Search

CN-122015924-A - Quick BOTDA sensing device and method based on noise chirp modulation

CN122015924ACN 122015924 ACN122015924 ACN 122015924ACN-122015924-A

Abstract

The invention relates to the technical field of distributed optical fiber sensing, and discloses a rapid BOTDA sensing device and method based on noise chirp modulation, wherein laser output by a narrow linewidth laser in the device is divided into a first beam and a second beam, the first beam is modulated by an electro-optical modulator to realize frequency shift and spectrum broadening into wide-frequency light, and then the wide-frequency light is transmitted to a first semiconductor optical amplifier and a first circulator and then is transmitted to a pulse light with chirp Bragg optical fiber grating output frequency continuously distributed in time and then is transmitted to one end of a sensing optical fiber as detection light; the second light beam is used as pumping light to enter from the other end of the sensing optical fiber after passing through the second semiconductor optical amplifier, the deflector and the second optical circulator, stimulated Brillouin scattering occurs in the sensing optical fiber between the detection light and the pumping light, and the detection light carrying the Brillouin scattering information is transmitted to the data acquisition and analysis system after being detected by the detection module to demodulate the sensing information. The invention can obviously improve the measurement speed and provides a basis for realizing dynamic strain measurement.

Inventors

  • ZHANG MINGJIANG
  • WANG XINYI
  • WANG TAO
  • WANG RUIXIN
  • DONG XIAONING
  • ZHANG JIANZHONG

Assignees

  • 太原理工大学

Dates

Publication Date
20260512
Application Date
20260127

Claims (10)

  1. 1. The rapid BOTDA sensing device based on noise chirp modulation is characterized by comprising a narrow linewidth laser (1), wherein laser output by the narrow linewidth laser (1) is divided into a first light beam and a second light beam after passing through a polarization maintaining coupler (2), the first light beam is incident to an electro-optical modulator (3) driven by mixing of noise and radio frequency signals, frequency shift and spectrum broadening are realized through modulation of the electro-optical modulator (3), the obtained wide spectrum light is modulated Cheng Maichong light through a first semiconductor optical amplifier (7), the pulse light is incident to a chirped Bragg fiber grating (10) after passing through a first circulator (9), the chirped Bragg fiber grating (10) is used for reflecting the pulse light to be dispersed into pulse light with continuous frequency distribution in time, the pulse light reflected by the chirped Bragg fiber grating (10) is output through the first circulator (9) and then is used as detection light to be incident to one end of a sensing fiber (14), and the second light beam is modulated into pulse light through a second semiconductor optical amplifier (11) and then sequentially passes through a scrambler (12) and a second circulator (13) and is used as pumping light from the other end of the sensing fiber (14); the detection light and the pumping light are transmitted in the sensing optical fiber (14) in opposite directions and generate stimulated Brillouin scattering, the detection light carrying the Brillouin scattering information is output through the second circulator (13), and is detected by the detection module and then sent to the data acquisition and analysis system (17) for acquisition, analysis and processing, and finally the temperature or strain distribution along the sensing optical fiber and the size information thereof are demodulated.
  2. 2. The rapid BOTDA sensing device based on noise chirp modulation according to claim 1, characterized in that the detection module comprises a filter (15) and a photo detector (16), the filter (15) is used for filtering stokes light or anti-stokes light in the detected light and sending the filtered light to the photo detector (16), and the photo detector (16) is used for performing photoelectric conversion.
  3. 3. A fast BOTDA sensing device based on noise chirp modulation according to claim 1, characterized by further comprising a microwave signal source (5), a noise source (6) and a mixer (4), the output ends of the microwave signal source (5) and the noise source (6) being connected to the input end of the mixer (4), respectively, the output end of the mixer (4) being connected to the radio frequency driving end of the electro-optical modulator (3), the noise source (6) being for outputting a gaussian white noise signal, the microwave signal source (5) being for outputting a microwave signal with a frequency equal to the brillouin shift.
  4. 4. A fast BOTDA sensing device based on noise chirp modulation according to claim 3, characterized in that the gaussian white noise signal bandwidth output by the noise source (6) is larger than 300MHz and the amplitude is larger than 20dBm.
  5. 5. A fast BOTDA sensing device based on noise chirped modulation according to claim 1, characterized in that the electro-optical modulator (3) is configured to perform carrier-suppressed modulation on the first light beam, to obtain two sidebands with a frequency shift equal to the brillouin frequency shift, and to implement spectral broadening of the first light beam.
  6. 6. A fast BOTDA sensing device based on noise chirped modulation according to claim 1, characterized in that the electro-optical modulator (3) is adapted to modulate the first light beam to achieve a frequency shift equal to the brillouin shift and to achieve a spectral broadening with a spectral width in the range of 200-300 MHz.
  7. 7. A rapid BOTDA sensing device based on noise chirp modulation according to claim 1, characterized by further comprising a pulse generator (8), the output of the pulse generator (8) being connected to the electrical driving terminals of the first and second semiconductor optical amplifiers (7, 11), respectively, for driving the first and second semiconductor optical amplifiers (7, 11) for pulse modulation simultaneously.
  8. 8. The rapid BOTDA sensing device based on noise chirp modulation according to claim 2, characterized in that the first port of the first circulator (9) is connected with the output end of the first semiconductor optical amplifier (7), the second port is connected with the input end of the chirped bragg fiber grating (10), the third port is connected with one end of the sensing optical fiber (14), the first port of the second circulator (13) is connected with the output end of the scrambler (12), the second port is connected with the other end of the sensing optical fiber (14), and the third port is connected with the input end of the filter (15).
  9. 9. The rapid BOTDA sensing device based on noise chirped modulation of claim 1, wherein the narrow linewidth laser (1) is a laser with linewidth smaller than 10kHz, and the dispersion coefficient of the chirped bragg fiber grating (10) is larger than-5000 ps/nm.
  10. 10. A rapid BOTDA sensing method based on noise chirp modulation, implemented based on a sensing device according to any one of claims 1-9, characterized by comprising the steps of: S1, starting a device to enable the detection light and the pumping light to generate stimulated Brillouin scattering effect in a sensing optical fiber (14); S2, acquiring Stokes light or anti-Stokes light signals carrying Brillouin scattering through a data acquisition and analysis system (17); S3, processing the acquired signals, reconstructing a Brillouin gain spectrum by analyzing the time domain waveform, and demodulating temperature or strain distribution information along the sensing optical fiber according to the Brillouin gain spectrum.

Description

Quick BOTDA sensing device and method based on noise chirp modulation Technical Field The invention relates to the technical field of distributed optical fiber sensing, in particular to a device and a method for sensing a fast BOTDA (Brillouin optical time domain analysis) based on noise chirp modulation. Background The Brillouin optical time domain analysis is an optical fiber sensing technology based on the Brillouin scattering principle, has the advantages of long sensing distance, high measurement accuracy and the like, and can realize accurate measurement of physical quantities such as temperature, strain and the like, so that the Brillouin optical time domain analysis is widely applied to various fields such as power equipment, oil gas pipelines, bridge tunnels and the like. The measurement speed of the BOTDA system is mainly limited by the length of a sensing optical fiber, the average number of signal acquisition, the number of scanning points of the frequency of detection light and the frequency switching time. In order to improve the measurement speed of the system, on one hand, the measurement time can be shortened by reducing the average frequency, such as a polarization independent scheme, and on the other hand, the measurement speed can be realized by improving the frequency switching rate during the acquisition of the Brillouin spectrum or avoiding the frequency scanning process, such as an optical agile frequency scheme, an optical frequency comb scheme, a Brillouin spectrum slope auxiliary scheme and an optical chirp chain scheme. The optical agile frequency conversion scheme realizes rapid measurement by rapidly switching the frequency of the detection light, but frequency sweep is still needed, and the used arbitrary waveform generator is high in price and high in system cost. The optical frequency comb scheme utilizes frequency comb component parallel detection, but spatial resolution is limited by frequency comb spacing and Fast Fourier Transform (FFT) time window, and system cost is high. The brillouin spectrum ramp assist scheme simplifies measurement by utilizing a BGS ramp linear region, but has a small dynamic range and is significantly affected by pump power fluctuation and polarization variation. The optical chirp chain scheme realizes quick measurement through series connection of chirp pulse segments, has uneven amplitude response of different frequency components, influences measurement accuracy, and needs a high-bandwidth arbitrary waveform generator to realize chirp pulse generation, thereby increasing system cost. In summary, an improvement is needed to be made on the existing BOTDA measurement device to solve the problems of limited measurement speed, high system cost and the like. Disclosure of Invention In order to improve the measurement speed of a BOTDA system and reduce the complexity and cost of the device, the invention provides a rapid BOTDA sensing device and a method based on noise chirp modulation. The technical scheme includes that the quick BOTDA sensing device based on noise chirp modulation comprises a narrow linewidth laser, wherein laser output by the narrow linewidth laser is divided into a first beam and a second beam after being output by a polarization maintaining coupler, the first beam is incident to an electro-optical modulator driven by noise and radio frequency signal mixing, frequency shift and spectrum broadening are achieved through modulation of the electro-optical modulator, obtained wide-spectrum light is modulated Cheng Maichong light through a first semiconductor optical amplifier, the pulse light is incident to a chirped Bragg fiber grating after passing through the first circulator, the chirped Bragg fiber grating is used for reflecting the pulse light to enable the pulse light to be dispersed into pulse light with continuous frequency distribution in time, the pulse light reflected by the chirped Bragg fiber grating is output by the first circulator and then is used as detection light to be incident to one end of a sensing fiber, and the second beam is modulated into pulse light through a second semiconductor optical amplifier and then sequentially passes through a scrambler and the second circulator and then is used as pumping light to be incident from the other end of the sensing fiber; The detection light and the pumping light are transmitted in the sensing optical fiber in opposite directions and generate stimulated Brillouin scattering, the detection light carrying the Brillouin scattering information is output through the second circulator, detected through the detection module and then sent to the data acquisition and analysis system for acquisition, analysis and processing, and finally the temperature or strain distribution along the sensing optical fiber and the size information of the temperature or strain distribution are demodulated. The detection module comprises a filter and a photoelectric detector, wherein the filter is