CN105784190B - A Differential Temperature Sensor Based on Stimulated Brillouin Effect - Google Patents

Abstract

The invention provides a differential temperature sensor based on the stimulated Brillouin effect. The continuous light generated by the light generation unit passes through the first modulation and amplification unit to obtain a signal including Stokes light and anti-Stokes light, and then The phase modulation signal is generated by the second modulation and amplification unit, and the modulation signal filters out the Stokes light and the anti-Stokes light through the filter, and the Stokes light passes through the delay fiber and the anti-Stokes light After the 3dB coupler synthesizes one optical signal, it passes through the polarizer to extract the polarized light. The extracted polarized light passes through the third modulation and amplification unit to obtain the pump pulse light, and then injects it into the beginning of the sensing fiber; the detection light on the other side is disturbed. The polarizer passes through an isolator and enters from the end of the sensing fiber. After being stimulated by the Brillouin action with the pump pulse light in the fiber, it passes through the circulator and is converted into an electrical signal by the photodetector. The invention can realize higher temperature resolution and longer sensing distance under the premise of high spatial resolution.

Description

A Differential Temperature Sensor Based on Stimulated Brillouin Effect

technical field

The invention relates to the technical field of temperature or stress sensors, in particular to a differential temperature sensor based on the stimulated Brillouin effect.

Background technique

The distributed optical fiber temperature and stress sensing system based on the stimulated Brillouin effect uses light waves as sensing signals and optical fibers as the transmission medium to sense and detect external measured temperature or stress signals. It not only has the advantages of general optical fiber sensors, Moreover, the continuous distribution information of temperature or stress with time and space can be obtained at the same time. Because the optical fiber itself has no electricity, small size, light weight, easy bending, anti-electromagnetic interference, and good anti-radiation performance, it is especially suitable for use in harsh environments such as flammable, explosive, and strong electromagnetic interference, making it suitable for future smart grids. , Oilfield pipeline safety monitoring, communication line intrusion warning and other important fields have a wide range of application requirements.

At present, sensing systems based on the stimulated Brillouin effect mainly include: Brillouin Optical Time Domain Reflectometer (BOTDR), Brillouin Optical Time Domain Analysis (BOTDA), and Brillouin Optical Frequency Domain Analysis (BOFDA). Among them, BOTDA has been widely concerned and researched for its high measurement accuracy and short response time. The basic principle can be summarized as follows: the pump pulse light with a fixed frequency difference and the continuous probe light transmitted in the opposite direction cause the refractive index of the fiber to fluctuate periodically with time and space through the electrostrictive effect at the place where the fiber meets, thereby generating stimulated Acoustic wave field, under the action of the acoustic wave field, energy transfer occurs between the pump light and the probe light, forming stimulated Brillouin scattering. The Lorentzian gain spectrum of continuous light under different frequency differences is obtained by continuously sweeping the frequency. The gain spectrum reaches a maximum value at the Brillouin frequency shift. Experiments have found that the Brillouin frequency shift has a strong relationship with temperature or stress. linear correlation. Therefore, as long as the change of the Brillouin frequency shift in the optical fiber is detected, the distribution of temperature or stress on the optical fiber can be obtained. The main technical indicators that need to be solved to realize the system include: spatial resolution, temperature resolution, measurement time, and measurement distance.

In order to effectively improve the above four indicators, various improvement schemes based on the traditional BOTDA system have emerged in recent years. It mainly includes: pre-pumping method, this method pre-injects a long pulse with low power before the pump pulse enters the sensing fiber, so that before the pump pulse arrives, the pre-pulse has interacted with the probe light to produce a stable State phonons. This method effectively breaks through the limitation of the phonon relaxation time on the spatial resolution and improves the spatial resolution; the dark pulse method, contrary to the bright pulse, has a stronger pump power when there is no pulse, and the pump has a stronger power when there is a pulse. When the pump has very low power. In this way, before the arrival of the dark pulse, the phonons will flood the entire sensing fiber, and the detection light will get the sum of the Brillouin gain of the entire fiber. Once the dark pulse arrives, the detection light will lose the Brillouin gain corresponding to the dark pulse part, In order to achieve higher spatial resolution; π pulse method, this method is similar to the dark pulse method, except that the dark pulse part is replaced by a π phase pulse with the same power as other parts. Similarly, when the π pulse arrives, what the probe light lacks is not only the Brillouin gain corresponding to the dark pulse part, but also the gain brought by the reflection of the π pulse superimposed on the probe light, and its signal-to-noise ratio has a significant decrease The improvement is about twice that of the dark pulse; the differential pulse pair method, that is, two pairs of pulses with a small pulse width difference are used to measure the traditional BOTDA scheme twice, and the difference between the two measured signals is the corresponding small differential pulse. Brillouin gain. This scheme can theoretically obtain the ultimate spatial resolution, and avoid the problem of broadening of the Brillouin gain spectrum and the limitation of phonon relaxation caused by short pulses.

In the course of realizing the present invention, the inventor finds that there are at least the following problems in the prior art:

In the traditional BOTDA system, due to the limitation of phonon relaxation, the pulse width cannot be smaller than the phonon relaxation time, otherwise the phonon will not reach a steady state, resulting in a decrease in signal-to-noise ratio, broadening of the Brillouin gain spectrum, and frequency The resolution is reduced, which greatly limits the further improvement of the spatial resolution. The pre-pumping method solves the limitation of phonon relaxation to a certain extent by pre-pumping a pulse in advance, but the sensing distance is limited, and the long-distance sensing will cause the Brillouin gain of the pulse base to be greater than the pulse itself. gain. In the dark pulse method, almost no phonons are excited between the pump pulse and the probe light in the dark pulse, resulting in a loss of Brillouin gain due to the lack of phonons in a period of time after the dark pulse, that is, " secondary echo", which in turn will increase the error in calculating the Brillouin frequency shift. Although the signal-to-noise ratio of the pulse method is twice as high as that of the dark pulse, it still suffers from the same defects as the dark pulse, which affects the practicability of the system. As for the differential pulse pair method, high spatial resolution and frequency resolution can indeed be obtained, as well as long-distance sensing, but due to the need to measure twice, it takes a long time, and its response time is twice that of traditional BOTDA.

Contents of the invention

(1) Technical problems to be solved

The invention proposes a differential temperature sensor based on the stimulated Brillouin effect, which simultaneously realizes high spatial resolution and long measurement distance sensing, and realizes higher frequency resolution.

(2) Technical solution

In order to solve the above technical problems, the present invention provides a differential temperature sensor based on the stimulated Brillouin effect, including:

A light generation unit for generating pump light and probe light, a first modulation and amplification unit, a second modulation and amplification unit, a filter, a delay fiber, a 3dB coupler, a polarizer, a third modulation and amplification unit, and a polarization scrambler , isolators, sensing fibers, circulators and photodetectors;

The pump light generated by the light generation unit is subjected to double sideband modulation by the first modulation and amplification unit to obtain a signal including Stokes light and anti-Stokes light, and then phase modulated by the second modulation and amplification unit, A phase modulation signal is obtained, and the phase modulation signal filters out Stokes light and anti-Stokes light through the filter, and the Stokes light passes through the delay fiber and the anti-Stokes light After the X-ray synthesizes one optical signal through the 3dB coupler, the polarized light is extracted through the polarizer, and the extracted polarized light is modulated with a preset intensity by the third modulation and amplification unit and amplified to obtain a pump pulse light, injecting the pump pulse light into the first end of the sensing fiber;

The probe light generated by the light generation unit is injected into the other end of the sensing fiber through the isolator after passing through the polarization scrambler, and is stimulated with the pump pulse light in the sensing fiber. After the deep action, it is transmitted to the photodetector through the circulator, and is converted into an electrical signal by the photodetector.

Preferably, the differential temperature sensor based on the stimulated Brillouin effect further includes an oscilloscope connected to the output terminal of the photodetector for outputting and displaying the electrical signal formed by the photodetector.

Preferably, the light generating unit includes a laser and a fiber coupler connected in sequence, the laser is used to emit laser light with a wavelength of 1550nm and a power of 15.5dBm, and the fiber coupler is used to split the laser light emitted by the laser into pump light and probe light.

Preferably, the optical splitting ratio of the fiber coupler is 10:90.

Preferably, the first modulation and amplification unit includes a first electro-optic modulator and a first optical fiber amplifier connected in sequence;

The first electro-optic modulator is used to modulate the pumping light into a carrier-suppressed double-sideband signal, the double-sideband signal includes Stokes light and anti-Stokes light, and the double-sideband signal passes through the first The fiber amplifier performs signal amplification.

Preferably, the second modulation and amplification unit includes a second electro-optic modulator and a second optical fiber amplifier connected in sequence;

The second electro-optic modulator is used to phase-modulate the double-sideband signal output by the first modulation and amplifying unit, and the phase-modulated signal is amplified through the second optical fiber amplifier.

Preferably, the third modulation and amplification unit includes a third electro-optic modulator and a third optical fiber amplifier connected in sequence;

The third electro-optic modulator is used to perform intensity modulation with a width of 60 ns on the polarized light extracted by the polarizer to obtain pump pulse light, and the pump pulse light is amplified by a third optical fiber amplifier.

Preferably, the differential temperature sensor based on the stimulated Brillouin effect further includes several polarization controllers, and the several polarization controllers are used to control the Stokes light and the anti-Stokes light to keep the same The peak power and polarization state enter the third electro-optic modulator.

Preferably, the sensing fiber is a single-mode fiber.

(3) Beneficial effects

The differential temperature sensor based on the stimulated Brillouin effect provided by the present invention enables the sensor to only detect the differential amount of temperature change on the optical fiber, that is to say, wherever there is a temperature change, the detection light will experience Brillouin gain, Whereas when there is no temperature change, the difference in Brillouin gain experienced by the probe light remains zero. And without increasing the measurement time, the invention can realize high spatial resolution and long measurement distance sensing at the same time, more importantly, it is extremely sensitive to temperature changes, and can realize higher frequency resolution.

Description of drawings

The features and advantages of the present invention will be more clearly understood by referring to the accompanying drawings, which are schematic and should not be construed as limiting the invention in any way. In the accompanying drawings:

Fig. 1 is a structural block diagram of a differential temperature sensor based on the stimulated Brillouin effect proposed by the present invention;

Fig. 2 is a schematic diagram of the working principle of a differential temperature sensor based on the stimulated Brillouin effect proposed by the present invention;

FIG. 3 is an experimental scheme diagram of a differential temperature sensor based on the stimulated Brillouin effect proposed by an embodiment of the present invention;

Figure 4 (a) is a schematic diagram of the three-dimensional Brillouin gain spectrum obtained by scanning at a frequency interval of 2KHz in an embodiment of the present invention;

Fig. 4 (b) is a three-dimensional diagram of the Brillouin gain obtained by scanning at a frequency interval of 2KHz as a function of frequency and position in an embodiment of the present invention;

Figure 5(a) is a schematic diagram of a three-dimensional Brillouin gain spectrum obtained by simulation when the Brillouin frequency shift difference between the temperature change region and the temperature constant region is 1 MHz in an embodiment of the present invention;

Figure 5(b) is a schematic diagram of the three-dimensional Brillouin gain spectrum obtained by simulation when the Brillouin frequency shift difference between the temperature changing region and the temperature constant region is 1MHz in the existing π pulse method

Fig. 6 is the time-domain curve of Brillouin gain at three typical frequencies at the end (at 13.7m) of the temperature variation region in an embodiment of the present invention;

Fig. 7 (a) is the Brillouin gain spectrum corresponding to the Brillouin frequency shift difference at 13.7m between the embodiment of the present invention and the existing π-pulse method for different temperature change regions and temperature constant regions;

Fig. 7(b) is a schematic diagram of the Brillouin frequency shift in the temperature change region obtained through fitting calculation according to the embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Fig. 1 is a structural block diagram of a differential temperature sensor based on the stimulated Brillouin effect proposed by the present invention, as shown in Fig. 1, including:

A light generation unit 1 for generating pump light and probe light, a first modulation amplifying unit 2, a second modulation amplifying unit 3, a filter 4, a delay fiber 5, a 3dB coupler 6, a polarizer 7, a third Modulation and amplification unit 8, polarization scrambler 9, isolator 10, sensing fiber 11, circulator 12 and photodetector 13;

The pump light generated by the light generation unit 1 is subjected to double-sideband modulation by the first modulation and amplification unit 2 to obtain a signal containing Stokes light and anti-Stokes light, and then the second modulation and amplification unit 3 performs Phase modulation to obtain a phase modulation signal, the phase modulation signal filters out Stokes light and anti-Stokes light through the filter 4, and the Stokes light passes through the delay fiber 5 and The anti-Stokes light synthesizes one optical signal through the 3dB coupler 6 and then passes through the polarizer 7 to extract polarized light, and the extracted polarized light is preset through the third modulation and amplification unit 8 Modulating and amplifying the intensity to obtain pump pulse light, injecting the pump pulse light into the first end of the sensing fiber 11;

The probe light generated by the light generation unit 1 is injected into the other end of the sensing fiber 11 through the isolator 10 after passing through the polarization scrambler 9 , and is combined with the pump pulse light in the sensing fiber 11 After the stimulated Brillouin action occurs, it is transmitted to the photodetector 13 through the circulator 12, and is converted into an electrical signal by the photodetector 13.

Fig. 2 is a schematic diagram of the working principle of a differential temperature sensor based on the stimulated Brillouin effect proposed by the present invention;

As shown in Figure 2, the working principle of the differential temperature sensor based on the stimulated Brillouin effect is as follows:

The pump light containing the anti-Stokes frequency v ₀ +f _m and the Stokes frequency v ₀ -f _m is injected from a section of the fiber, and they are phase-modulated at the same time, and are divided into two paths by the filter, so that one side band Delay T relative to the other sideband, and then adjust the polarization controllers on both sidebands to keep their peak power and polarization state consistent. After combining them with a 3dB coupler, they are modulated into pulses with a width of 60ns, and then passed through a fiber amplifier. The amplified and back-transmitted probe light of frequency _v0 meets the excitation Brillouin scattering in the sensing fiber. The common part of the probe light in front of the two pulses is amplified by the anti-Stokes pulse and attenuated by the Stokes pulse. The common part of the two pulses is only used to form steady-state phonons, and the influence on the carrier power is exactly Cancel each other out. In the delay T part, the probe light encounters the π-phase anti-Stokes pulse and reflects the amplification gain of the same amount of anti-Stokes pulse, so that the probe light receives the anti-Stokes pulse and the Stokes pulse at the same time. With the attenuation of the Sri Lankan pulse, the signal-to-noise ratio is significantly improved. After the delay part, both the upper and lower sidebands mainly manifest as π-phase phonons and gradually tend to a steady state, and the effects of the anti-Stokes pulse and the Stokes pulse on the carrier power gradually cancel each other out. By filtering out the carrier component through the filter, the temperature or stress information distributed along the length of the optical fiber can be obtained.

The sensing optical fiber 11 in the embodiment of the present invention is a single-mode optical fiber.

The differential temperature sensor based on the stimulated Brillouin effect proposed by the embodiment of the present invention further includes an oscilloscope connected to the output end of the photodetector for outputting and displaying the electrical signal formed by the photodetector.

In the embodiment of the present invention, the light generating unit 1 includes a laser and a fiber coupler connected in sequence, the laser is used to emit laser light with a wavelength of 1550nm and a power of 15.5dBm, and the fiber coupler is used to emit the laser light emitted by the laser Laser light is divided into pump light and probe light. Among them, the splitting ratio of the fiber coupler is 10:90.

In the embodiment of the present invention, the first modulation and amplification unit 2 includes a first electro-optic modulator and a first optical fiber amplifier connected in sequence;

The first electro-optic modulator is used to modulate the pumping light into a carrier-suppressed double-sideband signal, the double-sideband signal includes Stokes light and anti-Stokes light, and the double-sideband signal passes through the first The fiber amplifier performs signal amplification.

In the embodiment of the present invention, the second modulation and amplification unit 3 includes a second electro-optic modulator and a second optical fiber amplifier connected in sequence;

The second electro-optic modulator is used to phase-modulate the double-sideband signal output by the first modulation and amplifying unit, and the phase-modulated signal is amplified through the second optical fiber amplifier.

In the embodiment of the present invention, the third modulation and amplification unit 8 includes a third electro-optic modulator and a third optical fiber amplifier connected in sequence; intensity modulation to obtain pump pulse light, and the pump pulse light is amplified by the third optical fiber amplifier.

The differential temperature sensor based on the stimulated Brillouin effect proposed in the embodiment of the present invention also includes several polarization controllers, and the several polarization controllers are used to control the Stokes light and anti-Stokes light Keep the same peak power and polarization state entering the third electro-optic modulator.

The technical solution proposed by the present invention will be described in detail below through specific embodiments.

FIG. 3 is an experimental scheme diagram of a differential temperature sensor based on the stimulated Brillouin effect proposed by an embodiment of the present invention.

The embodiment of the present invention is shown in Figure 3. A narrow-linewidth laser with a wavelength of 1550nm emits laser light of 15.5dBm and is divided into two paths by a 10:90 fiber coupler. The upper path is used as pump light, and the lower path is used as probe light. . The continuous pump light on the way is first modulated by the first electro-optic modulator (EOM1) into a carrier-suppressed double-sideband signal, that is, light containing Stokes and anti-Stokes frequencies, which is amplified by the first fiber amplifier (EDFA1) The phase is modulated by the second electro-optical modulator (EOM2), and then amplified by the second fiber amplifier (EDFA2), and then filtered out by a programmable filter (Wave shaper 4000S) to filter out Stokes light and anti-Stokes light respectively. Among them, the Stokes light passes through a delay fiber, and then the anti-Stokes light is synthesized through a 3dB coupler, and then passes through a polarizer, and the polarization controllers PC1-PC5 of the two branches are respectively adjusted to maintain the same peak value. The power and polarization state enter the third electro-optic modulator (EOM3) for intensity modulation with a width of 60 ns, and the pump pulse light that comes out is amplified by the third fiber amplifier (EDFA3) and injected into the sensing fiber. On the other hand, the detection light enters from the end of the sensing fiber through an isolator through a scrambler, and undergoes a Brillouin interaction with the pump pulse light in the fiber, and then passes through a circulator, and is converted into an electrical signal by a photodetector. The signal is output to an oscilloscope.

The sensing optical fiber in the embodiment of the present invention is a common single-mode optical fiber with a length of 21.5m, and its Brillouin frequency at room temperature is 10.873GHz, wherein there is a 50cm heating zone between 13.2m and 13.7m, and the temperature ratio The room temperature is about 40 degrees higher, and its corresponding theoretical Brillouin frequency is 10.909GHz. The three-dimensional diagram of the Brillouin gain obtained after scanning at a frequency interval of 2MHz varies with position and frequency as shown in Figure 4 (a) and Figure 4 (b), and Figure 4 (a) is the embodiment of the present invention with a frequency of 2KHz The schematic diagram of the three-dimensional Brillouin gain spectrum obtained by interval scanning; Fig. 4 (b) is the three-dimensional diagram of the Brillouin gain obtained by frequency interval scanning of 2KHz with frequency and position variation for the embodiment of the present invention; By Fig. 4 (a) As can be seen in Fig. 4(b), the temperature change in the heated region is clearly detected, while the Brillouin gain of the other non-heated region is zero. In order to further demonstrate the effectiveness of the present invention, compare the three-dimensional Brillouin gain when the Brillouin frequency shift difference between the temperature change region and the temperature constant region is 1MHz between the technical scheme of the present invention and the scheme of the traditional π pulse method The spectrum is shown in Figure 5(a) and Figure 5(b), and Figure 5(a) is the three-dimensional simulation obtained when the Brillouin frequency shift difference between the temperature change region and the temperature constant region is 1MHz in the embodiment of the present invention Schematic diagram of the Brillouin gain spectrum; Figure 5(b) is a schematic diagram of the three-dimensional Brillouin gain spectrum obtained by simulation when the Brillouin frequency shift difference between the temperature change region and the temperature constant region is 1MHz in the existing π-pulse method; Fig. 4 (a) and Fig. 5 (a), it can be seen that the three-dimensional Brillouin gain spectrum obtained based on the differential temperature sensor based on the stimulated Brillouin effect proposed by the present invention is reliable, and it has also been demonstrated from the simulation feasibility of the invention. It can be seen from the comparison of Fig. 5(a) and Fig. 5(b), that the differential temperature sensor based on the stimulated Brillouin effect proposed by the present invention only detects the differential gain of the temperature change, and automatically filters out the DC part Gain, compared with other traditional schemes that simultaneously detect the DC part gain and the differential gain of the temperature change, effectively improves the signal-to-noise ratio. And, from these two figures, it can also be seen that in the case of a very small temperature change, such as a frequency offset of 1 MHz, the traditional π pulse method has been unable to detect the region of temperature change, but the present invention can quickly Changes in temperature are clearly detected. Therefore, the differential temperature sensor based on the stimulated Brillouin effect proposed by the present invention can effectively detect small temperature changes in the sensing fiber.

Fig. 6 is the time-domain curve of Brillouin gain at three typical frequencies at the end of the temperature change (at 13.7m) in the embodiment of the present invention, as shown in Fig. 6, for different frequency offsets, the Brillouin gain detected by the present invention The time-domain curve of the gain is anti-symmetrical. Compared with the single-peak Lorenz type, the fitting accuracy is higher, and the Brillouin frequency calculation is more accurate, and its peak gain increases significantly with the frequency offset. However, the traditional π-pulse method already presents a Lorentz-type gain spectrum with a high signal-to-noise ratio when there is no temperature change. As the frequency shifts, the Lorentz-type gain spectrum only shifts slightly. In the presence of system noise, it is difficult to accurately identify the corresponding Brillouin frequency of the two at the peak gain.

Fig. 7 (a) is the Brillouin gain spectrum corresponding to the Brillouin frequency shift difference at 13.7m in different temperature change regions and temperature constant regions for the embodiment of the present invention and the existing π pulse method; Fig. 7( b) is a schematic diagram of the Brillouin frequency shift in the temperature change region obtained through fitting calculation according to the embodiment of the present invention. As shown in Figure 7, the gain spectrum corresponding to the Brillouin frequency shift difference at z=13.7m in different temperature change regions and temperature constant regions in Fig. 7(a), wherein the solid line is the result of the present invention, and the dotted line is the result of the traditional π-pulse method; in order to reflect the spatial resolution of this example, Fig. 7(b) compares the curves from 10% to 90 % power response time, it can be concluded that the spatial resolution in our proposed scheme really only depends on the phase delay difference of the two pump pulses.

The differential temperature sensor based on the stimulated Brillouin effect provided by the present invention simultaneously realizes the main technical indicators of an ideal distributed Brillouin temperature sensor, including: high spatial resolution, high frequency resolution, long-distance measurement and Normal measurement time, and at the same time, because the invention only detects the relative amount of temperature change, it has higher detection efficiency and temperature resolution, which greatly promotes the practical use of Brillouin temperature or stress sensors.

The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Those of ordinary skill in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all Equivalent technical solutions also belong to the category of the present invention, and the scope of patent protection of the present invention should be defined by the claims.

Claims (9)

1. a kind of differential type temperature sensor based on stimulated Brillouin effect characterized by comprising

Unit, the first modulation amplifying unit, the second modulation amplifying unit, filtering are generated for generating pump light and detecting the light of light Device, time delay optical fiber, three-dB coupler, the polarizer, third modulation amplifying unit, scrambler, isolator, sensor fibre, circulator with And photodetector；

The light generates the pump light that unit generates Then the signal of stokes light and anti-Stokes light carries out phase-modulation by the second modulation amplifying unit, obtains phase Modulated signal, the phase modulated signal filter out stokes light and anti-Stokes light, this described support by the filter Ke Si light is after the time delay optical fiber and the anti-Stokes light after three-dB coupler synthesis all the way optical signal by passing through The extraction that the polarizer carries out polarised light is crossed, the polarised light extracted is modulated amplifying unit by the third and preset by force The modulation and amplification of degree obtain pumping pulse light, and the pumping pulse light is injected to the first end of the sensor fibre；

The light generates the detection light that unit generates and injects the sensor fibre by the isolator after the scrambler The other end, passed after excited Brillouin effect occurs with the pumping pulse light in the sensor fibre by the circulator It is defeated to arrive the photodetector, electric signal is converted by the photodetector.

2. the differential type temperature sensor according to claim 1 based on stimulated Brillouin effect, which is characterized in that also wrap Oscillograph is included, is connect with the output end of the photodetector, the electric signal for being formed to the photodetector carries out defeated It shows out.

3. the differential type temperature sensor according to claim 1 or 2 based on stimulated Brillouin effect, which is characterized in that It includes sequentially connected laser and fiber coupler that the light, which generates unit, and the laser is for launch wavelength 1550nm, power are the laser of 15.5dBm, and the fiber coupler is used to the laser that the laser emits being divided into pump light With detection light.

4. the differential type temperature sensor according to claim 3 based on stimulated Brillouin effect, which is characterized in that described The splitting ratio of fiber coupler is 10:90.

5. the differential type temperature sensor according to claim 1 or 2 based on stimulated Brillouin effect, which is characterized in that The first modulation amplifying unit includes sequentially connected first electrooptic modulator and the first fiber amplifier；

First electrooptic modulator is used to pump light being modulated to suppressed-carrier double side band signal, the double-sideband signal packet Containing stokes light and anti-Stokes light, the double-sideband signal carries out signal amplification by first fiber amplifier.

6. the differential type temperature sensor according to claim 1 or 2 based on stimulated Brillouin effect, which is characterized in that The second modulation amplifying unit includes sequentially connected second electrooptic modulator and the second fiber amplifier；

Second electrooptic modulator is used to carry out phase-modulation to the double-sideband signal of the first modulation amplifying unit output, Signal after phase-modulation carries out signal amplification by second fiber amplifier.

7. the differential type temperature sensor according to claim 1 or 2 based on stimulated Brillouin effect, which is characterized in that The third modulation amplifying unit includes sequentially connected third electrooptic modulator and third fiber amplifier；

The polarised light that the third electrooptic modulator is used to extract the polarizer carries out the intensity modulated that width is 60ns, obtains To pumping pulse light, the pumping pulse light is amplified by third fiber amplifier.

8. the differential type temperature sensor according to claim 7 based on stimulated Brillouin effect, which is characterized in that also wrap Several Polarization Controllers are included, several described Polarization Controllers are protected for controlling the stokes light and anti-Stokes light It holds identical peak power and polarization state enters the third electrooptic modulator.

9. the differential type temperature sensor according to claim 1 or 2 based on stimulated Brillouin effect, which is characterized in that The sensor fibre is single mode optical fiber.