OCC-BOTDA / TGD-OFDR fusion system capable of simultaneously measuring multiple parameters and working method of OCC-BOTDA / TGD-OFDR fusion system

Abstract

The invention discloses an OCC-BOTDA / TGD-OFDR fusion system capable of simultaneously measuring multiple parameters and a working method of the OCC-BOTDA / TGD-OFDR fusion system, and relates to the technical field of optical fiber sensors. The system comprises a narrow linewidth laser, an optical fiber coupler, an electro-optical modulator, an optical fiber circulator, a polarization maintaining fiber bragg grating, a semiconductor optical amplifier, a random scrambler, a delay optical fiber, an erbium-doped optical fiber amplifier, an adjustable grating filter, an optical attenuator, a photoelectric balance detector, a photoelectric detector, a data acquisition card, an arbitrary waveform generator, a direct-current power supply and the like. According to the integrated OCC-BOTDA system and the TGD-OFDR system provided by the invention, simultaneous detection of vibration and temperature / strain along the line can be simultaneously realized through a single sensing optical fiber; the device has the advantages of high fusion degree and low cost, cross aliasing and power competition between pulse light are effectively avoided, and simultaneous measurement of multiple parameters is achieved; the system is high in fusion degree and low in cost.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber sensors, and in particular to an OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement and a working method thereof. Background Art

[0002] Distributed optical fiber sensors (DOFS) have the unique advantage of distributed spatial continuous measurement compared to traditional point sensors, and have broad application prospects in industrial monitoring. Distributed optical fiber sensors based on the Brillouin scattering mechanism can only be used to measure temperature and strain signals along the sensing optical fiber; distributed optical fiber sensors based on the Raman scattering mechanism can only be used to measure temperature signals along the sensing optical fiber; distributed optical fiber sensors based on the Rayleigh scattering mechanism can only be used to measure vibration signals along the sensing optical fiber; in short, no matter which DOFS is used, the measurement parameters (usually temperature, strain or vibration) are relatively limited. However, in industrial monitoring, coordinated multi-parameter measurements are urgently needed to accurately identify fault events. Summary of the invention

[0003] In view of the above problems, the present invention proposes an OCC-BOTDA / TGD-OFDR fusion system for simultaneous measurement of multiple parameters and a working method thereof.

[0004] According to one aspect of the present invention, an OCC-BOTDA / TGD-OFDR fusion system for simultaneous measurement of multiple parameters is proposed, which comprises: a narrow linewidth laser 1, a first fiber coupler 2, a first electro-optic modulator 3, a first fiber circulator 4, a polarization-maintaining fiber Bragg grating 5, a first semiconductor optical amplifier 6, a random polarization scrambler 7, a second electro-optic modulator 8, a second fiber coupler 9, a delay fiber 10, a second semiconductor optical amplifier 11, a third fiber coupler 12, a first erbium-doped fiber amplifier 13, a second fiber circulator 14, a third electro-optic modulator 15, an adjustable grating filter 16, a second erbium-doped fiber amplifier 17, a fourth fiber coupler 18, an optical attenuator 19, a fifth fiber coupler 20, a photoelectric balanced detector 21, a photoelectric detector 22, a data acquisition card 23, an arbitrary waveform generator 24, and a DC power supply 25; wherein,

[0005] The optical signal output end of the narrow linewidth laser 1 is connected to the optical signal input end of the first optical fiber coupler 2, and the optical signal output end of the first optical fiber coupler 2 is respectively connected to the optical signal input end of the first electro-optic modulator 3, the optical signal input end of the optical attenuator 19, and the optical signal input end of the second electro-optic modulator 8;

[0006] The optical signal output end of the first electro-optic modulator 3 is connected to the first port 4-1 of the first optical fiber circulator 4, the second port 4-2 of the first optical fiber circulator 4 is connected to the polarization-maintaining fiber Bragg grating 5, the third port 4-3 of the first optical fiber circulator 4 is connected to the optical signal input end of the first semiconductor optical amplifier 6, the optical signal output end of the first semiconductor optical amplifier 6 is connected to the optical signal input end of the random polarization scrambler 7; the optical signal output end of the random polarization scrambler 7 is connected to the optical signal input end of the third optical fiber coupler 12;

[0007] The optical signal output end of the second electro-optic modulator 8 is connected to the optical signal input end of the second fiber coupler 9, the optical signal output end of the second fiber coupler 9 is respectively connected to one end of the delay fiber 10 and the optical signal input end of the third electro-optic modulator 15, the other end of the delay fiber 10 is connected to the optical signal input end of the second semiconductor optical amplifier 11, the optical signal output end of the second semiconductor optical amplifier 11 is connected to the optical signal input end of the third fiber coupler 12; the optical signal output end of the third electro-optic modulator 15 is connected to the optical signal input end of the tunable grating filter 16, the optical signal output end of the tunable grating filter 16 is connected to the optical signal input end of the second erbium-doped fiber amplifier 17, and the optical signal output end of the second erbium-doped fiber amplifier 17 is connected to one end of the sensing fiber;

[0008] The optical signal output end of the third optical fiber coupler 12 is connected to the optical signal input end of the first erbium-doped fiber amplifier 13, the optical signal output end of the first erbium-doped fiber amplifier 13 is connected to the first port 14-1 of the second optical fiber circulator 14, and the second port 14-2 of the second optical fiber circulator 14 is connected to the other end of the sensing optical fiber; the third port 14-3 of the second optical fiber circulator 14 is connected to the optical signal input end of the fourth optical fiber coupler 18, and the optical signal output end of the fourth optical fiber coupler 18 is respectively connected to the optical signal input end of the fifth optical fiber coupler 20 and the optical signal input end of the photodetector 22;

[0009] The optical signal output end of the optical attenuator 19 is connected to the optical signal input end of the fifth optical fiber coupler 20, the optical signal output end of the fifth optical fiber coupler 20 is connected to the optical signal input end of the photoelectric balance detector 21, and the electrical signal output end of the photoelectric balance detector 21 and the electrical signal output end of the photoelectric detector 22 are respectively connected to the data acquisition card 23;

[0010] The RF output end of the arbitrary waveform generator 24 is respectively connected to the RF signal input end of the first electro-optic modulator 3, the RF signal input end of the first semiconductor optical amplifier 6, the RF signal input end of the second electro-optic modulator 8, the RF signal input end of the second semiconductor optical amplifier 11, the RF signal input end of the third electro-optic modulator 15, and the trigger signal input end of the data acquisition card 23;

[0011] The output end of the DC power supply 25 is connected to the bias voltage input end of the first electro-optic modulator 3 , the bias voltage input end of the second electro-optic modulator 8 , and the bias voltage input end of the third electro-optic modulator 15 , respectively.

[0012] Furthermore, the narrow linewidth laser 1 is a polarization-maintaining laser with an output power of 40 mW, a wavelength of 1550.14 nm, and a linewidth of 1 kHz.

[0013] Furthermore, the first optical fiber coupler 2 is a 1×3 polarization-maintaining coupler with a splitting ratio of 33:33:33; the second optical fiber coupler 9 and the third optical fiber coupler 12 are 1×2 polarization-maintaining couplers with a splitting ratio of 50:50; the fourth optical fiber coupler 19 is a 1×2 coupler with a splitting ratio of 50:50; and the fifth optical fiber coupler 21 is a 2×2 coupler with a splitting ratio of 50:50.

[0014] Furthermore, the first electro-optic modulator 3 and the third electro-optic modulator 16 are polarization-maintaining modulators with a bandwidth of 10 GHz and an extinction ratio of 30 dB; the second electro-optic modulator 8 is a polarization-maintaining modulator with a bandwidth of 2 GHz and an extinction ratio of 30 dB.

[0015] Furthermore, the central wavelength of the polarization-maintaining fiber Bragg grating 5 is 1550.08 nm, and the 3dB reflection bandwidth is 0.08 nm.

[0016] Furthermore, the extinction ratios of the first semiconductor optical amplifier 6 and the second semiconductor optical amplifier 11 are both 45 dB.

[0017] Furthermore, the 3dB operating bandwidth of the photoelectric balanced detector 22 is 2 GHz, and the 3dB operating bandwidth of the photoelectric detector 23 is 100 MHz.

[0018] Furthermore, the sampling rate of the data acquisition card 24 is 5 GS / s, and the sampling resolution is 14 bits.

[0019] According to another aspect of the present invention, a working method of an OCC-BOTDA / TGD-OFDR fusion system for simultaneous measurement of multiple parameters is proposed. The working method is implemented based on the above-mentioned OCC-BOTDA / TGD-OFDR fusion system for simultaneous measurement of multiple parameters; the working method comprises:

[0020] The single-frequency continuous light output by the narrow linewidth laser 1 is divided into three paths, namely, upper, middle and lower paths, by the first fiber coupler 2. The upper path light is used as the pump pulse light modulation of the OCC-BOTDA system; the middle path light is used as the reference light of the TGD-OFDR system; the lower path light is used as the modulation of the optical chirp chain, and after beam splitting, it is used as the detection pulse light modulation of the TGD-OFDR system and as the detection light of the OCC-BOTDA system.

[0021] The added continuous light is intensity modulated by the first electro-optical modulator 3, and the frequency shift size is controlled by the arbitrary waveform generator 24. The double-sideband continuous light after the carrier frequency is suppressed by the DC power supply 25 is injected into the polarization-maintaining fiber Bragg grating 5 by the first fiber circulator 4 to filter out the lower sideband. The remaining upper sideband continuous light is periodically modulated into pulse light by the first semiconductor optical amplifier 6, and the polarization state is disrupted by the random polarization scrambler 7 as the pump pulse light of the OCC-BOTDA system.

[0022] The lower continuous light is subjected to linear frequency sweep modulation by the second electro-optic modulator 8, the frequency sweep range is controlled by the arbitrary waveform generator 24, and the double-sideband frequency sweep modulation is realized after the carrier frequency component is suppressed by the DC power supply 25. The modulated continuous light is divided into two upper and lower branches by the second optical fiber coupler 9: the upper branch is injected into the second semiconductor optical amplifier 11 through the delay optical fiber 10 to be periodically modulated into positive and negative chirped pulse light, which is used as the detection pulse light of the TGD-OFDR system, and then combined with the pump pulse light through the third optical fiber coupler 12, and power pre-amplified by the first erbium-doped fiber amplifier 13, and finally injected into the sensing optical fiber through the second optical fiber circulator 14; the lower double-sideband frequency sweep continuous light is subjected to frequency shift modulation by the third electro-optic modulator 15, and the high-frequency optical chirp chain filtered out by the adjustable grating filter 16 is used as the detection light of the OCC-BOTDA system, and power pre-amplified by the second erbium-doped fiber amplifier 17 and then reversely injected into the sensing optical fiber;

[0023] The back Rayleigh scattered light and high-frequency continuous light in the sensing optical fiber enter the fourth optical fiber coupler 18 through the second optical fiber circulator 14 and are divided into two parts: one part enters the fifth optical fiber coupler 20 for coherent frequency beat with the mid-path continuous light after the power is adjusted by the optical attenuator 19, and then undergoes photoelectric conversion by the photoelectric balance detector 21 and is recorded by the data acquisition card 23 as the sensing signal of the TGD-OFDR system for detecting the vibration information of the external environment along the sensing optical fiber; the other part undergoes photoelectric conversion by the photoelectric detector 22 and is recorded by the data acquisition card 23 as the sensing signal of the OCC-BOTDA system for detecting the temperature and strain information of the external environment along the sensing optical fiber.

[0024] Furthermore, the pump pulse light of the OCC-BOTDA system is expressed as:

[0025]

[0026] In the formula, A 2 is the pump pulse light E pump The amplitude of (t); T pump is the width of the pump pulse light; rect(.) is the rectangular function; ω 0 , are the angular frequency and initial phase of the continuous light output by the narrow linewidth laser 1; ω m1 is the angular frequency of the radio frequency signal output by the arbitrary waveform generator (24); and t is time.

[0027] Furthermore, the DC power supply 25 suppresses the carrier frequency component to realize double-sideband frequency sweep modulation, and the expression of the modulated continuous light is:

[0028]

[0029] In the formula, A m2 ,ω m2 , Δω s and T respectively represent the amplitude, starting frequency, bandwidth and chirp period of the chirp radio frequency signal output by the arbitrary waveform generator (24);

[0030] The expression of the positive and negative chirped pulse light, i.e., the detection pulse light of the TGD-OFDR system, is:

[0031]

[0032] In the formula, A probe is the positive and negative chirped pulse light E probe (t) amplitude; ω - =ω 0 -ω m2 ;ω + =ω 0 +ω m2 ; T probe represents the width of the chirped pulse light;

[0033] The expression of the detection light of the high-frequency optical chirp chain, namely the OCC-BOTDA system, is:

[0034]

[0035] In the formula, A occp For high frequency optical chirp chain E occp (t) amplitude; ω m3 It represents the radio frequency angular frequency that the arbitrary waveform generator 24 loads on the third electro-optic modulator 18 .

[0036] Furthermore, the sum of the radio frequency frequencies loaded by the arbitrary waveform generator 24 on the first electro-optical modulator 3, the second electro-optical modulator 8 and the third electro-optical modulator 15 satisfies the following relationship:

[0037] f B ∈(2π(ω m1 +ω m2 +ω m3 ),2π(ω m1 +ω m2 +ω m3 +Δω s )).

[0038] Furthermore, the sampling rate S of the data acquisition card 23 satisfies the following relationship:

[0039]

[0040] Wherein, c is the propagation speed of light waves in vacuum; n is the effective refractive index of the sensing optical fiber; and max represents the maximum value.

[0041] The beneficial technical effects of the present invention are:

[0042] The present invention proposes an OCC-BOTDA / TGD-OFDR fusion system for simultaneous measurement of multiple parameters and a working method thereof, which can realize simultaneous and rapid measurement of multiple parameters: the OCC-BOTDA system uses an optical chirp chain as a detection light, and the measurement speed of temperature and strain signals is limited to the length of the sensing fiber and the average number of Brillouin gain curves; the measurement speed of the TGD-OFDR system for vibration signals is limited to the length of the sensing fiber; the fusion OCC-BOTDA system and the TGD-OFDR system can simultaneously realize the measurement of vibration, temperature / strain along the line through a single sensing fiber. Simultaneous detection of changes; It has the advantages of high integration and low cost: in the fusion system, the chirped pulse light of the TGD-OFDR system and the detection light of the OCC-BOTDA system are both realized by secondary modulation based on the double-sideband optical chirp chain modulated by the same modulator; the pump pulse light of the OCC-BOTDA system and the chirped pulse light of the TGD-OFDR system are controlled by time division-frequency division multiplexing technology and are injected into the same sensing optical fiber in sequence, effectively avoiding cross-aliasing and power competition between the pulse lights while realizing simultaneous measurement of multiple parameters; the system has high integration and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, in which:

[0044] Figure 1A schematic diagram of the structure of an OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to an embodiment of the present invention;

[0045] Figure 2 This is an example diagram of the time-varying process of the vibration phase information measured by the TGD-OFDR system in an embodiment of the present invention;

[0046] Figure 3 This is an example diagram of the vibration phase information spectrum measured by the TGD-OFDR system in an embodiment of the present invention;

[0047] Figure 4 This is an example diagram of strain information measured by the OCC-BOTDA system in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided only to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0049] In order to solve the problem that coordinated multi-parameter measurement is urgently needed in industrial monitoring, but distributed optical fiber sensors can measure few parameters at the same time, the present invention proposes an OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement and its working method. The OCC-BOTDA (Optical Chirp Chain Brillouin Optical Time-DomainAnalysis) system is a Brillouin optical time domain analysis (BOTDA) system based on optical chirp chain (OCC) technology. The TGD-OFDR (Time-gated Digital Optical Frequency Domain Reflectometry system is a time-gated digital optical frequency domain reflectometer. The DOFS system that integrates multiple scattering mechanisms can realize the measurement of multiple parameters along the sensing optical fiber. The highly integrated sensing structure can effectively reduce the cost of sensors and can be used more efficiently in the field of industrial monitoring.

[0050] The embodiment of the present invention proposes an OCC-BOTDA / TGD-OFDR fusion system for simultaneous measurement of multiple parameters, such as Figure 1As shown, the system includes: a narrow linewidth laser 1, a first fiber coupler 2, a first electro-optic modulator 3, a first fiber circulator 4, a polarization-maintaining fiber Bragg grating 5, a first semiconductor optical amplifier 6, a random polarization scrambler 7, a second electro-optic modulator 8, a second fiber coupler 9, a delay fiber 10, a second semiconductor optical amplifier 11, a third fiber coupler 12, a first erbium-doped fiber amplifier 13, a second fiber circulator 14, a third electro-optic modulator 15, a tunable grating filter 16, a second erbium-doped fiber amplifier 17, a fourth fiber coupler 18, an optical attenuator 19, a fifth fiber coupler 20, a photoelectric balanced detector 21, a photoelectric detector 22, a data acquisition card 23, an arbitrary waveform generator 24, and a DC power supply 25; wherein,

[0051] The optical signal output end of the narrow linewidth laser 1 is connected to the optical signal input end of the first optical fiber coupler 2, and the optical signal output end of the first optical fiber coupler 2 is respectively connected to the optical signal input end of the first electro-optic modulator 3, the optical signal input end of the optical attenuator 19, and the optical signal input end of the second electro-optic modulator 8;

[0052] The optical signal output end of the first electro-optic modulator 3 is connected to the first port 4-1 of the first optical fiber circulator 4, the second port 4-2 of the first optical fiber circulator 4 is connected to the polarization-maintaining fiber Bragg grating 5, the third port 4-3 of the first optical fiber circulator 4 is connected to the optical signal input end of the first semiconductor optical amplifier 6, the optical signal output end of the first semiconductor optical amplifier 6 is connected to the optical signal input end of the random polarization scrambler 7; the optical signal output end of the random polarization scrambler 7 is connected to the optical signal input end of the third optical fiber coupler 12;

[0053] The optical signal output end of the second electro-optic modulator 8 is connected to the optical signal input end of the second fiber coupler 9, the optical signal output end of the second fiber coupler 9 is respectively connected to one end of the delay fiber 10 and the optical signal input end of the third electro-optic modulator 15, the other end of the delay fiber 10 is connected to the optical signal input end of the second semiconductor optical amplifier 11, the optical signal output end of the second semiconductor optical amplifier 11 is connected to the optical signal input end of the third fiber coupler 12; the optical signal output end of the third electro-optic modulator 15 is connected to the optical signal input end of the tunable grating filter 16, the optical signal output end of the tunable grating filter 16 is connected to the optical signal input end of the second erbium-doped fiber amplifier 17, and the optical signal output end of the second erbium-doped fiber amplifier 17 is connected to one end of the sensing fiber;

[0054] The optical signal output end of the third optical fiber coupler 12 is connected to the optical signal input end of the first erbium-doped fiber amplifier 13, the optical signal output end of the first erbium-doped fiber amplifier 13 is connected to the first port 14-1 of the second optical fiber circulator 14, and the second port 14-2 of the second optical fiber circulator 14 is connected to the other end of the sensing optical fiber; the third port 14-3 of the second optical fiber circulator 14 is connected to the optical signal input end of the fourth optical fiber coupler 18, and the optical signal output end of the fourth optical fiber coupler 18 is respectively connected to the optical signal input end of the fifth optical fiber coupler 20 and the optical signal input end of the photodetector 22;

[0055] The optical signal output end of the optical attenuator 19 is connected to the optical signal input end of the fifth optical fiber coupler 20, the optical signal output end of the fifth optical fiber coupler 20 is connected to the optical signal input end of the photoelectric balance detector 21, and the electrical signal output end of the photoelectric balance detector 21 and the electrical signal output end of the photoelectric detector 22 are respectively connected to the data acquisition card 23;

[0056] The RF output end of the arbitrary waveform generator 24 is respectively connected to the RF signal input end of the first electro-optic modulator 3, the RF signal input end of the first semiconductor optical amplifier 6, the RF signal input end of the second electro-optic modulator 8, the RF signal input end of the second semiconductor optical amplifier 11, the RF signal input end of the third electro-optic modulator 15, and the trigger signal input end of the data acquisition card 23;

[0057] The output end of the DC power supply 25 is connected to the bias voltage input end of the first electro-optic modulator 3 , the bias voltage input end of the second electro-optic modulator 8 , and the bias voltage input end of the third electro-optic modulator 15 , respectively.

[0058] In this embodiment, preferably, the narrow linewidth laser 1 is a polarization-maintaining laser with an output power of 40 mW, a wavelength of 1550.14 nm, and a linewidth of 1 kHz.

[0059] In this embodiment, preferably, the first optical fiber coupler 2 is a 1×3 polarization-maintaining coupler with a splitting ratio of 33:33:33; the second optical fiber coupler 9 and the third optical fiber coupler 12 are 1×2 polarization-maintaining couplers with a splitting ratio of 50:50; the fourth optical fiber coupler 19 is a 1×2 coupler with a splitting ratio of 50:50; and the fifth optical fiber coupler 21 is a 2×2 coupler with a splitting ratio of 50:50.

[0060] In this embodiment, preferably, the first electro-optical modulator 3 and the third electro-optical modulator 16 are polarization-maintaining modulators with a bandwidth of 10 GHz and an extinction ratio of 30 dB; the second electro-optical modulator 8 is a polarization-maintaining modulator with a bandwidth of 2 GHz and an extinction ratio of 30 dB.

[0061] In this embodiment, preferably, the central wavelength of the polarization-maintaining fiber Bragg grating 5 is 1550.08 nm, and the 3dB reflection bandwidth is 0.08 nm.

[0062] In this embodiment, preferably, the extinction ratios of the first semiconductor optical amplifier 6 and the second semiconductor optical amplifier 11 are both 45 dB.

[0063] In this embodiment, preferably, the 3dB operating bandwidth of the photoelectric balanced detector 22 is 2 GHz, and the 3dB operating bandwidth of the photoelectric detector 23 is 100 MHz.

[0064] In this embodiment, preferably, the sampling rate of the data acquisition card 24 is 5 GS / s, and the sampling resolution is 14 bits.

[0065] Another embodiment of the present invention provides a working method of an OCC-BOTDA / TGD-OFDR fusion system for simultaneous measurement of multiple parameters. The working method is implemented based on the above-mentioned OCC-BOTDA / TGD-OFDR fusion system for simultaneous measurement of multiple parameters; the working method includes:

[0066] The single-frequency continuous light output by the narrow linewidth laser 1 is divided into three paths, namely, upper, middle and lower paths, by the first fiber coupler 2. The upper path light is used as the pump pulse light modulation of the OCC-BOTDA system; the middle path light is used as the reference light of the TGD-OFDR system; the lower path light is used as the modulation of the optical chirp chain, and after beam splitting, it is used as the detection pulse light modulation of the TGD-OFDR system and as the detection light of the OCC-BOTDA system.

[0067] The added continuous light is intensity modulated by the first electro-optical modulator 3, and the frequency shift size is controlled by the arbitrary waveform generator 24. The double-sideband continuous light after the carrier frequency is suppressed by the DC power supply 25 is injected into the polarization-maintaining fiber Bragg grating 5 by the first fiber circulator 4 to filter out the lower sideband. The remaining upper sideband continuous light is periodically modulated into pulse light by the first semiconductor optical amplifier 6, and the polarization state is disrupted by the random polarization scrambler 7 as the pump pulse light of the OCC-BOTDA system.

[0068] The lower continuous light is subjected to linear frequency sweep modulation by the second electro-optic modulator 8, the frequency sweep range is controlled by the arbitrary waveform generator 24, and the double-sideband frequency sweep modulation is realized after the carrier frequency component is suppressed by the DC power supply 25. The modulated continuous light is divided into two upper and lower branches by the second optical fiber coupler 9: the upper branch is injected into the second semiconductor optical amplifier 11 through the delay optical fiber 10 and periodically modulated into positive and negative chirped pulse light, which is used as the detection pulse light of the TGD-OFDR system, and then combined with the pump pulse light through the third optical fiber coupler 12, and the power is pre-amplified by the first erbium-doped fiber amplifier 13, and finally transmitted through the second optical fiber ring The double-sideband swept continuous light of the lower branch is frequency-shift modulated by the third electro-optical modulator 15, and the high-frequency optical chirp chain filtered out by the adjustable grating filter 16 is used as the detection light of the OCC-BOTDA system, and is reversely injected into the sensing optical fiber after power pre-amplification by the second erbium-doped fiber amplifier 17; the frequency difference between the detection light and the pump pulse light is approximately equal to the Brillouin frequency shift. Due to the stimulated Brillouin scattering effect, when the high-frequency detection light meets the pump pulse light, part of the energy of the high-frequency detection light will pass through the acoustic wave field pump pulse light, and the energy transfer is maximum when the frequency difference between the two is equal to the Brillouin frequency shift;

[0069] The backscattered Rayleigh light and high-frequency continuous light in the sensing optical fiber enter the fourth optical fiber coupler 18 through the second optical fiber circulator 14 and are divided into two parts: one part enters the fifth optical fiber coupler 20 for coherent beat frequency with the middle continuous light after the power is adjusted by the optical attenuator 19, and then undergoes photoelectric conversion by the photoelectric balance detector 21 and is recorded by the data acquisition card 23 as the sensing signal of the TGD-OFDR system, which is used to detect the vibration information of the external environment along the sensing optical fiber; the other part undergoes photoelectric conversion by the photoelectric detector 22 and is recorded by the data acquisition card 23 as the sensing signal of the OCC-BOTDA system, which is used to detect the temperature and strain information of the external environment along the sensing optical fiber. Finally, the measurement of the external environment temperature, strain and vibration is realized simultaneously in a single sensing optical fiber, meeting the urgent need for collaborative multi-parameter measurement in industrial monitoring.

[0070] Figure 2 This is an example of the time-varying process of the vibration phase information measured by the TGD-OFDR system in the fusion system. The corresponding spectrum is Figure 3 , it can be seen that the frequency of the vibration signal is 40.1Hz. Figure 4 This is the strain information measured by the OCC-BOTDA system in the fusion system, and the strain magnitude is 600με.

[0071] In this embodiment, preferably, the pump pulse light modulation method of the OCC-BOTDA system in the fusion system is as follows:

[0072] Assume that the angular frequency, initial phase and amplitude of the continuous light output by the narrow linewidth laser 1 are ω 0, and A 0 The amplitude and angular frequency of the RF signal output by the arbitrary waveform generator 24 are A m1 and ω m1 The RF signal is loaded on the first electro-optical modulator 3, the continuous light is intensity modulated, and the modulated electric field expression is:

[0073]

[0074] After the double-sideband continuous light is subjected to the polarization-maintaining fiber Bragg grating 5 and the DC power supply 25 to suppress the carrier frequency and filter out the lower sideband, the expression of the obtained down-shifted continuous light is:

[0075]

[0076] In the formula, A 1 is the down-shifted continuous light E m2 The amplitude of (t). m2 (t) is periodically modulated into pulse light by the first semiconductor optical amplifier 6 and used as the pump pulse light of the OCC-BOTDR system, which is expressed as follows:

[0077]

[0078] Among them, A 2 is the pump pulse light E pump The amplitude of (t); T pump is the width of the pump pulse light; rect(.) is the rectangular function.

[0079] The modulation process of the detection light of the OCC-BOTDA system and the modulation process of the chirped pulse light of the TGD-OFDR system are as follows:

[0080] First, define A m2 ,ω m2 , Δω s and T are the amplitude, starting frequency, bandwidth and chirp period of the chirp RF signal output by the arbitrary waveform generator 24, respectively; after the chirp RF signal is loaded onto the second electro-optical modulator 8 and the carrier frequency is suppressed by the DC power supply 25, the expression of the output double-sideband optical chirp chain is:

[0081]

[0082] Double Sideband Optical Chirp Chain E occ (t) is divided into two paths, an upper path and an lower path, by the second optical fiber circulator 9. The upper path is periodically modulated into pulse light by the second semiconductor optical amplifier 11, and serves as the chirped pulse light of the TGD-OFDR system, which is expressed as follows:

[0083]

[0084] Among them, A probe For E probe (t) amplitude; ω - =ω 0 -ω m2 ;ω + =ω 0 +ω m2 ; t = nT; T probe is the width of the chirped pulse light. The lower double-sideband optical chirp chain is modulated by the third electro-optic modulator 15, and the low-frequency component is filtered out by the adjustable grating filter 16. The high-frequency component is used as the detection light of the OCC-BOTDA system, and the expression is:

[0085]

[0086] Among them, A occp For E occp (t) amplitude; ω m3 is the radio frequency angular frequency loaded by the arbitrary waveform generator 24 onto the third electro-optic modulator 18 .

[0087] Assume the Brillouin frequency shift of the sensing fiber is f B , the sum of the radio frequency frequencies loaded by the arbitrary waveform generator 24 on the first electro-optic modulator 3, the second electro-optic modulator 8 and the third electro-optic modulator 15 should satisfy the following relationship:

[0088] f B ∈(2π(ω m1 +ω m2 +ω m3 ),2π(ω m1 +ω m2 +ω m3 +Δω s ))(7)

[0089] The 3dB working bandwidth f of the photoelectric balanced detector 21 BPD Should be greater than or equal to 2π(ω m2 +Δω s ).

[0090] The sampling rate S of the data acquisition card 23 should satisfy the following relationship:

[0091]

[0092] Where c is the propagation speed of light waves in vacuum; n is the effective refractive index of the sensing optical fiber.

[0093] The present invention proposes an OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement and a working method thereof, which can realize rapid simultaneous multi-parameter measurement: the OCC-BOTDA system uses an optical chirp chain as a detection light, and the measurement speed of temperature and strain signals is limited to the sensing fiber length and the average number of Brillouin gain curves; the measurement speed of vibration signals of the TGD-OFDR system is limited to the sensing fiber length; the fusion of the OCC-BOTDA system and the TGD-OFDR system can realize simultaneous detection of vibration and temperature / strain along the line through a single sensing fiber. It has the advantages of high integration and low cost: in the integrated system, the chirped pulse light of the TGD-OFDR system and the detection light of the OCC-BOTDA system are both realized by secondary modulation based on the double-sideband optical chirp chain modulated by the same modulator; the pump pulse light of the OCC-BOTDA system and the chirped pulse light of the TGD-OFDR system are controlled by time division-frequency division multiplexing technology and injected into the same sensing optical fiber in sequence, effectively avoiding cross-aliasing and power competition between the pulse lights while realizing simultaneous measurement of multiple parameters; the system has high integration and low cost.

[0094] Although the spirit and principle of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the disclosed specific embodiments, and the division of various aspects does not mean that the features in these aspects cannot be combined to benefit, and such division is only for the convenience of expression. The present invention is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the attached claims.

Claims

1. An OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement, characterized in that: include: A narrow linewidth laser (1), a first fiber coupler (2), a first electro-optic modulator (3), a first fiber circulator (4), a polarization-maintaining fiber Bragg grating (5), a first semiconductor optical amplifier (6), a random polarization scrambler (7), a second electro-optic modulator (8), a second fiber coupler (9), a delay fiber (10), a second semiconductor optical amplifier (11), a third fiber coupler (12), a first erbium-doped fiber amplifier (13), a second fiber circulator (14), a third electro-optic modulator (15), a tunable grating filter (16), a second erbium-doped fiber amplifier (17), a fourth fiber coupler (18), an optical attenuator (19), a fifth fiber coupler (20), a photoelectric balanced detector (21), a photoelectric detector (22), a data acquisition card (23), an arbitrary waveform generator (24), and a DC power supply (25); wherein: The optical signal output end of the narrow linewidth laser (1) is connected to the optical signal input end of the first optical fiber coupler (2), and the optical signal output end of the first optical fiber coupler (2) is respectively connected to the optical signal input end of the first electro-optic modulator (3), the optical signal input end of the optical attenuator (19), and the optical signal input end of the second electro-optic modulator (8); The optical signal output end of the first electro-optic modulator (3) is connected to the first port (4-1) of the first optical fiber circulator (4), the second port (4-2) of the first optical fiber circulator (4) is connected to the polarization-maintaining fiber Bragg grating (5), the third port (4-3) of the first optical fiber circulator (4) is connected to the optical signal input end of the first semiconductor optical amplifier (6), the optical signal output end of the first semiconductor optical amplifier (6) is connected to the optical signal input end of the random polarization scrambler (7); the optical signal output end of the random polarization scrambler (7) is connected to the optical signal input end of the third optical fiber coupler (12); The optical signal output end of the second electro-optic modulator (8) is connected to the optical signal input end of the second optical fiber coupler (9), the optical signal output end of the second optical fiber coupler (9) is respectively connected to one end of the delay optical fiber (10) and the optical signal input end of the third electro-optic modulator (15), the other end of the delay optical fiber (10) is connected to the optical signal input end of the second semiconductor optical amplifier (11), and the optical signal output end of the second semiconductor optical amplifier (11) is connected to the optical signal input end of the third optical fiber coupler (12); The optical signal output end of the third electro-optical modulator (15) is connected to the optical signal input end of the adjustable grating filter (16), the optical signal output end of the adjustable grating filter (16) is connected to the optical signal input end of the second erbium-doped fiber amplifier (17), and the optical signal output end of the second erbium-doped fiber amplifier (17) is connected to one end of the sensing optical fiber; The optical signal output end of the third optical fiber coupler (12) is connected to the optical signal input end of the first erbium-doped optical fiber amplifier (13), the optical signal output end of the first erbium-doped optical fiber amplifier (13) is connected to the first port (14-1) of the second optical fiber circulator (14), and the second port (14-2) of the second optical fiber circulator (14) is connected to the other end of the sensing optical fiber; the third port (14-3) of the second optical fiber circulator (14) is connected to the optical signal input end of the fourth optical fiber coupler (18), and the optical signal output end of the fourth optical fiber coupler (18) is respectively connected to the optical signal input end of the fifth optical fiber coupler (20) and the optical signal input end of the photoelectric detector (22); The optical signal output end of the optical attenuator (19) is connected to the optical signal input end of the fifth optical fiber coupler (20), the optical signal output end of the fifth optical fiber coupler (20) is connected to the optical signal input end of the photoelectric balance detector (21), and the electrical signal output end of the photoelectric balance detector (21) and the electrical signal output end of the photoelectric detector (22) are respectively connected to the data acquisition card (23); The radio frequency output end of the arbitrary waveform generator (24) is respectively connected to the radio frequency signal input end of the first electro-optic modulator (3), the radio frequency signal input end of the first semiconductor optical amplifier (6), the radio frequency signal input end of the second electro-optic modulator (8), the radio frequency signal input end of the second semiconductor optical amplifier (11), the radio frequency signal input end of the third electro-optic modulator (15), and the trigger signal input end of the data acquisition card (23); The output end of the direct current power supply (25) is respectively connected to the bias voltage input end of the first electro-optic modulator (3), the bias voltage input end of the second electro-optic modulator (8), and the bias voltage input end of the third electro-optic modulator (15).

2. The OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to claim 1, characterized in that: The narrow linewidth laser (1) is a polarization-maintaining laser with an output power of 40 mW, a wavelength of 1550.14 nm, and a linewidth of 1 kHz.

3. The OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to claim 1, characterized in that: The first optical fiber coupler (2) is a 1×3 polarization-maintaining coupler with a splitting ratio of 33:33:33; the second optical fiber coupler (9) and the third optical fiber coupler (12) are 1×2 polarization-maintaining couplers with a splitting ratio of 50:50; the fourth optical fiber coupler (18) is a 1×2 coupler with a splitting ratio of 50:50; and the fifth optical fiber coupler (20) is a 2×2 coupler with a splitting ratio of 50:

50.

4. The OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to claim 1, characterized in that: The first electro-optic modulator (3) and the third electro-optic modulator (15) are polarization-maintaining modulators with a bandwidth of 10 GHz and an extinction ratio of 30 dB; the second electro-optic modulator (8) is a polarization-maintaining modulator with a bandwidth of 2 GHz and an extinction ratio of 30 dB.

5. The OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to claim 1, characterized in that: The central wavelength of the polarization-maintaining fiber Bragg grating (5) is 1550.08 nm, and the 3dB reflection bandwidth is 0.08 nm; the extinction ratios of the first semiconductor optical amplifier (6) and the second semiconductor optical amplifier (11) are both 45 dB; the 3dB working bandwidth of the photoelectric balanced detector (21) is 2 GHz, and the 3dB working bandwidth of the photoelectric detector (22) is 100 MHz; the sampling rate of the data acquisition card (23) is 5 GS / s, and the sampling resolution is 14 bits.

6. A method for operating an OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement, characterized in that: The working method is implemented based on an OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to any one of claims 1 to 5; the working method comprises: The single-frequency continuous light output by the narrow linewidth laser (1) is divided into three paths, namely, upper, middle and lower paths, through a first optical fiber coupler (2), wherein the upper path light is used as pump pulse light modulation of the OCC-BOTDA system; the middle path light is used as reference light of the TGD-OFDR system; the lower path light is used as modulation of the optical chirp chain, and after beam splitting, it is used as detection pulse light modulation of the TGD-OFDR system and as detection light of the OCC-BOTDA system respectively; The incoming continuous light is intensity modulated by a first electro-optical modulator (3), and the frequency shift is controlled by an arbitrary waveform generator (24). The double-sideband continuous light after the carrier frequency is suppressed by a direct current power supply (25) is injected into a polarization-maintaining fiber Bragg grating (5) to filter out the lower sideband by a first optical fiber circulator (4). The remaining upper sideband continuous light is periodically modulated into pulse light by a first semiconductor optical amplifier (6), and the polarization state is disrupted by a random polarization scrambler (7) to serve as the pump pulse light of the OCC-BOTDA system. The lower continuous light is subjected to linear frequency sweep modulation by a second electro-optical modulator (8), the frequency sweep range is controlled by an arbitrary waveform generator (24), and the double-sideband frequency sweep modulation is realized after the carrier frequency component is suppressed by a direct current power supply (25). The modulated continuous light is divided into upper and lower branches by a second optical fiber coupler (9): the upper branch is injected into a second semiconductor optical amplifier (11) through a time-delay optical fiber (10) and periodically modulated into positive and negative chirped pulse light, which serves as the detection pulse light of the TGD-OFDR system, and then is transmitted to a third optical fiber coupler (9). The combiner (12) combines the pump pulse light, performs power pre-amplification by the first erbium-doped fiber amplifier (13), and finally injects the light into the sensing fiber through the second fiber circulator (14); the lower branch double-sideband frequency-sweeping continuous light is frequency-shift modulated by the third electro-optic modulator (15), and the high-frequency optical chirp chain filtered out by the adjustable grating filter (16) is used as the detection light of the OCC-BOTDA system, and is reversely injected into the sensing fiber after power pre-amplification by the second erbium-doped fiber amplifier (17); The back Rayleigh scattered light and high-frequency continuous light in the sensing optical fiber enter the fourth optical fiber coupler (18) through the second optical fiber circulator (14) and are divided into two parts: one part enters the fifth optical fiber coupler (20) for coherent frequency beat with the middle continuous light after the power is adjusted by the optical attenuator (19), and then undergoes photoelectric conversion by the photoelectric balance detector (21) and is recorded by the data acquisition card (23) as a sensing signal of the TGD-OFDR system for detecting vibration information of the external environment along the sensing optical fiber; the other part undergoes photoelectric conversion by the photoelectric detector (22) and is recorded by the data acquisition card (23) as a sensing signal of the OCC-BOTDA system for detecting temperature and strain information of the external environment along the sensing optical fiber.

7. The working method of the OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to claim 6, characterized in that: The pump pulse light of the OCC-BOTDA system is expressed as: Where A2 is the pump pulse light E pump The amplitude of (t); T pump is the width of the pump pulse light; rect(.) is the rectangular function; ω0, are respectively the angular frequency and initial phase of the continuous light output by the narrow linewidth laser (1); ω m1 is the angular frequency of the radio frequency signal output by the arbitrary waveform generator (24); and t is time.

8. The working method of the OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to claim 7, characterized in that: The DC power supply (25) suppresses the carrier frequency component to realize double-sideband frequency sweep modulation, and the expression of the modulated continuous light is: In the formula, A m2 ,ω m2 , Δω s and T respectively represent the amplitude, starting frequency, bandwidth and chirp period of the chirp radio frequency signal output by the arbitrary waveform generator (24); The expression of the positive and negative chirped pulse light, i.e., the detection pulse light of the TGD-OFDR system, is: In the formula, A probe is the positive and negative chirped pulse light E probe (t) amplitude; ω - =ω0-ω m2 ;ω + =ω0+ω m2 ; T probe represents the width of the chirped pulse light; The expression of the detection light of the high-frequency optical chirp chain, namely the OCC-BOTDA system, is: In the formula, A occp For high frequency optical chirp chain E occp (t) amplitude; ω m3 It represents the radio frequency angular frequency that the arbitrary waveform generator (24) loads on the third electro-optic modulator (18).

9. The working method of the OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to claim 8, characterized in that: The sum of the radio frequency frequencies loaded by the arbitrary waveform generator (24) on the first electro-optical modulator (3), the second electro-optical modulator (8) and the third electro-optical modulator (15) satisfies the following relationship: f B ∈(2π(ω m1 +oh m2 +oh m3 ),2π(ω m1 +oh m2 +oh m3 +See s ))。 10. The working method of the OCC-BOTDA / TGD-OFDR fusion system for simultaneous multi-parameter measurement according to claim 9, characterized in that: The sampling rate S of the data acquisition card (23) satisfies the following relationship: Wherein, c is the propagation speed of light waves in vacuum; n is the effective refractive index of the sensing optical fiber; and max represents the maximum value.

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