CN-122015926-A - BOCDR distributed optical fiber sensing device and method based on chaotic optical path matching detection

CN122015926ACN 122015926 ACN122015926 ACN 122015926ACN-122015926-A

Abstract

The invention belongs to the field of distributed optical fiber sensing and monitoring, and discloses a BOCDR distributed optical fiber sensing device based on chaotic optical path matching detection, which comprises the following components: the invention realizes the determination of an optical path matching base point through the cross correlation of chaotic reference light and chaotic pump light, realizes the distributed measurement of Brillouin correlation domain reflection by using a chaotic optical path matching and coherent beat frequency method, and can improve the spatial resolution of a system.

Inventors

ZHANG JIANZHONG
ZHANG YUBO
MA ZHE
ZHANG MINGJIANG
LI JIAN
LI ZHUPING
WANG TINGYU
ZHANG XIAOLIN

Assignees

太原理工大学

Dates

Publication Date: 20260512
Application Date: 20260309

Claims (10)

1. The BOCDR distributed optical fiber sensing device based on chaotic optical path matching detection is characterized by comprising a chaotic light source, an optical isolator (6), a first optical fiber coupler (7), an erbium-doped optical fiber amplifier (8), a grating optical filter (9), a first optical fiber circulator (10), a sensing optical fiber (11), an optical delay line (12), a second optical fiber coupler (13), a first photoelectric detector (14), a second photoelectric detector (15) and a spectrometer (17); The output end of the chaotic light source is connected with the input end of a first optical fiber coupler (7) through an optical isolator (6), the first optical fiber coupler (7) is used for dividing chaotic laser output by the chaotic light source into chaotic pump light and chaotic reference light and outputting the chaotic laser from a first output end and a second output end respectively, the first output end of the first optical fiber coupler (7) is connected with one end of a sensing optical fiber (11) through an erbium-doped optical fiber amplifier (8), a grating optical filter (9) and a first optical fiber circulator (10), the second output end is connected with one end of an optical delay line (12), the other end of the optical delay line (12) is connected with the first input end of a second optical fiber coupler (13), and the second input end of the second optical fiber coupler (13) is connected with the reflecting end of the first optical fiber circulator (10), and the output end of the second optical fiber coupler (13) is connected with a first photoelectric detector (14) and the reflecting end of the first optical fiber circulator (10) is also connected with a second photoelectric detector (15); The output end of the first photoelectric detector (14) is connected with the frequency spectrograph (17), the frequency spectrograph (17) is used for collecting beat frequency spectrum, and the optical delay line (12) is used for realizing optical path matching of chaotic pump light and chaotic reference light.
2. The BOCDR distributed optical fiber sensing device based on chaotic optical path matching detection according to claim 1, further comprising a calculation unit, wherein the calculation unit is used for demodulating according to a beat spectrum acquired by a spectrometer (17) to obtain temperature strain information.
3. The BOCDR distributed optical fiber sensing device based on chaotic optical path matching detection according to claim 1, wherein the first optical fiber coupler (7) and the second optical fiber coupler (13) are 1×2 optical fiber couplers with 50:50 spectral ratio.
4. The BOCDR distributed optical fiber sensing device based on chaotic optical path matching detection according to claim 1 is characterized in that the chaotic light source comprises a laser (1), a second optical fiber circulator (2), a third optical fiber coupler (3), an attenuator (4) and a scrambler (5), wherein the output end of the laser (1) is connected with the input end of the second optical fiber circulator (2), the output end of the second optical fiber circulator (2) is connected with the input end of the third optical fiber coupler (3), the first output end of the third optical fiber coupler (3) is connected with the optical isolator (6), and the second output end is connected with the reflecting end of the second optical fiber circulator (2) after passing through the attenuator (4) and the scrambler (5).
5. The BOCDR distributed optical fiber sensing device based on chaotic optical path matching detection according to claim 4, wherein the third optical fiber coupler (3) is a1×2 optical fiber coupler with a 50:50 split ratio.
6. The BOCDR distributed optical fiber sensing device based on chaotic optical path matching detection according to claim 1, further comprising an optical switch (18), wherein an input end of the optical switch (18) is connected with a reflecting end of the first optical fiber circulator (10), a first output end is connected with a second input end of the second optical fiber coupler (13), and a second output end is connected with the second photoelectric detector (15).
7. The BOCDR distributed optical fiber sensing device based on chaotic optical path matching detection according to claim 1, further comprising an oscilloscope (16), wherein the output ends of the first photoelectric detector (14) and the second photoelectric detector (15) are connected with the oscilloscope (16).
8. A BOCDR distributed optical fiber sensing method based on chaotic optical path matching detection and realized based on the distributed optical fiber sensing device as claimed in any one of claims 1 to 7, which is characterized by comprising the following steps: Step 1, controlling the reflecting end of the first optical fiber circulator (10) to be connected with the second photoelectric detector (15); Step2 in the sensing fiber (11) An event area is arranged at the position, the first photoelectric detector (14) and the second photoelectric detector (15) respectively receive Brillouin scattering signals generated by chaotic reference light and chaotic pump light in the sensing optical fiber (11), and cross-correlation operation is carried out on the two paths of optical signals; step 3, determining the time delay of two paths of optical signals according to the peak value position of the cross-correlation operation And according to time delay Determining optical path matching base points of two paths of optical signals; The optical delay line (12) is adjusted to change the optical path of the chaotic reference light so that optical path matching points of the chaotic reference light are positioned at different positions along the sensing optical fiber (11), the beat frequency signals of the Brillouin scattering signal and the chaotic reference signal are received through the first photoelectric detector (14), and the beat frequency signals of the different optical path matching points are collected by the frequency spectrograph (17); and 5, extracting a Brillouin gain spectrum according to beat frequency signals corresponding to the optical path matching points, and demodulating to obtain temperature strain information along the sensing optical fiber (11) to realize distributed sensing.
9. The BOCDR distributed optical fiber sensing method based on chaotic optical path matching detection according to claim 8, wherein in the step 2, detection signals of the first photoelectric detector (14) and the second photoelectric detector (15) are output to an oscilloscope (16), and a cross-correlation operation is performed by using the oscilloscope (16) to obtain time delays of two paths of optical signals Is a value of (2).
10. The BOCDR distributed optical fiber sensing method based on chaotic optical path matching detection according to claim 8, wherein in step 4, an adjustment formula of the optical delay line (12) is: ); Wherein, the Represents the optical path adjustment amount of the optical delay line (12) in the measurement stage, And The lengths of the optical fibers corresponding to the measurement points and the optical path matching base points are respectively represented.

Description

BOCDR distributed optical fiber sensing device and method based on chaotic optical path matching detection Technical Field The invention belongs to the field of distributed optical fiber sensing monitoring, and particularly relates to BOCDR (Brillouin optical coherence domain reflection) distributed optical fiber sensing device and method based on chaotic optical path matching detection, which can be used for measuring high spatial resolution. Background The distributed optical fiber temperature sensing system has the advantages of electromagnetic interference resistance, chemical corrosion resistance, long-distance large-range temperature and strain monitoring, easiness in on-site implementation of architecture and the like, can detect the temperature and shape change of the optical fiber along the line with higher sensitivity, and has wide and important application from national defense security to daily life. An important theoretical basis for distributed optical fiber sensing technology based on brillouin scattering is brillouin frequency shift. Microscopic particles in the fiber medium spontaneously or stimulated produce a sound field, which can be seen as a grating that moves axially along the fiber, causing periodic modulation of the refractive index of the fiber. The acoustic field in the fiber reacts with the incident pump light causing a shift in the frequency of the scattered light, i.e. a brillouin shift. When the temperature and stress of the optical fiber along the line change, the physical parameters of the optical fiber medium change, so that the change of the Brillouin frequency shift is caused, namely the Brillouin frequency shift is subjected to temperature and stress modulation, and the Brillouin frequency shift obtained by calculating the difference value of the Brillouin peak value relative to the center frequency of the incident light contains the temperature change and the strain information of the optical fiber, so that the optical fiber sensing is realized. Based on the principle of temperature and strain positioning, various brillouin sensing technologies have been developed, namely an optical coherence domain analysis (Brillouin Optical Coherent Domain Analysis, BOTDA) technology based on stimulated brillouin scattering, an optical coherence domain reflection (Brillouin Optical Coherent Domain Reflectometry, BOCDR) technology based on self-brillouin scattering, an optical time domain analysis (Brillouin Optical Time Domain Analysis, BOTDA) technology based on stimulated brillouin scattering, and an optical time domain reflection (Brillouin Optical Time Domain Reflectometry, BOTDR) technology based on self-brillouin scattering. Four brillouin optical sensing technologies based on different technologies have advantages and disadvantages. The BOTDA and BOTDR technologies realize the positioning of temperature and strain by using a time flight method, the system has a simple structure, can realize long-distance measurement of tens of kilometers, but is limited by phonon service life, and the spatial resolution of the system measurement is lower, and is only in the meter level. The BOCDA and BOCDR technology realizes the positioning of temperature and strain by using a correlation method, has higher spatial resolution, but has a relatively complex system structure. Compared with a BOCDA system, the BOCDR system is a single-ended system, is easier to be practically applied, utilizes a coupler to divide a light source into two paths, detects the autocorrelation signals of scattered signal light and reference light through self heterodyning, and measures the frequency shift and the intensity of a Brillouin scattering signal, thereby obtaining the distribution condition of the temperature and the strain of an optical fiber. The BOCDR technology has the advantage of high spatial resolution, and can realize higher spatial resolution, for example, 2010, mizuno et al propose a double-modulation pulse BOCDR scheme to obtain the spatial resolution of 20cm, 2016, lee et al propose a slope auxiliary BOCDR technology to obtain the spatial resolution of 13.9 cm. The BOCDR spatial resolution of the techniques is limited by modulation parameters, which are only in the order of centimeters, and the techniques have higher system complexity and are difficult to deploy in practical application. Taking tunnel disaster monitoring as an example, in the tunnel lining crack degradation evaluation standard, the crack width d > 5mm is a serious crack, the crack width d < 5mm is a heavy crack, the crack width d <3 mm is a medium crack, and the general crack without development trend is a slight crack. If accurate monitoring and positioning of the crack of the long tunnel lining of the goaf of 2.0 km-5.0 km are to be realized, the spatial resolution of the distributed sensing is required to be less than 3 mm, the existing BOCDR technology is difficult to achieve the level, and it becomes particularly important to