CN113008281A - Distributed optical fiber sensing system based on fusion of Rayleigh and Brillouin scattering - Google Patents
Distributed optical fiber sensing system based on fusion of Rayleigh and Brillouin scattering Download PDFInfo
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- CN113008281A CN113008281A CN202110219127.2A CN202110219127A CN113008281A CN 113008281 A CN113008281 A CN 113008281A CN 202110219127 A CN202110219127 A CN 202110219127A CN 113008281 A CN113008281 A CN 113008281A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
- G01D5/35354—Sensor working in reflection
- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
- G01D5/35364—Sensor working in reflection using backscattering to detect the measured quantity using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
- G01D5/35354—Sensor working in reflection
- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
- G01D5/35361—Sensor working in reflection using backscattering to detect the measured quantity using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering
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Abstract
The invention relates to the technical field of distributed optical fiber sensing, in particular to a distributed optical fiber sensing system based on fusion of Rayleigh and Brillouin scattering, which comprises: the optical source is used for generating and outputting a detection optical signal and a local oscillator optical signal; the light source comprises an optical fiber light cone, and the optical fiber light cone is formed by melting and drawing a plurality of optical fibers; the modulation unit is used for receiving the detection light signal and modulating to generate pulse light; the coherent detection unit is used for mixing the local oscillator optical signal and the back reflection signal to obtain an optical heterodyne electrical signal; the Rayleigh demodulation unit is used for demodulating and obtaining reflection, attenuation and vibration information along the optical fiber according to the Rayleigh scattering signal; and the Brillouin demodulation unit is used for demodulating and obtaining the stress and temperature information of the optical fiber to be measured according to the Brillouin scattering signal. The optical fiber light cone is designed in the light source, so that the output power density of the light source can be effectively improved.
Description
Technical Field
The invention relates to the technical field of distributed optical fiber sensing, in particular to a distributed optical fiber sensing system based on fusion of Rayleigh and Brillouin scattering.
Background
As for the current optical fiber sensing technology, the method mainly includes point-type sensing and distributed sensing, the former is only suitable for monitoring a limited number of key positions, and when the positions to be monitored are increased, the number, cost and technical difficulty of the required sensing units are obviously increased; in the latter, each point along the optical fiber is regarded as a sensing unit, and the size (i.e. spatial resolution) of each point is determined by the input detection light signal, so that the number of the sensing units along the optical fiber can be greatly increased under the condition of relatively low cost. At present, in the field of distributed optical fiber sensing, an optical time domain reflection technology, an optical time domain analysis technology and an optical frequency domain analysis technology are commonly used, but optical fiber sensing parameters corresponding to each technology are few, and various environmental parameters are difficult to monitor.
To this end, chinese patent CN111486881A discloses a distributed optical fiber multi-parameter sensing device, which includes: the optical path unit is used for generating and outputting a detection optical signal and a local oscillator optical signal; the modulation unit is used for receiving the detection light signal, modulating the detection light signal to generate pulse light and outputting the pulse light to the optical fiber to be detected; the coherent detection unit is used for receiving the local oscillator optical signal and a back reflection signal generated by the optical fiber to be detected according to Rayleigh scattering and Brillouin scattering effects, and mixing the local oscillator optical signal and the back reflection signal to obtain an optical heterodyne electrical signal; the Rayleigh demodulation unit is used for receiving the optical heterodyne electrical signal and filtering to obtain a Rayleigh scattering signal, and demodulating to obtain reflection, attenuation and vibration information along the optical fiber according to the Rayleigh scattering signal; and the Brillouin demodulation unit is used for receiving the optical heterodyne electrical signal for filtering to obtain a Brillouin scattering signal, and demodulating according to the Brillouin scattering signal to obtain the stress and temperature information of the optical fiber to be measured.
In the technical scheme, multi-parameter fusion sensing including physical quantities such as optical fiber reflection, attenuation, vibration, temperature and stress can be realized at the same time, but the light source has high power, high brightness and good light beam quality. In order to increase the power of the light source, an incoherent light beam combining technique is generally adopted, for example, a fiber bundle is adopted to combine the diode laser array, when the number of coupled diode lasers is large, although the power of the light source can be increased, the area of an output light spot is large due to the large number of optical fibers, so that the power density is reduced.
Disclosure of Invention
The invention provides a distributed optical fiber sensing system based on Rayleigh and Brillouin scattering fusion, which solves the technical problem that the existing optical fiber sensing system is difficult to realize multi-parameter fusion sensing simultaneously due to low output power density of a light source.
The basic scheme provided by the invention is as follows: a distributed optical fiber sensing system based on fusion of Rayleigh and Brillouin scattering comprises:
the optical source is used for generating and outputting a detection optical signal and a local oscillator optical signal; the light source comprises an optical fiber light cone, and the optical fiber light cone is formed by melting and drawing a plurality of optical fibers; the optical fiber cone comprises a large end and a small end, the large end is provided with a scattered tail fiber, and each optical fiber of the scattered tail fiber is connected with a laser with a collimating lens combination through a connector;
the modulation unit is used for receiving the detection light signal, modulating the detection light signal to generate pulse light and outputting the pulse light to the optical fiber to be detected;
the coherent detection unit is used for receiving the local oscillator optical signal and a back reflection signal generated by the optical fiber to be detected according to Rayleigh scattering and Brillouin scattering effects, and mixing the local oscillator optical signal and the back reflection signal to obtain an optical heterodyne electrical signal;
the Rayleigh demodulation unit is used for receiving the optical heterodyne electrical signal and filtering to obtain a Rayleigh scattering signal, and demodulating to obtain reflection, attenuation and vibration information along the optical fiber according to the Rayleigh scattering signal;
and the Brillouin demodulation unit is used for receiving the optical heterodyne electrical signal for filtering to obtain a Brillouin scattering signal, and demodulating according to the Brillouin scattering signal to obtain the stress and temperature information of the optical fiber to be measured.
The working principle and the advantages of the invention are as follows: when the light source works, laser beams emitted by each laser are combined by the collimating lens and then are incident into corresponding optical fibers of the scattered tail fibers in a manner of being vertical to the end faces of the optical fibers, and then are output from the corresponding optical fibers at the small ends of the optical fiber light cones, and the laser beams emitted by the lasers are respectively coupled into the scattered optical fibers in a one-to-one manner and then are integrated into the small end faces, so that high-efficiency coupling is realized. Because the output end (namely the small end) of the optical fiber light cone can be drawn to be very small, even if the diameter of a single optical fiber is larger and the number of coupled lasers is more, the output light spot area is not limited because of overlarge, and the output power density of the light source is improved. In addition, the optical fiber light cone is only used for transmitting and converging laser energy, and the output power density of the light source can be flexibly controlled only by considering the transmittance and the taper ratio during design.
The optical fiber light cone is designed in the light source, so that the output power density of the light source can be effectively improved, and the technical problem that the multi-parameter fusion sensing is difficult to realize simultaneously due to the low output power density of the light source in the conventional optical fiber sensing system is solved.
Further, the Rayleigh demodulation unit comprises a first signal acquisition module and a first demodulation module, the first signal acquisition module is used for receiving the optical heterodyne electrical signal and filtering to obtain Rayleigh scattering signals, and the first demodulation module is used for receiving the Rayleigh scattering signals and demodulating to obtain reflection, attenuation and vibration information along the optical fiber to be detected.
Has the advantages that: after the optical heterodyne electrical signal is received and filtered to obtain a Rayleigh scattering signal, the reflection, attenuation and vibration information along the optical fiber line can be accurately obtained by demodulation.
Further, the brillouin demodulation unit includes a second signal acquisition module and a second demodulation module, the second signal acquisition module is used for receiving the optical heterodyne electrical signal and filtering to obtain a brillouin scattering signal, and the second demodulation module is used for receiving the brillouin scattering signal and demodulating to obtain the stress and temperature information of the optical fiber to be measured.
Has the advantages that: after the optical heterodyne electric signal is received and the Brillouin scattering signal is obtained through filtering, the stress and temperature information of the optical fiber to be measured can be accurately obtained through demodulation.
Further, the first signal acquisition module comprises an intermediate frequency filter and a first low noise amplifier, and the optical heterodyne electrical signal is filtered by the intermediate frequency filter and amplified by the first low noise amplifier in sequence to obtain a rayleigh scattering signal.
Has the advantages that: by adopting the intermediate frequency filtering, the low-power sideband can be ignored during the subsequent frequency spectrum recovery, thereby being beneficial to accurately recovering the high-power sideband.
Further, the second signal acquisition module comprises a high-frequency filter and a second low-noise amplifier, and the optical heterodyne electric signal is filtered by the high-frequency filter and amplified by the second low-noise amplifier in sequence to obtain a brillouin scattering signal.
Has the advantages that: by employing a high frequency filter, gain at high frequencies can be ensured.
The optical fiber detection device further comprises an optical circulator, wherein the first end of the optical circulator is connected with the modulation unit, the second end of the optical circulator is connected with the optical fiber to be detected, and the third end of the optical circulator is connected with the coherent detection unit.
Has the advantages that: the optical circulator has non-reciprocity and is beneficial to completing the separation task of forward/reverse transmission.
Drawings
Fig. 1 is a system structure block diagram of an embodiment of a distributed optical fiber sensing system based on rayleigh and brillouin scattering fusion according to the present invention.
Fig. 2 is a schematic structural diagram of a heat preservation box in embodiment 3 of a distributed optical fiber sensing system based on rayleigh and brillouin scattering fusion according to the present invention.
Detailed Description
The following is further detailed by the specific embodiments:
the reference numbers in the drawings of the specification include: the device comprises a shell 1, a spring 2, a partition plate 3, a heating layer 4 and an optical fiber 5.
Example 1
An embodiment is substantially as shown in figure 1, comprising:
the optical source is used for generating and outputting a detection optical signal and a local oscillator optical signal; the light source comprises an optical fiber light cone, and the optical fiber light cone is formed by melting and drawing a plurality of optical fibers; the optical fiber cone comprises a large end and a small end, the large end is provided with a scattered tail fiber, and each optical fiber of the scattered tail fiber is connected with a laser with a collimating lens combination through a connector;
the modulation unit is used for receiving the detection light signal, modulating the detection light signal to generate pulse light and outputting the pulse light to the optical fiber to be detected;
the coherent detection unit is used for receiving the local oscillator optical signal and a back reflection signal generated by the optical fiber to be detected according to Rayleigh scattering and Brillouin scattering effects, and mixing the local oscillator optical signal and the back reflection signal to obtain an optical heterodyne electrical signal;
the Rayleigh demodulation unit is used for receiving the optical heterodyne electrical signal and filtering to obtain a Rayleigh scattering signal, and demodulating to obtain reflection, attenuation and vibration information along the optical fiber according to the Rayleigh scattering signal;
and the Brillouin demodulation unit is used for receiving the optical heterodyne electrical signal for filtering to obtain a Brillouin scattering signal, and demodulating according to the Brillouin scattering signal to obtain the stress and temperature information of the optical fiber to be measured.
The specific implementation process is as follows:
first, the light source generates and outputs a probe optical signal and a local oscillator optical signal. In this embodiment, the light source includes a fiber taper and an optical coupler, the fiber taper is formed by fusion-drawing a plurality of optical fibers; the optical fiber cone comprises a large end and a small end, the large end is provided with a scattered tail fiber, and each optical fiber of the scattered tail fiber is connected with a laser with a collimating lens combination through a connector. Specifically, the laser adopts a diode laser, the collimating lens combination adopts two cylindrical lenses, and the connector adopts an FC type optical fiber connector; the optical fiber is composed of a fiber core made of quartz and a cladding made of quartz, and the fiber core and the cladding are made of quartz materials, so that the melting point of the whole optical fiber is the same, and the optical cone of the optical fiber can be conveniently melted and drawn. The scattered tail fiber adopts straight tail fiber, and is in a scattered state, so that heat release is facilitated; the optical fibers 5 of the optical fiber taper are arranged in a regular hexagon to maximize the distance between adjacent optical fibers, thereby increasing the optical power density. In addition, a laser signal generated by the laser is output to the optical coupler, the optical coupler divides the laser signal into a detection optical signal and a local oscillation optical signal and outputs the signals, and the splitting ratio of the optical coupler is set to 80:20, namely 80% of the detection optical signal and 20% of the local oscillation optical signal are output.
Then, the modulation unit receives the detection light signal to modulate and generate pulse light, and the pulse light is output to the optical fiber to be measured. In the embodiment, an acousto-optic modulator is adopted to receive a detection light signal to modulate and generate pulse light, and the pulse light is output to an optical fiber to be detected; meanwhile, the pulse generator is used to control the acousto-optic modulator to modulate the repetition frequency and pulse width of the pulsed light. After the pulse light is input into the optical fiber to be measured, rayleigh scattering and brillouin scattering occur, and a back reflection signal is generated.
And then, the coherent detection unit receives the local oscillator optical signal and the back reflection signal generated by the optical fiber to be detected according to the Rayleigh scattering and Brillouin scattering effect, and mixes the local oscillator optical signal and the back reflection signal to obtain an optical heterodyne electrical signal. In this embodiment, a balanced detector, such as a broadband balanced detector, is used to receive the local oscillator optical signal and the back reflection signal for mixing to obtain an optical heterodyne electrical signal.
Finally, a Rayleigh demodulation unit receives the optical heterodyne electrical signal and filters to obtain a Rayleigh scattering signal, and the reflection, attenuation and vibration information along the optical fiber line is obtained through the Rayleigh scattering signal demodulation; the Brillouin demodulation unit receives the optical heterodyne electrical signal for filtering to obtain a Brillouin scattering signal, and the stress and temperature information of the optical fiber to be detected is obtained through demodulation according to the Brillouin scattering signal.
In this embodiment, the rayleigh demodulation unit includes a first signal acquisition module and a first demodulation module, the first signal acquisition module receives the optical heterodyne electrical signal and filters to obtain a rayleigh scattering signal, and the first demodulation module receives the rayleigh scattering signal and demodulates to obtain reflection, attenuation and vibration information along the optical fiber to be measured; the first signal acquisition module comprises an intermediate frequency filter and a first low-noise amplifier, and the optical heterodyne electrical signal is filtered by the intermediate frequency filter and amplified by the first low-noise amplifier in sequence to obtain a Rayleigh scattering signal. The Brillouin demodulation unit comprises a second signal acquisition module and a second demodulation module, wherein the second signal acquisition module receives the optical heterodyne electrical signal for filtering to obtain a Brillouin scattering signal, and the second demodulation module receives the Brillouin scattering signal and demodulates the Brillouin scattering signal to obtain the stress and temperature information of the optical fiber to be detected; the optical heterodyne signal is filtered by the high-frequency filter and amplified by the second low-noise amplifier in sequence to obtain a Brillouin scattering signal.
Example 2
The difference from embodiment 1 is that the optical fiber testing device further includes an optical circulator, a first end of the optical circulator is connected to the modulation unit, a second end of the optical circulator is connected to the optical fiber to be tested, and a third end of the optical circulator is connected to the coherent detection unit. Laser emitted by the laser is divided into 80% of detection light and 20% of local oscillation light through the optical coupler, the detection light is modulated by the acousto-optic modulator to obtain pulse light, the pulse light is input from the first end of the optical circulator, and the second end of the pulse light is output to the optical fiber to be detected. And in consideration of Rayleigh scattering and Brillouin scattering effects in the optical fiber to be detected, a back reflection signal generated by the optical fiber to be detected is input through the second end and then is output through the third end.
Example 3
The difference from the embodiment 2 is that in the embodiment, the optical fiber 5 is applied in the northeast winter, the day-night temperature difference can be more than 20-30 ℃, and the temperature change rate can reach 4-6 ℃/h; a part of the optical fiber 5 is buried in the soil and the other part is exposed to the air. The soil temperature can show seasonal fluctuation and day-night change along with the change of the temperature near the earth surface; meanwhile, due to the influence of the periodic daily change and the annual change of solar radiation, the soil temperature also has corresponding change, so that the annual change of the soil temperature is expressed as a sine function, the change amplitude of the temperature is reduced along with the increase of the soil depth, and the amplitude is considered to be approximately zero when a certain depth is reached. In addition, because the heat conduction coefficients of soil and air are different, the temperature of soil is usually higher than that of air in winter, and the heat dissipation is faster due to the effect of thermal convection on the temperature of air, and the heat dissipation is slower because convection heat exchange does not exist in soil. Therefore, the temperature difference between the portion of the optical fiber 5 exposed to the air and the portion buried in the soil, or the temperature unevenness occurs.
In this embodiment, the working temperature of the optical fiber 5 is usually between-10 ℃ and 50 ℃, and measures are required to ensure that the optical fiber 5 can be kept at a constant temperature. Specifically, the method comprises the following steps:
for keeping the temperature of the portion of the optical fiber 5 exposed to the air constant, it is necessary to employ a temperature sensor, a controller, a heater, and a wind power generator. For example, the ambient temperature in the northeast region is reduced from-5 ℃ to-15 ℃ within 3 hours, and the temperature sensor detects the ambient temperature in real time and sends the ambient temperature to the controller. After receiving the ambient temperature, the controller firstly judges whether the ambient temperature is lower than the lowest value of the working temperature of the optical fiber 5, namely that the temperature of minus 15 ℃ is lower than minus 10 ℃; then, calculating the temperature change rate to be-5 ℃/h; and finally, sending a control command to the heater to heat the fusion splice of the optical fiber 5 in an inverse counteraction mode, namely heating at a temperature change speed of +5 ℃/h until the temperature is within the working temperature of the optical fiber 5. Meanwhile, due to the fact that wind blowing is more and wind power is large in the northeast region, the wind driven generator can convert wind energy into electric energy, and the electric energy is converted into heat energy to improve the temperature of the optical fibers 5.
For the part of the optical fiber 5 buried in the soil to keep constant temperature, a heat preservation box is needed, as shown in figure 2, the heat preservation box is composed of a shell 1, a spring 2, a partition plate 3 and a heating layer 4; the two springs 2 are respectively positioned at the left side and the right side of the inner space of the shell 1, and the upper ends of the springs 2 are welded on the upper surface of the shell 1; the partition plate 3 is made of metal material with good heat conduction, such as aluminum, the partition plate 3 is positioned below the spring 2, the lower end of the spring 2 is welded on the upper surface of the partition plate 3, and the left end and the right end of the partition plate 3 are respectively contacted with the left side wall surface and the right side wall surface of the shell 1 and can slide up and down; the heating layer 4 is made of calcium chloride, namely quicklime, and the heating layer 4 is fixedly connected with the lower surface of the partition plate 3 through viscose. The partition 3 forms a closed space with the left, right, and lower side walls of the case 1, and the closed space is filled with a certain amount of purified water and a certain amount of inert gas, such as nitrogen. Through holes are formed in the left side wall face and the right side wall face of the shell 1 and located above the partition plate 3, and the optical fibers 5 penetrate through the through holes respectively.
In this embodiment, the heat preservation box is buried in the soil, and when the temperature of the air is 300K, the springs 2 are all in a compressed state, and the pressure of the nitrogen, the gravity of the partition plate 3 and the heating layer 4, and the pressure of the springs 2 are in balance. When the temperature of the air is suddenly reduced, the temperature of the soil is gradually reduced, so that the temperature of the nitrogen is reduced, and the pressure of the nitrogen is reduced; under the action of the spring 2, the heating layer 4 moves downwards and is contacted with the purified water, so that heat is generated; the heat is transmitted into the air in the closed space formed by the partition plate 3 and the left side wall surface, the right side wall surface and the upper side wall surface of the housing 1 through the partition plate 3, the temperature of the air is increased, and the air heats and preserves the temperature of the optical fiber 5 in a heat conduction mode.
The foregoing is merely an example of the present invention, and common general knowledge in the field of known specific structures and characteristics is not described herein in any greater extent than that known in the art at the filing date or prior to the priority date of the application, so that those skilled in the art can now appreciate that all of the above-described techniques in this field and have the ability to apply routine experimentation before this date can be combined with one or more of the present teachings to complete and implement the present invention, and that certain typical known structures or known methods do not pose any impediments to the implementation of the present invention by those skilled in the art. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (6)
1. A distributed optical fiber sensing system based on fusion of Rayleigh and Brillouin scattering is characterized by comprising:
the optical source is used for generating and outputting a detection optical signal and a local oscillator optical signal; the light source comprises an optical fiber light cone, and the optical fiber light cone is formed by melting and drawing a plurality of optical fibers; the optical fiber cone comprises a large end and a small end, the large end is provided with a scattered tail fiber, and each optical fiber of the scattered tail fiber is connected with a laser with a collimating lens combination through a connector;
the modulation unit is used for receiving the detection light signal, modulating the detection light signal to generate pulse light and outputting the pulse light to the optical fiber to be detected;
the coherent detection unit is used for receiving the local oscillator optical signal and a back reflection signal generated by the optical fiber to be detected according to Rayleigh scattering and Brillouin scattering effects, and mixing the local oscillator optical signal and the back reflection signal to obtain an optical heterodyne electrical signal;
the Rayleigh demodulation unit is used for receiving the optical heterodyne electrical signal and filtering to obtain a Rayleigh scattering signal, and demodulating to obtain reflection, attenuation and vibration information along the optical fiber according to the Rayleigh scattering signal;
and the Brillouin demodulation unit is used for receiving the optical heterodyne electrical signal for filtering to obtain a Brillouin scattering signal, and demodulating according to the Brillouin scattering signal to obtain the stress and temperature information of the optical fiber to be measured.
2. The distributed optical fiber sensing system based on rayleigh and brillouin scattering fusion as claimed in claim 1, wherein the rayleigh demodulation unit comprises a first signal acquisition module and a first demodulation module, the first signal acquisition module is used for receiving optical heterodyne electrical signals and filtering to obtain rayleigh scattering signals, and the first demodulation module is used for receiving the rayleigh scattering signals and demodulating to obtain reflection, attenuation and vibration information along the optical fiber to be measured.
3. The distributed optical fiber sensing system based on rayleigh and brillouin scattering fusion as claimed in claim 2, wherein the brillouin demodulation unit comprises a second signal acquisition module and a second demodulation module, the second signal acquisition module is used for receiving the optical heterodyne electrical signal to filter and obtain the brillouin scattering signal, and the second demodulation module is used for receiving the brillouin scattering signal and demodulating and obtain the stress and temperature information of the optical fiber to be measured.
4. The distributed optical fiber sensing system based on rayleigh and brillouin scattering fusion as claimed in claim 3, wherein the first signal obtaining module comprises an intermediate frequency filter and a first low noise amplifier, and the optical heterodyne electrical signal is sequentially filtered by the intermediate frequency filter and amplified by the first low noise amplifier to obtain the rayleigh scattering signal.
5. The distributed optical fiber sensing system based on rayleigh and brillouin scattering fusion as claimed in claim 4, wherein the second signal acquiring module comprises a high frequency filter and a second low noise amplifier, and the optical heterodyne electrical signal is filtered by the high frequency filter and amplified by the second low noise amplifier in sequence to obtain the brillouin scattering signal.
6. The distributed optical fiber sensing system based on rayleigh and brillouin scattering fusion according to claim 5, further comprising an optical circulator, wherein a first end of the optical circulator is connected with the modulation unit, a second end of the optical circulator is connected with the optical fiber to be detected, and a third end of the optical circulator is connected with the coherence detection unit.
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