CN102252704A - High-speed, high-precision and multi-channel Bragg grating demodulation device - Google Patents
High-speed, high-precision and multi-channel Bragg grating demodulation device Download PDFInfo
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Abstract
The invention belongs to the optical fiber sensing technical field and discloses a high-speed, high-precision and multi-channel Bragg grating demodulation device. The system adopts a wavelength scanning laser light source and a corresponding wavelength control method, a method for realizing sensor multi-channel and an array device, a high-speed and high-precision demodulation method and a corresponding circuit, and an auxiliary circuit and a computer which are used to realize the function. The demodulation device can be used to realize high-speed, high-precision and multi-channel demodulation, calibrate the absolute value of the central wavelength of each fiber Bragg grating (FBG) and be suitable for various sensors of temperature, pressure, vibration and the like, which are based on the FBG principle.
Description
Technical field
The invention belongs to sensory field of optic fibre, specially refer to the method and the implement device that Bragg grating sensor are carried out high-speed, high precision demodulation and hyperchannel application.
Background technology
Fibre Optical Sensor is since coming out the seventies in last century, because its high sensitivity passes--and the sense unification, superior Electro Magnetic Compatibility or the like series of advantages is subjected in the industry great attention and expectation.
Compare with other type fiber sensor, fiber grating is because volume is little, be very easy to merge with sensing arrangement and material, constitute multiple sensors parts such as temperature, pressure, flow, strain, generally believe that in the industry fiber grating is an optical fiber sensing technology practicability, a technology path of large-scale application with very good prospect.
The essence of demodulation is that the wavelength variations with fiber grating detects, and it has carried the information that will detect physical quantity.High precision, fast, hyperchannel, realize demodulation cheaply, be an important prerequisite of fiber-optic grating sensor large-scale engineering application.
Domestic and international considerable research report and patented claim (mandate) relate 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 precision grating fibers demodulating system (Chinese patent CN1908713A)
Ultra high speed optical fiber grating sensor demodulating system and its implementation (Chinese patent CN1494237A)
Hyperchannel Bragg grating sensor (United States Patent (USP) 5426297)
Use the hypersensitivity sensor (United States Patent (USP) 5706079) of Chirp Bragg optical grating reflection
Although considerable similar work is arranged,, the method and apparatus of grating demodulation that can satisfy " high precision, hyperchannel and lower cost at a high speed, " simultaneously is very rare.
Summary of the invention
The problem to be solved in the present invention is, provides a kind of and can satisfy the demodulation techniques scheme of " high-precision multi-path and lower cost at a high speed, " simultaneously and realize the device of this scheme.
Particular content of the present invention comprises:
The length scanning LASER Light Source is by forming with the lower part: laser diode; Diode drive circuit, diode temperature sensor, refrigeration-heating temperature adjustment unit and control module; It connects control relation: the laser diode temperature information of control module receiving sensor, and produce the instruction of adjustment temperature and send the temperature adjustment unit, produce drive signal and send diode drive circuit; Diode drive circuit amplifies the back with drive signal and controls laser diode with it, and the temperature of laser diode is subjected to the control of thermoregulation circuit, and the input end of 1 * N splitter of multichannel array is sent in its laser output.The array apparatus of realizing the application of sensor hyperchannel is by forming with the lower part: 1 * N splitter; N-1 1 * 2 coupling mechanism.1 or several multifiber cable; Comprise m sensing grating in the sensor array.Wherein: 1 * N splitter N-1 output branch correspondence be connected to the output1 end of N-1 1 * 2 coupling mechanism, N-1 1 * 2 coupling mechanism input1 end is connected to sensor by multifiber cable.Multifiber cable is optical fiber of each sensor assignment.The output2 end of N-1 1 * 2 coupling mechanism is connected to the corresponding photoelectric commutator PIN of demodulating equipment.1 * N splitter N branch output in a road do not connect 1 * 2 coupling mechanism and directly connect gas absorption cell.
The high-speed, high precision demodulating equipment comprises the demodulation branch road and demarcates branch road; The demodulation branch road comprises photodetector; Signal amplifier, gain controller, comparer, counter, microprocessor, gas absorption cell, its connection control relation is: photodetector changes light signal into electrical signal and enters amplifier, and Amplifier Gain is controlled by automatic gain control able to programme, its output enters comparer, the reference signal that comparer is given with the signal of amplifier input and microprocessor compares, its comparative result flip-flop number, and the count results of this counter is used to obtain the wavelength information of sensing grating.Microprocessor is compared with the demodulation branch road, and the signal of demarcating branch road is gone into photodetector by gas absorption cell output is laggard, and all the other connections are identical with the demodulation branch road with control relation.
The laser diode that the present invention adopts is CW-DFB or CW-DBL type, in order to realize by electric current wavelength being carried out the continuous high speed modulation.Because laser diode can only provide a very narrow wavelength scanning range, so, the all sensors of the present invention all adopt the grating of identical wavelength, for distinguishing different sensors, adopt multifiber cable to be equipped with a passage that exclusively enjoys for each sensor, can adopt one or more optical cable according to practical situations, but the total core number of optical fiber 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 the laser diode spectral line is extremely narrow, energy height is concentrated, even carry out energy attenuation through 1: 128 splitter, each passage still has enough signal to noise ratio (S/N ratio)s, lays a good foundation for sharing laser instrument and gas standard of wavelength.More passage has guaranteed the economy of system, considers from practical application, and general 8-64 passage is more reasonable.
Wavelength high-velocity scanning of the present invention obtains by modulated laser diode feed-in electric current, and the wavelength low-velocity scanning is realized by the temperature of modulated laser diode.
The present invention comes the starting point of gated sweep wavelength by the temperature of control laser module and expands the coverage of length scanning.
The present invention adopts the LASER Light Source of a plurality of different centre wavelengths, and relay work under the control of microprocessor is expanded the scope of wavelength high-velocity scanning.
Wavelength demodulation of the present invention adopts: the time of drive current scanning is corresponding to certain wavelengths, reflected signal surpasses the forward position that the setting threshold proof detects FBG, be lower than the back edge that the threshold value proof detects FBG once more, get width and the centre wavelength that the position can obtain the FBG reflection peak thus by these two time saltus steps.
The present invention adopts high-speed counter with the intensive division of wavelength scanning range; Each scan period using gases absorption spectra is carried out dynamic calibration to laser instrument; Utilize the feature of the feed-in electric current-scanning wavelength curve of laser instrument, it is carried out technical measures such as linearization correction and guarantee high demodulation accuracy.The present invention adopts automatic gain control circuit able to programme, and for different passages provides different gains, all sensor signals are operated on the identical setting amplitude through behind the amplifier.This method has significantly been improved the reliability and the practicality of system
The present invention is adopted as the method that different passages provides different sample mean number of times, makes system can measure the high and low frequency signal simultaneously.This method has been improved the reliability and the practicality of system effectively.
The beneficial effect of the invention:
The technical scheme that the present invention is proposed at a high speed can realize high speed, high precision, the hyperchannel demodulation of FBG sensor.The typical technology index is: sample frequency can reach 2kHz, and the wavelength resolution under the 1kHz sampling rate reaches 0.11pm, and precision reaches 1pm; Wavelength resolution precision under the 10H sampling rate reaches 0.01pm, and precision reaches 0.1pm; The simultaneously treated number of channels of detuner is at least 16 passages, and system has enough abilities to reach 96 passages.The number of channels that the present invention realizes has guaranteed the lower cost under the optical fiber sensing system high-performance.
Description of drawings
Fig. 1 is a system diagram of the present invention
Fig. 2 is a sensing passage distribution diagram of the present invention
Fig. 3 has showed the waveform and the time relationship of the main signal of the present invention
Fig. 4 Wavelength demodulation schematic diagram
Fig. 5 wavelength calibration schematic diagram
Fig. 6 is the starting point of serviceability temperature regulation and control length scanning in the embodiment of the invention 1
Fig. 7 is a multibeam laser light source relay expansion length scanning coverage synoptic diagram in the embodiment of the invention 2
Fig. 8 is a structured flowchart of the present invention
Below in conjunction with drawings and Examples the present invention is further elaborated, but the invention is not restricted to these embodiment.
Embodiment 1: 16 passage FBG earthquake data acquisition stations
Demand analysis: the work characteristics of seismic prospecting detector is, environment temperature is from may-40 ℃-70 ℃, during work all sensors all be positioned under the uniform temp and temperature variation little.System is in holding state at ordinary times, writes down from the seismic signal of several seconds (tens seconds at the most) that excite beginning, this system requirements high speed, high precision, multichannel collecting signal.
Consult Fig. 1, Fig. 2 and Fig. 3, Fig. 4, the method and the implement device of the FBG high speed of present embodiment, high precision, hyperchannel demodulation comprise: the length scanning LASER Light Source is by forming with the lower part: laser diode 11; Diode drive circuit 12, diode temperature sensor 13, refrigeration-heating temperature adjustment unit 14 and control module 15; It connects control relation: the laser diode temperature information of control module 15 receiving sensors 13, and produce the instruction of adjustment temperature and send temperature adjustment unit 14, produce drive signal and send diode drive circuit 12; Diode drive circuit 12 amplifies the back with drive signal and controls laser diode 11 with it, and the temperature of laser diode 11 is subjected to the control of thermoregulation circuit 14, and the input end (1 end) of 1 * 16 splitter of multichannel array is sent in its laser output.
From Fig. 3, see on Fig. 4, from the waveform of diode drive circuit 12 output 1., be the sawtooth wave of a current amplitude modulation, its scan period is 0.5ms in the present embodiment, current amplitude is that 50mA-250mA. is further from Fig. 3, from the waveform of laser diode 11 output 2., be that a wavelength scans in time, the sweep limit of present embodiment medium wavelength is 1.2nm, at this, the range 1.2nm of wavelength and time cycle 0.5ms have set up and have got in touch.
Consult Fig. 2, the array apparatus 2 of realizing the application of sensor hyperchannel is by forming with the lower part: one 1 * 16 splitter 21; 15 1 * 2 coupling mechanisms 22.Multifiber cable 3, totally 28 core optical cables (31 and 32) totally 16 optical fiber; Comprise 401 altogether in the sensor array 4,12 grating seismic sensors such as 401...412.Wherein: 1 * 16 splitter 15 output branch correspondences be connected to the output1 end of 15 1 * 2 coupling mechanisms 22, the input1 of 15 1 * 2 coupling mechanisms 22 end and 28 core cables 31 link to each other respectively (wherein 8 core optical cables 32 vacant backup of optical fiber) with 32, are optical fiber of each sensor assignment.The output2 of 15 1 * 2 coupling mechanisms end is connected to the corresponding photoelectric commutator PIN of demodulating equipment, and 1 * 16 splitter wherein one the road directly connects gas absorption cell 50 without 1 * 2 coupling mechanism.
Nearer one the step, in the present embodiment (Fig. 6-2), from detuner to the left and right two directions connect 28 core optical cables respectively, 4 optical fiber have wherein connected grating sensor, the spacing distance of these sensors is 50 meters.
Consult Fig. 3, consistent with sensing grating when wavelength, wavelength inquiry laser can reflect, and 3. the waveform that reflects from sensing grating is an optical grating reflection spectrum, and its distribution has in time reflected the information of wavelength in fact.
Consult Fig. 1, high-speed, high precision demodulating equipment 5 comprises the demodulation branch road and demarcates branch road; The demodulation branch road comprises photodetector 51; Signal amplifier 52 gain controllers 53, comparer 54, counter 55, microprocessor 56, it connects control relation: photodetector 51 changes light signal into electrical signal and enters amplifier 52, the gain controlled of amplifier 52 controls 53 in automatic gain able to programme, its output enters comparer 54, comparer 54 compares the signal of amplifier 52 input and first microprocessor 15 given reference signals, its comparative result flip-flop number 55, the count results of this counter send second microprocessor 56 to be used to obtain the wavelength information of sensing grating.Compare with the demodulation branch road, the signal of demarcating branch road is gone into photodetector 51 by gas absorption cell 50 outputs are laggard, and all the other connections are identical with the demodulation branch road with control relation.
Consult Fig. 3, the optical grating reflection signal waveform 3., enter after the diode 51,3. its light signal is converted into the similar electric signal of profile 4. so that handle, after further amplifying, 5. variation has taken place in its amplitude, but the wavelength information that profile comprised continues to keep.In order to extract the wavelength information of Bragg grating, the signal of enlargement range 5. enters comparer and a reference amplitude compares, and the time location in two unique point place scan periods of comparer has comprised the information of wavelength.Each scanning beginning, first microprocessor 15 triggers a counter and begins counting, the output of comparer is as the another one trigger pip, second microprocessor 56 is read and delivered to the count value of counter with the place moment, obtain the forward position and the edge, back of the optical grating reflection ripple of two-digitization to this, that is: obtained the width information and the centre wavelength information of grating.
The wavelength high-velocity scanning of present embodiment obtains by modulated laser diode feed-in electric current, and the wavelength low-velocity scanning is realized by the temperature of modulated laser diode.Wherein the scan laser light source of Cai Yonging is wavelength adjustable continuously (CW) distributed feed-back (DFB) the laser diode FRL15DCWD of a 40mW, to the wavelength scanning range that 80% amplitude modulation(PAM) has obtained 1.2nm of carrying out of feed-in electric current.
Scanning light source with present embodiment carries out Wavelength demodulation, and system can obtain following advantage:
The first, can carry out the high speed demodulation.Because wavelength does not almost postpone (picosecond response speed) to the response of electric current, in theory, system can obtain the sample frequency of hundred KHz, and the FBG system is enough to carry out sound wave or the more collection of high-frequency signal.
Second, because the spectral line extremely narrow (given index 5MHz) of this kind laser instrument, the energy height of laser is concentrated, actual measurement was through 1: 128 splitting loss, its energy still can obtain good signal-to-noise, this means that a laser instrument has enough energy simultaneously roads up to a hundred sensing grating to be scanned demodulation.
The 3rd, because the spectral line of this kind laser instrument is extremely narrow, be segmentation scanning step pitch, and then the raising demodulation accuracy stay sufficient leeway.There are the following problems and the method that solves is as follows with the length scanning of present embodiment
The first, because the narrow range of wavelength high-velocity scanning covers all sensors for guaranteeing scanning, require sensor spectrum width less (less than 0.3nm), sensors all in the system will guarantee good consistance.
The second, because the variation of environment temperature, the sensing grating wavelength of wave detector can drift about, and present embodiment adopts the temperature of adjusting laser instrument, makes the scope of dynamic scan cover whole sensing gratings best.
In the present embodiment, the possible temperature of field work environment is-40 ℃-+70 ℃, so temperature influences about 12pm/1 ℃ to grating wavelength. temperature is approximately (110 ℃ * 12) to maximum effect of sensing system, and 1300pm. is on the other hand, wavelength/the temperature coefficient of this model laser diode is approximately 100pm/1 ℃, the attainable range of control to wavelength that is obtained by the control laser temperature of present embodiment is approximately 2200pm, is enough to the compensate for ambient Temperature Influence.Like this, the design that makes the high-velocity scanning scope optimally cover grating wavelength with the adjustment laser temperature finally is achieved.
Three important measures have guaranteed that present embodiment obtains the superelevation demodulation accuracy.The first, adopt high-speed counter with the intensive division of wavelength scanning range; The second, each scan period using gases absorption spectra is carried out dynamic calibration to laser instrument; The 3rd, utilize the feature of the feed-in electric current-scanning wavelength curve of laser instrument, it is carried out linearization proofread and correct, below in conjunction with synoptic diagram, its principle of work is described in detail.
The waveform of consulting Fig. 4 1., drive circuit for laser produces initial current 50mA, stop electric current 270mA, the sawtooth current of scan period 1mS is applied to laser instrument, this laser instrument has produced laser Lp (waveform 2.), on time shaft, laser Lp scans terminal point from the starting point of sawtooth wave, and the time stroke is 0.5mS, to stopping wavelength X e. like this, sweep time and wavelength have had the relation of determining to the wavelength of laser Lp from initial wavelength X s continuous sweep on wavelength axis.When the optical maser wavelength of incident overlaps with grating wavelength, incident light can produce reflection, this grating reflection light signal Sg (waveform 3.) has promptly comprised the information of its place wavelength in the temporal position of scan period, inherited the wavelength characteristic of optical grating reflection signal Sg through the voltage signal Vs after the detection amplification, in comparer (waveform 6.), reference signal Vrf and grating signal Vs compare, two the some P1 and the P2 of its voltage amplitude unanimity had both expressed the wavelength width feature of grating, had also expressed the wavelength location feature of grating.Reading the data of P1 and P2 point on time shaft can have several different methods, but which kind of method no matter, with time shaft divide thin more, can obtain high more wavelength accuracy.Present embodiment adopts high-speed counter that time shaft is divided, and each sawtooch sweep is initial, triggers a counter and starts working, the reference voltage Vrf time location T identical with signal voltage Vs amplitude in comparer
1T
2, flip-flop number (waveform is 7.) is produced counting N1 and N2, this counting has finally been finished measurement and the conversion from grating wavelength information (analog quantity) to digital signal.Counter low price and speed are exceedingly fast, and a common 20M counter is equivalent to the time range of 0.5mS is divided into 10K, just wavelength scanning range is divided into 10
4In the step, the length scanning of laser instrument is 1.1nm in the present embodiment, and like this, its wavelength step pitch (resolution) is approximately 0.11pm like this.
Second measure that guarantees that present embodiment obtains the superelevation demodulation accuracy be each scan period all the using gases absorption spectra laser instrument is carried out dynamic calibration, consult Fig. 5 a Fig. 5 b. in Fig. 5 a, we can think that temperature and noise are constant in this each cycle, but the temperature and the electronic noise in different scanning cycle are non-constant, this will influence the wavelength starting point of each scanning, just under the different cycles, the wavelength value of an identical numerical value correspondence of counter is different, for this reason, present embodiment adopts the method that compares with the calibrating gas absorption to eliminate this error.At first, under 25 ℃ of standard demarcation states,, the N that we obtain with reference channel
R1, N
R2Calculate gas absorption peak N
Rs(N
Rs=(N
R2-N
R1)/2) this numerical value (present embodiment measured value 1870=gas absorption peak 1550.231nm).Secondly, we are with the reference channel meter reading N of dynamic actual measurement
R1, N
R2, N
R3... N
RkPoor with this standard value (1870) obtains a series of dynamic error N
δ 1, N
δ 2, N
δ 3... N
δ k, last, we carry out addition with the reading in each identical sampling period of sensing passage with corresponding dynamic error, the numerical value after having obtained to correct.This numerical value has eliminated because the wavelength shake that temperature or other low-frequency disturbance cause.See Table one
Table one: the sensing passage reading behind the dynamic calibration
| Sample number | Dynamic error N δ | CH1 | CH2 | ...... | |
| 1 | ?N r1-N rs＝N δ1 | N 11+N δ1 | N 21+N δ1 | ? | ?N
141+ |
| 2 | ?N r2-N rs＝N δ2 | N 12+N δ2 | N 22+N δ2 | ? | ?N
142+ |
| 3 | ?N r3-N rs＝N δ3 | N 13+N δ3 | N 23+N δ3 | ? | ?N 143+N δ3 |
| ...... | ?...... | ...... | ...... | ...... | ?...... |
| k | ?N rk-N rs＝N δk | N 1k+N δk | N 2k+N δk | ? | ?N 14k+N δk |
[0058]The 3rd measure that guarantees that present embodiment obtains the superelevation demodulation accuracy is that the electric current-wavelength curve to laser instrument carries out linearization and proofreaies and correct, and gives each meter reading a corresponding unique wavelength value simultaneously.
Because the electric current-wavelength curve of semiconductor laser and nonideal linearity for improving precision, must adopt certain method to carry out linearization process.Usually the method for linearization correction is fitting process or look-up table, and look-up table and fitting process have been adopted in the present embodiment mixing.Specific practice is: at first produce electric current-wavelength-reading and concern the table of comparisons, because the starting point electric current of scanning is 50mA, terminal point is 270mA, in scanning process, counter is finished from 0 to 10000 counting, and the sweep current that applies can be thought more satisfactory linearity, and we apply different electric currents to laser instrument, read the wavelength value that respective electrical flows down with wavemeter, obtain table two
Table two: the wavelength-electric current-reading table of comparisons
| Measuring point | Apply electric current (mA) | Reading wavelength (theory) | Actual |
| 1 | 50 | 1 | 1549.376 |
| 2 | 55 | 227 | 1549.392 |
| 3 | 65 | 682 | 1549.428 |
| 4 | 75 | 1136 | 1549.458 |
| ... | ... | ... | ... |
| 20 | 160 | 5000 | 1549.792 |
| 21 | 170 | 5454 | 1549.846 |
| 22 | 180 | 5909 | 1549.902 |
| ... | ... | ... | ... |
| 29 | ... | ... | ... |
| 30 | 270 | 10000 | 1550.548 |
Secondly, be benchmark with table two data, by approximating method and expand fill data, finally obtain the corresponding tables three of reading wavelength-actual wavelength.Because can not 10000 all contrasting datas of also unnecessary test, feasible method is to be divided into several region and to test the employing of some spots present embodiment being divided into point of every 10mA between 3 district A:50mA-110mA, point of 10mA between the 110-220, point of every 5mA between the 220-270) adopts fitting process then, to form table three from the whole polishings of data of reading wavelength from 1 to 10000 correspondence
At last table three is stored in the computing machine, the meter reading (table one) of per each passage of sampling period can obtain unique wavelength readings by look-up table three.
The safeguard measure of reliability and practicality:
In the open air in the use, because operating personnel's difference, the connection of optical cable, the angle of coiling all has the inconsistency that is difficult to avoid, present embodiment adopts the method for automatic gain control, for different passages provides different gains, make all sensor signals through behind the amplifier, be operated on the identical setting amplitude.Be different from general agc circuit, present embodiment adopts and is undertaken providing a series of different gain coefficients according to program by computing machine, and the width of while detection of reflected grating, on this basis, each sensing passage is carried out self check and initialization, improve the reliability of system and the convenience of operation greatly.
Embodiment 2: 96 passage hull health monitoring data acquisition system (DAS)s
Present embodiment is identical with embodiment one on overall plan, its improvement part (consulting Fig. 7-1 and Fig. 7-2) is, use the high-power CW-DBL laser diode XL15DCWX of two customizations, 1 * N wavelength splitter 21 is merged into and entered to the output of two laser of its laser power 200mW through coupling mechanism 11-4.The centre wavelength of two laser diodes is respectively 1550nm and 1551nm, can obtain the dynamic scan scope of 2.7nm under 80% current amplitude modulation, (is shown as λ on Fig. 7-2
1s-λ
1eλ
2s-λ
2e).During work, it is the sawtooth signal of 0.25mS, cycle 2K that MCU1 provides width for sequentially driving circuit 12-1 and 12-2 in turn, MCU1 control 13-1/14-1 and 13-2/14-2 simultaneously, with laser setup 2 with fixed temperature control point T1 and T2 on.Suitably choose T1 and T2, make 2 optical maser wavelengths form relay, the overlapping scope (λ of wavelength
2s-λ
1e) be 0.4nm, finally reach 5nm and (see Fig. 7-2, λ
Combination) the scanning wavelength bandwidth.
Present embodiment is the reliability and the practicality of improvement system, and adopting can distortion with the collection of guaranteeing high-frequency vibration signal to the equal high-speed sampling of all signals (2K employing rate).Owing to have multiple different sensor in the system, need measure the high and low frequency signal simultaneously, present embodiment has adopted to different passages the method with 100 different average times such as average is provided respectively 10 times, the needs that detect the high and low frequency signal had simultaneously both been satisfied, simplify system's formation again, improved precision.
Above-mentioned two specific embodiments are not the range of application that is used to limit invention, and all non-intrinsically safe simple modification of being done in the principle of invention are replaced, and all should be included within protection scope of the present invention.
Claims (10)
- One kind to FBG (Fiber Bragg Grating FBG) at a high speed, the method and the implement device of high precision, hyperchannel demodulation, its feature comprises: the length scanning LASER Light Source is by forming with the lower part: laser diode 11; Diode drive circuit 12, diode temperature sensor 13, refrigeration-heating temperature adjustment unit 14 and control module 15; It connects control relation: the laser diode temperature information of control module 15 receiving sensors 13, and produce the instruction of adjustment temperature and send temperature adjustment unit 14, produce drive signal and send diode drive circuit 12; Diode drive circuit 12 amplifies the back with drive signal and controls laser diode 11 with it, and the temperature of laser diode 11 is subjected to the control of thermoregulation circuit 14, and the input end (1 end) of 1 * N splitter of multichannel array is sent in its laser output.The array apparatus 2 of realizing the application of sensor hyperchannel is by forming with the lower part: 1 * N splitter 21; N-1 1 * 2 coupling mechanism 22.Multifiber cable 3 wherein can comprise 31,32 ... 3K is K root multifiber cable altogether; Comprise 41,42 altogether in the sensor array 4 ... m such as a 4m sensing grating.Wherein: 1 * N splitter N-1 output branch correspondence be connected to the output1 end of N-1 1 * 2 coupling mechanism 22, the input1 end of N-1 1 * 2 coupling mechanism 22 is connected to sensor by multifiber cable.Multifiber cable is optical fiber of each sensor assignment, and sensor array and coupling mechanism 22 are connected one by one.The output2 of 1 * 2 coupling mechanism end is connected to the corresponding photoelectric commutator PIN of demodulating equipment, and N branch wherein one the tunnel needn't connect 1 * 2 coupling mechanism and directly connects gas absorption cell.High-speed, high precision demodulating equipment 5 comprises the demodulation branch road and demarcates branch road; The demodulation branch road comprises photodetector 51; Signal amplifier 52 gain controllers 53, comparer 54, counter 55, microprocessor 56, gas absorption cell 50, it connects control relation: photodetector 51 changes light signal into electrical signal and enters amplifier 52, the gain controlled of amplifier 52 controls 53 in automatic gain able to programme, its output enters comparer 54, comparer 54 compares the signal of amplifier 52 input and microprocessor 15 given reference signals, its comparative result flip-flop number 55, the count results of this counter is used to obtain the wavelength information of sensing grating.Compare with the demodulation branch road, the signal of demarcating branch road is gone into photodetector 51 by gas absorption cell 50 outputs are laggard, and all the other connections are identical with the demodulation branch road with control relation.Composition of the present invention also comprises: the computing machine 62. of finishing the general circuit 61 of functions such as power supply, protection and being used for the storage of demodulating data display process
- According to the described FBG of claim 1 at a high speed, the high-precision multi-path method and the implement device that carry out demodulation, it is characterized in that: laser diode is CW-DFB diode or CW-DBL type.
- According to the described FBG of claim 1 at a high speed, the high-precision multi-path method and the implement device that carry out demodulation, it is characterized in that: its total number of channels N is for more than or equal to 8 smaller or equal to 64 integer, and m is less than N-1 for sensing grating quantity.The total core of the optical fiber that multifiber cable provides is counted K greater than N, and said multifiber cable can be one, also can be many.
- According to the described FBG of claim 1 at a high speed, the high-precision multi-path method and the implement device that carry out demodulation, it is characterized in that: the wavelength high-velocity scanning obtains by modulated laser diode feed-in electric current, and the wavelength low-velocity scanning is realized by the temperature of modulated laser diode.
- 5. according to claim 1,4 described FBG high speeds, high-precision multi-path carry out the method for demodulation and the length scanning LASER Light Source of implement device, it is characterized in that: the LASER Light Source that adopts a plurality of different centre wavelengths, relay work under the control of MCU is expanded the scope of wavelength high-velocity scanning.
- 6. according to claim 1,4 described length scanning LASER Light Source, the implementation method that enlarges its wavelength scanning range is: come the starting point of gated sweep wavelength and expand the coverage of length scanning by the temperature of control laser module.
- According to the described FBG of claim 1 at a high speed, the high-precision multi-path method and the implement device that carry out demodulation be characterised in that: Wavelength demodulation method is: the time of drive current scanning is corresponding to certain wavelengths, reflected signal surpasses the forward position that the setting threshold proof detects FBG, be lower than the back edge that the threshold value proof detects FBG once more, get width and the centre wavelength that the position can obtain the FBG reflection peak thus by these two time saltus steps.
- 8. be characterised in that according to the described FBG high speed of claim 1, high-precision multi-path demodulation method and implement device its method that obtains the superelevation demodulation accuracy is: adopt high-speed counter with the intensive division of wavelength scanning range; Each scan period using gases absorption spectra is carried out dynamic calibration to laser instrument; Utilize the feature of the feed-in electric current-scanning wavelength curve of laser instrument, it is carried out linearization proofread and correct.
- 9. be characterised in that according to the described FBG high speed of claim 1, high-precision multi-path demodulation method and implement device, for improving the reliability and the practicality of system, adopt automatic gain control circuit able to programme, for different passages provides different gains, all sensor signals are operated on the identical setting amplitude through behind the amplifier.
- 10. be characterised in that according to the described FBG high speed of claim 1, high-precision multi-path demodulation method and implement device, for improving the reliability and the practicality of system, being adopted as different passages provides the method for different sample mean number of times, makes system can measure the high and low frequency signal simultaneously.
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| CN116989832B (en) * | 2023-09-26 | 2023-12-26 | 北京大学 | Variable multi-space sensing scale seismic exploration method and system |
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Application publication date: 20111123 |