type of amplified signal using P(L1).

[0096]

[0097] In Formula (3), H EDFA (l) represents the second power gain factor of the first fiber amplifier, and P in-e represents the actual power value of the detection pulse signal, α represents the configured fiber loss factor, and l represents the distance between the fiber unit and the starting position of the gradient scattering enhanced fiber. For example, l represents the distance between the first fiber unit of the second enhanced fiber and the starting position of the gradient scattering enhanced fiber, or l represents the distance between the last fiber unit of the second enhanced fiber and the starting position of the gradient scattering enhanced fiber, or l represents the distance between any fiber unit of the second enhanced fiber and the starting position of the gradient scattering enhanced fiber.

[0098] It can be seen from Formula (3) that the actual power value P in-e of the detection pulse signal can be adjusted based on the second power gain factor to obtain the actual power value P(L1) of the first type of amplified signal, and the amplification of the mid-section power can be achieved. When the first fiber amplifier transmits the first type of amplified signal using the actual power value P(L1), the detection pulse signal transmitted in the mid-section (i.e., the second enhanced fiber) can be enhanced.

[0099] Exemplarily, for the third power gain factor, the third power gain factor is used to control the transmission power of the second fiber amplifier when transmitting the second type of amplified signal. For example, the transmission power P(L2) of the second fiber amplifier when transmitting the second type of amplified signal can be determined by the following formula (4). In this way, when the second fiber amplifier transmits the second type of amplified signal, it transmits the second type of amplified signal using P(L2).

[0100]

[0101] In formula (4), H R (l) represents the third power gain factor of the second fiber amplifier, P in-e represents the actual power value of the detection pulse signal, α represents the configured fiber loss factor, l represents the distance between the fiber unit and the starting position of the gradient scattering enhanced fiber. For example, l represents the distance between the first fiber unit of the third enhanced fiber and the starting position of the gradient scattering enhanced fiber, or l represents the distance between the last fiber unit of the third enhanced fiber and the starting position of the gradient scattering enhanced fiber, or l represents the distance between any fiber unit of the third enhanced fiber and the starting position of the gradient scattering enhanced fiber.

[0102] It can be seen from formula (4) that the actual power value P in-e of the detection pulse signal can be adjusted based on the third power gain factor to obtain the actual power value P(L2) of the second type of amplified signal, and the amplification of the tail power can be achieved. When the second fiber amplifier transmits the second type of amplified signal using the actual power value P(L2), it can enhance the detection pulse signal transmitted in the tail section (i.e., the third enhanced fiber).

[0103] Step 502: Obtain multiple scattering rate sets. For each scattering rate set, the scattering rate set includes the candidate scattering rates of each fiber unit, and the candidate scattering rate is any scattering rate supported by the fiber unit.

[0104] For example, for each fiber unit, multiple candidate scattering rates of the fiber unit can be selected from within the scattering rate range. The minimum value of the scattering rate range can be the minimum scattering rate supported by the fiber unit, and the maximum value of the scattering rate range can be the maximum scattering rate supported by the fiber unit. For example, the multiple candidate scattering rates of fiber unit a1 are candidate scattering rate b11, candidate scattering rate b12, candidate scattering rate b13,... The multiple candidate scattering rates of fiber unit a2 are candidate scattering rate b21, candidate scattering rate b22, candidate scattering rate b23,... and so on. In this way, multiple candidate scattering rates of each fiber unit can be obtained.

[0105] Then, multiple sets of scattering rates can be obtained. For each set of scattering rates, the set of scattering rates can include the candidate scattering rates of each optical fiber unit (all optical fiber units), and it is only necessary that different sets of scattering rates are not exactly the same. For example, taking 3 optical fiber units as an example, the set of scattering rates c1 includes the candidate scattering rate b11 of the optical fiber unit a1, the candidate scattering rate b21 of the optical fiber unit a2, and the candidate scattering rate b31 of the optical fiber unit a3. The set of scattering rates c2 includes the candidate scattering rate b11 of the optical fiber unit a1, the candidate scattering rate b21 of the optical fiber unit a2, and the candidate scattering rate b32 of the optical fiber unit a3. The set of scattering rates c3 includes the candidate scattering rate b11 of the optical fiber unit a1, the candidate scattering rate b22 of the optical fiber unit a2, and the candidate scattering rate b31 of the optical fiber unit a3. The set of scattering rates c4 includes the candidate scattering rate b11 of the optical fiber unit a1, the candidate scattering rate b22 of the optical fiber unit a2, and the candidate scattering rate b32 of the optical fiber unit a3, and so on, and multiple sets of scattering rates can be obtained.

[0106] Step 503: Based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit in each set of scattering rates, select a target set of scattering rates from multiple sets of scattering rates.

[0107] Exemplarily, based on the order of multiple sets of scattering rates, traverse each set of scattering rates in multiple sets of scattering rates in sequence. For example, first traverse the set of scattering rates c1, then traverse the set of scattering rates c2, and so on.

[0108] For the currently traversed set of scattering rates, based on the candidate scattering rates of each optical fiber unit in the set of scattering rates and the optical fiber power distribution of each optical fiber unit, determine the reference power value of each optical fiber unit. The reference power value is the product value of the candidate scattering rate of the optical fiber unit and the optical fiber power distribution of the optical fiber unit. For example, for each optical fiber unit, the reference power value of each optical fiber unit is σ(L)·P(L), where σ(L) represents the candidate scattering rate of the optical fiber unit, and P(L) represents the optical fiber power distribution of the optical fiber unit.

[0109] Then, select the minimum reference power value and the maximum reference power value from the reference power values of each optical fiber unit. For example, given the reference power values of each optical fiber unit in the set of scattering rates, the minimum reference power value and the maximum reference power value can be selected. Among them, the minimum reference power value of the set of scattering rates can be denoted as That is, the minimum value among all reference power values, and the maximum reference power value of the set of scattering rates can be denoted as That is, the maximum value among all reference power values.

[0110] Then, if it is determined that the set of scattering rates satisfies the preset condition based on the minimum reference power value and the maximum reference power value, the set of scattering rates can be selected as the target set of scattering rates, and the traversal process of the set of scattering rates ends. If it is determined that the set of scattering rates does not satisfy the preset condition based on the minimum reference power value and the maximum reference power value, the next set of scattering rates can be traversed from multiple sets of scattering rates, and the next set of scattering rates is used as the currently traversed set of scattering rates, and the above steps are repeated. And so on, until a set of scattering rates satisfies the preset condition, and the set of scattering rates is selected as the target set of scattering rates.

[0111] In a possible implementation manner, if the difference between the maximum reference power value and the minimum reference power value is less than the first power value, and the minimum reference power value is greater than the second power value, the set of scattering rates satisfies the preset condition. If the difference between the maximum reference power value and the minimum reference power value is not less than the first power value, and / or, the minimum reference power value is not greater than the second power value, the set of scattering rates does not satisfy the preset condition. For example, for the first power value and the second power value, the first power value is the difference between the configured upper limit value of the scattered light power and the configured lower limit value of the scattered light power, and the second power value is the lower limit value of the scattered light power.

[0112] For example, the satisfaction of the preset condition by the set of scattering rates can be represented by formula (5):

[0113]

[0114] In formula (5), represents the difference between the maximum reference power value and the minimum reference power value, represents the minimum reference power value. DR represents the difference between the upper limit value of the scattered light power and the lower limit value of the scattered light power, and TH PD represents the lower limit value of the scattered light power.

[0115] In summary, the scattering rate distribution σ(L) can be designed according to the power distribution, and the scattering rate distribution σ(L) can satisfy formula (5). For example, for each set of scattering rates, if holds, and holds, then the set of scattering rates satisfies the preset condition. In addition, if does not hold, and / or, does not hold, then the set of scattering rates does not satisfy the preset condition.

[0116] In the above formula (5), DR can represent the difference between the upper limit value and the lower limit value of the scattered light power. DR can also be the set link signal equalization degree, that is, the dynamic range. The upper limit value of the scattered light power can also be called the upper limit value of the detector dynamic range, which is the upper limit value of the power of the scattered light signal sent by the optical fiber unit to the distributed acoustic wave detection host. The upper limit value of the scattered light power can be configured according to experience or determined by an algorithm, and there is no limitation on this. The lower limit value of the scattered light power can also be called the lower limit value of the detector dynamic range, and the lower limit value of the scattered light power can be denoted as TH PD , which is the lower limit value of the power of the scattered light signal sent by the optical fiber unit to the distributed acoustic wave detection host. The lower limit value of the scattered light power can be configured according to experience or determined by an algorithm, and there is no limitation on this.

[0117] The working principle of formula (5) is described below in combination with specific application scenarios.

[0118] In the distributed acoustic wave detection system, any combination of the pump structure, pump direction, and pump wavelength is selected according to the detection requirements. The detection pulse signal is amplified by three amplification methods (multi-laser amplification, first fiber amplifier amplification, second fiber amplifier amplification), and the link power distribution is obtained in combination with the transmission fiber loss. See Figure 6A shown, which is a schematic diagram of the link power distribution obtained by the three amplification methods.

[0119] In Figure 6A , the amplified and unamplified link power distributions are compared. When the link power reaches the lower limit of the PD dynamic range, the transmission distance after amplification is significantly improved compared with that before amplification. The amplified link power distribution refers to the link power distribution when the detection pulse signal is amplified by the three amplification methods, and the unamplified link power distribution refers to the link power distribution when the detection pulse signal is not amplified by the three amplification methods. EDFA refers to the amplification of the detection pulse signal by the first fiber amplifier, and Raman amplification refers to the amplification of the detection pulse signal by the second fiber amplifier. The lower limit of the PD dynamic range refers to the lower limit value of the detector dynamic range, that is, the lower limit value TH of the scattered light power in the above embodiment PD .

[0120] Furthermore, since the large power difference between the near end and the far end on the link will introduce additional noise, in order to ensure the equalization of the signal-to-noise ratio of the entire link, the scattering rate of the optical fiber is designed according to the link power distribution P(L) to obtain the gradient scattering enhanced optical fiber. The link scattering enhancement intensity distribution of the gradient scattering enhanced optical fiber is shown in Figure 6B shown, and the link scattering enhancement intensity distribution is the scattering rate distribution σ(L), that is, the target scattering rate of each optical fiber unit.

[0121] In Figure 6BAmong them, the scattering rate distribution of the gradient scattering enhanced fiber (GDSEF) is compared with that of the ordinary single-mode fiber (SMF). Obviously, the target scattering rates of different fiber units can be different for the GDSEF, while for the SMF, the target scattering rates of different fiber units need to be the same. For the gradient scattering enhanced fiber, according to the detected optical power distribution, different intensities of target scattering rates are designed for fiber units at different positions. Weaker scattering enhancement is performed at the proximal end with stronger optical power to save the detected optical energy as much as possible, that is, the target scattering rate is smaller. Stronger scattering enhancement is performed at the distal end with weaker optical power to increase the scattered optical power, that is, the target scattering rate is larger.

[0122] For example, a high signal-to-noise ratio needs to meet conditions such as the minimum scattering enhancement intensity and the maximum dynamic range. Therefore, at the location with a larger power distribution, the scattering enhancement intensity is kept minimum, only 3 dB higher than that of the ordinary single-mode fiber to save power. As the distance increases, the backscattered power will decrease. At this time, a stronger scattering intensity is set to meet the dynamic range condition. In addition, for the convenience of fiber preparation, the scattering intensity of the fiber is changed in steps of 5 km. Based on the above principle, the target scattering rate of the fiber unit can be designed, that is, the scattering rate distribution σ(L) is designed according to the power distribution, and the scattering rate distribution σ(L) can satisfy the formula (5).

[0123] Finally, by combining the link power distribution and the scattering rate distribution of the gradient scattering enhanced fiber, the signal power distribution received by the distributed acoustic wave detection host can be obtained. See Figure 6C shown, which is a schematic diagram of the backscattered power distribution of the entire fiber link, that is, the power distribution of the scattered optical signals sent by each fiber unit to the distributed acoustic wave detection host. In Figure 6C Among them, when the detected optical power is the same, the signal power of the gradient scattering enhanced fiber is compared with that of the ordinary single-mode fiber. It can be seen that after the gradient scattering enhanced fiber combines three amplification technologies, the signal power is much larger than that of the ordinary single-mode fiber, the signal-to-noise ratio is significantly improved, and the link signal power is flatter, realizing high-quality acoustic wave detection over a long-distance full link.

[0124] In a possible implementation, when sequentially traversing each scattering rate set from multiple scattering rate sets, if the last scattering rate set is traversed and the last scattering rate set still does not meet the preset conditions, the target scattering rate set cannot be obtained. In this case, the first power gain factor, the second power gain factor, and the third power gain factor can also be dynamically adjusted, that is, the first power gain factor, the second power gain factor, and the third power gain factor are optimized. Then, based on the adjusted gain factors, the above steps are repeated until the target scattering rate set is obtained. In this way, the optimal first power gain factor, second power gain factor, and third power gain factor can be obtained, so that the gradient scattering enhanced optical fiber meets the long-distance detection requirements, realizes full-link amplification, and improves the detection distance.

[0125] Step 504: Determine the target scattering rate of each optical fiber unit based on the target scattering rate set.

[0126] For example, assume that the target scattering rate set can include the candidate scattering rate b11 of the optical fiber unit a1, the candidate scattering rate b22 of the optical fiber unit a2, and the candidate scattering rate b31 of the optical fiber unit a3. Then, the target scattering rate of the optical fiber unit a1 can be the candidate scattering rate b11, the target scattering rate of the optical fiber unit a2 can be the candidate scattering rate b22, and the target scattering rate of the optical fiber unit a3 can be the candidate scattering rate b31.

[0127] In the design process of the gradient scattering enhanced optical fiber, the scattering rate of the gradient scattering enhanced optical fiber is designed according to the link power distribution after multiple amplifications. The proximal scattering rate of the gradient scattering enhanced optical fiber is weak to reduce losses, and the distal scattering rate is strong to increase the signal power. The scattering rate distribution is opposite to the link power distribution.

[0128] Exemplarily, the gradient scattering enhanced optical fiber can be prepared by technologies such as ultraviolet exposure and femtosecond laser etching, that is, the scattering rate of the gradient scattering enhanced optical fiber is realized by technologies such as ultraviolet exposure and femtosecond laser etching. That is to say, the target scattering rate of the optical fiber unit is configured at the position where the optical fiber unit is located.

[0129] Exemplarily, after designing the gradient scattering enhanced optical fiber, the Figure 3 shown distributed acoustic wave detection system can be adopted, and the distributed acoustic wave detection system includes a gradient scattering enhanced optical fiber. For each optical fiber unit of the gradient scattering enhanced optical fiber, when the optical fiber unit receives a detection pulse signal, the signal reflection power is determined based on the received power of the detection pulse signal and the target scattering rate of the optical fiber unit, and a scattered light signal corresponding to the detection pulse signal is sent to the distributed acoustic wave detection host based on the signal reflection power.

[0130] For example, when the optical fiber unit receives a detection pulse signal through power A (i.e., the received power of the detection pulse signal), it will send a scattered light signal corresponding to the detection pulse signal to the distributed acoustic wave detection host through power B (i.e., the signal reflection power), and the target scattering rate is used to reflect the functional relationship between power B and power A. Based on this, the signal reflection power can be determined based on power A and the target scattering rate. There is no limitation on this determination method, as long as the signal reflection power can be obtained. In this way, the optical fiber unit can send a scattered light signal corresponding to the detection pulse signal to the distributed acoustic wave detection host based on the signal reflection power.

[0131] In a possible implementation, refer to Figure 7 As shown, it is a schematic flowchart of the design method of the gradient scattering enhanced optical fiber. The gradient scattering enhanced optical fiber σ(L) can be designed and optimized, that is, the scattering rate distribution σ(L) of the gradient scattering enhanced optical fiber is designed and optimized. Then, it is judged whether formula (5) is satisfied. If it is satisfied, the design of the scattering rate distribution σ(L) is completed, and the full link of the sensing optical fiber (i.e., the gradient scattering enhanced optical fiber) is amplified to improve the detection distance. If it is not satisfied, the multi-wavelength light source eliminates the MI nonlinearity, increases the incident optical power, the remote pump EDFA (i.e., the first optical fiber amplifier) increases the mid-section power, and the Raman distribution (i.e., the second optical fiber amplifier) amplifies to increase the tail-end optical power. Then, the power distribution P(L) of the sensing optical fiber is calculated, that is, the optical fiber power distribution of each optical fiber unit is determined, and then, the step of designing and optimizing the gradient scattering enhanced optical fiber σ(L) is returned.

[0132] As can be seen from the above technical solutions, in the embodiments of the present application, multiple distance detections for distributed acoustic wave detection are achieved. Even when the detection distance is relatively long, transmission loss can be reduced, the signal power at the fiber tail section is relatively strong, the noise of the signal at the fiber tail section is reduced, the sensitivity of the signal at the fiber tail section is improved, high signal-to-noise ratio detection for the entire link is achieved, and reliability is improved. Multiple single-frequency lasers can be used to form a multi-wavelength fiber light source. The wavelengths of the single-frequency lasers are set at the peak gain positions within the MI gain spectra of adjacent lasers, so that the incident power is amplified instead of amplified spontaneous emission noise, effectively suppressing MI nonlinearity, improving the peak power of the incident detection light pulse, and increasing the incident light power. A first fiber amplifier is used to increase the optical power in the middle section, and a second fiber amplifier is used to increase the optical power at the tail section. The sensing fiber can be used as a gain medium, and remote pump EDFA and Raman distributed amplification are used to increase the optical power in the middle and tail sections of the fiber, effectively extending the sensing distance of the distributed acoustic wave detection system. The problem of uneven signal power between the proximal and distal ends of the link can be solved, and the detection distance of the distributed acoustic wave detection can be significantly increased. The link power distribution is obtained by various amplification methods, and the scattering rate distribution of the gradient scattering enhanced fiber is designed and optimized according to the link power distribution. Weaker scattering enhancement is performed at the proximal end where the optical power is stronger to save the detection light energy as much as possible, and stronger scattering enhancement is performed at the distal end where the optical power is weaker to increase the scattered light power, achieving ultra-long distance high-quality distributed acoustic wave detection for the entire link.

[0133] Based on the same application concept as the above method, in the embodiments of the present application, a design device for a gradient scattering enhanced fiber is proposed. The gradient scattering enhanced fiber includes a first enhanced fiber, a second enhanced fiber, and a third enhanced fiber. Among them, the detection pulse signals sent by multiple lasers enter the first enhanced fiber through a first WDM device; the detection pulse signals transmitted by the first enhanced fiber and the first type of amplification signal sent by a first fiber amplifier enter the second enhanced fiber through a second WDM device; the detection pulse signals transmitted by the second enhanced fiber and the second type of amplification signal sent by a second fiber amplifier enter the third enhanced fiber through a third WDM device. Among them, the gradient scattering enhanced fiber includes multiple fiber units. See Figure 8 As shown, for the structural schematic diagram of the device, the device may include:

[0134] A determination module 81 is configured to determine, for each optical fiber unit, a target scattering rate of the optical fiber unit based on a first power gain factor of the laser, a second power gain factor of the first optical fiber amplifier, a third power gain factor of the second optical fiber amplifier, and a distance between the optical fiber unit and a starting position of the gradient scattering enhanced optical fiber; wherein the first power gain factor is used to control the transmission power of the laser when sending the detection pulse signal, the second power gain factor is used to control the transmission power of the first optical fiber amplifier when sending the first type of amplified signal, and the third power gain factor is used to control the transmission power of the second optical fiber amplifier when sending the second type of amplified signal;

[0135] A configuration module 82 is configured to configure the target scattering rate for each optical fiber unit, and the target scattering rates of different optical fiber units may be different or the same; wherein, when an optical fiber unit receives a detection pulse signal, it determines a signal reflection power based on the received power of the detection pulse signal and the target scattering rate of the optical fiber unit, and sends a scattered light signal corresponding to the detection pulse signal to the distributed acoustic wave detection host based on the signal reflection power.

[0136] Exemplarily, when the determination module 81 determines the target scattering rate of the optical fiber unit based on the first power gain factor, the second power gain factor, the third power gain factor, and the distance between the optical fiber unit and the starting position of the gradient scattering enhanced optical fiber, it is specifically configured to: determine the optical fiber power distribution of the optical fiber unit based on the first power gain factor, the second power gain factor, the third power gain factor, and the distance between the optical fiber unit and the starting position of the gradient scattering enhanced optical fiber; obtain multiple scattering rate sets, for each scattering rate set, the scattering rate set includes candidate scattering rates of each optical fiber unit, and the candidate scattering rate is any scattering rate supported by the optical fiber unit; select a target scattering rate set from the multiple scattering rate sets based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit in each scattering rate set; and determine the target scattering rate of each optical fiber unit based on the target scattering rate set.

[0137] Exemplarily, when the determining module 81 selects a target scattering rate set from multiple scattering rate sets based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit within each set of scattering rates, it is specifically configured to: sequentially traverse each scattering rate set from the multiple scattering rate sets; for the currently traversed scattering rate set, determine the reference power value of each optical fiber unit based on the candidate scattering rate of each optical fiber unit within the scattering rate set and the optical fiber power distribution of each optical fiber unit; the reference power value is the product value of the candidate scattering rate of the optical fiber unit and the optical fiber power distribution of the optical fiber unit; select the minimum reference power value and the maximum reference power value from the reference power values of each optical fiber unit; if it is determined that the scattering rate set satisfies a preset condition based on the minimum reference power value and the maximum reference power value, then select the scattering rate set as the target scattering rate set; if it is determined that the scattering rate set does not satisfy the preset condition based on the minimum reference power value and the maximum reference power value, traverse another scattering rate set from the multiple scattering rate sets.

[0138] Exemplarily, if the difference between the maximum reference power value and the minimum reference power value is less than a first power value, and the minimum reference power value is greater than a second power value, then the scattering rate set satisfies the preset condition; if the difference between the maximum reference power value and the minimum reference power value is not less than the first power value, and / or, the minimum reference power value is not greater than the second power value, then the scattering rate set does not satisfy the preset condition;

[0139] The first power value is the difference between the configured upper limit value of the scattered light power and the configured lower limit value of the scattered light power, and the second power value is the lower limit value of the scattered light power.

[0140] Based on the same application concept as the above method, an electronic device is proposed in an embodiment of the present application. Refer to Figure 9 As shown, the electronic device includes: a processor 91 and a machine-readable storage medium 92. The machine-readable storage medium 92 stores machine-executable instructions that can be executed by the processor 91; the processor 91 is configured to execute the machine-executable instructions to implement the design method of the gradient scattering enhanced optical fiber disclosed in the above examples of the present application.

[0141] Based on the same application concept as the above method, an embodiment of the present application also provides a machine-readable storage medium. A number of computer instructions are stored on the machine-readable storage medium. When the computer instructions are executed by a processor, the design method of the gradient scattering enhanced optical fiber disclosed in the above examples of the present application can be implemented.

[0142] Among them, the above-mentioned machine-readable storage medium can be any electronic, magnetic, optical, or other physical storage device that can contain or store information, such as executable instructions, data, etc. For example, the machine-readable storage medium can be: RAM (Random Access Memory), volatile memory, non-volatile memory, flash memory, storage drives (such as hard disk drives), solid-state drives, any type of storage disk (such as optical discs, DVDs, etc.), or similar storage media, or a combination thereof.

[0143] Based on the same application concept as the above method, an embodiment of the present application also provides a computer program product. The computer program product may include a computer program, which when executed by a processor, can implement the design method of the gradient scattering enhanced optical fiber disclosed in the above examples of the present application.

[0144] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the embodiments of the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program code.

[0145] The above are only the embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A gradient scattering enhanced optical fiber, characterized in that, The gradient scattering enhanced optical fiber includes a first enhanced optical fiber, a second enhanced optical fiber, and a third enhanced optical fiber; wherein, the detection pulse signals sent by multiple lasers enter the first enhanced optical fiber through a first wavelength division multiplexing (WDM) device; the detection pulse signals transmitted by the first enhanced optical fiber and the first type of amplified signals sent by a first optical fiber amplifier enter the second enhanced optical fiber through a second WDM device; the detection pulse signals transmitted by the second enhanced optical fiber and the second type of amplified signals sent by a second optical fiber amplifier enter the third enhanced optical fiber through a third WDM device. Wherein, the gradient scattering enhanced optical fiber includes multiple optical fiber units, and a target scattering rate of each optical fiber unit is configured at the position where each optical fiber unit is located, and the target scattering rates of different optical fiber units are different or the same. For each optical fiber unit, when the optical fiber unit receives a detection pulse signal, it determines a signal reflection power based on the received power of the detection pulse signal and the target scattering rate of the optical fiber unit, and sends a scattered light signal corresponding to the detection pulse signal to a distributed acoustic wave detection host based on the signal reflection power.

2. The gradient scattering enhanced optical fiber according to claim 1, wherein for each optical fiber unit, the target scattering rate of the optical fiber unit is determined based on a first power gain factor of the laser, a second power gain factor of the first optical fiber amplifier, a third power gain factor of the second optical fiber amplifier, and the distance between the optical fiber unit and the starting position of the gradient scattering enhanced optical fiber; wherein, the first power gain factor is used to control the transmission power of the laser when sending the detection pulse signal, the second power gain factor is used to control the transmission power of the first optical fiber amplifier when sending the first type of amplified signal, and the third power gain factor is used to control the transmission power of the second optical fiber amplifier when sending the second type of amplified signal.

3. The gradient scattering enhanced optical fiber according to claim 2, wherein for each optical fiber unit, the process of determining the target scattering rate of the optical fiber unit includes: determining the optical fiber power distribution of the optical fiber unit based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between the optical fiber unit and the starting position of the gradient scattering enhanced optical fiber; obtaining multiple scattering rate sets, and for each scattering rate set, the scattering rate set includes candidate scattering rates of each optical fiber unit, and the candidate scattering rate is any scattering rate supported by the optical fiber unit; selecting a target scattering rate set from the multiple scattering rate sets based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit in each scattering rate set; determining the target scattering rate of each optical fiber unit based on the target scattering rate set.

4. The gradient scattering enhanced optical fiber according to claim 3, characterized in that, Determining the optical fiber power distribution of the optical fiber unit based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between the optical fiber unit and the starting position of the gradient scattering enhanced optical fiber includes: Determining the optical fiber power distribution of the optical fiber unit by using the following formula: where P(L) represents the optical fiber power distribution of the optical fiber unit; H R (l) represents the third power gain factor, H EDFA (l) represents the second power gain factor, E p represents the first power gain factor, P in represents the initial power value, α represents the configured optical fiber loss factor, and l represents the distance between this optical fiber unit and the starting position of the gradient scattering enhanced optical fiber.

5. The gradient scattering enhanced optical fiber according to claim 3, characterized in that Selecting a target scattering rate set from the multiple scattering rate sets based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rate of each optical fiber unit within each set of scattering rates includes: Traversing each scattering rate set in sequence from the multiple scattering rate sets; For the currently traversed scattering rate set, determining the reference power value of each optical fiber unit based on the candidate scattering rate of each optical fiber unit within the scattering rate set and the optical fiber power distribution of each optical fiber unit; wherein the reference power value is the product value of the candidate scattering rate of the optical fiber unit and the optical fiber power distribution of the optical fiber unit; Selecting the minimum reference power value and the maximum reference power value from the reference power values of each optical fiber unit; If it is determined that the scattering rate set meets the preset condition based on the minimum reference power value and the maximum reference power value, then select the scattering rate set as the target scattering rate set; If it is determined that the scattering rate set does not meet the preset condition based on the minimum reference power value and the maximum reference power value, then traverse the next scattering rate set from the multiple scattering rate sets.

6. The gradient scattering enhanced optical fiber according to claim 5, characterized in that If the difference between the maximum reference power value and the minimum reference power value is less than the first power value and the minimum reference power value is greater than the second power value, then the scattering rate set meets the preset condition; if the difference between the maximum reference power value and the minimum reference power value is not less than the first power value, and / or, the minimum reference power value is not greater than the second power value, then the scattering rate set does not meet the preset condition; wherein the first power value is the difference between the configured upper limit value of the scattered light power and the configured lower limit value of the scattered light power, and the second power value is the lower limit value of the scattered light power.

7. The gradient scattering enhanced optical fiber according to claim 2, characterized in that Based on the first power gain factor, the transmission power P of the laser when sending the detection pulse signal is determined by the following formula in-e : P in-e = E p · P in ; Based on the second power gain factor, the transmission power P(L1) of the first fiber optic amplifier when transmitting the first type of amplified signal is determined using the following formula: Based on the third power gain factor, the transmission power P(L2) of the second fiber optic amplifier when transmitting the second type of amplified signal is determined using the following formula: Among them, E p represents the first power gain factor, P in represents the initial power value, H EDFA (l) represents the second power gain factor, H R (l) represents the third power gain factor, α represents the configured optical fiber loss factor, and l represents the distance between the optical fiber unit and the starting position of the gradient scattering enhanced optical fiber.

8. The gradient scattering enhanced optical fiber according to any one of claims 1-7, characterized in that The multiple lasers include at least two single-frequency lasers, the at least two single-frequency lasers correspond to different wavelengths, and detection pulse signals of different wavelengths are sent through the at least two single-frequency lasers; The first optical fiber amplifier includes a remotely pumped erbium-doped optical fiber amplifier, the pumping structure of the remotely pumped erbium-doped optical fiber amplifier is co-pumping or by-pass pumping, and the pumping direction of the remotely pumped erbium-doped optical fiber amplifier is forward pumping, backward pumping or bi-directional pumping; wherein, when the remotely pumped erbium-doped optical fiber amplifier sends a first type of amplified signal, the wavelength of the first type of amplified signal is different from the wavelength of the detection pulse signal; The second optical fiber amplifier includes a Raman distributed optical fiber amplifier. The pumping structure of the Raman distributed optical fiber amplifier is co-path pumping or by-pass pumping, and the pumping direction of the Raman distributed optical fiber amplifier is forward pumping, backward pumping or bidirectional pumping. Among them, when the Raman distributed optical fiber amplifier sends the second type of amplified signal, the wavelength of the second type of amplified signal is different from the wavelength of the detection pulse signal.

9. A design method for a gradient scattering enhanced optical fiber, characterized in that, The gradient scattering enhanced optical fiber includes a first enhanced optical fiber, a second enhanced optical fiber and a third enhanced optical fiber. Among them, the detection pulse signals sent by multiple lasers enter the first enhanced optical fiber through a first wavelength division multiplexing (WDM) device; the detection pulse signals transmitted by the first enhanced optical fiber and the first type of amplified signals sent by the first optical fiber amplifier enter the second enhanced optical fiber through a second WDM device; the detection pulse signals transmitted by the second enhanced optical fiber and the second type of amplified signals sent by the second optical fiber amplifier enter the third enhanced optical fiber through a third WDM device. Among them, the gradient scattering enhanced optical fiber includes multiple optical fiber units, and the method includes: For each optical fiber unit, based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between this optical fiber unit and the starting position of the gradient scattering enhanced optical fiber, determine the target scattering rate of this optical fiber unit. Among them, the first power gain factor is used to control the emission power of the laser when sending the detection pulse signal, the second power gain factor is used to control the emission power of the first optical fiber amplifier when sending the first type of amplified signal, and the third power gain factor is used to control the emission power of the second optical fiber amplifier when sending the second type of amplified signal. Configure the target scattering rate of each optical fiber unit, and the target scattering rates of different optical fiber units can be different or the same. Among them, when an optical fiber unit receives a detection pulse signal, based on the received power of the detection pulse signal and the target scattering rate of this optical fiber unit, determine the signal reflection power, and send the scattered light signal corresponding to the detection pulse signal to the distributed acoustic wave detection host based on the signal reflection power.

10. The method according to claim 9, wherein The determining the target scattering rate of the optical fiber unit based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between this optical fiber unit and the starting position of the gradient scattering enhanced optical fiber includes: Based on the first power gain factor of the laser, the second power gain factor of the first optical fiber amplifier, the third power gain factor of the second optical fiber amplifier, and the distance between this optical fiber unit and the starting position of the gradient scattering enhanced optical fiber, determine the optical fiber power distribution of this optical fiber unit. Obtain multiple scattering rate sets. For each scattering rate set, the scattering rate set includes the candidate scattering rate of each optical fiber unit, and the candidate scattering rate is any scattering rate supported by the optical fiber unit. Select a target scattering rate set from the multiple scattering rate sets based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit within each set of scattering rates; Determine the target scattering rate of each optical fiber unit based on the target scattering rate set; Among them, the selecting a target scattering rate set from the multiple scattering rate sets based on the optical fiber power distribution of each optical fiber unit and the candidate scattering rates of each optical fiber unit within each set of scattering rates includes: Traverse each scattering rate set in turn from the multiple scattering rate sets; For the currently traversed scattering rate set, determine the reference power value of each optical fiber unit based on the candidate scattering rate of each optical fiber unit within this scattering rate set and the optical fiber power distribution of each optical fiber unit; wherein, the reference power value is the product value of the candidate scattering rate of the optical fiber unit and the optical fiber power distribution of the optical fiber unit; Select the minimum reference power value and the maximum reference power value from the reference power values of each optical fiber unit; If it is determined that this scattering rate set meets the preset condition based on the minimum reference power value and the maximum reference power value, then select this scattering rate set as the target scattering rate set; If it is determined that this scattering rate set does not meet the preset condition based on the minimum reference power value and the maximum reference power value, then traverse a standard scattering rate set from the multiple scattering rate sets; Among them, if the difference between the maximum reference power value and the minimum reference power value is less than the first power value and the minimum reference power value is greater than the second power value, then this scattering rate set meets the preset condition; if the difference between the maximum reference power value and the minimum reference power value is not less than the first power value, and / or, the minimum reference power value is not greater than the second power value, then this scattering rate set does not meet the preset condition; The first power value is the difference between the configured upper limit value of the scattered light power and the configured lower limit value of the scattered light power, and the second power value is the lower limit value of the scattered light power.

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