OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology

Abstract

The invention discloses an OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology. The system modulates a continuous optical signal output by a narrow linewidth laser into an optical pulse signal through a semiconductor optical amplifier, and modulates it into a narrower pulse optical signal by an acousto-optic modulator. The narrow pulse optical signal is amplified by an erbium-doped fiber amplifier and then injected into a wavelength division multiplexer and an output optical signal of a Raman amplifier through a first circulator. The Raman amplifier distributes and amplifies the optical signal in the optical fiber to be tested, thereby improving the sensing distance of the system. At the same time, a remote pump is provided for the erbium-doped fiber to realize remote pump amplification, thereby further improving the sensing distance of the system. The backward Rayleigh scattered optical signal is amplified by a second erbium-doped fiber amplifier, and then ASE noise is filtered out by an optical filter, and then detected and collected by a photoelectric detector and a data acquisition card. The system can be used for long-distance monitoring of OPGW optical cables.

Description

Technical Field

[0001] The invention relates to the field of optical technology, in particular to an OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology. Background Art

[0002] OPGW (Optical Fiber Composite Overhead Ground Wire) optical cables are widely used in ultra-high voltage (UHV) long-distance transmission lines. During long-term operation, they are inevitably affected by complex external environmental factors such as wind vibration, icing, and lightning strikes, which can easily lead to local stress concentration and increase sag, thereby reducing the distance between the ground wire and the conductor, reducing the effective range, and even causing the ground wire to connect; it may also cause the optical fiber to break due to mechanical fatigue, which can also be manifested as increased attenuation, and in severe cases, it can cause accidents such as tower collapse. Once the ground wire function or optical fiber communication function is lost during the use of OPGW optical cables, it may cause huge power outage losses and impacts, and endanger the safe and stable operation of the power grid. Traditionally, icing, dancing, and lightning strikes are monitored by manual inspections, which cannot be discovered and handled in time, resulting in the interruption of optical cables or fiber cores, affecting communication services.

[0003] Φ-OTDR (phase-sensitive optical time-domain reflectometer) uses the backward Rayleigh scattered light signal in the optical fiber to reflect the vibration information of each point along the sensing optical fiber. When there is no vibration event in the outside world, the backward Rayleigh scattered light signal is relatively stable; when a vibration event occurs locally, the Rayleigh scattered light signal at the corresponding position fluctuates. By performing differential processing and time-domain Fourier transform demodulation on the backward Rayleigh scattered light signal at different times before and after the vibration event, the location and frequency information of the vibration event can be obtained to achieve distributed vibration monitoring. Φ-OTDR has been widely used in perimeter security, oil and gas pipeline monitoring and other fields.

[0004] In recent years, Φ-OTDR has been applied to OPGW optical cable ice, dancing, and lightning monitoring, and has achieved certain results. Φ-OTDR realizes sensing based on backward Rayleigh scattered light signals, and its signal strength is weak. At a sensing distance of 50km, the tail-end signal-to-noise ratio is poor, and a longer sensing distance cannot be achieved. Due to the long station distance of OPGW optical cables, the use of Φ-OTDR double-end opposite measurement cannot cover the entire OPGW optical cable, and there is a monitoring blind area. Therefore, improving the monitoring distance of Φ-OTDR is of great significance for its application in OPGW optical cable ice, dancing, and lightning monitoring. Summary of the invention

[0005] To this end, the present invention provides an OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology, in an effort to solve or at least alleviate at least one of the above problems.

[0006] According to one aspect of the present invention, a long-distance vibration monitoring system for OPGW optical cables based on Φ-OTDR technology is provided, wherein the monitoring system comprises a narrow linewidth laser, a semiconductor optical amplifier, an acousto-optic modulator, a first erbium-doped fiber amplifier, a first circulator, a Raman amplifier, a wavelength division multiplexer, an optical fiber to be tested, an erbium-doped fiber, a second erbium-doped fiber amplifier, a second circulator, an optical filter, a photodetector, a data acquisition card, and a pulse generator; the optical signal output end of the narrow linewidth laser is connected to the optical signal input end of the semiconductor optical amplifier, the optical signal output end of the semiconductor optical amplifier is connected to the optical signal input end of the acousto-optic modulator, the optical signal output end of the acousto-optic modulator is connected to the optical signal input end of the first erbium-doped fiber amplifier, the optical signal output end of the first erbium-doped fiber amplifier is connected to the first optical signal port of the first circulator, and the optical signal output end of the second erbium-doped fiber amplifier is connected to the optical signal input end of the second circulator. The second optical signal port of a circulator is connected to the first port of a wavelength division multiplexer, the optical signal output end of a Raman amplifier is connected to the second port of the wavelength division multiplexer, the third port of the wavelength division multiplexer is connected to the optical fiber to be tested, and the optical fiber to be tested is simultaneously connected to the erbium-doped optical fiber; the third optical signal port of the first circulator is connected to the optical signal input end of a second erbium-doped optical fiber amplifier, the optical signal output end of the second erbium-doped optical fiber amplifier is simultaneously connected to the first optical signal port of the second circulator, the second optical signal port of the second circulator is connected to the optical filter, the third optical signal port of the second circulator is connected to the optical signal input end of a photodetector, the electrical signal output end of the photodetector is connected to the electrical signal input end of an acquisition card, and the microwave signal output end of a pulse generator is simultaneously connected to a semiconductor optical amplifier, a microwave signal loading end of an acousto-optic modulator, and a trigger signal input end of a data acquisition card.

[0007] Furthermore, the narrow linewidth laser adopts a single-frequency narrow linewidth fiber laser with an output optical power of 11 mW and a wavelength of 1550.172 nm.

[0008] Furthermore, the extinction ratio of the semiconductor optical amplifier is 60 dB.

[0009] Furthermore, the first acousto-optic modulator has a shift frequency of -200 MHz and an extinction ratio of 50 dB.

[0010] Furthermore, the output optical power of the Raman amplifier is 600mW and the wavelength is 1480nm.

[0011] Furthermore, the central wavelength of the optical filter is 1550.17 nm and the bandwidth is 2 GHz.

[0012] Furthermore, the detection bandwidth of the photoelectric balance detector is 50 MHz.

[0013] According to the OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology of the present invention, a direct detection type Φ-OTDR system based on the cascade of semiconductor optical amplifier and acousto-optic modulator, front-end distributed amplification technology and remote pump technology is provided, which realizes the OPGW optical cable long-distance monitoring system and can achieve at least one of the following beneficial effects:

[0014] 1. The system of the present invention adopts a hybrid of front-end distributed first-order Raman amplification technology and remote pumping technology to realize long-distance OPGW optical cable vibration monitoring. Compared with relay EDFA amplification and double-end amplification, the system eliminates the necessity of on-site remote power supply and has the significance of remote sensing in practical applications.

[0015] 2. The system of the present invention adopts a cascaded semiconductor optical amplifier and an acousto-optic modulator to fully improve the extinction ratio of the detection light pulse; effectively avoids the continuous light signal leakage caused by the limited extinction ratio and the high duty cycle of the detection pulse light in the long-distance sensing system, which causes system signal jitter, and further improves the stability of the long-distance sensing system.

[0016] 3. The system of the present invention has a large sensing distance and good system stability. The traditional Φ-OTDR technology is affected by the nonlinear threshold of the optical fiber, and the detection light pulse power cannot be too high, resulting in limited sensing distance. The system adopts a mixture of front-end distributed amplification technology and remote pumping technology to fully improve the sensing distance and has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To achieve the above and related purposes, certain illustrative aspects are described herein in conjunction with the following description and accompanying drawings, which indicate various ways in which the principles disclosed herein can be practiced, and all aspects and their equivalents are intended to fall within the scope of the claimed subject matter. The above and other purposes, features and advantages of the present disclosure will become more apparent by reading the following detailed description in conjunction with the accompanying drawings. Throughout the present disclosure, the same reference numerals generally refer to the same parts or elements.

[0018] Figure 1 A schematic diagram of an OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology according to an embodiment of the present invention is shown;

[0019] Figure 2 A schematic diagram of the cascade connection of a semiconductor optical amplifier and an acousto-optic modulator of the present invention is shown;

[0020] Figure 3 The time domain diagram of the sensing signal at 153 km of the system of the present invention is shown;

[0021] Figure 4 A local enlarged view of the 153km sensing signal of the system of the present invention is shown. DETAILED DESCRIPTION

[0022] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0023] The embodiment of the present invention provides an OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology, wherein the monitoring system comprises a narrow linewidth laser, a semiconductor optical amplifier, an acousto-optic modulator, a first erbium-doped fiber amplifier, a first circulator, a Raman amplifier, a wavelength division multiplexer, an optical fiber to be tested, an erbium-doped fiber, a second erbium-doped fiber amplifier, a second circulator, an optical filter, a photodetector, a data acquisition card and a pulse generator; the optical signal output end of the narrow linewidth laser is connected to the optical signal input end of the semiconductor optical amplifier, the optical signal output end of the semiconductor optical amplifier is connected to the optical signal input end of the acousto-optic modulator, the optical signal output end of the acousto-optic modulator is connected to the optical signal input end of the first erbium-doped fiber amplifier, the optical signal output end of the first erbium-doped fiber amplifier is connected to the first optical signal port of the first circulator, and the first circulator The second optical signal port of the shaper is connected to the first port of the wavelength division multiplexer, the optical signal output end of the Raman amplifier is connected to the second port of the wavelength division multiplexer, the third port of the wavelength division multiplexer is connected to the optical fiber to be tested, and the optical fiber to be tested is simultaneously connected to the erbium-doped optical fiber; the third optical signal port of the first circulator is connected to the optical signal input end of the second erbium-doped fiber amplifier, the optical signal output end of the second erbium-doped fiber amplifier is simultaneously connected to the first optical signal port of the second circulator, the second optical signal port of the second circulator is connected to the optical filter, the third optical signal port of the second circulator is connected to the optical signal input end of the photodetector, the electrical signal output end of the photodetector is connected to the electrical signal input end of the acquisition card, and the microwave signal output end of the pulse generator is simultaneously connected to the semiconductor optical amplifier, the microwave signal loading end of the acousto-optic modulator and the trigger signal input end of the data acquisition card.

[0024] Figure 1 A schematic structural diagram of an OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology according to an embodiment of the present invention is shown.

[0025] like Figure 1As shown, the OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology includes a narrow linewidth laser 1, a semiconductor optical amplifier 2, an acousto-optic modulator 3, a first erbium-doped fiber amplifier 4, a first circulator 5, a Raman amplifier 6, a wavelength division multiplexer 7, an optical fiber to be tested 8, an erbium-doped fiber 9, a second erbium-doped fiber amplifier 10, a second circulator 11, an optical filter 12, a photodetector 13, a data acquisition card 14 and a pulse generator 15.

[0026] The optical signal output end of the narrow linewidth laser 1 is connected to the optical signal input end of the semiconductor optical amplifier 2, the optical signal output end of the semiconductor optical amplifier 2 is connected to the optical signal input end of the acousto-optic modulator 3, the optical signal output end of the acousto-optic modulator 3 is connected to the optical signal input end of the first erbium-doped fiber amplifier 4, the optical signal output end of the first erbium-doped fiber amplifier 4 is connected to the first optical signal port of the first circulator 5, the second optical signal port of the first circulator 5 is connected to the first port of the wavelength division multiplexer 7, the optical signal output end of the Raman amplifier 6 is connected to the second port of the wavelength division multiplexer 6, the third port of the wavelength division multiplexer 7 is connected to the optical fiber 8 to be tested, the optical fiber 8 to be tested is connected to the erbium-doped fiber 9, and the third optical signal port of the first circulator 5 is connected to the optical fiber 8 to be tested. The optical signal port is connected to the optical signal input end of the second erbium-doped fiber amplifier 10, the optical signal output end of the second erbium-doped fiber amplifier 10 is connected to the first optical signal port of the second circulator 11, the second optical signal port of the second circulator 11 is connected to the optical filter 12, the third optical signal port of the second circulator 11 is connected to the optical signal input end of the photodetector 13, the electrical signal output end of the photodetector 13 is connected to the electrical signal input end of the acquisition card 14, and the microwave signal output end of the pulse generator 15 is connected to the microwave signal loading end of the semiconductor optical amplifier 2, the acousto-optic modulator 3 and the trigger signal input end of the data acquisition card 14 respectively, so as to drive the semiconductor optical amplifier 2, the acousto-optic modulator 3 and the data acquisition card 14 to work.

[0027] For example, a section of erbium-doped optical fiber 9 can be fused into the optical fiber 8 to be tested. Figure 1 As shown, the optical fiber 8 to be tested has two sections, and there is an erbium-doped optical fiber 9 in the middle. It should be understood that the erbium-doped optical fiber 9 can be set in the middle position of the optical fiber 8 to be tested, or it can be set in other positions of the optical fiber 8 to be tested, that is, Figure 1 As shown, an erbium-doped optical fiber 9 is fused between two sections of optical fiber 8 to be tested, and the lengths of the two sections of optical fiber 8 to be tested can be the same or different.

[0028] like Figure 1 As shown, the continuous light signal output by the narrow linewidth laser 1 is modulated into an optical pulse signal by the semiconductor optical amplifier 2. The optical pulse signal is further modulated into a narrower pulse light signal by the acousto-optic modulator 3 by adjusting the time delay to improve the extinction ratio and avoid continuous light leakage caused by the low duty cycle of the optical pulse and the limited extinction ratio of the modulation device. The modulation process is as follows Figure 2 As shown. Figure 2 As shown, the corresponding shaded part below the semiconductor optical amplifier 2 represents the pulse light signal obtained by modulation of the semiconductor optical amplifier 2, and the corresponding shaded part below the acousto-optic modulator 3 represents the pulse light signal obtained after being modulated by the semiconductor optical amplifier 2 and the acousto-optic modulator 3 in sequence. It can be seen that the cascade connection of the semiconductor optical amplifier and the acousto-optic modulator can fully improve the extinction ratio of the detection light pulse. In this embodiment, the inventors found that there is a sequential relationship between the semiconductor optical amplifier and the acousto-optic modulator in the optical path, that is, there is a time delay, and the time needs to be matched to ensure that the high level position of the pulse light signal modulated by the semiconductor optical amplifier can just correspond to the modulation signal of the acousto-optic modulator in time, and then it is modulated into a narrow light pulse signal again to improve the extinction ratio; if the time delay is not compensated, the acousto-optic modulator and the optical pulse signal output by the semiconductor optical amplifier cannot correspond, resulting in the acousto-optic modulator modulating the input optical pulse signal from a high level to a low level, resulting in no optical pulse signal output or weak output, which deteriorates the performance.

[0029] The narrow pulse optical signal (i.e., the narrower pulse optical signal mentioned above) is amplified by the erbium-doped fiber amplifier 4 and then injected into the wavelength division multiplexer 7 through the first circulator 5. The output optical signal of the Raman amplifier 6 is simultaneously injected into the optical fiber to be tested 8. The Raman amplifier 6 realizes distributed amplification of the optical signal in the optical fiber to be tested, thereby improving the sensing distance of the system. At the same time, it provides remote pumping for the erbium-doped fiber 9 to realize remote pumping amplification, thereby further improving the sensing distance of the system.

[0030] The backward Rayleigh scattered light signal in the optical fiber is output by the first circulator 5 and enters the second erbium-doped fiber amplifier 10 for optical power amplification, and then is injected into the optical filter 12 through the second circulator 11 to filter out ASE noise and improve the signal-to-noise ratio, and then is detected by the photodetector 13. The output photocurrent is collected by the data acquisition card 14, and the pulse generator 15 realizes the control of the semiconductor optical amplifier 2, the acousto-optic modulator 3 and the acquisition card 14.

[0031] As an example, the narrow linewidth laser 1 may be a single-frequency narrow linewidth fiber laser, with an output optical power of, for example, 11 mW and a wavelength of, for example, 1550.172 nm.

[0032] As an example, the extinction ratio of the semiconductor optical amplifier 2 is, for example, 60 dB.

[0033] As an example, the shift frequency of the first AOM 3 is, for example, -200 MHz, and the extinction ratio is, for example, 50 dB.

[0034] As an example, the output optical power of the Raman amplifier 6 is, for example, 600 mW, and the wavelength is, for example, 1480 nm.

[0035] As an example, the central wavelength of the optical filter 12 is, for example, 1550.17 nm, and the bandwidth is, for example, 2 GHz.

[0036] As an example, the detection bandwidth of the photoelectric balanced detector is, for example, 50 MHz.

[0037] The OPGW optical cable long-distance vibration monitoring system based on the Φ-OTDR technology of the present invention comprises the following steps: a continuous optical signal output by a narrow line width laser is modulated into an optical pulse signal by a semiconductor optical amplifier; the optical pulse signal is further modulated into a narrower pulse optical signal by an acousto-optic modulator and injected into an optical fiber to be tested through a first circulator after optical power amplification by an erbium-doped optical fiber amplifier; an output optical signal of a wavelength division multiplexer and a Raman amplifier is injected into the optical fiber to be tested at the same time; an erbium-doped optical fiber is locally connected to the optical fiber to be tested to realize remote pump amplification of the detection pulse optical signal; a backward Rayleigh scattered optical signal in the optical fiber is output by the first circulator and then enters the second erbium-doped optical fiber amplifier for optical power amplification; the backward Rayleigh scattered optical signal in the optical fiber is injected into the second erbium-doped optical fiber amplifier for optical power amplification; the optical signal is injected into the optical filter through the second circulator to filter out ASE noise and improve the signal-to-noise ratio; the optical signal is detected by a photoelectric detector; the output photocurrent is collected by a data acquisition card; and a pulse generator realizes control of the semiconductor optical amplifier, the acousto-optic modulator and the acquisition card.

[0038] Figure 3 This is the backward Rayleigh scattered light signal collected by the acquisition card 14. It can be seen in the figure that the Raman amplifier 6 performs distributed amplification on the Rayleigh scattered light signal in the optical fiber to achieve 87km distributed sensing. The Raman amplifier 6 also provides remote pumping for the erbium-doped optical fiber 9 connected at the 87km position to achieve remote pumping amplification, successfully increasing the sensing distance to 150km and achieving long-distance sensing. Figure 4 The local amplification of the backward Rayleigh scattered light signal collected by the acquisition card 14 shows that the erbium-doped fiber 9 has a good signal-to-noise ratio before the remote pump amplification and 150 km at the end of the fiber. Figure 3 and Figure 4 In the figure, the distance is the distance between the current measurement position and the measurement starting point, and the intensity is the intensity of the backscattered Rayleigh light signal.

[0039] In order to avoid pulse aliasing in the optical fiber to be tested in the Φ-OTDR system, it is required that only a single optical pulse signal with a width of T can exist in the optical fiber to be tested at the same time; the length of the optical fiber to be tested is set to L, the refractive index is n, the light wave propagation speed in vacuum is c, and the light wave propagation speed in the optical fiber is c / n, and the duty cycle D of the optical pulse signal is obtained as shown in Formula 1.

[0040] Formula 1:

[0041] In a long-distance Φ-OTDR system, T << L, the duty cycle D of the optical pulse signal is low. To avoid continuous optical leakage caused by the low duty cycle and the limited extinction ratio of the modulation device, which deteriorates the system performance, the present invention uses a semiconductor optical amplifier cascaded with an acousto-optic modulator to improve the extinction ratio.

[0042] Furthermore, the semiconductor optical amplifier 2 and the acousto-optic modulator 3 are cascaded for modulation, and the process of improving the extinction ratio is described as follows.

[0043] Set the single-frequency continuous light output by the narrow linewidth laser, with an amplitude of A and a carrier frequency of f c , and the initial phase is Within the time t, the optical wave expression E(t) is as shown in Equation 2.

[0044] Equation 2:

[0045] The continuous light E(t) is modulated by the semiconductor optical amplifier 2 into an optical pulse signal E 1 (t), as shown in Equation 3.

[0046] Equation 3:

[0047] Where, A 1 is the amplitude of the optical pulse signal; T 1 is the width of the optical pulse signal.

[0048] The optical pulse signal E 1 (t) is further modulated by the acousto-optic modulator 3 into a narrow optical pulse signal E with an optical extinction ratio 2 (t), as shown in Equation 4.

[0049] Equation 4:

[0050] Where, A 2 is the amplitude of the optical pulse signal; △f is the frequency shift of the acousto-optic modulator 3; T 2 is the width of the optical pulse signal.

[0051] In the above process, T 2 < T 1 , and at the same time, it is necessary to effectively adjust the time delay between the semiconductor optical amplifier 2 and the acousto-optic modulator 3 through the pulse generator 15. The extinction ratio of the optical pulse signal E 1 (t) generated by the modulation of the semiconductor optical amplifier 2 is 50 dB, and E 1 (t) is further modulated by the acousto-optic modulator 3 with an extinction ratio of 52 dB into a narrow optical pulse signal E with an extinction ratio greater than 100 dB 2 (t), effectively avoiding the deterioration of the system performance caused by continuous optical leakage.

[0052] The OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology described in this embodiment adopts a hybrid of front-end distributed first-order Raman amplification technology and remote pumping technology to achieve long-distance OPGW optical cable vibration monitoring. Compared with relay EDFA amplification and double-ended amplification, the system eliminates the necessity of on-site remote power supply and has the significance of remote sensing in practical applications.

[0053] The OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology described in this embodiment adopts a cascade method of semiconductor optical amplifier and acousto-optic modulator to fully improve the extinction ratio of the detection light pulse; effectively avoids the continuous light signal leakage caused by the limited extinction ratio and the high duty cycle of the detection pulse light in the long-distance sensing system, which causes system signal jitter, and further improves the stability of the long-distance sensing system.

[0054] The OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology described in this embodiment has a large sensing distance and good system stability; traditional Φ-OTDR technology is affected by the nonlinear threshold of the optical fiber, and the detection light pulse power cannot be too high, resulting in limited sensing distance. The system adopts a mixture of front-end distributed amplification technology and remote pumping technology to fully improve the sensing distance and has good stability.

[0055] The OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology described in this embodiment adopts a hybrid of front-end distributed first-order Raman amplification technology and remote pumping technology to achieve long-distance OPGW optical cable vibration monitoring. Compared with relay EDFA amplification and double-ended amplification, it eliminates the necessity of on-site remote power supply, and has the significance of remote sensing in practical applications. The semiconductor optical amplifier and the acousto-optic modulator are cascaded to fully improve the extinction ratio of the detection light pulse; the continuous light signal leakage caused by the limited extinction ratio and the high duty cycle of the detection pulse light in the long-distance sensing system is effectively avoided, which leads to system signal jitter, and further improves the stability of the long-distance sensing system. The traditional Φ-OTDR technology is affected by the nonlinear threshold of the optical fiber, and the detection light pulse power cannot be too high, resulting in limited sensing distance. The system adopts a hybrid of front-end distributed amplification technology and remote pumping technology to fully improve the sensing distance and has good stability.

[0056] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0057] Similarly, it should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the following intention: that the claimed invention requires more features than the features explicitly recited in each claim. More specifically, as reflected in the claims below, inventive aspects lie in less than all the features of the individual embodiments disclosed above. Therefore, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, with each claim itself serving as a separate embodiment of the present invention.

[0058] Those skilled in the art will appreciate that the modules or units or components of the devices in the examples disclosed herein may be arranged in the devices described in the embodiment, or alternatively may be located in one or more devices different from the devices in the examples. The modules in the foregoing examples may be combined into one module or may be divided into multiple submodules.

[0059] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and arranged in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and in addition they may be divided into a plurality of submodules or subunits or subcomponents. Except that at least some of such features and / or processes or units are mutually exclusive, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this manner may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature providing the same, equivalent or similar purpose.

[0060] In addition, those skilled in the art will appreciate that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims below, any one of the claimed embodiments may be used in any combination.

[0061] In addition, some of the embodiments are described herein as methods or combinations of method elements that can be implemented by a processor of a computer system or by other devices that perform the functions. Therefore, a processor with necessary instructions for implementing the method or method elements forms a device for implementing the method or method elements. In addition, the elements described herein of the device embodiments are examples of devices for implementing the functions performed by the elements for the purpose of implementing the invention.

[0062] As used herein, unless otherwise specified, the use of ordinal numbers "first," "second," "third," etc. to describe common objects merely indicates that different instances of similar objects are involved, and is not intended to imply that the objects so described must have a given order in time, space, order, or in any other manner.

[0063] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative and not restrictive with respect to the scope of the present invention, and the scope of the present invention is defined by the appended claims.

Claims

1. The OPGW optical cable long-distance vibration monitoring system based on Φ-OTDR technology is characterized by: The monitoring system includes a narrow linewidth laser, a semiconductor optical amplifier, an acousto-optic modulator, a first erbium-doped fiber amplifier, a first circulator, a Raman amplifier, a wavelength division multiplexer, an optical fiber to be tested, an erbium-doped fiber, a second erbium-doped fiber amplifier, a second circulator, an optical filter, a photodetector, a data acquisition card and a pulse generator; The optical signal output end of the narrow linewidth laser is connected to the optical signal input end of the semiconductor optical amplifier, the optical signal output end of the semiconductor optical amplifier is connected to the optical signal input end of the acousto-optic modulator, the optical signal output end of the acousto-optic modulator is connected to the optical signal input end of the first erbium-doped fiber amplifier, the optical signal output end of the first erbium-doped fiber amplifier is connected to the first optical signal port of the first circulator, the second optical signal port of the first circulator is connected to the first port of the wavelength division multiplexer, the optical signal output end of the Raman amplifier is connected to the second port of the wavelength division multiplexer, the third port of the wavelength division multiplexer is connected to the optical fiber to be tested, and the optical fiber to be tested is simultaneously connected to the erbium-doped fiber; The third optical signal port of the first circulator is connected to the optical signal input end of the second erbium-doped fiber amplifier, the optical signal output end of the second erbium-doped fiber amplifier is connected to the first optical signal port of the second circulator at the same time, the second optical signal port of the second circulator is connected to the optical filter, the third optical signal port of the second circulator is connected to the optical signal input end of the photodetector, the electrical signal output end of the photodetector is connected to the electrical signal input end of the acquisition card, and the microwave signal output end of the pulse generator is connected to the semiconductor optical amplifier, the microwave signal loading end of the acousto-optic modulator and the trigger signal input end of the data acquisition card respectively; The working process of the monitoring system is as follows: the continuous optical signal output by the narrow line width laser (1) is modulated into an optical pulse signal by a semiconductor optical amplifier (2), and the optical pulse signal is further modulated into a narrower pulse optical signal by an acousto-optic modulator (3) by adjusting the time delay; the narrower pulse optical signal is then amplified in optical power by an erbium-doped fiber amplifier (4) and injected into a wavelength division multiplexer (7) through a first circulator (5), and the output optical signal is injected into the optical fiber to be tested (8) together with the output optical signal of the Raman amplifier (6); The backscattered Rayleigh light signal returned by the optical fiber (8) to be tested is outputted by the first circulator (5) and then enters the second erbium-doped fiber amplifier (10) for optical power amplification, then passes through the second circulator (11) and is injected into the optical filter (12) to filter out noise, and then is detected by the photodetector (13). The output photocurrent is collected by the data acquisition card (14). The pulse generator (15) is used to control the semiconductor optical amplifier (2), the acousto-optic modulator (3) and the data acquisition card (14) so ​​that the high level position of the pulse light signal modulated by the semiconductor optical amplifier (2) can correspond to the modulation signal of the acousto-optic modulator (3) in time.

2. The monitoring system according to claim 1, characterized in that: The narrow linewidth laser adopts a single-frequency narrow linewidth fiber laser, the output optical power is 11mW, and the wavelength is 1550.172nm.

3. The monitoring system according to claim 1 or 2, characterized in that: The extinction ratio of the semiconductor optical amplifier is 60 dB.

4. The monitoring system according to claim 1 or 2, characterized in that: The shift frequency of the acousto-optic modulator is -200 MHz, and the extinction ratio is 50 dB.

5. The monitoring system according to claim 1 or 2, characterized in that: The output optical power of the Raman amplifier is 600mW and the wavelength is 1480nm.

6. The monitoring system according to claim 1 or 2, characterized in that: The central wavelength of the optical filter is 1550.17 nm and the bandwidth is 2 GHz.

7. The monitoring system according to claim 1 or 2, characterized in that: The detection bandwidth of the photoelectric balanced detector is 50MHz.

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