CN112880715A - Optical fiber sensing system based on OFDR technology - Google Patents
Optical fiber sensing system based on OFDR technology Download PDFInfo
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- 239000013307 optical fiber Substances 0.000 title claims abstract description 205
- 238000005516 engineering process Methods 0.000 title claims abstract description 11
- 238000002168 optical frequency-domain reflectometry Methods 0.000 title claims abstract 7
- 230000005540 biological transmission Effects 0.000 claims abstract description 46
- 230000035559 beat frequency Effects 0.000 claims abstract description 32
- 230000003287 optical effect Effects 0.000 claims description 42
- 239000000835 fiber Substances 0.000 claims description 39
- 238000012545 processing Methods 0.000 claims description 16
- 238000006243 chemical reaction Methods 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 7
- 238000012360 testing method Methods 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims 1
- 238000003780 insertion Methods 0.000 abstract description 5
- 230000037431 insertion Effects 0.000 abstract description 5
- 230000010287 polarization Effects 0.000 description 6
- 238000004364 calculation method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000010408 sweeping Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 2
- 230000001788 irregular Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005562 fading Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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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
- G01D5/35306—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 an interferometer arrangement
- G01D5/35329—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 an interferometer arrangement using interferometer with two arms in transmission, e.g. Mach-Zender interferometer
Abstract
The invention provides an optical fiber sensing system based on OFDR technology, comprising: the OFDR sensing equipment comprises a tunable laser, a first coupler, an auxiliary interferometer, a second coupler, a third coupler and an optical fiber circulator which are sequentially connected through a first transmission optical fiber, and further comprises a wavelength division multiplexer and a mode matcher which are connected through a second transmission optical fiber, wherein the core diameter of the optical fiber to be detected is larger than that of the first transmission optical fiber, and the core diameter of the second transmission optical fiber is equal to that of the optical fiber to be detected; the OFDR sensing equipment is used for generating beat frequency interference signals and external clock signals; and the data processing center is used for obtaining the sensing data of the optical fiber to be detected. The invention can solve the problem of insertion loss of the Rayleigh scattering signal from the large-core-diameter optical fiber to the small-core-diameter optical fiber in the optical fiber sensing system.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to an optical fiber sensing system based on an OFDR technology.
Background
The optical fiber sensing technology means that when light is transmitted in an optical fiber, the intensity, wavelength, phase, frequency and other characteristics of the light can be changed along with the change of stress and temperature applied by the outside; the optical signal is converted into an electric signal, and the digital signal is subjected to data demodulation by using a specific algorithm, so that the external change condition can be obtained, and the sensor can play a role. An Optical Frequency Domain Reflectometer (OFDR) is a distributed optical fiber sensor with high spatial resolution, high sensing sensitivity and high positioning accuracy.
In the prior art, an application scenario of the OFDR system is mainly based on single-mode fiber sensing, and the sensing method is that pump light and test light of the OFDR system are respectively connected to two input ends of a single-mode wavelength division multiplexer, and then two optical signals at the input ends are multiplexed into one GDF fiber to be tested, so that the two optical signals are respectively transmitted. Because the core diameter of the GDF optical fiber to be tested is larger than that of the single-mode optical fiber, a mode matcher needs to be connected between the single-mode wavelength division multiplexer and the GDF optical fiber to be tested.
However, when the GDF fiber to be tested generates a backward rayleigh scattering signal and needs to be transmitted backward, the problem of backward insertion loss occurs because the pattern matcher is unidirectional transmission, so that the backward rayleigh scattering signal is attenuated, and the sensing result is affected.
Disclosure of Invention
It is an object of the present invention to provide an optical fiber sensing system based on OFDR technology, which solves at least one of the above mentioned technical problems. The specific scheme is as follows:
according to an embodiment of the present invention, an optical fiber sensing system based on OFDR technology comprises: the OFDR sensing equipment comprises a tunable laser, a first optical fiber coupler, an auxiliary interferometer, a second optical fiber coupler, a third optical fiber coupler, an optical fiber circulator, a wavelength division multiplexer and a mode matcher, wherein the first optical fiber coupler is connected with the second optical fiber coupler; the tunable laser, the first optical fiber coupler, the auxiliary interferometer, the second optical fiber coupler, the third optical fiber coupler and the optical fiber circulator are connected through a first transmission optical fiber;
one end of the wavelength division multiplexer is connected with the optical fiber circulator through a second transmission optical fiber, and the other end of the wavelength division multiplexer is connected with an optical fiber to be tested;
one end of the pattern matcher is connected with the optical fiber circulator through a second transmission optical fiber, and the other end of the pattern matcher is connected with the third optical fiber coupler through the first transmission optical fiber; the core diameter of the optical fiber to be detected is larger than that of the first transmission optical fiber, and the core diameter of the second transmission optical fiber is equal to that of the optical fiber to be detected;
the OFDR sensing equipment is used for generating beat frequency interference signals and external clock signals; and the data processing center is used for receiving the beat frequency interference signal and the external clock signal and processing the beat frequency interference signal and the external clock signal to obtain the sensing data of the optical fiber to be detected.
Optionally, the core diameter of the first transmission optical fiber ranges from 9 μm to 10 μm.
Optionally, the core diameter of the second transmission fiber ranges from 20 μm to 100 μm.
Optionally, the second transmission fiber and the fiber to be tested are passive GDF single-mode double-clad fibers.
Optionally, the auxiliary interferometer is a mach-zehnder interferometer.
Optionally, the pattern matcher is configured to convert a backward rayleigh scattering signal returned by the optical fiber to be detected, and transmit the backward rayleigh scattering signal to the third optical fiber coupler through the first transmission optical fiber.
Optionally, the optical fiber sensing system further includes a pump light source connected between the wavelength division multiplexer and the optical fiber to be tested, where the pump light source is used to input an optical signal to be transmitted to the optical fiber to be tested.
Optionally, the second optical fiber coupler is configured to divide the swept-frequency optical signal output by the first optical fiber coupler into two paths, one path of the swept-frequency optical signal enters the third optical fiber coupler, the other path of the swept-frequency optical signal enters the optical fiber to be detected to generate a backward rayleigh scattering signal, and the backward rayleigh scattering signal and the swept-frequency optical signal are mixed in the third optical fiber coupler to generate a beat-frequency interference signal.
Optionally, the third optical fiber coupler is a 50:50 optical fiber coupler.
Optionally, the data processing center includes a photoelectric conversion module, a data acquisition module, and a data processing module, which are connected in sequence, where the photoelectric conversion module is configured to convert a beat frequency interference optical signal output by the third optical fiber coupler into an electrical signal, the data acquisition module is configured to acquire the beat frequency interference optical signal based on the external clock signal, and the data processing module is configured to control the data acquisition module to acquire and process the acquired beat frequency interference signal, so as to obtain a sensing result of each optical fiber to be detected.
Compared with the prior art, the scheme of the embodiment of the invention at least has the following beneficial effects:
the invention provides an optical fiber sensing system, which solves the problem of insertion loss of Rayleigh scattering signals entering a small core diameter from a large core diameter in the OFDR sensing system by changing the core diameter size of a transmission optical fiber in the traditional OFDR sensing system and the connection relation of a mode matcher, and can improve the sensing efficiency.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort. In the drawings:
FIG. 1 shows an overall schematic diagram of a fiber optic sensing system according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a specific structure of a data processing center according to an embodiment of the present invention;
fig. 3 shows a schematic diagram of a data processing module according to an embodiment of the present invention performing a processing procedure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
It should be understood that although the terms first, second, third, etc. may be used to describe embodiments of the present invention, they should not be limited to these terms.
It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in the article or device in which the element is included.
Alternative embodiments of the present invention are described in detail below with reference to the accompanying drawings.
As shown in fig. 1, according to the first embodiment of the present invention, the optical fiber sensing system based on the OFDR technique provided by the present invention solves the insertion loss problem of rayleigh scattering signals entering a small core diameter from a large core diameter in the OFDR sensing system by changing the core diameter size of the transmission optical fiber in the conventional OFDR sensing system and the connection relationship of the pattern matcher, and can improve the sensing efficiency and widen the applicable scene of the OFDR system; and the manufacturing cost of the optical fiber sensing system can be further saved.
The schematic diagram of an optical fiber sensing system based on the OFDR technology of the present invention is shown in fig. 1, and the whole optical fiber sensing system is composed of two parts, namely, an OFDR sensing device 10 and a data processing center 20, wherein the OFDR sensing device 10 is used for generating beat frequency interference signals and external clock signals; the data processing center 20 is configured to receive the beat frequency interference signal and the external clock signal, and process the beat frequency interference signal and the external clock signal to obtain sensing data of the optical fiber to be measured.
As shown in fig. 1, the OFDR sensing apparatus 10 includes a tunable laser 1, a first fiber coupler 2, an auxiliary interferometer 3, a second fiber coupler 4, a third fiber coupler 5, a fiber circulator 6, a wavelength division multiplexer 7, and a mode matcher 8.
The tunable laser 1 is configured to emit a frequency-sweeping optical signal, where the frequency-sweeping optical signal is divided into two paths by a first optical fiber coupler 2, and one path of the frequency-sweeping optical signal enters the auxiliary interferometer 3 to generate an external clock signal used by the data processing center 20; the other path enters the second optical fiber coupler 4 to generate a beat frequency interference signal which is finally acquired by the data processing center 20. The tunable laser 1 has a high scanning speed, and the scanning speed can reach 2000 nm/s. In this embodiment, the scanning speed of the tunable laser 1 is 80nm/s, and the scanning range is 16 nm. The first optical fiber coupler 1 is a 10:90 coupler, 90% of the swept-frequency optical signal enters the second optical fiber coupler 4, and 10% of the swept-frequency optical signal enters the auxiliary interferometer 3.
The auxiliary interferometer 3 is built based on a Mach-Zehnder interferometer and is used for enabling sweep-frequency light emitted by a light source to generate beat-frequency effect in the auxiliary interferometer and generating sweep-frequency light carrying phase information of the light source, namely external clock signals. In this embodiment, the auxiliary interferometer 3 is formed by two 50:50 fiber couplers and two single-mode fibers with a length difference of 200 m. After the optical signal output by the first optical fiber coupler 2 is input into the auxiliary interferometer 3, the optical signal is divided into two paths by the first optical fiber coupler, and because the optical path difference exists between the two paths of light, beat frequency interference can occur at the second optical fiber coupler. The auxiliary interferometer 3 supports the access of the OFDR sensing equipment to the sensing fiber with the length of 200/4-50 m at most.
The beat frequency signal generated by the auxiliary interferometer is a sine signal with certain change, and under the ideal condition, the frequency is stable and unchanged, but due to the nonlinear tuning effect of the light source, the beat frequency signal generates irregular frequency change, the irregular frequency change represents the nonlinear frequency sweep of the laser, when the beat frequency signal is used as an external clock of the data acquisition card, the clock jitter phenomenon is similar, and the jitter clock is used for acquiring the signal of the main interferometer, so that the aim of eliminating the nonlinearity of the light source is fulfilled.
One end of the second optical fiber coupler 4 is connected with the first optical fiber coupler 1 and used for receiving the sweep frequency light output by the first optical fiber coupler 1, dividing the sweep frequency light into two paths, and enabling the sweep frequency light to enter the third optical fiber coupler 5 through the second optical fiber coupler 4 and the third optical fiber coupler 5 which are sequentially connected and the other path of the sweep frequency light enters the optical fiber circulator 6 through the second optical fiber coupler 4, the optical fiber circulator 6, the wavelength division multiplexer 7, the optical fiber to be tested and the third optical fiber coupler 5 which are sequentially connected. In this embodiment, the second optical fiber coupler 4 is a 1:99 coupler. The third optical fiber coupler 5 is a 50:50 optical fiber coupler.
The tunable laser 1, the first optical fiber coupler 2, the auxiliary interferometer 3, the second optical fiber coupler 4, the third optical fiber coupler 5 and the optical fiber circulator 6 are connected through a first transmission optical fiber 30. Preferably, the core diameter of the first transmission fiber is in the range of 9 μm to 10 μm. In this embodiment, the first transmission fiber is a single mode fiber, the core diameter is 9 μm, and the cladding diameter is 125 μm.
Optionally, the OFDR sensing apparatus 10 further includes a polarization controller 11 for controlling the frequency-swept optical signal to be mixed with the backward rayleigh scattering signal at the third fiber coupler 5 to generate a beat frequency interference signal. One end of the polarization controller 11 is connected to the second optical fiber coupler 4 through the first transmission optical fiber 30, and the other end is connected to the third optical fiber coupler 5 through the first transmission optical fiber 30.
The optical fiber circulator 6 is configured to output the swept-frequency light to an optical fiber to be measured, and output rayleigh scattered light of the optical fiber to be measured to the third optical fiber coupler 5. Specifically, the first interface of the optical fiber circulator 6 is connected to the second optical fiber coupler 4 through a first transmission optical fiber 30, and the second interface is connected to the wavelength division multiplexer through a second transmission optical fiber 40; the interface port is connected to the third fiber coupler 5 through a second transmission fiber 40.
One end of the wavelength division multiplexer 7 is connected with the optical fiber circulator 6 through a second transmission optical fiber 40, and the other end is connected with an optical fiber to be tested. The core diameter of the optical fiber to be measured is larger than that of the first transmission optical fiber, and the core diameter of the second transmission optical fiber is equal to that of the optical fiber to be measured. Preferably, the second transmission fiber is a specialty fiber. The core diameter range of the second transmission optical fiber is 20-100 mu m. In this embodiment, the second transmission fiber and the fiber to be tested are both passive GDF single-mode double-clad fibers.
In the embodiment of the invention, when the optical fiber sensing system starts to work, pump light is required to be input to the optical fiber to be detected, and the pump light is a high-power optical signal required to be transmitted by the optical fiber to be detected, so that the optical fiber to be detected is in a working state; because the optical fiber to be detected can generate temperature change when transmitting high-power optical signals, the temperature/stress change of the optical fiber to be detected in a working state is monitored through sweep light. Preferably, a pump light source (not shown) is connected between the wavelength division multiplexer 7 and the optical fiber to be tested, and the pump light source is used for inputting an optical signal to be transmitted to the optical fiber to be tested. And the wavelength division multiplexer 7 is used for converging the pump light and the sweep light and outputting the converged pump light and the sweep light to the optical fiber to be tested.
The pattern matcher 8 is used for unidirectionally transmitting a backward rayleigh scattering signal generated by the optical fiber to be detected. One end of the pattern matcher 8 is connected to the optical fiber circulator 6 through a second transmission optical fiber 40, and the other end is connected to the third optical fiber coupler through the first transmission optical fiber 30. In this embodiment, since the backward rayleigh scattered light signal is output from the optical fiber circulator 6 to the third optical fiber coupler 5, the large diameter interface end of the pattern matching unit 8 is connected to the optical fiber circulator 6, and the small diameter interface end is connected to the third optical fiber coupler 5.
Optionally, the OFDR sensing apparatus 10 further includes a polarization beam splitter 12, wherein one end of the polarization beam splitter 12 is connected to the third fiber coupler 5, and the other end is connected to the data processing center 20. The polarization beam splitter 12 is configured to receive the beat frequency interference optical signal output by the third optical fiber coupler 5, divide the beat frequency interference optical signal into a P optical signal and an S optical signal that are orthogonal to each other, and output the P optical signal and the S optical signal to the data processing center 20. Wherein the P optical signal and the S optical signal have a phase difference. The polarization beam splitter 12 can suppress the optical power fading of the beat frequency interference optical signal in the transmission process, and improve the sensing efficiency.
Optionally, the OFDR sensing apparatus 10 further includes a fourth optical fiber coupler (not shown), one end of the fourth optical fiber coupler is connected to the first optical fiber coupler 2, and the other end of the fourth optical fiber coupler is connected to the second optical fiber coupler 4, and is configured to divide the swept-frequency light output by the first optical fiber coupler 2 into N paths, where N is a natural number greater than or equal to 2, and each path of swept-frequency light enters one second optical fiber coupler 4, so that sensing can be simultaneously achieved on multiple sections of optical fibers to be measured.
The data processing center 20 acquires and processes the beat frequency interference optical signal based on the external clock signal, and obtains sensing results of the optical fibers to be measured. Specifically, as shown in fig. 2, the data processing center 20 includes a photoelectric conversion module 21, a data acquisition module 22, and a data processing module 23, which are connected in sequence.
The photoelectric conversion module 21 is configured to convert the beat frequency interference optical signal output by the third optical fiber coupler 5 into an electrical signal. In this embodiment, the photoelectric conversion module 21 includes at least one photoelectric detector, and each photoelectric detector receives one path of P optical signals and one path of S optical signals.
One end of the data acquisition module 22 is connected to the photoelectric conversion module 21, the other end is connected to the data processing module 23, the third end is connected to the tunable laser 1, and the fourth end is connected to the auxiliary interferometer 3. The data acquisition module 22 is configured to receive a sweep frequency trigger signal sent by the tunable laser 1, where the sweep frequency trigger signal is used to control the on/off time of the data acquisition module 22 for acquiring data. The data acquisition module 22 is further configured to acquire and digitize the electrical signal output by the photoelectric conversion module 21 according to an external clock signal output by the auxiliary interferometer 3. Specifically, as shown in fig. 3, when the tunable laser 1 starts to sweep frequency, the sweep frequency trigger signal may have a falling edge, and at this time, the data acquisition module 22 starts an acquisition mode; when each rising edge of the external clock signal occurs, the data acquisition module 22 acquires and stores the once electrical signal, stops acquiring after acquiring for a specified time, and then waits for the next falling edge of the sweep frequency trigger signal to acquire again. In this embodiment, the data acquisition module 22 is a data acquisition card.
One end of the data processing module 23 is connected to the data acquisition module 22, and the other end is connected to the computer 30. The data processing module 23 is configured to control the data collecting module 22 to collect beat frequency interference signals of the optical fiber to be measured in the OFDR sensing apparatus 10 in the current working state as test data, and collect beat frequency interference signals of the optical fiber to be measured in the OFDR sensing apparatus 10 in the initial working state as reference data, where the initial working state includes that the optical fiber to be measured is in a normal stressed state, for example, a certain strain is applied to the optical fiber to straighten the optical fiber, and at this time, the optical fiber is in a normal stressed state; the working state comprises the state of the optical fiber to be tested when the optical fiber is subjected to strain or the temperature is changed compared with the initial state; and then, calculating the reference data and the test data by using an FPGA technology to obtain a sensing result of the optical fiber to be tested. In this embodiment, the data processing module 23 performs two-dimensional FFT calculation on the reference data output by the OFDR sensing apparatus 10, converts the original data into the distribution of the scattered and reflected light intensities along the length of the optical fiber, and stores the frequency domain data; then selecting a sliding window for the frequency domain data, carrying out zero padding interpolation and IFFT calculation on the data of the sliding window, transforming the data into a time domain and storing the data; after the same FFT, zero padding interpolation and IFFT calculation are performed on the test data output by the OFDR sensing apparatus 10, the time domain data and the frequency domain data in each sliding window are subjected to cross-correlation calculation to obtain a sensing result of the optical fiber to be measured, for example, stress information or temperature information received by the GDF optical fiber.
The computer 30 is respectively connected to the tunable laser 1 and the data processing module 23, and is configured to control the tunable laser 1 to perform frequency sweeping, and is further configured to receive and display sensing data of the optical fibers to be tested, which is output by the data processing module 23. Based on the high scanning speed of the tunable laser 1, the data processing module 23 sends the sensing result of the optical fiber to be detected to a computer for real-time display, thereby realizing real-time sensing of the optical fiber to be detected.
According to the optical fiber sensing system based on the OFDR technology, the problem of insertion loss of Rayleigh scattering signals entering a small core diameter from a large core diameter in the OFDR sensing system is solved by changing the core diameter size of a transmission optical fiber in the traditional OFDR sensing system and the connection relation of a mode matcher, the sensing efficiency can be improved, and the applicable scene of the OFDR system is widened; furthermore, the manufacturing cost of the optical fiber sensing system can be saved by only changing the core diameter of part of the transmission optical fiber.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. An optical fiber sensing system based on OFDR technology, comprising:
the OFDR sensing equipment comprises a tunable laser, a first optical fiber coupler, an auxiliary interferometer, a second optical fiber coupler, a third optical fiber coupler, an optical fiber circulator, a wavelength division multiplexer and a mode matcher, wherein the first optical fiber coupler is connected with the second optical fiber coupler; wherein the content of the first and second substances,
the tunable laser, the first optical fiber coupler, the auxiliary interferometer, the second optical fiber coupler, the third optical fiber coupler and the optical fiber circulator are connected through a first transmission optical fiber;
one end of the wavelength division multiplexer is connected with the optical fiber circulator through a second transmission optical fiber, and the other end of the wavelength division multiplexer is connected with an optical fiber to be tested;
one end of the pattern matcher is connected with the optical fiber circulator through a second transmission optical fiber, and the other end of the pattern matcher is connected with the third optical fiber coupler through the first transmission optical fiber; the core diameter of the optical fiber to be detected is larger than that of the first transmission optical fiber, and the core diameter of the second transmission optical fiber is equal to that of the optical fiber to be detected;
the OFDR sensing equipment is used for generating beat frequency interference signals and external clock signals; and the data processing center is used for receiving the beat frequency interference signal and the external clock signal and processing the beat frequency interference signal and the external clock signal to obtain the sensing data of the optical fiber to be detected.
2. The fiber sensing system of claim 1, wherein the first transmission fiber has a core diameter in the range of 9 μ ι η to 10 μ ι η.
3. The fiber sensing system of claim 1, wherein the second transmission fiber has a core diameter in the range of 20 μm to 100 μm.
4. The fiber sensing system of claim 1, wherein the second transmission fiber and the fiber under test are passive GDF single mode double clad fibers.
5. The fiber optic sensing system of claim 1, wherein the auxiliary interferometer is a mach-zehnder interferometer.
6. The optical fiber sensing system according to claim 1, wherein the pattern matcher is configured to convert a backward rayleigh scattering signal returned by the optical fiber to be measured, and output the backward rayleigh scattering signal to the third optical fiber coupler through the first transmission optical fiber.
7. The optical fiber sensing system according to claim 1, further comprising a pump light source connected between the wavelength division multiplexer and the optical fiber under test, wherein the pump light source is configured to input an optical signal to be transmitted to the optical fiber under test.
8. The optical fiber sensing system according to claim 1, wherein the second optical fiber coupler is configured to divide the swept-frequency optical signal output by the first optical fiber coupler into two paths, one path enters the third optical fiber coupler, the other path enters the optical fiber to be measured to generate a backward rayleigh scattering signal, and the backward rayleigh scattering signal and the swept-frequency optical signal are mixed in the third optical fiber coupler to generate a beat-frequency interference signal.
9. The fiber optic sensing system of claim 1, wherein the third fiber coupler is a 50:50 fiber coupler.
10. The optical fiber sensing system according to claim 1, wherein the data processing center includes a photoelectric conversion module, a data acquisition module, and a data processing module, which are connected in sequence, wherein the photoelectric conversion module is configured to convert the beat frequency interference optical signal output by the third optical fiber coupler into an electrical signal, the data acquisition module is configured to acquire the beat frequency interference optical signal based on the external clock signal, and the data processing module is configured to control the data acquisition module to acquire and process the acquired beat frequency interference signal, so as to obtain a sensing result of each optical fiber to be measured.
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