CN103115632A - Multi-wavelength brillouin optical time domain analyzer - Google Patents

Abstract

The invention discloses a multi-wavelength Brillouin optical time-domain analyzer, which includes a multi-wavelength laser, a coupler, a detection pulse optical path, a continuous pump optical path, a detector and a signal acquisition processor; wherein, the detection pulse optical path includes Detection pulse light modulation unit, first erbium-doped fiber amplifier, first circulator, the continuous pump optical path includes continuous pump light modulation unit, second erbium-doped fiber amplifier, second circulator, Bragg grating, polarization scrambler The multi-wavelength laser emits continuous light, and the continuous light is respectively input into the detection pulse light path and the continuous pump light path through the coupler; the present invention can increase the number of wavelengths of the detection light and the pump light without causing stimulated Brillouin scattering. Under the premise of increasing the total optical power entering the optical fiber, the system signal-to-noise ratio can be effectively improved. At the same time, the measurement efficiency can be improved, the measurement time is shortened for a certain sensing distance, and the sensing range is increased for a certain measurement time.

Description

Multi-Wavelength Brillouin Optical Time Domain Analyzer

technical field

The invention relates to a Brillouin optical time domain analyzer based on a multi-wavelength light source, which is used for the Brillouin optical time domain analyzer in the fields of optical fiber sensing and optical cable health monitoring.

Background technique

The fully distributed optical fiber sensing technology uses the entire optical fiber as the sensing element, and utilizes the scattering phenomenon in the optical fiber to realize the continuous distribution measurement of the physical quantity to be measured (strain, temperature, etc.) on the sensing optical fiber as a function of time and space. BOTDA (Brillouin optical time-domain analysis, Brillouin optical time domain analyzer) is a distributed optical fiber sensing system based on the stimulated Brillouin amplification effect, because the Brillouin optical time domain analyzer has a long sensing distance , high sensitivity, and high measurement accuracy have been applied in many structural monitoring.

Traditional BOTDA based on direct detection all use a single-wavelength narrow-linewidth light source, and its probe light and pump light are only single-wavelength optical signals. In lossy BOTDA, the frequency of the continuous pump light is higher than that of the probe pulse light, and the frequency difference between the two is about the Brillouin frequency shift of the fiber under test (about 11 GHz). Probe pulse light and continuous pump light are respectively injected from both ends of the fiber. Due to the stimulated Brillouin amplification, part of the energy of the continuous pump light is transferred to the probe pulse light through the vibrating acoustic field. Using OTDR technology (Optical fiber time-domain reflectometer, optical time domain reflectometer), by detecting the change of continuous pump light power, the size of energy transfer along the optical fiber can be obtained. Since the magnitude of the energy transfer is related to the frequency difference between the two light waves, and when the frequency difference between the two is the Brillouin frequency shift of the fiber, the energy transfer is the largest. By actively changing the frequency difference between the two light waves and recording the energy transfer under each frequency difference, the Brillouin gain spectrum along the fiber can be obtained, and the peak frequency of the Brillouin spectrum can be obtained by Lorentz fitting. Corresponds to the Brillouin frequency shift. By comparing the Brillouin frequency shift at different positions in the optical fiber, according to the linear relationship between the Brillouin frequency shift and strain or temperature, the continuous distribution of strain and temperature on the optical fiber can be obtained, and distributed optical fiber sensing and health monitoring can be realized.

Signal-to-noise ratio (SNR) is an important parameter of BOTDA, which determines the dynamic range and measurement accuracy of the system. The improvement of the signal-to-noise ratio is mainly achieved by increasing the power of the probe pulse light and the continuous pump light, and increasing the number of cumulative and average measurements. However, due to the limitation of nonlinear effects in the optical fiber, the optical power incident on the optical fiber under test should be lower than the stimulated Brillouin threshold; in addition, increasing the number of averages will not only increase the measurement time, but also after the number of averages exceeds a certain number, Even if it is increased, it will not significantly help the improvement of the signal-to-noise ratio. Therefore, the improvement of the system signal-to-noise ratio will be restricted in the above two aspects.

Contents of the invention

The technical problem to be solved by the present invention is to propose a Brillouin optical time domain analyzer based on a multi-wavelength light source for the defects in the background technology. The Brillouin optical time domain analyzer uses multiple The detection pulse light of a wavelength and the continuous pump light of multiple wavelengths, the detection light of each wavelength corresponds to the corresponding pump light one by one, and energy transfer occurs between each other, so that the detected light power increases, and the system collects The signal-to-noise ratio of the detected optical signal is higher than that of the single-wavelength system.

The present invention is to solve above technical problem, and the technical solution that adopts is as follows:

A multi-wavelength Brillouin optical time-domain analyzer, comprising a multi-wavelength laser, a coupler, a detection pulse optical path, a continuous pump optical path, a detector, and a signal acquisition processor; wherein the detection pulse optical path includes a detection pulse light modulation unit, a first erbium-doped fiber amplifier, and a first circulator, and the continuous pump optical path includes a continuous pump light modulation unit, a second erbium-doped fiber amplifier, a second circulator, a Bragg grating, and a polarization scrambler; a multi-wavelength laser Send out continuous light with frequencies of υ ₁ , υ ₁ +Δυ,...,υ ₁ +(N-1)Δυ, Δυ is the frequency interval, N is the number of wavelengths, and N is a natural number; the continuous light is respectively input into the detection pulse through the coupler Optical path, continuous pumping optical path; where:

On the detection pulse light path, the continuous light is modulated into multi-wavelength detection pulse light by the detection pulse light modulation unit, and the multi-wavelength detection pulse light is amplified by the first erbium-doped fiber amplifier, and then injected into the measured transmission through the first circulator. One end of the sensing fiber;

On the continuous pump light path, the continuous light is subjected to double sideband modulation by the continuous pump light modulation unit to obtain continuous light with a frequency shifted up and down by _υS , that is, the frequency of the modulated continuous light is υ ₁ ±υ _S , υ ₁ +Δυ±υ _S ,…,υ ₁ +(N-1)Δυ±υ _S ; the initial value of υ _S is set to the corresponding Brillouin frequency shift of the fiber at room temperature and in the relaxed state, which can be changed by changing the pump The modulation frequency of the optical modulation unit changes the value of _υS ; the modulated continuous pump light passes through the filter unit composed of the second circulator and the Bragg grating to filter out the wavelength components with a frequency lower than that of the detection pulse light, and obtain a frequency of υ ₁ +υ _S ,υ ₁ +Δυ+υ _S ,…,υ ₁ +(N-1)Δυ+υ _S continuous pumping light, the pumping light is injected into another part of the sensing fiber under test after passing through the polarization scrambler one end;

In the sensing fiber under test, N pairs of detection pulsed light and continuous pumping light interact respectively. After the interaction, the signal of the continuous light is output to the detector through the first circulator, and after photoelectric conversion by the detector, it is sent to the The signal acquisition processor obtains the time-domain trace corresponding to a certain frequency in the Brillouin scattering spectrum on the fiber; by changing υ _S at equal intervals, the Brillouin scattering spectrum on the entire measured sensing fiber is obtained, and then the Brillouin scattering spectrum on the fiber is obtained. temperature and strain distribution.

As a further optimization of the multi-wavelength Brillouin optical time-domain analyzer of the present invention, the detection pulse light modulation unit includes a pulse generator and a light modulator, wherein the modulation signal input of the pulse generator and the light modulator The optical modulator is an electro-optic modulator or an acousto-optic modulator.

As a further optimization of the multi-wavelength Brillouin optical time-domain analyzer of the present invention, the continuous pump optical modulation unit includes a microwave source and an electro-optic modulator, wherein the microwave source and the modulation signal input end of the electro-optic modulator Connected, used to control the size of the frequency shift υ _S required for continuous pumping of the optical modulation unit.

As a further optimization of the multi-wavelength Brillouin optical time-domain analyzer of the present invention, the detector is a conventional intermediate frequency detector with a bandwidth of about several hundred megahertz.

As a further optimization of the multi-wavelength Brillouin optical time-domain analyzer of the present invention, the signal acquisition processor is an oscilloscope or a spectrum analyzer, or a device composed of an acquisition card and a computer.

As a further optimization of the multi-wavelength Brillouin optical time-domain analyzer of the present invention, the range of wavelengths corresponding to the frequency interval Δυ of the continuous light emitted by the multi-wavelength laser is [0.01nm, 0.1nm].

As a further optimization of the multi _- wavelength Brillouin optical time-domain analyzer of the present invention, the value range of the _υS is related to the measured temperature and strain range _; The Liavin frequency shift is υ _B0 , the measured temperature is T ₀ +ΔT, then the value range of υ _S is:

[υ _B0 +ΔT·1MHz/°C-100MHz,υ _B0 +ΔT·1MHz/°C+100MHz];

The measured strain is ε ₀ +Δε, then the value range of υ _S is:

[υ _B0 +Δε·5×10 ⁴ MHz-100MHz,υ _B0 +Δε·5×10 ⁴ MHz+100MHz].

The present invention adopts the above technical scheme, and compared with the prior art, the beneficial effects are:

The present invention proposes a new type of Brillouin optical time domain analyzer based on multi-wavelength light sources. By increasing the number of wavelengths of detection pulsed light and continuous pumping light, the input can be increased without causing stimulated Brillouin scattering. The total optical power of the fiber can effectively improve the signal-to-noise ratio of the system. At the same time, the measurement efficiency can be improved, that is, the cumulative effect of multiple measurements can be obtained within the measurement time of a traditional single-wavelength method. For a certain sensing distance, the measurement time is shortened; for a certain measurement time, the sensing range is increased.

Description of drawings

Fig. 1 is a schematic diagram of the method of the Brillouin optical time domain analyzer based on the multi-wavelength light source of the present invention.

Fig. 2 is a device schematic diagram of the Brillouin optical time domain analyzer based on the multi-wavelength light source of the present invention.

Fig. 3 is a working principle diagram of a specific embodiment of the present invention.

Fig. 4 is a comparison chart of single-wavelength and three-wavelength Brillouin optical power measurement results of a specific embodiment of the present invention.

Fig. 5 is a comparison chart of measurement results of single-wavelength and three-wavelength Brillouin frequency shifts according to a specific embodiment of the present invention.

Detailed ways

The technical solution of the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

First, _as shown in Figure 1, _it is _a schematic diagram of the method of the Brillouin optical time domain analyzer based on the multi-wavelength light source of the present invention. N-1) Δυ laser light source, the laser light source is divided into two paths:

One path is pulse-modulated to become multi-wavelength detection pulsed light, the frequency of which is υ ₁ ,υ ₁ +Δυ,…,υ ₁ +(N-1)Δυ, which is injected from one end of the optical fiber under test.

The other path is modulated into multi-wavelength continuous pumping light, and the frequency of each wavelength of light is shifted up by υ _S , so the frequency of multi-wavelength continuous pumping light is υ ₁ +υ _S , υ ₁ +Δυ+υ _S , …,υ ₁ +(N-1)Δυ+υ _S , injected from the other end of the optical fiber under test.

In the optical fiber under test, multiple probe pulses interact with their corresponding continuous pump light, and the continuous pump light with higher frequency will transfer energy to the probe pulse light with lower frequency. When the frequency difference between the two is When the Liavin frequency shifts υ _B , the amount of energy transfer reaches the maximum. Using the detector to directly detect the signal of the continuous pump light after the interaction is equivalent to the accumulated signal of N detections using a single wavelength.

The Brillouin optical time domain analyzer based on the multi-wavelength light source of the present invention includes the following features:

1. The wavelength interval of multi-wavelength probe light and multi-wavelength pump light is equal, and the wavelength interval is less than 0.1nm;

2. Using a multi-wavelength laser light source, one end of the optical fiber under test injects multi-wavelength detection pulse light, whose wavelength is the same as that of the multi-wavelength laser light source;

3. The other end of the optical fiber under test injects multi-wavelength continuous pump light, whose wavelength is obtained by modulating the frequency of the multi-wavelength laser light source;

4. There is only one continuous pump light corresponding to the wavelength in the Brillouin gain spectrum of each wavelength of the multi-wavelength probe pulse light, so that the interaction of each pair of energy transfer between the multi-wavelength probe light and the multi-wavelength pump light Independent of each other, no additional coupling or nonlinear effects occur;

5. The bandwidth of the detector only needs to meet the requirements of the spatial resolution determined by the pulse width.

Multi-wavelength detection pulsed light and multi-wavelength continuous pump light are transmitted in opposite directions in the sensing fiber, resulting in stimulated Brillouin amplification effect, part of the energy of the continuous pump light is transferred to the detection pulse light, and the detector directly detects the power of the continuous light .

Based on the above working principle, the present invention proposes a Brillouin optical time-domain analyzer based on a multi-wavelength light source, as shown in Figure 2, including a multi-wavelength laser, a coupler, a detection pulse light modulation unit, 1 continuous pump optical modulation unit, 2 erbium-doped fiber amplifiers (EDFA), 2 circulators, 1 Bragg grating (FBG), 1 polarization scrambler, 1 detector and 1 signal acquisition processor. When working specifically, the continuous light emitted by the multi-wavelength laser (frequency is υ ₁ , υ ₁ +Δυ,...,υ ₁ +(N-1)Δυ) is divided into two paths by the coupler: one is the detection pulse light path, and the other is It is a continuous pump light path.

Among them, the continuous light on the detection pulse optical path is modulated into pulsed light by the detection pulse light modulation unit (frequency is υ ₁ , υ ₁ +Δυ,...,υ ₁ +(N-1)Δυ), and the multi-wavelength detection pulse light is mixed with The erbium fiber amplifier is amplified and injected into the sensing fiber through a circulator. On the continuous pump light path, the continuous light with frequency up-shifted and down-shifted (frequency is υ ₁ ±υ _S ,υ ₁ +Δυ±υ _S ,...,υ ₁ +( N-1) Δυ± _υS ). The modulated continuous light passes through a filtering unit composed of a circulator and a Bragg grating to filter out wavelength components whose frequency is lower than that of the detection pulse light, and the obtained frequency is υ ₁ +υ _S ,υ ₁ +Δυ+υ _S ,…, The continuous pump light of υ ₁ +(N-1)Δυ+υ _S constitutes a lossy BOTDA, and can effectively filter the spontaneous emission noise (ASE) generated by the amplifier. The probe light passes through a polarization scrambler to reduce the effects of polarization noise, and is then injected into the other end of the sensing fiber. In the optical fiber under test, N pairs of detection pulsed light and continuous pumping light respectively generate stimulated Brillouin scattering, and the continuous pumping light is output to the detector through the circulator, and after photoelectric conversion by the detector, it is sent to the signal acquisition process The time-domain trace corresponding to a certain frequency in the Brillouin scattering spectrum on the fiber can be obtained. By changing υS at equal intervals, the Brillouin scattering spectrum on the entire fiber can be obtained, and then the temperature and strain distribution on the fiber can be obtained.

The relationship between the SNR improvement and the number of wavelengths N is shown in the following formula:

$\mathrm{<span\; class="notranslate">\; SNRI</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="SNR\; N\; SNR"\; filenames="130124133838.png"\; state="\{\{state\}\}">SNR</figure-callout></span><figure-callout\; id="1"\; label="SNR\; N\; SNR"\; filenames="130124133838.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}{{}_{}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; q</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; cw</span>}}\mathrm{<span\; class="notranslate">\; RB</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; kT</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="noise"\; filenames="130124133838.png"\; state="\{\{state\}\}">noise</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ></span><span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; Q</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; cw</span>}}\mathrm{<span\; class="notranslate">\; RB</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; kT</span>}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="noise"\; filenames="130124133838.png"\; state="\{\{state\}\}">noise</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ></span>}$

为信号采集处理系统中其他器件（如放大器和示波器等）产生的电噪声功率。Where N is the number of wavelengths, T is the thermodynamic temperature, k is the Boltzmann constant, _RL is the load resistance, q is the elementary charge, R is the photodiode responsivity, B is the detector bandwidth, and P _cw is the continuous optical power. The first term (2NqP _cw RB ) and the second term (4kTB/ _RL ) in the denominator are shot noise and thermal noise respectively, and the third term

It is the electrical noise power generated by other devices (such as amplifiers and oscilloscopes) in the signal acquisition and processing system.

As a preferred embodiment of the present invention, the polarization scrambler can be active or passive; the detector can be a balanced detector or other types of detectors. The signal acquisition processor can be an oscilloscope or a spectrum analyzer, and can also be composed of an acquisition card and a computer.

Embodiment: The measurement method of the present invention is illustrated in conjunction with specific measurement methods and accompanying drawings. This embodiment uses three wavelengths, but the present invention is not limited to three wavelengths.

As shown in Figure 3, the single-wavelength laser emits a single-wavelength laser of 1549.886nm, which is modulated by the electro-optic modulator 1 and the microwave source 1 to generate laser light sources with three wavelengths. The wavelength interval is 0.028nm, and the corresponding frequency interval Δυ is 3.5 GHz. Afterwards, it is divided into two paths by the coupler, and one path is modulated into a 50ns optical pulse by the electro-optic modulator 2 and the pulse generator, and then amplified by the erbium-doped fiber amplifier 1, and enters port 1 of the circulator 1 as the detection pulse light, from the 2 The port is injected with a 23.6km-long optical fiber to be tested, and about 45m of the end of the optical fiber to be tested is placed in the heating device; the other is modulated by the electro-optic modulator 3 and the microwave source 2, and the modulated sideband signal is used as a continuous pumping optical signal. Afterwards, it is amplified by the erbium-doped fiber amplifier 2, and the sidebands shifted down in frequency and the spontaneous emission noise (ASE) generated by the erbium-doped fiber amplifier 2 are filtered out by the filtering unit composed of the circulator 2 and the Bragg grating. After that, it passes through a polarization scrambler to reduce the influence of polarization noise, and is injected into the other end of the fiber under test. After the probe pulse light and the continuous pump light interact in the fiber under test, the continuous pump light is output through port 3 of the circulator 1 and directly detected by the detector. The photoelectrically converted signal is received by an oscilloscope to obtain a time-domain signal, and the frequency of the microwave source 2 is changed to realize frequency sweep. The frequency sweep range is set from 10.82GHz to 10.96GHz, and the frequency interval of the sweep is 10MHz. The Brillouin scattering spectrum on the entire fiber can be obtained, and then the temperature and strain distribution on the fiber can be obtained.

Figure 4 and Figure 5 show the comparison of the measurement results of the BOTDA system with three-wavelength detection pulsed light and three-wavelength continuous pump light and the common single-wavelength system. Figure 4 shows the comparison of Brillouin peak power. The voltage signal-to-noise ratio of the three-wavelength measurement results is 4.5dB higher than that measured by ordinary BOTDA. Figure 5 shows the Brillouin frequency shift measurement results of the entire fiber and the heated section. In the three-wavelength system and the single-wavelength system, the standard deviations of the Brillouin frequency shift of the unheated fiber section are 0.7MHz and 1.2MHz respectively. ; The standard deviations of the Brillouin frequency shifts of the heated fiber sections are 0.2MHz and 0.5MHz, respectively. It can be seen that the fluctuation of the measurement results of the three-wavelength system is approximately half of the fluctuation of the measurement value of the ordinary single-wavelength system, and the temperature measurement errors of the three-wavelength system and the single-wavelength system are 0.2°C and 0.5°C, respectively.

Compared with the Brillouin optical time-domain analyzer based on the traditional single-wavelength light source, the signal-to-noise ratio and dynamic range of the invention are improved. The invention increases the number of wavelengths of the probe light and the pump light, and enhances the light power entering the optical fiber, thereby improving the utilization efficiency of the sensing optical fiber, and obtaining the accumulation effect of multiple measurements within the measurement time of a traditional method. For a certain sensing distance, the measurement time is shortened; for a certain measurement time, the sensing range is increased.

Claims (7)

1. A multi-wavelength Brillouin optical time-domain analyzer, characterized in that: comprise a multi-wavelength laser, a coupler, a detection pulse optical path, a continuous pumping optical path, a detector and a signal acquisition processor; wherein the detection pulse The optical path includes a detection pulse optical modulation unit, a first erbium-doped fiber amplifier, and a first circulator, and the continuous pump optical path includes a continuous pump optical modulation unit, a second erbium-doped optical fiber amplifier, a second circulator, a Bragg grating, and a scrambler. Polarizer; the multi-wavelength laser emits continuous light with frequencies of υ ₁ , υ ₁ +Δυ,...,υ ₁ +(N-1)Δυ, Δυ is the frequency interval, N is the number of wavelengths, and N is a natural number; the continuous light passes through The coupler is respectively input into the detection pulse optical path and the continuous pump optical path; where: On the detection pulse light path, the continuous light is modulated into multi-wavelength detection pulse light by the detection pulse light modulation unit, and the multi-wavelength detection pulse light is amplified by the first erbium-doped fiber amplifier, and then injected into the measured transmission through the first circulator. One end of the sensing fiber; On the continuous pump light path, the continuous light is subjected to double sideband modulation by the continuous pump light modulation unit to obtain continuous light with a frequency shifted up and down by _υS , that is, the frequency of the modulated continuous light is υ ₁ ±υ _S , υ ₁ +Δυ±υ _S ,…,υ ₁ +(N-1)Δυ±υ _S ; the initial value of υ _S is set to the Brillouin frequency shift corresponding to the fiber at room temperature and in the relaxed state, which can be changed by changing the continuous pump The modulation frequency of the pump light modulation unit changes the value of _υS ; the modulated continuous pump light passes through a filter unit composed of a second circulator and a Bragg grating to filter out wavelength components with a frequency lower than that of the detection pulse light, and obtain a frequency of υ ₁ +υ _S ,υ ₁ +Δυ+υ _S ,…,υ ₁ +(N-1)Δυ+υ _S continuous pumping light, the pumping light is injected into the sensor fiber under test after passing through the scrambler another side; In the sensing fiber under test, N pairs of detection pulsed light and continuous pumping light interact respectively. After the interaction, the signal of the continuous light is output to the detector through the first circulator, and after photoelectric conversion by the detector, it is sent to the The signal acquisition processor obtains the time-domain trace corresponding to a certain frequency in the Brillouin scattering spectrum on the fiber; by changing υ _S at equal intervals, the Brillouin scattering spectrum on the entire measured sensing fiber is obtained, and then the Brillouin scattering spectrum on the fiber is obtained. temperature and strain distribution. 2. A kind of multi-wavelength Brillouin optical time-domain analyzer according to claim 1, characterized in that: the detection pulse optical modulation unit comprises a pulse generator and an optical modulator, wherein the pulse generator and optical The modulation signal input end of the modulator is connected, and the optical modulator is an electro-optic modulator or an acousto-optic modulator. 3. A kind of multi-wavelength Brillouin optical time-domain analyzer according to claim 1, characterized in that: said continuous pump light modulation unit comprises microwave source and electro-optic modulator, wherein said microwave source and electro-optic modulator The modulation signal input end of the device is connected to control the size of the frequency shift υ _S required by the continuous pumping of the optical modulation unit. 4. A multi-wavelength Brillouin optical time-domain analyzer according to claim 1, characterized in that: the detector is a conventional intermediate frequency detector with a bandwidth of about several hundred megahertz. 5. A multi-wavelength Brillouin optical time-domain analyzer according to claim 1, characterized in that: the signal acquisition processor is an oscilloscope or a spectrum analyzer, or a device consisting of an acquisition card and a computer. 6. A multi-wavelength Brillouin optical time-domain analyzer according to claim 1, characterized in that: the wavelength range corresponding to the frequency interval Δυ of the continuous light emitted by the multi-wavelength laser is [0.01nm, 0.1nm nm]. 7. a kind of multi-wavelength Brillouin optical time-domain analyzer according to claim 1, is characterized in that: the value range of described υ _S is relevant with measured temperature and strain range, specifically as follows: If the Brillouin frequency shift of the optical fiber at room temperature T ₀ and the relaxed state ε ₀ is υ _B0 , and the measured temperature is T ₀ +ΔT, then the value range of υ _S is: [υ _B0 +ΔT·1MHz/°C-100MHz,υ _B0 +ΔT·1MHz/°C+100MHz]; The measured strain is ε ₀ +Δε, then the value range of υ _S is: [υ _B0 +Δε·5×10 ⁴ MHz-100MHz,υ _B0 +Δε·5×10 ⁴ MHz+100MHz].

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