CN112798025B - Method for improving OFDR measurement spatial resolution and OFDR system - Google Patents
Method for improving OFDR measurement spatial resolution and OFDR system Download PDFInfo
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- 238000005259 measurement Methods 0.000 title claims abstract description 89
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- 238000002168 optical frequency-domain reflectometry Methods 0.000 title claims abstract description 20
- 239000013307 optical fiber Substances 0.000 claims abstract description 95
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- 238000013459 approach Methods 0.000 claims abstract description 4
- 239000000835 fiber Substances 0.000 claims description 20
- 230000035559 beat frequency Effects 0.000 claims description 16
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- 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
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- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
- G01S17/34—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
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Abstract
The invention discloses a method for improving OFDR measurement spatial resolution, which obtains the accurate position of an event point by a two-side clamping approach method, and specifically comprises the following steps: setting a light source frequency sweeping range to be widest, and acquiring the position of an event point of an optical fiber link to be detected; changing the sweep frequency range of the OFDR system to obtain the position information of the event point under different measurement spatial resolutions; and (4) carrying out inductive analysis on the position information measured for multiple times, and acquiring the accurate position of the event point by a two-side approximation method. The mutual supplement of the measurement results under the adjacent spatial resolution is equivalent to the thinning of the distance between the measurement points, thereby effectively improving the spatial resolution of the measurement. The invention can improve the measurement spatial resolution of the OFDR system only by measuring and inductive analysis for many times without improving the hardware performance of the system, and is simple and easy to implement.
Description
Technical Field
The invention relates to the field of optical fiber sensing measurement, in particular to a method for improving OFDR measurement space resolution and an OFDR system.
Background
The optical frequency domain reflection technology (OFDR) is an advanced optical fiber sensing technology based on optical heterodyne detection and frequency domain analysis, and realizes positioning of events such as fusion joints, bending and breakpoints along a link, length, distributed insertion return loss and spectral measurement by detecting Rayleigh scattering signals generated at different positions in an optical fiber. In the aspects of fault location and length measurement, the developed mature optical time domain reflection technology is limited by the contradiction between the pulse width of the detection light, the spatial resolution and the dynamic range, and the spatial resolution can only reach the meter level. The optical frequency domain reflection technology effectively breaks through the limitation, and has the characteristics of high spatial resolution, large dynamic range, high measurement sensitivity and the like.
The OFDR system adopts linear sweep laser as a light source, and the sweep rate, the sweep linearity and the sweep range of the light source are key parameters influencing the system performance. The system measurement spatial resolution is determined by the maximum frequency scanning range which can be realized by the light source. The maximum sweep range that can be achieved by the sweep light source that can be used in the field of optical coherent detection is about 100nm, which means that the maximum spatial resolution that can be achieved by the OFDR system is about 10 μm, and detection within a smaller distance cannot be achieved.
Disclosure of Invention
The invention provides a method capable of effectively improving the spatial resolution of OFDR measurement, aiming at the problems that the conventional OFDR system has limited measurement resolution and cannot realize micron-scale detection.
The technical scheme adopted by the invention is as follows:
the invention provides a method for improving OFDR measurement spatial resolution, which obtains the accurate position of an event point by a two-side clamping approach method, and specifically comprises the following steps:
setting the light source sweep frequency range of the OFDR system to be the widest, acquiring the position of an event point of the optical fiber link to be measured, wherein the measurement position of the event point is
Or
Determining the measured position of the event pointLThe measurement position range of (2):
，
for measuring the widest sweep frequencyAn inter-resolution;
calculating the spatial resolution as
、
、
、...、
The sweep range of time OFDR systems, where,
，m、kis an integer;
sequentially setting the frequency sweeping range of the light source of the OFDR system according to the calculated frequency sweeping range;
acquiring and demodulating signals in the optical fiber link to be measured in different sweep frequency ranges to obtain the measurement positions of the event points in different measurement spatial resolutions, and determining corresponding measurement position ranges;
and continuously reducing the measurement position range of the event point according to the measurement position ranges corresponding to the two adjacent spatial resolutions until the final measurement position of the event point is deduced.
In connection with the above-mentioned technical solution,
。
according to the technical scheme, the measurement spatial resolution is
When the measured position of the event point is
Or
Then the range of the event point position L is
；
Continuously reducing the position range of the event point by the measuring position range corresponding to two adjacent spatial resolutions until the spatial resolution is
When the measured position of the event point is 0 or
Then, thenLIn the range of
Finally measuring the position
，qAre integers.
According to the technical scheme, the signal in the optical fiber link to be measured is a beat frequency interference signal formed by the Rayleigh scattering light and the reference light in the optical fiber link to be measured collected by the OFDR system, the beat frequency interference signal is subjected to inverse FFT (fast Fourier transform), the frequency domain information is corresponding to the distance of each position on the optical fiber, and the measurement position of the event point is obtained.
According to the technical scheme, the method is based on a formula
And calculating the sweep range of the light source, wherein,
in order to measure the spatial resolution of the image,cin order to be the speed of light,nis the refractive index of the optical fiber,
the source is swept over a range.
The present invention also provides an OFDR system comprising:
linear broomThe frequency laser sequentially sets frequency sweep ranges according to a preset frequency sweep range; the preset scanning range is based on the spatial resolution
、
、
、...、
The calculated sweep range, wherein,
，m、kis an integer which is the number of the whole,
the measurement spatial resolution is the widest sweep frequency;
the optical fiber beam splitter is connected with the linear frequency-sweeping laser;
the input end of the main interferometer is connected with one output end of the optical fiber beam splitter, and the output end of the main interferometer is connected with the optical fiber link to be tested;
the input end of the auxiliary interferometer is connected with the other output end of the optical fiber beam splitter;
the first photoelectric detector is connected with the other output end of the main interferometer;
the second photoelectric detector is connected with the output end of the auxiliary interferometer;
the data acquisition card is connected with the first photoelectric detector and the second photoelectric detector and is used for acquiring signals in the optical fiber link to be detected in different sweep frequency ranges;
the processor is connected with the data acquisition card, demodulates the acquired signals, obtains the measurement positions of the event points under different measurement spatial resolutions, and determines the corresponding measurement position range; and continuously reducing the measurement position range of the event point according to the measurement position ranges corresponding to the two adjacent spatial resolutions until the final measurement position of the event point is deduced.
According to the technical scheme, the main interferometer comprises a first optical fiber coupler, an optical fiber circulator and a second optical fiber coupler; the input end of the second optical fiber coupler is connected with one output end of the optical fiber beam splitter, and the output end of the second optical fiber coupler is respectively connected with the first port of the optical fiber circulator and the second optical fiber coupler; and a second port of the optical fiber circulator is connected with the optical fiber link to be tested, and a third port of the optical fiber circulator is connected with the other input end of the second optical fiber coupler.
In connection with the above technical solution, the auxiliary interferometer includes a third optical fiber coupler, a delay coil and a fourth optical fiber coupler, an input end of the third optical fiber coupler is connected to another output end of the optical fiber splitter, output ends of the third optical fiber coupler are respectively connected to the delay coil and the fourth optical fiber coupler, and an output end of the delay coil is connected to another input end of the fourth optical fiber coupler.
In connection with the above technical scheme
Measuring spatial resolution of
When the measured position of the event point is
Or
Position of event pointLIn the range of
；
The processor continuously reduces the position range of the event point according to the measuring position ranges corresponding to the two adjacent spatial resolutions until the spatial resolution is
When the measured position of the event point is 0 or
Then, thenLIn the range of
Finally measuring the position
，qAre integers.
The invention also provides a processor storage medium, in which a processor program executable by a processor is stored, and the processor program executes the method for improving the spatial resolution of OFDR measurement according to the technical scheme.
The invention has the following beneficial effects: according to the invention, the sweep frequency range is inversely pushed according to the relation between the spatial resolution and the spatial resolution, after the sweep frequency range under the corresponding spatial resolution is calculated, then under different sweep frequency ranges, a light frequency domain reflection system is used for collecting beat frequency interference signals formed by Rayleigh scattering light and reference light in an optical fiber link to be detected, the position information of event points under different spatial resolutions is obtained, and the distance between measuring points is refined by sequentially summarizing and analyzing the position information under the adjacent spatial resolutions, so that the measuring spatial resolution is effectively improved, and micron-scale detection is realized. The invention can improve the measurement spatial resolution of the OFDR system only by measuring and inductive analysis for many times without improving the hardware performance of the system, and is simple and easy to implement.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic diagram of an optical frequency domain reflection system according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for improving spatial resolution of OFDR measurement according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a process of sequentially analyzing position information under adjacent spatial resolutions to obtain an accurate position of the event point.
In fig. 1, 1 is a linear swept-frequency laser, 2 is an optical fiber beam splitter, 3 is a first optical fiber coupler, 4 is an optical fiber circulator, 5 is an optical fiber link to be tested, 6 is a second optical fiber coupler, 7 is a third optical fiber coupler, 8 is a delay coil, 9 is a fourth optical fiber coupler, 10 is a first photodetector, 11 is a second photodetector, 12 is a data acquisition card, and 13 is a processor.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
An optical frequency domain reflectometry system (OFDR system) used in the embodiment of the present invention is shown in fig. 1, and the OFDR system includes a linear swept-frequency laser 1, a fiber beam splitter 2, a main interferometer, an auxiliary interferometer, a first photodetector 10, a second photodetector 11, a data acquisition card 12, and a processor 13.
The linear frequency-sweeping laser 1 sequentially sets frequency sweeping ranges according to a preset frequency sweeping range; the preset scanning range is based on the spatial resolution
、
、
、...、
The calculated sweep range, wherein,
，m、kis an integer which is the number of the whole,
the measurement spatial resolution is the widest sweep frequency; optical fiber splittingThe device 2 is connected with the linear frequency-sweeping laser 1; the input end of the main interferometer is connected with one output end of the optical fiber beam splitter 2, and the output end of the main interferometer is connected with the optical fiber link to be tested; the input end of the auxiliary interferometer is connected with the other output end of the optical fiber beam splitter; the first photodetector 10 is connected to the other output of the main interferometer; the second photoelectric detector 11 is connected with the output end of the auxiliary interferometer; the data acquisition card 12 is connected with the first photoelectric detector 10 and the second photoelectric detector 11, and is used for acquiring signals in the optical fiber link 5 to be detected in different sweep frequency ranges; the processor 13 is connected with the data acquisition card 12, demodulates the acquired signals, obtains the measurement positions of the event points under different measurement spatial resolutions, and determines the corresponding measurement position range; and continuously reducing the measurement position range of the event point according to the measurement position ranges corresponding to the two adjacent spatial resolutions until the final measurement position of the event point is deduced.
In one embodiment of the invention, the main interferometer comprises a first fiber coupler 3, a fiber circulator 4, and a second fiber coupler 6. The input end of the first optical fiber coupler 3 is connected with one output end of the optical fiber beam splitter 1, and the output end of the first optical fiber coupler 3 is respectively connected with the 1 st port of the optical fiber circulator 4 and the second optical fiber coupler 6. The 2 nd port of the optical fiber circulator 4 is connected with the optical fiber link 5 to be tested, and the 3 rd port is connected with the other input end of the second optical fiber coupler 6; the auxiliary interferometer comprises a third fiber coupler 7, a delay coil 8 and a fourth fiber coupler 9. The input end of the third optical fiber coupler 7 is connected with the other output end of the optical fiber beam splitter 1, and the output end of the third optical fiber coupler 7 is respectively connected with the delay coil 8 and the fourth optical fiber coupler 9. The output end of the delay coil 8 is connected with the other input end of the fourth optical fiber coupler 9.
When the system works, the frequency-swept laser emitted by the linear frequency-swept laser 1 is divided into two beams by the optical fiber beam splitter 2, 90% of light enters the main interferometer, and 10% of light enters the auxiliary interferometer. The light entering the main interferometer is split by the first fiber coupler 3 into signal light and reference light in a ratio of 50: 50. The reference light directly enters the second optical fiber coupler 6, and the signal light enters the 1 st port of the optical fiber circulator 4 and exits from the 2 nd port to enter the optical fiber link 5 to be tested. Rayleigh scattering signals reflected by various positions on the optical fiber link 5 to be detected enter the second optical fiber coupler 6 through the 3 rd port of the optical fiber circulator and generate beat frequency interference with reference light at the position to generate a first beat frequency signal. The light entering the auxiliary interferometer is also divided into two beams in a ratio of 50:50 by the third fiber coupler 7, wherein one beam directly enters the fourth fiber coupler 9 as reference light, and the other beam enters the fourth fiber coupler 9 after passing through the delay coil 8 and is subjected to beat frequency interference with the reference light, so that a second beat frequency signal is generated. The first beat frequency signal is converted into an electrical signal by the first photoelectric detector 10, and the second beat frequency signal is converted into an electrical signal by the second photoelectric detector 11 and used as an external clock to trigger the data acquisition card 12 to perform equal-frequency domain interval sampling on the first beat frequency signal. The processor 13 performs operation processing and demodulation on the acquired signal and controls the frequency-sweeping laser 1 to work.
As shown in fig. 2, the method for improving the spatial resolution of OFDR measurement according to the embodiment of the present invention mainly obtains the accurate position of the event point by a two-sided approximation method, specifically:
s1, setting the sweep frequency range of the light source of the OFDR system to be the widest, obtaining the position of the event point of the optical fiber link to be measured, wherein the measurement position of the event point is
Or
Determining the measured position of the event pointLThe measurement position range of (2):
，
the measurement spatial resolution is the widest sweep frequency;
s2, calculating the spatial resolution as
、
、
、...、
The sweep range of time OFDR systems, where,
，m、kis an integer;
s3, sequentially setting the sweep frequency range of the light source of the OFDR system according to the calculated sweep frequency range;
s4, acquiring and demodulating signals in the optical fiber link to be measured in different sweep frequency ranges to obtain the measurement positions of the event points in different measurement spatial resolutions, and determining the corresponding measurement position ranges;
and S5, continuously reducing the measuring position range of the event point according to the measuring position ranges corresponding to the two adjacent spatial resolutions until the final measuring position of the event point is deduced.
During specific implementation, firstly, the sweep frequency range of the light source is set to be the widest, a beat frequency interference signal formed by Rayleigh scattering light and reference light in an optical fiber link to be detected is collected by using an optical frequency domain reflection system, inverse FFT (fast Fourier transform) is carried out on the signal, frequency domain information corresponds to the distance of each position on the optical fiber, and the position of an event point is obtained.
And secondly, changing the sweep frequency range of the OFDR system to obtain the position information of the event point under different measurement spatial resolutions. To be provided with
For example, the method specifically comprises the following steps:
according to the formula
Calculating the spatial resolution as
、
、
、...、
Time OFDR system sweep range. Wherein the content of the first and second substances,
in order to measure the spatial resolution of the image,cin order to be the speed of light,nis the refractive index of the optical fiber,
for the optical source sweep range of the OFDR system,
the measurement spatial resolution of the system when the sweep frequency range is widest,
、
the measured position of the event point (m is an integer) is the widest sweep range.
And sequentially setting the sweep frequency range of the light source, collecting beat frequency interference signals in the optical fiber by using the OFDR system, and demodulating to obtain the measurement positions of the event points under different measurement spatial resolutions.
And finally, carrying out inductive analysis on the position information measured for multiple times, namely acquiring the accurate position of the event point by a two-side approximation method. The method specifically comprises the following steps:
measuring spatial resolution of
When the measured position of the event point is
、
(ii) a Measuring spatial resolution of
When the measured position of the event point is
、
Then the precise position of the event point can be obtainedLIn the range of
。
According to the mode, the position range of the event point is continuously reduced by the measuring results of two adjacent space resolutions until the space resolution is
Time, event point measurement locationLIs 0,
Then, thenLIn the range of
I.e. by
Wherein q is less than
。
As shown in FIG. 3, the measurement spatial resolution of the OFDR system is set to be the widest when the source sweep range is set to be the maximum
The measured event point is set as
、
。
According to the formula
Calculating the spatial resolution of
、
、...、
Time OFDR system sweep range. And sequentially setting the sweep frequency range of the light source, collecting beat frequency interference signals in the optical fiber by using the OFDR system, and demodulating to obtain the measurement positions of the event points under different measurement spatial resolutions.
Wherein the measurement spatial resolution is
When the measured position of the event point is
、
The range of the location L of the event point can be expressed as
(ii) a Measuring spatial resolution of
The measurement position of the event point is 0,
The position of the event pointLCan be reduced to
Then, then
. The original spatial resolution is obtained by the method
The method carries out equal thinning, and effectively improves the measurement spatial resolution of the OFDR system.
In another embodiment of the present invention, if the measurement spatial resolution when the OFDR system is swept to the widest is 10 μm, when the position of the event point is between 10 μm and 20 μm, such as 15 μm, and the measurement spatial resolution is 10 μm, L is greater than 10 μm and less than or equal to 20 μm; if it is
Sweep ranges corresponding to spatial resolutions of 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm are calculated in advance. When the linear sweep frequency laser 1 is adjusted to correspond to the sweep frequency range with the spatial resolution of 11 mu m, L is more than 11 mu m and less than or equal to 22 mu m, and L is more than 10 mu m and less than or equal to 20 mu m, then L is more than 11 mu m and less than or equal to 20 mu m; when the linear sweep frequency laser 1 is adjusted to correspond to the sweep frequency range with the spatial resolution of 12 mu m, L is more than 12 mu m and less than or equal to 24 mu m, and L is more than 10 mu m and less than or equal to 20 mu m, then L is more than 12 mu m and less than or equal to 20 mu m; when the linear sweep frequency laser 1 is adjusted to correspond to the sweep frequency range with the spatial resolution of 13 mu m, L is more than 13 mu m and less than or equal to 26 mu m, and L is more than 10 mu m and less than or equal to 20 mu m, then L is more than 13 mu m and less than or equal to 20 mu m; when the linear sweep frequency laser 1 is adjusted to correspond to the sweep frequency range with the spatial resolution of 14 mu m, L is more than 14 mu m and less than or equal to 28 mu m, and L is more than 10 mu m and less than or equal to 20 mu m, then L is more than 14 mu m and less than or equal to 20 mu m; when the linear sweep frequency laser 1 is adjusted to correspond to the sweep frequency range with the spatial resolution of 15 μm, L is more than 0 and less than or equal to 15 μm, L is more than 10 μm and less than or equal to 20 μm, and then L is more than 14 μm and less than or equal to 15 μm, and then L =15 μm.
The present invention also provides a processor storage medium having stored therein a processor program executable by a processor, the processor program executing the method of improving spatial resolution of OFDR measurement of the above embodiments.
In summary, in the present invention, the sweep frequency range is inverted according to the relationship between the spatial resolution and the spatial resolution, and after the sweep frequency range under the corresponding spatial resolution is calculated, the optical frequency domain reflection system is used to collect the beat frequency interference signal formed by the rayleigh scattered light and the reference light in the optical fiber link to be measured under different sweep frequency ranges, so as to obtain the position information of the event point under different spatial resolutions. And by sequentially summarizing and analyzing the position information under the adjacent spatial resolution, the mutual supplement of the measurement results under the adjacent spatial resolution is equivalent to the thinning of the distance between the measurement points, thereby effectively improving the measurement spatial resolution. The invention can improve the measurement spatial resolution of the OFDR system only by measuring and inductive analysis for many times without improving the hardware performance of the system, and is simple and easy to implement.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (10)
1. A method for improving OFDR measurement spatial resolution is characterized in that the method obtains the accurate position of an event point by a two-face clamping approach method, and specifically comprises the following steps:
setting the light source sweep frequency range of the OFDR system to be the widest, acquiring the position of an event point of the optical fiber link to be measured, wherein the measurement position of the event point is
Or
Determining the measured position of the event pointLThe measurement position range of (2):
，
the measurement spatial resolution is the widest sweep frequency;
calculating the spatial resolution as
、
、
、...、
The sweep range of time OFDR systems, where,
，m、kis an integer;
sequentially setting the frequency sweeping range of the light source of the OFDR system according to the calculated frequency sweeping range;
acquiring and demodulating signals in the optical fiber link to be measured in different sweep frequency ranges to obtain the measurement positions of the event points in different measurement spatial resolutions, and determining corresponding measurement position ranges;
and continuously reducing the measurement position range of the event point according to the measurement position ranges corresponding to the two adjacent spatial resolutions until the final measurement position of the event point is deduced.
2. The method for improving the spatial resolution of OFDR measurements according to claim 1,
。
3. the method for improving the spatial resolution of OFDR measurement as recited in claim 2, wherein the spatial resolution of the measurement is
When the measured position of the event point is
Or
Position of event pointLIn the range of
；
Continuously reducing the position range of the event point by the measuring position range corresponding to two adjacent spatial resolutions until the spatial resolution is
When the measured position of the event point is 0 or
Then, thenLIn the range of
Finally measuring the position
，qAre integers.
4. The method of claim 1, wherein the signal in the optical fiber link to be measured is a beat frequency interference signal formed by the rayleigh scattered light and the reference light in the optical fiber link to be measured collected by the OFDR system, the beat frequency interference signal is subjected to inverse FFT transformation, and the frequency domain information is mapped to the distance of each position on the optical fiber to obtain the measurement position of the event point.
5. Method for increasing the spatial resolution of OFDR measurements according to any of claims 1 to 4, whereinCharacterised by being based in particular on formulae
And calculating the sweep range of the light source, wherein,
in order to measure the spatial resolution of the image,cin order to be the speed of light,nis the refractive index of the optical fiber,
the source is swept over a range.
6. An OFDR system comprising:
the linear frequency-sweeping laser is used for sequentially setting frequency-sweeping ranges according to a preset frequency-sweeping range; the preset scanning range is based on the spatial resolution
、
、
、...、
The calculated sweep range, wherein,
，m、kis an integer which is the number of the whole,
the measurement spatial resolution is the widest sweep frequency;
the optical fiber beam splitter is connected with the linear frequency-sweeping laser;
the input end of the main interferometer is connected with one output end of the optical fiber beam splitter, and the output end of the main interferometer is connected with the optical fiber link to be tested;
the input end of the auxiliary interferometer is connected with the other output end of the optical fiber beam splitter;
the first photoelectric detector is connected with the other output end of the main interferometer;
the second photoelectric detector is connected with the output end of the auxiliary interferometer;
the data acquisition card is connected with the first photoelectric detector and the second photoelectric detector and is used for acquiring signals in the optical fiber link to be detected in different sweep frequency ranges;
the processor is connected with the data acquisition card, demodulates the acquired signals, obtains the measurement positions of the event points under different measurement spatial resolutions, and determines the corresponding measurement position range; and according to the measuring position range corresponding to the two adjacent spatial resolutions, obtaining the accurate position of the event point by adopting a two-side clamping approach method for the measuring position.
7. The OFDR system of claim 6 wherein the primary interferometer comprises a first fiber coupler, a fiber circulator and a second fiber coupler; the input end of the second optical fiber coupler is connected with one output end of the optical fiber beam splitter, and the output end of the second optical fiber coupler is respectively connected with the first port of the optical fiber circulator and the second optical fiber coupler; and a second port of the optical fiber circulator is connected with the optical fiber link to be tested, and a third port of the optical fiber circulator is connected with the other input end of the second optical fiber coupler.
8. The OFDR system of claim 6 or 7, wherein the auxiliary interferometer comprises a third fiber coupler, a delay coil and a fourth fiber coupler, wherein an input end of the third fiber coupler is connected to another output end of the fiber splitter, output ends of the third fiber coupler are respectively connected to the delay coil and the fourth fiber coupler, and an output end of the delay coil is connected to another input end of the fourth fiber coupler.
9. The OFDR system of claim 6 wherein when said OFDR system is in operation
Measuring spatial resolution of
When the measured position of the event point is
Or
Position of event pointLIn the range of
；
The processor continuously reduces the position range of the event point according to the measuring position ranges corresponding to the two adjacent spatial resolutions until the spatial resolution is
When the measured position of the event point is 0 or
Then, thenLIn the range of
Finally measuring the position
，qAre integers.
10. Processor storage medium, having stored therein a processor program executable by a processor, the processor program performing the method of improving spatial resolution of OFDR measurements as claimed in any one of claims 1 to 5.
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