CN106404015A - High-speed high-precision multichannel Bragg grating demodulation instrument - Google Patents
High-speed high-precision multichannel Bragg grating demodulation instrument Download PDFInfo
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- CN106404015A CN106404015A CN201510492460.5A CN201510492460A CN106404015A CN 106404015 A CN106404015 A CN 106404015A CN 201510492460 A CN201510492460 A CN 201510492460A CN 106404015 A CN106404015 A CN 106404015A
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Abstract
The invention belongs to the technical field of fiber sensing and discloses a high-speed high-precision multichannel Bragg grating demodulation instrument. The system includes a wavelength scanning laser light source and a corresponding wavelength control method; a sensor multi-channel realization method and an array device; a high-speed high-precision demodulation method and a corresponding circuit; and an auxiliary circuit and a computer for completing the above functions. The instrument can demodulate and calibrate the absolute value of each FBG center wavelength in a sensing array in a high-speed high-precision multi-channel manner and is suitable for temperature, pressure, vibration and other sensors based on the GBG principle.
Description
Technical field
The invention belongs to sensory field of optic fibre, it is related specifically to Bragg grating sensor is carried out the method for high-speed, high precision demodulation and multichannel application and realizes device.
Background technology
Fibre Optical Sensor, since the appearance seventies in last century, due to its high sensitivity, has passed -- and sense unification, superior Electro Magnetic Compatibility etc. series of advantages, by great attention in the industry and expectation.
Compared with other type fiber sensors, fiber grating is due to small volume, it is very easy to and sensing arrangement and material fusion, constitute the multiple sensors parts such as temperature, pressure, flow, strain, generally believe that in the industry fiber grating is that optical fiber sensing technology is practical, a technology path with very good prospect of large-scale application.
The essence of demodulation is to detect the wavelength change of fiber grating, and it carries the information of physical quantity to be detected.In high precision, quickly, the realization demodulation of multichannel, low cost, is an important prerequisite of fiber-optic grating sensor large-scale engineeringization application.
Considerable research report and patent application both at home and abroad（Authorize）It is related to the demodulation work of optical fiber grating sensing, for example：
High-precision multi-path optical fiber grating sensing system（Chinese patent CN101021443A）
High precision optical fiber grating sensing signal demodulation instrument（Chinese patent CN101216327A）
High accuracy grating fibers demodulating system（Chinese patent CN1908713A）
Ultra high speed optical fiber grating sensor demodulating system and its implementation（Chinese patent CN1494237A）
Multichannel Bragg grating sensor（United States Patent (USP)
5426297）
Hypersensitivity sensor using Chirp Bragg optical grating reflection（United States Patent (USP) 5706079）
Despite considerable similar work, but it is possible to the method and apparatus meeting the grating demodulation of " at a high speed, in high precision, multichannel and lower cost " is extremely rare simultaneously.
Content of the invention
The problem to be solved in the present invention is to provide one kind and can meet the demodulation techniques scheme of " at a high speed, high-precision multi-path and lower cost " and the device realizing the program simultaneously.
The particular content of the present invention includes：
Length scanning LASER Light Source is made up of following part：Laser diode；Diode drive circuit, diode temperature sensor, refrigeration-heating thermostat units and control unit；It connects control planning：Control unit receives the laser diode temperature information of sensor, produces adjustment temperature instruction and send thermostat units, produces drive signal and send diode drive circuit；Diode drive circuit controls laser diode with it after amplifying drive signal, and the temperature of laser diode is controlled by thermoregulation circuit, and the input of 1 × N splitter of multichannel array is sent in the output of its laser.
The array apparatus realizing the application of sensor multichannel are made up of following part：One 1 × N splitter；N-1 1 × 2 bonder.1 or several multifiber cable；Sensor array includes m sensing grating.Wherein：1 × N splitter N-1 output branch correspondence be connected to the output1 end of N-1 1 × 2 bonder, N-1 1 × 2 bonder input1 end is connected to sensor by multifiber cable.Multifiber cable distributes an optical fiber for each sensor.The output2 end of N-1 1 × 2 bonder is connected to the corresponding optical-electrical converter PIN of demodulating equipment.1 × N splitter N branch output Zhong mono- tunnel be not connected to 1 × 2 bonder and be directly connected to gas absorption cell.
High-speed, high precision demodulating equipment includes demodulating branch road and demarcates branch road；Demodulation branch road includes photodetector；Signal amplifier, gain controller, comparator, enumerator, microprocessor, gas absorption cell, its connect control planning be：Photodetector converts light signals into electrical signal and enters amplifier, amplifier gain controlled in programmable automatic gain control, its output enters comparator, the reference signal that the signal that amplifier inputs is given with microprocessor is compared by comparator, its comparative result flip-flop number, the count results of this enumerator are used for obtaining the wavelength information of sensing grating.Microprocessor, compared with demodulation branch road, the signal of demarcation branch road enters photodetector after being exported by gas absorption cell, and remaining connects identical with demodulation branch road with control planning.
The laser diode that the present invention adopts is CW-DFB or CW-DBL type, in order to realize carrying out continuous high speed modulation by electric current to wavelength.
Because laser diode can only provide a very narrow wavelength scanning range, so, the all of sensor of the present invention all adopts the grating of identical wavelength, for distinguishing different sensors, it is that each sensor is equipped with a passage exclusively enjoying using multifiber cable, one or more optical cable can be adopted according to practical situations, but optical fiber total core number is more than the overall channel number of demodulating equipment, and the port number of demodulating equipment should be more than the total quantity of sensor.
The scheme that the present invention adopts, because laser diode spectral line is extremely narrow, energy height is concentrated, even across 1：128 splitters carry out energy attenuation, and each passage still has enough signal to noise ratios, are shared laser instrument and gas wavelength standard is laid a good foundation.More passage ensure that the economy of system, considers from practical application, and general 8-64 passage is more reasonable.
The wavelength high-velocity scanning of the present invention is obtained by modulating laser diode feed-in electric current, and wavelength low-velocity scanning is realized by the temperature modulating laser diode.
The present invention is controlled the starting point of scanning wavelength and is extended the coverage of length scanning by the temperature controlling laser module.
The present invention adopts the LASER Light Source of multiple difference centre wavelengths, and relay work, makes the scope of wavelength high-velocity scanning be expanded under control of the microprocessor.
The Wavelength demodulation of the present invention adopts：The time of driving current scanning corresponds to specific wavelength, reflected signal exceedes given threshold to be proved the forward position of FBG is detected, prove to detect the tailing edge of FBG again below threshold value, obtain, by this two time saltus steps, width and the centre wavelength that position thus can get FBG reflection peak.
The present invention adopts high-speed counter by intensive for wavelength scanning range division；Each scan period carries out dynamic calibration using gas absorption spectrum to laser instrument；Using the feature of the feed-in current scanning wavelength curve of laser instrument, it is carried out with the technical measures such as Linearized correction and ensures high demodulation accuracy.
The present invention adopts programmable automatic gain control circuit, provides different gains for different passages, all of sensor signal is on after amplifier, being operated in identical setting amplitude.The method significantly improves the dependable with function of system.
The present invention is adopted as the method that different passages provide different sample mean number of times, enables the system to measure high and low frequency signal simultaneously.The method effectively improves the dependable with function of system.
The beneficial effect of the invention：
The technical scheme that the present invention is proposed at a high speed, it is possible to achieve the high speed of FBG, in high precision, multichannel demodulation.Typical technology index is：Sample frequency reaches 0.11pm up to 2kHz, the wavelength resolution under 1 kHz sample rate, and precision reaches 1pm；Wavelength resolution precision under 10H sample rate reaches 0.01pm, and precision reaches 0.1pm；The number of channels that demodulator is processed simultaneously is at least 16 passages, and system has enough abilities to reach 96 passages.The number of channels that the present invention realizes ensure that the lower cost under optical fiber sensing system high-performance.
Brief description
Fig. 1 is the system diagram of the present invention
Fig. 2 is the sensing passage distribution diagram of the present invention
Fig. 3 illustrates waveform and the time relationship of main signal of the present invention
Fig. 4 Wavelength demodulation schematic diagram
Fig. 5 wavelength calibration schematic diagram
Fig. 6 is the starting point in the embodiment of the present invention 1 using temperature adjusting length scanning
Fig. 7 is multibeam laser light source relay extension length scanning coverage schematic diagram in the embodiment of the present invention 2
Below in conjunction with drawings and Examples, the present invention is further elaborated on, but the invention is not restricted to these embodiments.
Embodiment
1
：
16
Passage
FBG
Earthquake data acquisition station
Demand analyses：The work characteristics of seismic prospecting detector is that from possible -40Co 70Co, during work, all of sensor is all located at identical temperature ambient temperature and temperature change is little.System is in holding state at ordinary times, records from excite beginning several seconds（At most tens seconds）Seismic signal, this system requirements at a high speed, in high precision, multichannel collecting signal.
Refering to Fig. 1, Fig. 2 and Fig. 3, Fig. 4, the FBG of the present embodiment at a high speed, in high precision, the method for multichannel demodulation and realize device and include：
Length scanning LASER Light Source is made up of following part：Laser diode 11；Diode drive circuit 12, diode temperature sensor 13, refrigeration-heating thermostat units 14 and control unit 15；It connects control planning：Control unit 15 receives the laser diode temperature information of sensor 13, produces adjustment temperature instruction and send thermostat units 14, produces drive signal and send diode drive circuit 12；Diode drive circuit 12 controls laser diode 11 with it after amplifying drive signal, and the temperature of laser diode 11 is subject to controlling of thermoregulation circuit 14, and the input of 1 × 16 splitter of multichannel array is sent in the output of its laser（1 end）.
See on Fig. 3, Fig. 4, from the waveform of diode drive circuit 12 output
, be the sawtooth waveforms of a current amplitude modulation, in the present embodiment its scan period be 0.5ms, current amplitude be 50mA 250mA. further from Fig. 3, from laser diode 11 output waveform, it is that a wavelength scans in time, the sweep limitss of the present embodiment medium wavelength are 1.2nm, here, the range 1.2nm of wavelength is established with time cycle 0.5ms and contacts.
Refering to Fig. 2, the array apparatus 2 realizing the application of sensor multichannel are made up of following part：One 1 × 16 splitter 21；15 1 × 2 bonders 22.Multifiber cable 3, totally 28 core optical cables（31 and 32）Totally 16 optical fiber；The 12 grating seismic sensors of 412 grade that include 401,401 in sensor array 4 altogether ....Wherein：1 × 16 splitter 15 output branches correspondence be connected to the output1 end of 15 1 × 2 bonders 22, the input1 end of 15 1 × 2 bonders 22 is respectively connected with 28 core cables 31 and 32（The vacant backup of a piece optical fiber of wherein 8 core optical cables 32）, distribute an optical fiber for each sensor.The output2 end of 15 1 × 2 bonders is connected to the corresponding optical-electrical converter PIN of demodulating equipment, and 1 × 16 splitter wherein tunnel is directly connected to gas absorption cell 50 without 1 × 2 bonder.
More further, in the present embodiment（Fig. 6-2）, from demodulator, two directions connect 28 core optical cables respectively to the left and right, and 4 optical fiber therein are connected to grating sensor, and the spacing distance of these sensors is 50 meters.
Refering to Fig. 3, when wavelength is consistent with sensing grating, wavelength inquiry laser can reflect, the waveform reflecting from sensing grating, it is an optical grating reflection spectrum, its distribution in time, substantially reflect the information of wavelength.
Refering to Fig. 1, high-speed, high precision demodulating equipment 5 includes demodulating branch road and demarcates branch road；Demodulation branch road includes photodetector 51；Signal amplifier 52 gain controller 53, comparator 54, enumerator 55, microprocessor 56, its connect control planning be：Photodetector 51 converts light signals into electrical signal and enters amplifier 52, the gain controlled of amplifier 52 controls 53 in programmable automatic gain, its output enters comparator 54, the reference signal that the signal that amplifier 52 inputs is given with first microprocessor 15 is compared by comparator 54, its comparative result flip-flop number 55, the count results of this enumerator send the second microprocessor 56 to be used for obtaining the wavelength information of sensing grating.Compared with demodulation branch road, the signal of demarcation branch road enters photodetector 51 after being exported by gas absorption cell 50, and remaining connects identical with demodulation branch road with control planning.
Refering to Fig. 3, optical grating reflection signal waveform, enter diode 51 after, its optical signalIt is converted into the signal of telecommunication that profile is similar toIn order to process, after amplifying further, its amplitudeThere occurs change, but the wavelength information that profile is comprised continues to retain.In order to extract the wavelength information of Bragg grating, the signal of enlargement rangeEnter comparator to be compared with a reference amplitude, the time location in two characteristic points place scan periods of comparator, contain the information of wavelength.Scanning starts every time, first microprocessor 15 triggers an enumerator and starts counting up, the output of comparator is as another one trigger, the count value of the moment enumerator that is located is read and delivers to the second microprocessor 56, obtain the lead and trail edge of the optical grating reflection ripple of two-digit to this, that is,：Obtain width information and the centre wavelength information of grating.
The wavelength high-velocity scanning of the present embodiment is obtained by modulating laser diode feed-in electric current, and wavelength low-velocity scanning is realized by the temperature modulating laser diode.The scanning laser light source of wherein employing is the wavelength continuously adjustabe of a 40mW（CW）Distributed feed-back（DFB）Laser diode FRL15DCWD, obtains the wavelength scanning range of 1.2nm to the amplitude modulation(PAM) carrying out 80% of feed-in electric current.
Carry out Wavelength demodulation with the scanning light source of the present embodiment, system can advantage is obtained that：
First, can carry out demodulating at a high speed.Because wavelength does not almost postpone to the response of electric current（Picosecond response speed）, in theory, system can obtain the sample frequency of hundred KHz, and FBG system is sufficient for sound wave or the collection of higher frequency signal.
Second, because the spectral line of this kind of laser instrument is extremely narrow（Given index 5MHz）, the energy height of laser is concentrated, and surveys through 1：128 splitting loss, its energy still can obtain good signal to noise ratio it means that a laser instrument has enough energy roads up to a hundred sensing grating to be scanned demodulating simultaneously.
3rd, because the spectral line of this kind of laser instrument is extremely narrow, for segmenting Scanning step, and then raising demodulation accuracy stays sufficient leeway.
With the length scanning of the present embodiment, there are the following problems and the method for solution is as follows：
First, due to the narrow range of wavelength high-velocity scanning, for ensureing the scanning all of sensor of covering it is desirable to sensor spectrum width is less（Less than 0.3nm）, in system, all of sensor will ensure good concordance.
Second, due to the change of ambient temperature, the sensing grating wavelength of cymoscope can drift about, and the present embodiment, using the temperature of adjustment laser instrument, makes the scope of dynamic scan most preferably cover whole sensing gratings.
In the present embodiment, the possible temperature of field work environment is -40Co
+ 70Co, temperature affects about 12pm/1Co. to grating wavelength so temperature is about (110Co × 12) 1300pm. to maximum effect of sensing system
On the other hand, the wavelength/temperature coefficient of this model laser diode is about 100pm/1Co, and the attainable span of control to wavelength being obtained by controlling laser temperature of the present embodiment is about 2200pm it is sufficient to compensate the impact of ambient temperature.So, the design that high-velocity scanning scope optimally covers grating wavelength is made finally to be achieved to adjust laser temperature.
Three important measures ensure that the present embodiment obtains superelevation demodulation accuracy.First, using high-speed counter by intensive for wavelength scanning range division；Second, each scan period carries out dynamic calibration using gas absorption spectrum to laser instrument；3rd, using the feature of the feed-in current scanning wavelength curve of laser instrument, Linearized correction is carried out to it, below in conjunction with schematic diagram, its operation principle is described in detail.
Waveform refering to Fig. 4, drive circuit for laser generation initial current 50mA, terminate electric current 270mA,
The sawtooth current of scan period 1mS, is applied to laser instrument, and this laser instrument creates laser Lp（Waveform）, on a timeline, from the origin scans of sawtooth waveforms to terminal, time stroke is 0.5mS to laser Lp,
In wavelength axis, the wavelength of laser Lp continuously scans termination wavelength X e. so from start wavelength λ s, and sweep time and wavelength are provided with the relation of determination.When incident optical maser wavelength is overlapped with grating wavelength, incident illumination can produce reflection, the reflected light signal Sg of this grating（Waveform）Temporal position in the scan period contains the information of its place wavelength, and the voltage signal Vs after detection is amplified inherits the wavelength characteristic of optical grating reflection signal Sg, in a comparator（Waveform）, reference signal Vrf is compared with grating signal Vs, and two consistent point P1 and P2 of its voltage amplitude both have expressed the wavelength width feature of grating, also have expressed the wavelength location feature of grating.Reading P1 and P2 point data on a timeline can have multiple methods, but no matter which kind of method, by time shafts divide thinner, you can obtain higher wavelength accuracy.The present embodiment is divided to time shafts using high-speed counter, and each sawtooth sweep initiates, and one enumerator of triggering is started working, as reference voltage Vrf and signal voltage Vs amplitude identical time location T1 T2 in comparator, by flip-flop number（Waveform）Produce and count N1 and N2, this counting has been finally completed from grating wavelength information（Analog quantity）Measurement and conversion to digital signal.Enumerator low price and speed is exceedingly fast, a common 20M enumerator, is equivalent to and for the time range of 0.5mS to be divided into 10K, that is, wavelength scanning range is divided into 104 steps, and in the present embodiment, the length scanning of laser instrument is 1.1nm,
So, such its wavelength step pitch（Resolution）It is about 0.11pm.
Section 2 ensures that the measure that the present embodiment obtains superelevation demodulation accuracy is to carry out dynamic calibration using gas absorption spectrum to laser instrument in each scan period, refering to Fig. 5-1 Fig. 5-2. in Fig. 5-1, one can consider that in this each cycle, temperature and noise are constant, but the temperature in different scanning cycle and electronic noise are non-constant, this will affect the starting wavelength point of each scanning, namely under different cycles, the corresponding wavelength value of one identical numerical value of enumerator is different, for this, the present embodiment eliminates this error using with the method that standard gas adsorption is compared.
First, under 25Co standard calibration state, the Nr1 that we are obtained with reference channel, Nr2 calculate GAS ABSORPTION peak Nrs（Nrs =（Nr2 -Nr1)/2）This numerical value (the present embodiment measured value 1870=GAS ABSORPTION peak 1550.231nm).Secondly, we are with the reference channel meter reading Nr1 of Actual metering on kinetic state, Nr2, Nr3... ... Nrk and this standard value（1870）Difference, obtain a series of dynamic error N δ 1, N δ 2, N δ 3 ... ... N δ k, finally, the reading in identical for each sensing passage sampling period is added by we with corresponding dynamic error, obtains the numerical value after correction.This numerical value eliminates the wavelength dither causing due to temperature or other low-frequency disturbance.It is shown in Table one.
Table one：Sensing passage reading after dynamic calibration
Section 3 ensures that the measure that the present embodiment obtains superelevation demodulation accuracy is that the current-wavelength curve to laser instrument carries out Linearized correction, and gives each meter reading one corresponding unique wavelength value simultaneously.
Due to the current-wavelength curve of semiconductor laser nonideal linear, for improving precision it is necessary to linearization process is carried out using certain method.The method of generally Linearized correction is fitting process or look-up table, and the present embodiment mixing employs look-up table and fitting process.Specific practice is：Produce current-wavelength-reading comparison table first, because the starting point electric current of scanning is 50mA, terminal is 270mA, in scanning process, enumerator completes the counting from 0 to 10000, and the sweep current applying may be considered more satisfactory linear, and we apply different electric currents to laser instrument, read the wavelength value under phase induced current with band meter, obtain table two
Table two：Wavelength-electric current-reading synopsis
Secondly, on the basis of table two data, by approximating method and extend and fill up data, the final corresponding table three obtaining reading wavelength actual wavelength.
Due to can not possibly also all of 10000 contrasting datas of unnecessary test, feasible method is divided into several areas and tests several points the present embodiment using being divided into 3 area A:Every mono- point of 10mA between 50mA-110mA, mono- point of 10mA between 110-220, every mono- point of 5mA between 220-270）Then adopt fitting process, table three will be formed from reading wavelength from the whole polishing of 1 to 10000 corresponding data.
Finally table three is stored in a computer, the meter reading of per sampling period each passage（Table one）Unique wavelength readings can be obtained by look-up table three.
The safeguard measure of dependable with function：
During using in the wild, because operator are different, the connection of optical cable, the angle of coiling all has the discordance being difficult to avoid that, the method that the present embodiment adopts automatic growth control, there is provided different gains for different passages, make all sensor signals on after amplifier, being operated in identical setting amplitude.Different from general agc circuit, the present embodiment carries out providing a series of different gain coefficients according to program using by computer, and detects the width of reflecting grating, on this basis simultaneously, self-inspection and initialization are carried out to each sensing passage, greatly improves the reliability of system and the convenience of operation.
Embodiment 2：96 passage hull health monitoring data collecting systems
Embodiment 2 is the mixing sensing and monitoring system of hull health status, and construction party requires to install 80 sensors, and Contents for Monitoring includes the abnormal vibrations state of electromotor（High-frequency signal）, temperature and pressure in boiler, hull strains（Low frequency signal）Situation etc., due to any state being likely to be at transducer range of these data, and needs real time data acquisition simultaneously, the dependence temperature adjustment in embodiment 1, and the method that selectivity covers whole grating dynamic area is difficult to.
The present embodiment is identical with embodiment one in overall plan, its improvement part（Refering to Fig. 7-1 and Fig. 7-2）It is, using the high-power CW-DBL laser diode XL15DCWX of two customizations,
The output of its bis- laser of laser power 200mW is merged into through bonder 11-4 and is entered 1 × N wavelength splitter 21.The centre wavelength of two laser diodes is respectively 1550nm and 1551nm, can obtain the dynamic scan scope of 2.7nm, (be shown as λ 1s λ 1e on Fig. 7-2 under 80% current amplitude modulation；λ2s—λ2e).During work, sequentially to drive circuit 12-1 and 12-2, to provide width in turn be 0.25mS to MCU1, the sawtooth signal of cycle 2K, and MCU1 controls 13-1/14-1 and 13-2/14-2 simultaneously, by laser setup on temperature control point T1 and T2 of 2 fixations.Suitably choose T1 and T2, make 2 optical maser wavelengths form relay, overlapping wavelengths scope（λ2s—λ1e）For 0.4nm, it is finally reached the scanning wavelength bandwidth of 5nm (see 7-2, λ combination).
The present embodiment is the dependable with function of improvement system, using the equal high-speed sampling to all signals（2K adopts rate）Will not distortion with the collection guaranteeing high-frequency vibration signal.Due to there are multiple different sensors in system, need to measure high and low frequency signal simultaneously, the present embodiment employs the method providing the 10 times and 100 times different average times such as average respectively for different passages, both the needs simultaneously detecting high and low frequency signal had been met, the system that in turn simplify is constituted, and improves precision.
Above-mentioned two specific embodiments are not intended to limit the range of application of invention, and the non-intrinsically safe made in all principles in invention is simply changed replacement, all should be included within protection scope of the present invention.
Claims (10)
1. a kind of to FBG (Fiber Bragg Grating FBG) at a high speed, in high precision, multichannel demodulation method and realize device, its feature includes：
Length scanning LASER Light Source is made up of following part：Laser diode 11；Diode drive circuit 12, diode temperature sensor 13, refrigeration-heating thermostat units 14 and control unit 15；It connects control planning：Control unit 15 receives the laser diode temperature information of sensor 13, produces adjustment temperature instruction and send thermostat units 14, produces drive signal and send diode drive circuit 12；Diode drive circuit 12 controls laser diode 11 with it after amplifying drive signal, and the temperature of laser diode 11 is subject to controlling of thermoregulation circuit 14, and the input of 1 × N splitter of multichannel array is sent in the output of its laser（1 end）；The array apparatus 2 realizing the application of sensor multichannel are made up of following part：One 1 × N splitter 21；N-1 1 × 2 bonder 22；Multifiber cable 3, the 3K common K root multifiber cable that wherein may include 31,32 ...；The m sensing grating such as 4m that include 41,42 in sensor array 4 altogether ...；Wherein：1 × N splitter N-1 output branch correspondence be connected to the output1 end of N-1 1 × 2 bonder 22, the input1 end of N-1 1 × 2 bonder 22 is connected to sensor by multifiber cable；Multifiber cable distributes an optical fiber for each sensor, and sensor array and bonder 22 are connected one by one；The output2 end of 1 × 2 bonder is connected to the corresponding optical-electrical converter PIN of demodulating equipment, and wherein one tunnel of N branch need not connect 1 × 2 bonder and be directly connected to gas absorption cell；High-speed, high precision demodulating equipment 5 includes demodulating branch road and demarcates branch road；Demodulation branch road includes photodetector 51；Signal amplifier 52, gain controller 53, comparator 54, enumerator 55, microprocessor 56, gas absorption cell 50, its connect control planning be：Photodetector 51 converts light signals into electrical signal and enters amplifier 52, the gain controlled of amplifier 52 controls 53 in programmable automatic gain, its output enters comparator 54, the reference signal that the signal that amplifier 52 inputs is given with microprocessor 15 is compared by comparator 54, its comparative result flip-flop number 55, the count results of this enumerator are used for obtaining the wavelength information of sensing grating；Compared with demodulation branch road, the signal of demarcation branch road enters photodetector 51 after being exported by gas absorption cell 50, and remaining connects identical with demodulation branch road with control planning；The composition of the present invention also includes：Complete general circuit 61 and the computer 62 for the storage of demodulating data display processing of the functions such as power supply, protection.
2. according to the FBG described in claim 1 at a high speed, the method that is demodulated of high-precision multi-path and realize device it is characterised in that：Laser diode is CW-DFB diode or CW-DBL type.
3. according to the FBG described in claim 1 at a high speed, the method that is demodulated of high-precision multi-path and realize device it is characterised in that：Its total number of channels N be less than or equal to more than or equal to 8 64 integer, sensing grating quantity m be less than N-1；Multifiber cable provides
Optical fiber total core number K is more than N, and described multifiber cable can be one or many.
4. according to the FBG described in claim 1 at a high speed, the method that is demodulated of high-precision multi-path and realize device it is characterised in that：Wavelength high-velocity scanning is obtained by modulating laser diode feed-in electric current, and wavelength low-velocity scanning is realized by the temperature modulating laser diode.
5. according to the FBG described in claim Isosorbide-5-Nitrae at a high speed, the high-precision multi-path method being demodulated and the length scanning LASER Light Source of realizing device it is characterised in that：Using the LASER Light Source of multiple difference centre wavelengths, under the control of MCU, relay work, makes the scope of wavelength high-velocity scanning be expanded.
6., according to the length scanning LASER Light Source described in claim Isosorbide-5-Nitrae, the implementation method expanding its wavelength scanning range is：Control the starting point of scanning wavelength and extend the coverage of length scanning by the temperature controlling laser module.
7. according to the FBG described in claim 1 at a high speed, the method that is demodulated of high-precision multi-path and realize device and be characterised by：Wavelength demodulation method is：The time of driving current scanning corresponds to specific wavelength, reflected signal exceedes given threshold to be proved the forward position of FBG is detected, prove to detect the tailing edge of FBG again below threshold value, obtain, by this two time saltus steps, width and the centre wavelength that position thus can get FBG reflection peak.
8. according to the FBG described in claim 1 at a high speed, high-precision multi-path demodulation method and realize device and be characterised by, it obtains the method for superelevation demodulation accuracy is：Using high-speed counter by intensive for wavelength scanning range division；Each scan period carries out dynamic calibration using gas absorption spectrum to laser instrument；Using the feature of the feed-in current scanning wavelength curve of laser instrument, Linearized correction is carried out to it.
9. according to the FBG described in claim 1 at a high speed, high-precision multi-path demodulation method and realize device and be characterised by, for improving the dependable with function of system, using programmable automatic gain control circuit, there is provided different gains for different passages, all of sensor signal is on after amplifier, being operated in identical setting amplitude.
10. according to the FBG described in claim 1 at a high speed, high-precision multi-path demodulation method and realize device and be characterised by, for improving the dependable with function of system, it is adopted as the method that different passages provide different sample mean number of times, enable the system to measure high and low frequency signal simultaneously.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109489801A (en) * | 2018-12-17 | 2019-03-19 | 电子科技大学 | Multi-core optical fiber distribution acoustic wave sensing system based on space division multiplexing |
| CN109506684A (en) * | 2018-12-05 | 2019-03-22 | 山东微感光电子有限公司 | The wavelength modification method and system of quick laser scanning device demodulation FBG sensor |
| CN114485901A (en) * | 2021-12-31 | 2022-05-13 | 武汉烽理光电技术有限公司 | High-speed modulation and demodulation system and method based on tunable laser light source |
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