CN100491924C - Ultra-long-range distributed fiber-optic Raman and Brillouin photonic sensors - Google Patents

Abstract

The invention discloses super-far distributed fiber Raman and Brillouin photon sensors; by using the stimulated Raman scattering effect of fiber, the self Raman scattering effect of fiber, the Brillouin scattering effect of fiber and the light time-field reflection principle, distributed fiber Raman photon temperature sensors, distributed fiber Brillouin photon strain sensors and distributed fiber Raman amplifier are integrated together. Fiber consumption is overcome by using the gain of amplifier, and strengths of self Raman scattering light and Brillouin scattering light in fiber is enhanced, the signal to noise ratio of the system of distributed fiber Raman photon sensor and distributed fiber Brillouin photon strain sensor is enhanced, meanwhile, the transmission distances of distributed fiber Raman photon sensor and distributed fiber Brillouin photon strain sensor are increased, finally, the temperature and stress measuring accuracy is enhanced.

Description

Ultra-long-range distributed fiber-optic Raman and Brillouin photonic sensors

technical field

The invention relates to an ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor, belonging to the technical field of optical fiber sensors.

Background technique

In the field of distributed optical fiber sensors, there are distributed optical fiber Raman photon temperature sensors using the temperature effect of spontaneous Raman scattering of optical fibers at home and abroad; there are distributed optical fiber strain and temperature sensors using the Brillouin scattering effect abroad (Xiaoyi Bao, University of Ottawa, Canada Bao, Newson, University of Southampton, UK), and distributed optical fiber Brillouin strain and temperature sensors with integrated fiber Raman amplifiers (Newson, University of Southampton, UK). Although distributed optical fiber Brillouin photon sensors have a broad application market, due to the narrow spectral bandwidth of optical fiber Brillouin scattering, the accuracy of measuring strain and temperature using the intensity ratio of optical fiber Brillouin scattering light is very low.

Contents of the invention

The purpose of the present invention is to provide an ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor which is beneficial to improve the measurement distance, temperature and strain measurement accuracy.

In order to achieve the above object, the technical solution of the present invention is: the ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor includes distributed optical fiber Raman photon temperature sensor, distributed optical fiber Brillouin photon strain sensor, distributed optical fiber Raman Amplifier and 100km single-mode fiber, distributed fiber Raman photon temperature sensor consists of semiconductor pulse laser, multiplexer, one-way device, 1 x 2 fiber bidirectional coupler, fiber grating narrow-band reflection filter, wavelength division multiplexer, reflection Composed of Stokes Raman scattered light filter, Stokes Raman scattered light filter and photoelectric direct detection system, distributed optical fiber Brillouin photonic strain sensor consists of external cavity semiconductor narrowband pulsed fiber laser, wave splitter, Composed of the first narrowband fiber grating filter, the second narrowband fiber grating filter, a circulator and a coherent detection system, the distributed fiber Raman amplifier is composed of a pump fiber laser and a pump-signal fiber coupler; a semiconductor pulse laser It is connected to one input end of the wave combiner, and the external cavity semiconductor narrow-band pulsed fiber laser is connected to the input end of the wave splitter. The laser output from the wave splitter is divided into two paths, one of which is connected to the other input end of the wave combiner, The other path is connected to an input end of the circulator through the second narrow-band fiber grating filter, and the laser light of the semiconductor pulse laser output by the multiplexer and the laser light of the external-cavity semiconductor narrow-band pulse fiber laser pass through the one-way device and the pump-signal fiber One input end of the coupler is connected, the other input end of the pump-signal fiber coupler is connected to the pump fiber laser, the output end of the pump-signal fiber coupler is connected to the input end of the 1 x 2 fiber bidirectional coupler, One output end of the 1 x 2 fiber bidirectional coupler is connected to a 100km single-mode fiber, the other output end of the fiber 1 x 2 bidirectional coupler is connected to the input end of the fiber grating narrowband reflection filter, and the output of the fiber grating narrowband reflection filter is The end is connected to the input end of the wavelength division multiplexer, and the back anti-Stokes Raman scattered light and the Stokes Raman scattered light of each section of the optical fiber output by the wavelength division multiplexer are respectively passed through the anti-Stokes The Slarman scattered light filter and the Stokes Raman scattered light filter are connected to the photoelectric direct detection system, and the back Brillouin scattered light of each section of the optical fiber output by the wavelength division multiplexer passes through the first narrow-band fiber grating The optical filter is connected to the other input end of the circulator, and the circulator beats the local light from the first narrowband fiber grating filter and the signal light from the second narrowband fiber Bragg grating filter and then enters the coherent detection system .

It works as follows:

与温度的关系(见式1)，可以得到光纤上各段处的温度，从而获得空间的温度场分布T。The laser generated by semiconductor pulse laser, external cavity semiconductor narrow-band pulse fiber laser and pump fiber laser is coupled by pump-signal fiber coupler and 1 x 2 fiber bidirectional coupler, and then input into 100km single-mode fiber, each section of 100km single-mode fiber The generated amplified back Rayleigh scattered light, back Brillouin scattered light and Stokes and anti-Stokes back Raman scattered light are input to fiber grating narrowband reflection filter through 1 x 2 fiber bidirectional coupler The device uses fiber grating narrow-band reflection filters to suppress the back Rayleigh scattered light generated by the pump fiber laser in the 100km single-mode fiber, and at the same time allows the amplified spontaneous Raman scattered light generated on each section of the 100km single-mode fiber and Brillouin scattered light passes through and enters the fiber optic wavelength division multiplexer. Here, the pump fiber laser is combined with the pump-signal fiber coupler and 100km single-mode fiber to form a distributed fiber Raman amplifier with adjustable gain. The laser light of the laser is amplified, and at the same time, the back spontaneous Raman scattered light and the back Brillouin scattered light of each segment on the fiber are enhanced. The back spontaneous Raman scattered light of each section of the optical fiber output by the wavelength division multiplexer is divided into two paths, one is anti-Stokes Raman scattered light, which is input to the photoelectric direct detection system through the anti-Stokes scattered light filter , the other way is the Stokes Raman scattered light, which is input to the photoelectric direct detection system through the Stokes Raman scattered light filter, and the back anti-Stokes Raman scattered light measured by the photoelectric direct detection system After photoelectric conversion, it is converted into an electrical signal V _a , and the measured back-to-Stowe Raman scattered light is converted into an electrical signal V _s through photoelectric conversion. By measuring the ratio of the two Ratio from electrical signal

The relationship with temperature (see formula 1), the temperature at each section of the optical fiber can be obtained, so as to obtain the spatial temperature field distribution T.

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; h\&Delta;v</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

v _a =v ₀ +Δv

v _s =v ₀ -Δv

In the formula, k is Boltzmann's constant, h is Planck's constant, v _a and v _s are anti-Stokes and Stokes Raman scattering frequencies respectively, v ₀ is the laser of semiconductor pulsed laser, Δv is The frequency of the fiber's molecular vibrational levels.

The strain- and temperature-modulated Brillouin backscattered light of each segment of the optical fiber output by the wavelength division multiplexer is filtered by the first narrow-band fiber grating filter, and the signal light is output to the circulator, and the signal light is combined with the circulator. The local light beat frequency of the external-cavity semiconductor narrow-band fiber laser passing through the wave splitter and the second narrow-band fiber grating filter is input to the coherent detection system for coherent detection, and the frequency shift Δv of the Brillouin scattered light is measured to obtain each section of the optical fiber strain information. The frequency shift of the fiber back to the Brillouin scattered light is modulated by the strain and temperature of the fiber. The strain and temperature of each segment of the fiber are different, and the frequency shift Δv of the Brillouin scattered light is also different.

$\mathrm{<span\; class="notranslate">\; \&Delta;v</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; nv</span>}}{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}$

where _λp is the laser wavelength of the external-cavity semiconductor narrow-band pulsed fiber laser, n is the refractive index of the fiber at the pump wavelength, v is the velocity of the elastic wave in the fiber, and changes in fiber temperature and stress can cause changes in the velocity.

The intensity of spontaneous Raman scattered light of a 100km single-mode fiber is modulated by temperature. The temperature of each section of the fiber is different, and the intensity of Raman scattered light is also different. Therefore, the spontaneous Raman scattering temperature effect of the fiber and the time domain reflection of the fiber can be used (OTDR) principle to manufacture a distributed optical fiber Raman photon temperature sensor, through which to measure the temperature of each section of the optical fiber, so as to know the temperature distribution of the space where the optical fiber is located.

The present invention determines the temperature of each segment on the optical fiber by a distributed optical fiber Raman photon temperature sensor, measures the frequency shift of each segment of the optical fiber by a distributed optical fiber Brillouin photon strain sensor to obtain the strain of each segment on the optical fiber, and obtains the strain of each segment on the optical fiber by the optical fiber time domain The principle of reflection (OTDR) locates the position of each segment of optical fiber, and obtains the stress distribution of the space where the optical fiber is located by measuring the strain of each segment on the optical fiber. In the present invention, a fiber grating narrow-band reflection filter is specially set to suppress the back Rayleigh scattered light, which can avoid the back Rayleigh scattered light caused by the pump light of the distributed optical fiber Raman amplifier from affecting the normal operation of the optical fiber Raman photon temperature sensor. Work.

The beneficial effects of the present invention are:

The invention utilizes the distributed optical fiber Raman amplifier to generate light amplification in the optical fiber, so that the semiconductor pulse laser in the distributed optical fiber Raman photon temperature sensor and the external cavity semiconductor narrowband pulsed optical fiber laser in the distributed optical fiber Brillouin photon strain sensor continuously The gain of the distributed fiber Raman amplifier can be effectively obtained, because the gain of the amplifier overcomes the fiber loss, and at the same time enhances the intensity of the back spontaneous Raman scattered light and the Brillouin scattered light in each section of the fiber, and improves the distributed fiber Raman The signal-to-noise ratio of the photonic temperature sensor and the distributed optical fiber Brillouin photonic strain sensor system increases the transmission distance of the distributed optical fiber Raman photonic temperature sensor and the distributed optical fiber Brillouin photonic strain sensor, and improves the temperature and strain. measurement accuracy. The invention skillfully utilizes the stimulated Raman scattering effect of optical fiber, spontaneous Raman scattering of optical fiber, Brillouin scattering effect of optical fiber and optical time domain reflection principle to combine distributed optical fiber Raman amplifier with distributed optical fiber Raman temperature sensor, distributed optical fiber Brillouin photonic strain sensor technology is fused together, and the position of each section of optical fiber is positioned by the principle of optical fiber time domain reflection (OTDR), realizing an ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor.

Description of drawings

Fig. 1 is a schematic diagram of the composition of the ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor of the present invention.

Detailed ways

Referring to Figure 1, the invented ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor includes distributed optical fiber Raman photon temperature sensor, distributed optical fiber Brillouin photon strain sensor, distributed optical fiber Raman amplifier and 100km single-mode Optical fiber 19, distributed optical fiber Raman photon temperature sensor consists of semiconductor pulse laser 11, multiplexer 14, one-way device 15, 1 x 2 fiber bidirectional coupler 18, fiber grating narrow-band reflection filter 20, wavelength division multiplexer 21 , an anti-Stokes scattered light filter 22, a Stokes Raman scattered light filter 23 and a photoelectric direct detection system 24, the distributed optical fiber Brillouin photonic strain sensor consists of an external cavity semiconductor narrowband pulsed fiber laser 12, The wave splitter 13, the first narrowband fiber grating filter 25, the second narrowband fiber grating filter 26, the circulator 27 and the coherent detection system 28 are composed, and the distributed fiber Raman amplifier is composed of a pumping fiber laser 16 and a pumping -The signal fiber coupler 17 is composed; the semiconductor pulse laser 11 is connected to an input end of the multiplexer 14, the external cavity semiconductor narrowband pulsed fiber laser 12 is connected to the input end of the wave splitter 13, and the laser light output by the wave splitter 13 is divided into two Road, wherein, one road is connected with the other input end of the wave combiner 14, and the other road is connected with an input end of the circulator 27 through the second narrowband fiber grating optical filter 26, the laser light of the semiconductor pulse laser of the wave combiner 14 output The laser of the external cavity semiconductor narrowband pulsed fiber laser is connected to one input end of the pump-signal fiber coupler 17 through the one-way device 15, and the pump fiber laser 16 is connected to the other input end of the pump-signal fiber coupler 17 , the output end of the pump-signal fiber coupler 17 is connected with the input end of the 1 x 2 fiber bidirectional coupler 18, and an output port of the 1 x 2 fiber bidirectional coupler 18 is connected with the 100km single-mode fiber 19, and the optical fiber 1 x 2 Another output end of the bidirectional coupler 18 is connected with the input end of the fiber grating narrowband reflective filter 20, and the output end of the fiber grating narrowband reflective filter 20 is connected with the input end of the wavelength division multiplexer 21, and the wavelength division multiplexer 21 The anti-Stokes Raman scattered light and the Stokes Raman scattered light of each section on the output optical fiber pass through the anti-Stokes scattered light filter 22 and the Stokes Raman scattered light filter 23 respectively. The photoelectric direct detection system 24 is connected, and the Brillouin scattered light of each segment on the optical fiber output by the wavelength division multiplexer 21 is connected with the other input end of the circulator 27 through the first narrow-band fiber grating filter 25, and is connected by the circulator. The detector 27 beats the local light from the first narrowband fiber grating filter 25 and the signal light from the second narrowband fiber grating filter 26 and then inputs it into the coherent detection system 28 .

In the present invention, the semiconductor pulsed fiber laser 11 can be a high-power fiber laser with a pulse width less than 30ns and a wavelength of 1550nm with a semiconductor Fabry-Peilow (FP) cavity.

In the present invention, the external-cavity semiconductor narrow-band pulsed fiber laser 12 can be an external-cavity semiconductor pulsed fiber laser with a spectral width of 10 MHz and a wavelength of 1555 nm.

In the present invention, the pumping fiber laser 16 can be a high-power tunable fiber Raman laser with a wavelength of 1455 nm.

In the present invention, the fiber grating narrow-band reflective filter 20 can be a fiber grating filter with a reflectivity>99.5%, an isolation degree>35dB, a wavelength of 1455m, and a narrow-band spectral interval of 1nm.

In the present invention, the anti-Stokes Raman scattering wave filter 22 can be a filter with a wavelength of 1450nm, a bandwidth >30nm, and an isolation >30dB.

In the present invention, the Stokes Raman scattered wave filter 23 can be a filter with a wavelength of 1660nm, a bandwidth >30nm, and an isolation >30dB.

Claims (7)

1. Ultra-long-range distributed optical fiber Raman and Brillouin photon sensor, which is characterized by distributed optical fiber Raman photon temperature sensor, distributed optical fiber Brillouin photon strain sensor, distributed optical fiber Raman amplifier and 100km single-mode optical fiber (19), the distributed optical fiber Raman photon temperature sensor consists of a semiconductor pulse laser (11), a multiplexer (14), a one-way device (15), a 1x2 fiber bidirectional coupler (18), a fiber grating narrowband reflection filter ( 20), a wavelength division multiplexer (21), an anti-Stokes Raman scattering filter (22), a Stokes Raman scattering filter (23) and a photoelectric direct detection system (24), The distributed optical fiber Brillouin photonic strain sensor consists of an external cavity semiconductor narrowband pulse fiber laser (12), a wave splitter (13), a first narrowband fiber grating filter (25), a second narrowband fiber grating filter (26 ), a circulator (27) and a coherent detection system (28), the distributed fiber Raman amplifier is made up of a pump fiber laser (16) and a pump-signal fiber coupler (17); the semiconductor pulse laser (11) and One input end of the multiplexer (14) is connected, and the external cavity semiconductor narrow-band pulse fiber laser (12) is connected with the input end of the wave splitter (13), and the laser light output by the wave splitter (13) is divided into two paths, wherein, one path Be connected with the other input end of multiplexer (14), another way is connected with an input end of circulator (27) through the second narrow-band fiber grating optical filter (26), the semiconductor pulse of multiplexer (14) output The laser of the laser and the laser of the external cavity semiconductor narrow-band pulsed fiber laser are connected to one input end of the pump-signal fiber coupler (17) through the one-way device (15), and the other of the pump-signal fiber coupler (17) The input end is connected with the pump fiber laser (16), the output end of the pump-signal fiber coupler (17) is connected with the input end of the 1x2 fiber bidirectional coupler (18), and an output of the 1x2 fiber bidirectional coupler (18) end is connected with 100km single-mode optical fiber (19), the other output end of optical fiber 1x2 bidirectional coupler (18) is connected with the input end of fiber grating narrow-band reflection filter (20), and the output of fiber grating narrow-band reflection filter (20) end is connected with the input end of the wavelength division multiplexer (21), the back anti-Stokes Raman scattered light and the Stokes Raman scattered light of each section on the optical fiber of the wavelength division multiplexer (21) output Respectively through anti-Stokes Raman scattered light filter (22) and Stokes Raman scattered light filter (23) to be connected with photoelectric direct detection system (24), the wavelength division multiplexer (21) output The Brillouin backscattered light of each section on the optical fiber is connected with the other input end of the circulator (27) through the first narrow-band fiber grating filter (25), and the light from the first narrow-band fiber grating is connected by the circulator (27). The local light of the optical filter (25) and the signal light from the second narrowband fiber grating optical filter (26) are frequency-beated and then input into the coherent detection system (28). 2. ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor according to claim 1, it is characterized in that semiconductor pulse fiber laser (11) is that pulse width is less than 30ns, and wavelength is the semiconductor Fabry-Bailuo of 1550nm Cavity high power fiber lasers. 3. ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor according to claim 1, it is characterized in that external cavity semiconductor narrowband pulse fiber laser (12) is that spectral width is 10MHz, and wavelength is the external cavity semiconductor pulse of 1555nm fiber-optic laser. 4. The ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor according to claim 1, characterized in that the pumping optical fiber laser (16) is a high-power tunable optical fiber Raman laser with a wavelength of 1455nm. 5. ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor according to claim 1, it is characterized in that fiber grating narrow-band reflection filter (20) is that the wavelength of reflectivity>99.5%, isolation degree>35dB is 1455nm , Fiber Bragg grating filter with narrow-band spectral interval of 1nm. 6. ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor according to claim 1, it is characterized in that anti-Stokes Raman scattering wave filter (22) is that wavelength is 1450nm, broadband > 30nm, isolation filter with degree>30dB. 7. ultra-long-distance distributed optical fiber Raman and Brillouin photon sensor according to claim 1, it is characterized in that the filter (23) of Stokes Raman scattering wave is that wavelength is 1660nm, bandwidth > 30nm, isolation filter with degree>30dB.

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