CN102998025A - Measuring method for pulse pre-pump rayleigh BOTDA (Brilouin optical time domain analysis) temperature and strain - Google Patents
Measuring method for pulse pre-pump rayleigh BOTDA (Brilouin optical time domain analysis) temperature and strain Download PDFInfo
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Abstract
Provided is a measuring method for pulse pre-pump rayleigh BOTDA (Brillouin optical time domain analysis) temperature and strain. Step pulsed light is injected into a sensing optical fiber, backward rayleigh scattering generated by a pre-pump pulsed light 1-order sideband serves as detection light to generate stimulated Brillouin scattering effect with sensing pulsed light in opposite-direction transmission, simultaneously sensing pulse and spontaneous Brillouin scattering signals generated by pre-pump pulsed light 0-order base band preexciting sound saves generate the stimulated Brillouin scattering effect, then the detection light returning to an incidence end and carrying stimulated Brillouin scattering information is utilized to obtain Brillouin frequency shift of each point of the optical fiber, and measurement of the temperature and the strain along the optical fiber is achieved according to the relations between the Brillouin frequency shift and the temperature/strain. According to the measuring method, the influence of non-local effect on system performance is greatly reduced, the conflict between the spatial resolution and measurement accuracy is effectively overcome, and the spatial resolution and the measurement accuracy are improved simultaneously.
Description
Technical field
The present invention relates to a kind of pre-pumping Rayleigh of pulse BOTDA temperature based on time domain and spectral domain shaping and the measuring method of strain, belong to field of measuring technique.
Background technology
Have measuring accuracy height, accurate positioning, distance based on the optical fiber distributed temperature/strain measurement technique of Brillouin scattering principle and can reach the particular advantages such as kilometers up to a hundred, have broad application prospects in Gernral Check-up, localization of fault and the fields such as life appraisal and Geological Hazards Monitoring of electric power cable, heavy construction and hydraulic engineering structure, long distance oil-gas pipeline, jet chimney etc.
At present domestic and international research on Brillouin scattering distributed optic fiber sensing field comparatively proven technique comprises following four kinds: Brillouin optical time domain analysis (Brillouin Optical Time Domain Analysis, BOTDA), Brillouin light Time Domain Reflectometry (Brillouin Optical Time Domain Reflectometry, BOTDR), the Brillouin light domain of dependence is analyzed (Brillouin Optical Correlation Domain Analysis, BOCDA) and Brillouin light frequency-domain analysis (Brillouin Optical Frequency Domain Analysis, BOFDA).Wherein, the BOTDA technology is utilized stimulated Brillouin scattering (Stimulated Brillouin Scattering, SBS) effect, received signal strength is large, and measuring accuracy is high, and attainable measurement dynamic range is large, obtain widely research, and obtained great progress.On traditional B OTDA technical foundation, following several schemes have been developed: 1. 2004, K. Kishida etc. proposes the pre-pumping of pulse (Pulsed Pre-pump first, PPP) BOTDA technology, this technology refers to increase the pre-pumping pulse that can fully encourage phonon before pulsed light, thereby effectively improves the Brillouin shift measuring accuracy.2. 2008, the people such as X.Bao adopted differential pulse pumping method in the BOTDA system, were about in the different pulse injection fibre of a pair of width, with its Brillouin's spectral difference that produces separately, thereby improved system signal noise ratio and Brillouin shift measuring accuracy.3. 2009, the people such as Q.Cui proposed a kind of BOTDA technology of utilizing end reflection microwave modulating pulse substrate light to make to survey light, and this technology adopts single-ended incident simplification device, and the possibility of long-distance sensing and high-acruracy survey is provided; On this basis, proposed a kind of BOTDA temperature-sensing system based on Rayleigh scattering in 2011, this system uses the Rayleigh scattering of microwave modulating pulse substrate generation as surveying light, can effectively reduce the polarization sensitivity of system.4. 2010, the people such as F.R.Barrios used the Raman amplifying technique in the BOTDA system, greatly prolonged distance sensing.
In the BOTDA sensor-based system of the new mechanism of above-mentioned employing, new method, on the one hand, owing to be subjected to the restriction of phonon lifetime, spatial resolution and measuring accuracy restrict mutually, can't improve simultaneously; On the other hand, because the SBS effect occurs in continuous light and pulsed light, optical fiber status information beyond having comprised between the sensing pulse area in the measured signal of test side, namely there is the impact of non-local effect, cause Brillouin spectrum to produce distortion, measured signal intensity is produced rise and fall, and then measuring accuracy is descended, be difficult to realize simultaneously long distance, high spatial resolution and high-precision Quick Measurement.Wherein, Q. the Rayleigh BOTDA system of Cui proposition has single light source, single-ended work and nondestructive advantage, but because the Rayleigh scattering of utilizing the continuous impulse substrate of microwave modulation to produce is done to survey light, non-local effects is serious, and system performance is difficult to further raising.Therefore, in the urgent need to exploring new mechanism and the new method that realizes high-performance temperature/strain measurement.
Summary of the invention
The object of the invention is to the drawback for prior art, a kind of pre-pumping Rayleigh of pulse BOTDA temperature based on time domain and spectral domain shaping and the measuring method of strain are provided, reduce non-local effect, improve simultaneously temperature/strain measurement precision and spatial resolution.
The method of the invention realizes with following technical proposals:
The measuring method of the pre-pumping Rayleigh of a kind of pulse BOTDA temperature and strain, the measuring system that described method adopts comprises narrow linewidth laser, Polarization Controller, electrooptic modulator by microwave signal source and step pulse generator driving, microwave switch, Erbium-Doped Fiber Amplifier, optical circulator, grating filter, optical filter, photoelectric detector, data acquisition and processing unit and computing machine, described laser instrument, Polarization Controller, electrooptic modulator, image intensifer, after connecting successively, grating filter connects the first light mouth of circulator, the second light mouth of circulator connects sensor fibre, and the 3rd light mouth is successively through optical filter, photoelectric detector, data acquisition and processing unit connect computing machine;
Measure as follows operation:
The light that narrow linewidth laser sends enters electrooptic modulator through Polarization Controller, by electrooptic modulator with optical signal modulation for by width less than the sensing pulsed light of phonon lifetime and the step pulse light that forms greater than the pre-pumping pulse light of phonon lifetime through time-limited microwave modulation and width, this step pulse light amplified by image intensifer and grating filter filtering spontaneous heating radiated noise after, enter sensor fibre through circulator, the backward Rayleigh scattering that 1 rank sideband of pre-pumping pulse light produces is as surveying light, with the in opposite directions sensing pulsed light generation stimulated Brillouin scattering effect of transmission; Pre-pumping pulse light 0 rank base band preexciting acoustic wavefield, and generation spontaneous brillouin scattering signal, sensing pulse and the effect of spontaneous brillouin scattering signal generation stimulated Brillouin scattering, return the detection light that the incident end carries stimulated Brillouin scattering information and enter optical filter through circulator, enter photoelectric detector and convert electric signal to through optical filter filtering upper side band signal is laggard, tried to achieve again the Brillouin shift at each point place on the optical fiber according to electric signal by data acquisition and processing unit, and according to the relation of Brillouin shift and temperature/strain, parse the temperature/strain information on the optical fiber, realize the measurement along fiber optic temperature/strain.
The measuring method of the pre-pumping Rayleigh of above-mentioned pulse BOTDA temperature and strain, described step pulse generator comprises t connector, signal synthesizer and two pulse signal generators, the signal input part of the output termination t connector of the first pulse signal generator, a signal output part of t connector connects an input end of signal synthesizer through time delay device, another signal output part of t connector connects the trigger pip input end of the second pulse signal generator, another input end of the output termination signal synthesizer of the second pulse signal generator, the output termination electrooptic modulator of signal synthesizer
Described step pulse generator is worked as follows: at first produce the electric pulse of a width less than phonon lifetime by the first pulse signal generator, this electric pulse is divided into two-way behind t connector, one tunnel trigger pip as the second pulse signal generator wherein, when rising edge appears in this trigger pip, the second pulse signal generator sends the input end that a width is lower than the pulse signal of sensing pulse greater than phonon lifetime and amplitude and this pulse signal is delivered to signal synthesizer, another pulse signal of t connector output enters another input end of signal synthesizer after the time delay device time-delay, by signal synthesizer the input signal of its two input end is synthesized a stepped electrical pulse.
The measuring method of the pre-pumping Rayleigh of above-mentioned pulse BOTDA temperature and strain, described time-limited microwave modulation signal, to open microwave switch by the rising edge triggering of pre-pumping pulse in the step pulse signal, the rising edge of sensing pulse triggers closes microwave switch, control enters that time of electrooptic modulator radio-frequency head microwave signal realizes, its duration equals the duration of pre-pumping pulse.
The present invention introduces pre-pumping pulse in the Rayleigh Brillouin optical time domain analysis system, time-limited microwave is modulated the Rayleigh scattering of pre-pumping pulse light 1 rank sideband generation as surveying light and the effect of sensing pulsed light generation stimulated Brillouin scattering, the reach of restriction stimulated Brillouin scattering realizes the time domain shaping of Brillouin's response; Utilize microwave to modulate 0 rank base band preexciting acoustic wavefield of pre-pumping pulse light, the synthetic Brillouin spectrum of pre-pumping pulse light and the acting in conjunction of sensing pulsed light realizes the shaping of Brillouin spectrum.Described method can reduce non-local effect greatly on the impact of system performance, effectively solves the contradiction between spatial resolution and the measuring accuracy, and spatial resolution and measuring accuracy are improved simultaneously.In addition, this method also can improve system signal noise ratio, increases distance sensing, reduces Measuring Time.
Description of drawings
The invention will be further described below in conjunction with accompanying drawing.
Fig. 1 is the pre-pumping Rayleigh of pulse BOTDA time domain shaping principle schematic;
Fig. 2 is the pre-pumping Rayleigh of pulse BOTDA spectral domain shaping principle schematic;
Fig. 3 is that the energy of SBS effect shifts synoptic diagram;
Fig. 4 is the step pulse generator theory diagram;
Fig. 5 is measuring system block diagram of the present invention.
Used list of reference numerals is among the figure: LD, narrow linewidth laser, PC, Polarization Controller, MSS, microwave signal source, MS, microwave switch, SPG, step pulse generator, EOM, electrooptic modulator, EDFA, Erbium-Doped Fiber Amplifier, OC, optical circulator, GF, grating filter, OF, optical filter, PD, photoelectric detector, DAQ, data acquisition and processing unit, C, computing machine, FUT, sensing testing optical fiber.
Embodiment
The present invention introduces the thought of pre-pumping pulse in Rayleigh BOTDA system, add one section pre-pumping pulse light and consist of step pulse light before the sensing pulsed light.The SBS effect occurs as surveying light and sensing pulsed light in the Rayleigh scattering that described method utilizes time-limited microwave to modulate pre-pumping pulse light 1 rank sideband generation, the reach of restriction stimulated Brillouin scattering, realize the time domain shaping of Brillouin's response, reduce non-local effect to the impact of system performance; Utilize microwave to modulate 0 rank base band preexciting acoustic wavefield of pre-pumping pulse light, produce the spontaneous brillouin scattering signal.Width remains unchanged less than the sensing pulsed frequency of phonon lifetime, because the difference on the frequency between sensing pulse and the spontaneous brillouin scattering signal is Brillouin shift, the spontaneous brillouin scattering signal that the sensing pulse produces pre-pumping pulse 0 rank base band carries out SBS and amplifies, return like this Brillouin spectrum (the Brillouin Scattering Spectrum of incident end, BSS) BSS that the BSS that is produced by the very wide sensing pulse of spectrum width and the very narrow pre-pumping pulse of the spectrum width after amplifying produce is formed by stacking, strengthen the spectrum composition of pre-pumping pulse light in the Brillouin spectrum, realize the spectral domain shaping of Brillouin's response, can effectively solve the contradiction between spatial resolution and the measuring accuracy, the two is improved simultaneously, improve simultaneously system signal noise ratio, increase distance sensing, reduce Measuring Time.
Described time domain shaping, refer in Rayleigh BOTDA system, the SBS effect occurs as surveying light and sensing pulsed light in the Rayleigh scattering of time-limited microwave being modulated pre-pumping pulse light 1 rank sideband generation, because the time control of microwave modulation, the SBS effect is limited in fiber lengths corresponding to step pulse, only carry temperature/strain information on the corresponding length of fibre of step pulse through the detection light of SBS effect, can effectively reduce by pump light and survey the energy conversion accumulation of light and the non-local effect that causes on the impact of system performance.
Described spectral domain shaping refers to when the step pulse light beam enters sensor fibre, and wherein width is modulated pre-pumping pulse light 0 rank base band greater than the microwave of phonon lifetime and at first entered predispersed fiber excite sound waves field, produces the spontaneous brillouin scattering signal.Width remains unchanged less than the sensing pulsed light frequency of phonon lifetime, its in optical fiber with survey light the SBS effect occur in, because the difference on the frequency between sensing pulse and the spontaneous brillouin scattering signal is Brillouin shift, the spontaneous brillouin scattering signal that the sensing pulse produces pre-pumping pulse 0 rank base band carries out SBS and amplifies, the BSS that the BSS that the BSS that returns like this incident end is produced by the very wide sensing pulse of spectrum width and the very narrow pre-pumping pulse of the spectrum width after amplifying produce is formed by stacking, and strengthens the spectrum composition of pre-pumping pulse light in the Brillouin spectrum.
Described step pulse light is to replace the offset side of Dc bias input electrooptic modulator and the radio-frequency head of microwave signal input electrooptic modulator to modulate the light signal that produces by the step pulse signal, and it is made of sensing pulsed light and pre-pumping pulse light.
Described step pulse signal, refer to enter the signal that the electrooptic modulator offset side is modulated, the stepped electrical pulse that its step pulse generator that is comprised of t connector, signal synthesizer and the first pulse signal generator, the second pulse signal generator produces, its pre-pumping pulse by the sensing pulse of narrow pulsewidth, high amplitude and wide pulse width, low amplitude value consists of.In the production process of stepped electrical pulse, should suitably choose width and the amplitude of sensing pulse and pre-pumping pulse, the SBS effect between the two is controlled at reasonable level, better realize time domain and spectral domain shaping that Brillouin responds.
Described time-limited microwave modulation signal, refer to control and enter the microwave signal time that the electrooptic modulator radio-frequency head is modulated, it is to open microwave switch by the rising edge triggering of pre-pumping pulse in the step pulse signal, the microwave switch realization is closed in the rising edge triggering of sensing pulse, and the duration equals the duration of pre-pumping pulse.
Principle of the present invention is as follows:
In the pre-pumping Rayleigh of the pulse BOTDA system based on time domain and spectral domain shaping, electrooptic modulator is under the driving of microwave signal and step pulse signal, with the input optical signal modulation be step pulse light, wherein microwave signal is opened microwave switch by the rising edge triggering of pre-pumping pulse in the step pulse signal, the microwave switch realization is closed in the rising edge triggering of sensing pulse, and the duration equals the duration of pre-pumping pulse, so the modulating time of microwave signal was limited in the time of pre-pumping pulse.When the step pulse light beam entered sensor fibre, what at first enter optical fiber was pre-pumping pulse light.The SBS effect occurs as surveying light and sensing pulsed light in the Rayleigh scattering of time-limited microwave being modulated pre-pumping pulse light 1 rank sideband generation, as shown in Figure 1, be equivalent to the whole piece measuring optical fiber is divided into the segment optical fiber that N part length equals the corresponding length of step pulse, thereby the reach of restriction SBS, survey light through the Rayleigh of SBS effect and only carry temperature/strain information on the corresponding length of fibre of step pulse, realize the time domain shaping of Brillouin's response, can greatly reduce non-local effect to the impact of system performance; Width is modulated pre-pumping pulse light 0 rank base band greater than the microwave of phonon lifetime and is entered predispersed fiber excite sound waves field, produces the spontaneous brillouin scattering signal.Width remains unchanged less than the sensing pulsed frequency of phonon lifetime, its in optical fiber with survey light the SBS effect occur in, because the difference on the frequency between sensing pulse and the spontaneous brillouin scattering signal is Brillouin shift, the spontaneous brillouin scattering signal that the sensing pulse produces pre-pumping pulse 0 rank base band carries out SBS and amplifies, principle with the time domain shaping is the same, and the spontaneous brillouin scattering signal that pre-pumping pulse 0 rank base band produces is with in the SBS reach of sensing pulse generation is limited in the corresponding length of fibre of step pulse equally.The BSS that the BSS that the BSS that returns like this incident end is produced by the very wide sensing pulse of spectrum width and the very narrow pre-pumping pulse of the spectrum width after amplifying produce is formed by stacking, strengthened the spectrum composition of pre-pumping pulse light in the Brillouin spectrum, thereby realized the spectral domain shaping of Brillouin's response, as shown in Figure 2.In the time domain shaping, produce frequency after the pre-pumping pulse optical modulation and be respectively
0-
sWith
0+
s1 rank sideband, the Rayleigh scattering light of its generation as surveying light and frequency is
0The process of sensing pulse generation SBS effect in, energy by frequency is simultaneously
0+
sRayleigh scattering light be transferred to the sensing pulse and be transferred to frequency by the sensing pulse and be
0-
sRayleigh scattering light.In the spectral domain shaping, after pre-pumping pulse entered optical fiber, its 0 rank base band excited sound field, and the generation frequency is
0-
BWith
0+
BStokes (Stokes) light and anti-Stokes (anti-Stokes) light, with the process of sensing pulse generation SBS effect in, identical with the SBS effect in the time domain shaping, energy is transferred to the sensing pulse and is transferred to Stokes light by the sensing pulse by anti-Stokes light simultaneously, as shown in Figure 3.The energy reduction of sensing pulse is very little in whole SBS mechanism, has reduced the pumping depletion effect.This moment, the spatial resolution of system was mainly determined by the sensing pulse width of narrower in width, frequency measurement accuracy is mainly determined by the very narrow pre-pumping pulse Brillouin spectrum of spectrum width, thereby effectively solved the contradiction between spatial resolution and the measuring accuracy, the two is improved simultaneously.Secondly, because the synthetic new Brillouin spectrum of the acting in conjunction of pre-pumping pulse and sensing pulse has been amplified brillouin scattering signal, system signal noise ratio also is improved, thereby increases distance sensing and reduce Measuring Time.
The present invention detects the detection light intensity of carrying SBS information, by changing within the specific limits the frequency of microwave signal, realizes the scanning to Brillouin's frequency spectrum.Carry out match after the detection light signal collection that carries the SBS of difference place information on the optical fiber processed, can obtain the Brillouin spectrum of every bit on the optical fiber, the frequency at intensity maximum point place is the Brillouin shift at each point place on the optical fiber on this scattering spectra, relation according to Brillouin shift and temperature/strain, parse the temperature/strain information on the optical fiber, realize the measurement along fiber optic temperature/strain.
The present invention also comprises the generation of step pulse signal, by t connector, signal synthesizer and the first pulse signal generator, the second pulse signal generator acting in conjunction, produces best stepped electrical pulse.
The present invention also comprises the pre-pumping Rayleigh of pulse BOTDA temperature based on time domain and spectral domain shaping/strain sensing system.
Figure 4 shows that the step pulse signal that the present invention designs produces scheme.At first produced the electric pulse (pulsewidth and amplitude are set, and pulsewidth is the width of sensing pulse) of a narrow pulsewidth, high amplitude by the first pulse signal generator in the first pulse signal generator, behind t connector, be divided into two-way.Wherein one the tunnel be input to the second pulse signal generator as trigger pip, when rising edge appears in trigger pip, the second pulse signal generator sends the pulse signal (pulsewidth and amplitude are set, and pulsewidth is the width of step pulse) of a wide pulse width, low amplitude value in the second pulse signal generator.Another road narrow pulse signal synthesizes a stepped electrical pulse with the broad pulse that the second pulse signal generator sends by signal synthesizer through the time-delay (being pre-pumping pulse width) of certain hour.
Figure 5 shows that the pre-pumping Rayleigh of the pulse BOTDA temperature based on time domain and spectral domain shaping that the present invention intends adopting/Strain Distribution formula sensor-based system.1550nm distributed feedback type semiconductor narrow linewidth laser sends frequency
0Continuous light, enter EOM through Polarization Controller, adjust Polarization Controller and make and incide EOM input end polarisation of light attitude and overlap with the polarization axle of EOM, (frequency is light signal via microwave signal source
s) and the EOM that drives of step pulse generator be modulated to the step pulse light that is formed by sensing pulsed light and pre-pumping pulse light, behind EDFA amplification and grating filter filtering spontaneous heating radiated noise, enter sensor fibre through circulator again.At first enter sensor fibre through the modulation of time-limited microwave and width greater than the pre-pumping pulse light of phonon lifetime, the frequency that its 1 rank sideband is produced is
0-
sWith
Backward Rayleigh scattering as surveying light, with the frequency of in opposite directions transmission be
0The sensing pulsed light SBS effect occurs, when
sWith Brillouin shift
BWhen equating, the SBS effect is the strongest; Microwave is modulated pre-pumping pulse light 0 rank base band preexciting acoustic wavefield, and generation spontaneous brillouin scattering signal is that frequency is
0-
BWith
0+
BStokes (Stokes) light and anti-Stokes (anti-Stokes) light, width remains unchanged less than the sensing pulsed frequency of phonon lifetime, its in optical fiber with survey light the SBS effect occur in, because the difference on the frequency between sensing pulse and the spontaneous brillouin scattering signal is Brillouin shift, the spontaneous brillouin scattering signal that the sensing pulse produces pre-pumping pulse 0 rank base band carries out SBS and amplifies.The BSS that the BSS that the BSS that returns like this incident end is produced by the very wide sensing pulse of spectrum width and the very narrow pre-pumping pulse of the spectrum width after amplifying produce is formed by stacking.Carry the detection light of SBS information behind OF filtering upper side band signal, frequency is
Lower sideband signal enter photoelectric detector and convert electric signal to, carry out again data acquisition at a high speed, and the data that gather carried out the superposed average denoising.In the native system by changing within the specific limits the frequency of microwave signal
Realization is to the scanning of Brillouin's frequency spectrum, detect and carry the detection light signal strength of the SBS of difference place information on the optical fiber, after the acquisition process to microwave signal frequency
Carry out match, can obtain the Brillouin spectrum of every bit on the optical fiber, the frequency at intensity maximum point place is the Brillouin shift at each point place on the optical fiber on this scattering spectra, relation according to Brillouin shift and temperature/strain, parse the temperature/strain information on the optical fiber, realize the measurement along fiber optic temperature/strain.
Claims (3)
1. the measuring method of the pre-pumping Rayleigh of a pulse BOTDA temperature and strain, it is characterized in that, the measuring system that described method adopts comprises narrow linewidth laser (LD), Polarization Controller (PC), electrooptic modulator (EOM) by microwave signal source (MSS) and step pulse generator (SPG) driving, microwave switch (MS), Erbium-Doped Fiber Amplifier (EDFA), optical circulator (OC), grating filter (GF), optical filter (OF), photoelectric detector (PD), data acquisition and processing unit (DAQ) and computing machine (C), described laser instrument (LD), Polarization Controller (PC), electrooptic modulator (EOM), Erbium-Doped Fiber Amplifier (EDFA), after connecting successively, grating filter (GF) connects the first light mouth of circulator (OC), the second light mouth of circulator (OC) connects sensing testing optical fiber (FUT), and the 3rd light mouth is successively through optical filter (OF), photoelectric detector (PD), data acquisition and processing unit (DAQ) connect computing machine (C);
Measure as follows operation:
The light that described narrow linewidth laser (LD) sends enters electrooptic modulator (EOM) through Polarization Controller (PC), by electrooptic modulator (EOM) with optical signal modulation for by width less than the sensing pulsed light of phonon lifetime and the step pulse light that forms greater than the pre-pumping pulse light of phonon lifetime through time-limited microwave modulation and width, this step pulse light amplified by Erbium-Doped Fiber Amplifier (EDFA) and grating filter (GF) filtering spontaneous heating radiated noise after, enter sensing testing optical fiber (FUT) through optical circulator (OC), the backward Rayleigh scattering that 1 rank sideband of pre-pumping pulse light produces is as surveying light, with the in opposite directions sensing pulsed light generation stimulated Brillouin scattering effect of transmission; Pre-pumping pulse light 0 rank base band preexciting acoustic wavefield, and generation spontaneous brillouin scattering signal, sensing pulse and the effect of spontaneous brillouin scattering signal generation stimulated Brillouin scattering, return the detection light that the incident end carries stimulated Brillouin scattering information and enter optical filter (OF) through optical circulator (OC), enter photoelectric detector (PD) and convert electric signal to through optical filter (OF) filtering upper side band signal is laggard, tried to achieve again the Brillouin shift at each point place on the optical fiber according to electric signal by data acquisition and processing unit (DAQ), and according to the relation of Brillouin shift and temperature/strain, parse the temperature/strain information on the optical fiber, realize the measurement along fiber optic temperature/strain.
2. the measuring method of a kind of pulse according to claim 1 pre-pumping Rayleigh BOTDA temperature and strain, it is characterized in that, described step pulse generator (SPG) comprises t connector, signal synthesizer and two pulse signal generators, the signal input part of the output termination t connector of the first pulse signal generator, a signal output part of t connector connects an input end of signal synthesizer through time delay device, another signal output part of t connector connects the trigger pip input end of the second pulse signal generator, another input end of the output termination signal synthesizer of the second pulse signal generator, the direct current biasing end of the output termination electrooptic modulator of signal synthesizer.
Described step pulse generator is worked as follows: at first produce the electric pulse of a width less than phonon lifetime by the first pulse signal generator, this electric pulse is divided into two-way behind t connector, one tunnel trigger pip as the second pulse signal generator wherein, when rising edge appears in this trigger pip, the second pulse signal generator sends the input end that a width is lower than the pulse signal of sensing pulse greater than phonon lifetime and amplitude and this pulse signal is delivered to signal synthesizer, another pulse signal of t connector output enters another input end of signal synthesizer after the time delay device time-delay, by signal synthesizer the input signal of its two input end is synthesized a stepped electrical pulse.
3. the measuring method of a kind of pulse according to claim 1 pre-pumping Rayleigh BOTDA temperature and strain, it is characterized in that, described time-limited microwave modulation signal, to open microwave switch by the rising edge triggering of pre-pumping pulse in the step pulse signal, the rising edge of sensing pulse triggers closes microwave switch, control enters that microwave signal time of electrooptic modulator radio-frequency head realizes, its duration equals the duration of pre-pumping pulse.
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