Distributed vibration and temperature simultaneous measurement device

Abstract

The invention provides a distributed vibration and temperature simultaneous measurement device. The device is characterized by comprising a laser, a pulse modulation module, a signal generation module, an optical amplification module, an optical circulator, a sensing optical fiber, a wavelength division multiplexing module, an optical Rayleigh filtering module, an optical Raman filtering module, a high-frequency detection module, a low-frequency detection module, a data acquisition and processing module and a data display module. Based on an optical fiber continuous back Rayleigh scattering and Raman scattering principle, efficient acquisition of back scattering of different wavelengths in the sensing optical fiber is realized by utilizing a wavelength multiplexing method, and diversity reception of Rayleigh scattering and Raman scattering signals is realized by applying frequency filtering; through joint demodulation of Rayleigh scattering and Raman scattering signals in the data acquisition and processing module, a long-distance, high-spatial-resolution, high-precision and distributed vibration and temperature simultaneous measurement function is realized. The invention provides a distributed vibration and temperature simultaneous measurement device which can be applied to the fields of long-distance pipeline leakage monitoring, geological disaster monitoring, power transmission line safety monitoring and the like.

Description

(I) Technical field

[0001] The present invention relates to a distributed vibration and temperature simultaneous measurement device, mainly to the field of distributed optical fiber sensing, and more specifically to a device for simultaneously collecting backscattered Rayleigh scattering and Raman scattering signals of a single sensing optical fiber, wherein the above-mentioned signals are highly correlated with the vibration and temperature information along the optical fiber. Based on the joint demodulation of the backscattered Rayleigh scattering and Raman scattering signals of the optical fiber, the function of distributed vibration and temperature simultaneous measurement can be realized with long distance, high spatial resolution, high precision, and high precision. (II) Background technology

[0002] Distributed fiber optic sensing technology is widely used in oil and gas exploration, pipeline monitoring, geological disaster monitoring, civil engineering, building health monitoring, power cable monitoring and other fields. Distributed fiber optic sensors can measure signals such as temperature, stress, strain, vibration, and sound waves along the optical fiber. The main methods currently implemented are distributed Rayleigh scattering, distributed Raman scattering, and distributed Brillouin scattering. Among them, the distributed Rayleigh scattering method has the function of vibration and sound wave measurement, the distributed Raman scattering method has the function of temperature measurement, and the distributed Brillouin scattering method has the function of temperature and strain measurement. Sensors based on distributed Rayleigh scattering and Raman scattering have the advantages of fast measurement speed, wide application range, high signal demodulation accuracy, and moderate price, and are widely used in the field of distributed monitoring and detection.

[0003] Chinese patent CN219224065U discloses an optical cable monitoring device and a distributed optical fiber vibration system. The system uses distributed Rayleigh scattering to monitor in real time whether a sewage treatment pool has leaked. However, it only realizes the abnormal detection of a single event and cannot realize the temperature monitoring function. The scene adaptability is low. Chinese patent CN118781723B discloses a perimeter security intrusion signal recognition method based on distributed optical fiber sensing in a migration scene. The method uses distributed Rayleigh scattering to classify and pattern recognize perimeter intrusion signals, so that the system can distinguish complex vibration signals and respond to different events. However, due to the limitation of the principle, the above two systems can only realize vibration measurement, but cannot realize temperature measurement.

[0004] Chinese patent CN113218494A discloses a distributed optical fiber acoustic sensing system. Compared with the distributed optical fiber vibration sensing system, this system uses the distributed Rayleigh scattering method to achieve the demodulation of the acoustic waveform along the optical fiber, and has the advantages of high sensitivity, low noise, and a large response range. However, due to the measurement principle of the distributed Rayleigh scattering method, the system is also unable to achieve temperature measurement.

[0005] Chinese patent CN116625541A discloses a distributed optical fiber temperature sensing system, which can use the distributed Raman scattering method to achieve temperature measurement along the optical fiber, but the temperature measurement accuracy of the system is low. Chinese patent CN116007782 discloses a distributed optical fiber temperature sensor, which introduces coding technology into the distributed Raman scattering method, combined with the photoelectric modulation of the detection light signal, to achieve the improvement of the system signal-to-noise ratio and temperature measurement accuracy, temperature measurement speed, and temperature measurement distance parameters. However, the system can only achieve distributed temperature measurement, and cannot achieve vibration measurement along the optical fiber.

[0006] It can be seen that the distributed optical fiber sensors reported so far do not have the function of distributed vibration and temperature simultaneous measurement. However, in the fields of long-distance pipeline leakage monitoring, geological disaster monitoring, and power transmission line safety monitoring, there is a wide demand for distributed vibration and temperature simultaneous measurement devices. The present invention proposes a distributed vibration and temperature simultaneous measurement device. Based on the principle of continuous backscattering Rayleigh and Raman scattering of optical fiber, the wavelength multiplexing method is used to realize the efficient collection of backscattering of different wavelengths in the sensing optical fiber, and frequency filtering is applied to realize the diversity reception of Rayleigh and Raman scattering signals. By jointly demodulating the Rayleigh and Raman scattering signals in the data acquisition and processing module, the long-distance, high spatial resolution, high precision, distributed vibration and temperature simultaneous measurement functions are realized. Compared with the existing distributed optical fiber sensors, the technical advantages of this device include: the introduction of wavelength multiplexing methods and modules to achieve simultaneous acquisition of optical fiber back-continuous Rayleigh scattering and Raman scattering, the use of a single sensing optical fiber and a single laser to achieve distributed vibration and temperature simultaneous measurement functions, and the equipment size and cost are significantly reduced; the introduction of joint demodulation of optical fiber back-Rayleigh scattering and Raman scattering signals, by one-to-one correspondence of the spatial position information of the collected Rayleigh scattering signals and Raman scattering signals, significantly improves the spatial resolution of the equipment and the temperature and vibration measurement accuracy. The technical advantages of the device proposed by the present invention enable it to be applicable to the fields of long-distance pipeline leakage monitoring, geological disaster monitoring, and power transmission line safety monitoring. (III) Summary of the invention

[0007] The purpose of the present invention is to overcome the problems existing in the existing distributed optical fiber technology, such as the difficulty in simultaneously collecting backscattered Rayleigh scattering and Raman scattering signals, the inability to simultaneously measure vibration and temperature due to various factors such as different types of required sensing optical fibers, the large size of the sensing device, and the high price, and to provide a distributed vibration and temperature simultaneous measurement device. The device is based on the principle of continuous backscattered Rayleigh scattering and Raman scattering of optical fibers, uses a wavelength multiplexing method to achieve efficient collection of backscattering of different wavelengths in the sensing optical fiber, applies frequency filtering to achieve diversity reception of Rayleigh scattering and Raman scattering signals, and achieves long-distance, high spatial resolution, high precision, distributed vibration and temperature simultaneous measurement functions by jointly demodulating Rayleigh scattering and Raman scattering signals in a data acquisition and processing module.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A distributed vibration and temperature simultaneous measurement device consists of a laser, a pulse modulation module, a signal generation module, an optical amplification module, an optical circulator, a sensing optical fiber, a wavelength division multiplexing module, an optical Rayleigh filter module, an optical Raman filter module, a high-frequency detection module, a low-frequency detection module, a data acquisition and processing module, and a data display module.

[0010] The continuous optical signal emitted by the laser is modulated into a pulse optical signal by the pulse modulation module, and the pulse parameters are determined by the signal generation module. After the optical amplifier module amplifies the pulse optical signal, the optical circulator guides the pulse optical signal into the sensing optical fiber.

[0011] The optical fiber backscattering signal enters the wavelength division multiplexing module after passing through the circulator. The wavelength division multiplexing module separates the optical fiber backscattering signal into Rayleigh scattered light signal and Raman scattered light signal. The Rayleigh scattered light signal is filtered out by the optical Rayleigh filter module to remove the residual Raman scattered light signal and background noise, and enters the high-frequency detection module to obtain the Rayleigh scattered voltage signal; the Raman scattered light signal is filtered out by the optical Raman filter module to remove the residual Rayleigh scattered light signal and background noise, and enters the low-frequency detection module to obtain the Raman scattered voltage signal. The two voltage signals are simultaneously injected into the data acquisition and processing module for joint demodulation of the Rayleigh scattered signal and the Raman scattered signal to obtain the vibration and temperature information along the optical fiber, which is displayed in the data display module.

[0012] The device comprises no more than one set of lasers, whose output wavelengths match the working wavelengths of the optical amplification module, optical circulator, sensing optical fiber, wavelength division multiplexing module, optical Rayleigh filter module and optical Raman filter module.

[0013] The device uses no more than one single-mode or multi-mode sensing optical fiber to achieve distributed vibration and temperature measurement functions.

[0014] The wavelength division multiplexing module adopts the optical fiber fused taper design to ensure that the backscattered signal of the sensing optical fiber is separated into Rayleigh scattered light signal and Raman scattered light signal.

[0015] The bandwidth range of the high-frequency detection module covers the frequency range of the vibration signal carried in the Rayleigh scattered light signal, and the bandwidth range of the low-frequency detection module covers the frequency range of the temperature signal carried in the Raman scattered light signal.

[0016] The data acquisition and processing module includes the joint demodulation of Rayleigh scattering and Raman scattering signals

[0017] Compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

[0018] 1. Compared with the prior art, the present invention provides a distributed vibration and temperature simultaneous measurement device, which introduces a wavelength multiplexing method and module to realize the simultaneous collection of optical fiber back-continuous Rayleigh scattering and Raman scattering. A single sensing optical fiber and a single laser can be used to realize the distributed vibration and temperature simultaneous measurement function, and the equipment size and cost are significantly reduced.

[0019] 2. The scheme of the present invention introduces the joint demodulation of the optical fiber backscattered Rayleigh and Raman scattering signals, and significantly improves the spatial resolution and temperature and vibration measurement accuracy of the equipment by making one-to-one correspondence between the spatial position information of the collected Rayleigh scattering signals and Raman scattering signals. (IV) Description of the drawings

[0020] Figure 1 It is a distributed vibration and temperature simultaneous measurement device, which consists of laser, pulse modulation module, signal generation module, optical amplification module, optical circulator, sensing fiber, wavelength division multiplexing module, optical Rayleigh filter module, optical Raman filter module, high frequency detection module, low frequency detection module, data acquisition and processing module, and data display module.

[0021] Figure 2 It is a distributed vibration signal diagram collected by the device.

[0022] Figure 3 It is a distributed temperature signal diagram collected by the device. (V) Specific implementation methods

[0023] The present invention is further described below with reference to the accompanying drawings and examples.

[0024] like Figure 1 As shown, a distributed vibration and temperature simultaneous measurement device comprises a laser (1), a pulse modulation module (2), a signal generation module (3), an optical amplification module (4), an optical circulator (5), a sensing optical fiber (6), a wavelength division multiplexing module (7), an optical Rayleigh filter module (8), an optical Raman filter module (9), a high-frequency detection module (10), a low-frequency detection module (11), a data acquisition and processing module (12), and a data display module (13).

[0025] The laser (1) is a narrow linewidth semiconductor laser, which emits continuous light with a wavelength of 1550.12nm, a power of 22mW and a linewidth of 100kHz.

[0026] The pulse modulation module (2) is an acousto-optic modulator, and its radio frequency input port is connected to the signal generation module (3). The generated optical pulse width is 50ns and the repetition frequency is 40kHz.

[0026] The optical amplifier module (4) is an erbium-doped optical fiber amplifier, and its small signal gain coefficient is 30 dB.

[0027] The sensing optical fiber (6) is a single-mode optical fiber, model SMF-28, and has a length of 300 meters.

[0028] The operating wavelengths of the wavelength division multiplexing module (7) are 1550.12nm and 1630.43nm.

[0029] The central wavelength of the optical Rayleigh filter module (8) is 1550.12 nm.

[0030] The central wavelength of the optical Raman filter module (9) is 1630.43 nm.

[0031] The high-frequency detection module (10) has an operating wavelength range of 1100 nm-1700 nm and a frequency range of DC-150 kHz.

[0032] The working wavelength range of the low-frequency detection module (11) is 1100nm-1700nm, and the frequency range is DC-20Hz.

[0033] The data acquisition and processing module (12) has a data sampling rate of 200 MHz. Vibration measurement and positioning are achieved by averaging and interpolating Rayleigh scattering signals, and temperature measurement is achieved by measuring the intensity changes of Stokes and anti-Stokes Raman peaks. The spatial positioning accuracy of the correction device is corrected by matching the vibration position with the temperature change position.

[0034] The data display module (13) is composed of a PC.

[0035] To facilitate understanding of the present invention, the present invention is further described below in conjunction with specific embodiments. The present invention can be implemented in many different forms and is not limited to the embodiments described in this specification.

[0036] Step 1: Start the power supply of the device. The continuous light output by the laser passes through the acousto-optic modulator and the signal generator to generate a pulse light signal.

[0037] Step 2: Adjust the gain value of the erbium-doped fiber amplifier to ensure that the amplified pulse optical signal has no distortion and saturation limit.

[0038] Step 3: Use an optical circulator to introduce the pulsed light signal into the sensing optical fiber, adjust the laser power, and ensure that the return signal has no obvious nonlinear characteristics.

[0039] Step 4: Adjust the cutoff frequencies of the optical Rayleigh filter and the optical Raman filter to ensure that the signal-to-noise ratio parameters of the collected Rayleigh scattering voltage signal and Raman scattering voltage signal are better than 15 dB.

[0040] Step 5: Use the data acquisition and processing module to collect and demodulate the two electrical signals respectively, obtain the vibration information and temperature information along the optical fiber, and display them visually on the PC.

[0041] Taking this system as an example, the total length of the sensing optical fiber used is 300 meters. It is heated in a water bath at 120 meters and the sensing optical fiber is struck with a metal stick at the same position. The vibration signal collected by the device is as follows: Figure 2 As shown, the temperature signal is Figure 3 shown.

Claims

1. A distributed vibration and temperature simultaneous measurement device, characterized in that: It consists of a laser (1), a pulse modulation module (2), a signal generation module (3), an optical amplifier module (4), an optical circulator (5), a sensing optical fiber (6), a wavelength division multiplexing module (7), an optical Rayleigh filter module (8), an optical Raman filter module (9), a high-frequency detection module (10), a low-frequency detection module (11), a data acquisition and processing module (12), and a data display module (13). The continuous optical signal emitted by the laser (1) is modulated into a pulse optical signal by the pulse modulation module (2), and the pulse parameter is determined by the signal generation module (3). After the optical amplifier module (4) amplifies the pulse optical signal, the optical circulator (5) guides the pulse optical signal into the sensing optical fiber (6). The optical fiber backscattering signal enters the wavelength division multiplexing module (7) after passing through the circulator (5), and the wavelength division multiplexing module (7) separates the optical fiber backscattering signal into a Rayleigh scattered light signal and a Raman scattered light signal. The Rayleigh scattered light signal is filtered out by an optical Rayleigh filter module (8) to remove residual Raman scattered light signal and background noise, and then enters a high-frequency detection module (10) to obtain a Rayleigh scattered voltage signal; the Raman scattered light signal is filtered out by an optical Raman filter module (9) to remove residual Rayleigh scattered light signal and background noise, and then enters a low-frequency detection module (11) to obtain a Raman scattered voltage signal. The two voltage signals are simultaneously injected into a data acquisition and processing module (12) to perform joint demodulation of the Rayleigh scattered signal and the Raman scattered signal, thereby obtaining vibration and temperature information along the optical fiber, and displaying the information in a data display module (13).

2. A distributed vibration and temperature simultaneous measurement device according to claim 1, characterized in that: Contains not more than one laser.

3. A distributed vibration and temperature simultaneous measurement device according to claim 1, characterized in that: The output wavelength of the laser matches the working wavelength of the optical amplification module, the optical circulator, the sensing optical fiber, the wavelength division multiplexing module, the optical Rayleigh filtering module and the optical Raman filtering module.

4. A distributed vibration and temperature simultaneous measurement device according to claim 1, characterized in that: Distributed vibration and temperature measurement functions are achieved using no more than one sensing fiber.

5. A distributed vibration and temperature simultaneous measurement device according to claim 1, characterized in that: The wavelength division multiplexing module ensures that the backscattering signal of the sensing optical fiber is separated into a Rayleigh scattered light signal and a Raman scattered light signal.

6. A distributed vibration and temperature simultaneous measurement device according to claim 1, characterized in that: The sensing optical fiber is one of a single-mode optical fiber and a multi-mode optical fiber.

7. A distributed vibration and temperature simultaneous measurement device according to claim 1, characterized in that: The bandwidth range of the high-frequency detection module needs to cover the frequency range of the vibration signal carried in the Rayleigh scattered light signal.

8. A distributed vibration and temperature simultaneous measurement device according to claim 1, characterized in that: The bandwidth range of the low-frequency detection module needs to cover the frequency range of the temperature signal carried in the Raman scattered light signal.

9. A distributed vibration and temperature simultaneous measurement device according to claim 1, characterized in that: The data acquisition and processing module includes joint demodulation of Rayleigh scattering and Raman scattering signals.

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