CN-121977622-A - BOCDA optical fiber sensing device and method based on linear frequency modulation pulse pumping

CN121977622ACN 121977622 ACN121977622 ACN 121977622ACN-121977622-A

Abstract

The invention belongs to the technical field of distributed optical fiber sensing, in particular to a BOCDA optical fiber sensing device and method based on linear frequency modulation pulse pumping, the system comprises a laser, an optical fiber coupler, a first electro-optic phase modulator, a first erbium-doped optical fiber amplifier, an optical isolator, a sensing optical fiber, a second electro-optic phase modulator, an electro-optic intensity modulator, an electro-optic pulse signal modulator, a scrambler, a second erbium-doped optical fiber amplifier, an optical circulator, an optical filter, a photoelectric detector, a low-pass filter and a data acquisition and analysis system. According to the invention, as the frequency of the pumping light pulse is linearly changed, the change of the amplitude of the detection light along with the time directly carries the Brillouin gain spectrum information, so that the scanning of pumping detection light frequency difference is avoided, and therefore, one-time measurement can be completed only by one-dimensional scanning, and the measurement time of the BOCDA optical fiber sensor is greatly shortened.

Inventors

LI ZONGLEI
WU QICHAO
Xiao Mengqian
YE JIA
ZOU XIHUA
PAN WEI
YAN LIANSHAN

Assignees

西南交通大学

Dates

Publication Date: 20260505
Application Date: 20260227

Claims (10)

1. The BOCDA optical fiber sensing device based on the linear frequency modulation pulse pumping is characterized by comprising a laser, an optical fiber coupler, a first electro-optic phase modulator, a first erbium-doped optical fiber amplifier, an optical isolator, a sensing optical fiber, a second electro-optic phase modulator, an electro-optic intensity modulator, an electro-optic pulse signal modulator, a scrambler, a second erbium-doped optical fiber amplifier, an optical circulator, an optical filter, a photoelectric detector, a low-pass filter and a data acquisition and analysis system; the output end of the laser is connected with the input end of the optical fiber coupler; The first output end of the optical fiber coupler is sequentially connected with a first electro-optic phase modulator, a first erbium-doped optical fiber amplifier, an optical isolator and a sensing optical fiber; the second output end of the optical fiber coupler is sequentially connected with a second electro-optic phase modulator, an electro-optic intensity modulator, an electro-optic pulse signal modulator, a scrambler and a second erbium-doped optical fiber amplifier; The output ends of the sensing optical fiber and the second erbium-doped optical fiber amplifier are respectively connected with a first input port and a second input port of the optical circulator; And the output port of the optical circulator is sequentially connected with an optical filter, a photoelectric detector, a low-pass filter and a data acquisition and analysis system.
2. The BOCDA fiber sensing device based on chirped pulse pumping of claim 1 further comprising a PRBS signal generator having a first output and a second output connected to inputs of the first electro-optic phase modulator and the second electro-optic phase modulator, respectively.
3. The BOCDA fiber sensing device based on chirped pulse pumping of claim 2 wherein the codewords of the first PRBS signal and the second PRBS signal output by the first output and the second output of the PRBS signal generator are synchronized in the same time and the time delay between them is adjustable.
4. A BOCDA fiber sensing device based on chirping according to claim 1, further comprising a chirp generator, the output of which is connected to the input of the electro-optical intensity modulator.
5. The BOCDA fiber sensing device based on chirped pulse pumping of claim 4 further comprising a pulse signal generator having an output connected to an input of the electro-optic pulse signal modulator.
6. The BOCDA optical fiber sensing device based on the chirp pumping according to claim 5, wherein the chirp signals output by the chirp signal generator and the pulse signal generator are synchronous in time with the electric pulse signals respectively and the time delay between the chirp signals and the electric pulse signals is adjustable.
7. A BOCDA optical fiber sensing method based on chirped pulse pumping, which is characterized by being realized by the BOCDA optical fiber sensing device based on chirped pulse pumping as claimed in any one of claims 1-6, and specifically comprising the following steps: step S1, starting a device, wherein a laser emits optical carriers, and the optical carriers are divided into two paths by an optical fiber coupler; S2, the uplink optical carrier is modulated by a first phase modulator, and an optical signal output by the first phase modulator is further amplified by an erbium-doped optical fiber amplifier and then is input into a sensing optical fiber through an isolator to serve as detection light; S3, the phase of the optical carrier wave of the lower way is modulated by a second phase modulator with the same characteristic as the first phase modulator, the phase modulation optical signal output by the second phase modulator is further modulated by an intensity modulator, two optical sidebands output by the intensity modulator are further modulated into optical pulses by an electro-optical pulse signal modulator, the optical pulses are further filtered by an optical filter to obtain a high-frequency sideband or a low-frequency sideband, the filtered sidebands are further amplified by an erbium-doped optical fiber amplifier, and the amplified sidebands are input into a sensing optical fiber through a circulator to serve as pumping light; S4, after the detection light and the pump light interact in the optical fiber, the detection light and the pump light are led out through the circulator and are filtered out of out-of-band ASE noise generated by the erbium-doped optical fiber amplifier through the optical band pass filter, the filtered detection light is further converted into an electric signal by the photoelectric detector, and the electric signal is filtered out of-band noise by the low-pass filter and is input into the data acquisition and analysis system; And S5, the data acquisition and analysis system processes the measured original data to estimate the Brillouin frequency shift of different positions of the optical fiber.
8. The BOCDA optical fiber sensing method based on the linear frequency modulation pulse pumping according to claim 7, wherein when the data acquisition and analysis system in the step S5 processes the data, the original data acquired under different PRBS signal time delays are segmented according to the period of the PRBS signal, so as to obtain brillouin gain spectrums at different positions of the whole optical fiber, and further, brillouin frequency shift corresponding to each brillouin gain spectrum is obtained through a signal processing method, so that the temperature and stress distribution on the whole sensing optical fiber can be further obtained through the temperature and strain coefficients.
9. The method of claim 7, wherein the first PRBS signal driving the phase modulator and the second PRBS signal driving the phase modulator in step S2 and step S3 are both from a PRBS signal generator.
10. The BOCDA optical fiber sensing method according to claim 7, wherein the microwave signal driving the intensity modulator in step S3 is a chirp signal generated by a chirp signal generator, and the electric pulse signal driving the electric pulse signal modulator is from the pulse signal generator.

Description

BOCDA optical fiber sensing device and method based on linear frequency modulation pulse pumping Technical Field The invention relates to a BOCDA optical fiber sensing device and method based on linear frequency modulation pulse pumping, and belongs to the technical field of distributed optical fiber sensing. Background Brillouin Optical Correlation Domain Analysis (BOCDA) is a high-precision distributed optical fiber sensing technology that can achieve spatial resolution at the centimeter level. The BOCDA optical fiber sensor is mainly of three types, namely a sine frequency modulation type, a phase modulation type and a chaotic light source type. All three kinds of BOCDA optical fiber sensors often need two-dimensional scanning to finish one measurement, namely 1) scanning the frequency difference of the pump detection light to measure the Brillouin gain spectrum of the cross-correlation position, and 2) scanning the cross-correlation position to measure the whole sensing optical fiber. These two-dimensional scans result in extremely slow BOCDA sensing speeds, often taking tens of minutes or even hours to complete a measurement. Disclosure of Invention The invention aims to solve the problems in the prior art and provides a BOCDA optical fiber sensing device and method based on linear frequency modulation pulse pumping. The technical scheme provided by the invention for solving the technical problems is that the BOCDA optical fiber sensing device based on the linear frequency modulation pulse pumping comprises a laser, an optical fiber coupler, a first electro-optic phase modulator, a first erbium-doped optical fiber amplifier, an optical isolator, a sensing optical fiber, a second electro-optic phase modulator, an electro-optic intensity modulator, an electro-optic pulse signal modulator, a scrambler, a second erbium-doped optical fiber amplifier, an optical circulator, an optical filter, a photoelectric detector, a low-pass filter and a data acquisition and analysis system; the output end of the laser is connected with the input end of the optical fiber coupler; The first output end of the optical fiber coupler is sequentially connected with a first electro-optic phase modulator, a first erbium-doped optical fiber amplifier, an optical isolator and a sensing optical fiber; the second output end of the optical fiber coupler is sequentially connected with a second electro-optic phase modulator, an electro-optic intensity modulator, an electro-optic pulse signal modulator, a scrambler and a second erbium-doped optical fiber amplifier; The output ends of the sensing optical fiber and the second erbium-doped optical fiber amplifier are respectively connected with a first input port and a second input port of the optical circulator; And the output port of the optical circulator is sequentially connected with an optical filter, a photoelectric detector, a low-pass filter and a data acquisition and analysis system. The device further comprises a PRBS signal generator, wherein a first output end and a second output end of the PRBS signal generator are respectively connected with input ends of the first electro-optic phase modulator and the second electro-optic phase modulator. According to a further technical scheme, codewords of a first PRBS signal and a second PRBS signal output by a first output end and a second output end of the PRBS signal generator are synchronous in the same time and time delay between the first PRBS signal and the second PRBS signal is adjustable. The device further comprises a linear frequency modulation signal generator, wherein the output end of the linear frequency modulation signal generator is connected with the input end of the electro-optic intensity modulator. The device further comprises a pulse signal generator, wherein the output end of the pulse signal generator is connected with the input end of the electro-optic pulse signal modulator. According to a further technical scheme, the chirp signals respectively output by the chirp signal generator and the pulse signal generator are synchronous in time with the electric pulse signals, and time delay between the chirp signals and the electric pulse signals is adjustable. A BOCDA optical fiber sensing method based on linear frequency modulation pulse pumping specifically comprises the following steps: step S1, starting a device, wherein a laser emits optical carriers, and the optical carriers are divided into two paths by an optical fiber coupler; S2, the uplink optical carrier is modulated by a first phase modulator, and an optical signal output by the first phase modulator is further amplified by an erbium-doped optical fiber amplifier and then is input into a sensing optical fiber through an isolator to serve as detection light; S3, the phase of the optical carrier wave of the lower way is modulated by a second phase modulator with the same characteristic as the first phase modulator, the phase modulation optical signal output