The method and the device that are used for the distributed optical fiber temperature sensing system data calibration
Technical field
The present invention relates to distributed optical fiber temperature sensing system, particularly the data in the distributed optical fiber temperature sensing system are carried out Calibration Method and device.
Background technology
In industry and daily life, often have many occasions and need survey the temperature of growing every along the line of distance, such as the cable temperature monitoring of growing distance or oil and gas pipes monitoring etc.Under similarly using, be best selection based on the distributed temperature sensing system (Distributed TemperatureSensor is called for short DTS) of optical fiber Raman scattering.
In DTS, one or a series of laser pulse go into to inject in the optical fiber, and this laser pulse was propagated in optical fiber in the process, and the every bit along the line at optical fiber all can produce the Raman scattering phenomenon.In the Raman scattered light that produces, some is propagated along the direction that laser pulse advances, and is called as forward scattering light; Some is caught again by optical fiber and returns along the opposite direction of laser propagation, and this part Raman scattered light is called as back-scattering light.In scattered light, optical wavelength greater than the composition of incident laser pulse wavelength be called as stokes light (Stokes, S); Wavelength less than the composition of incident laser pulse wavelength be called as anti-Stokes light (Anti-Stokes, AS).These two kinds of signals are that Raman's Stokes and Raman's anti-Stokes are that current scattering is produced the temperature sensitive of point.Therefore can calculate the temperature data of current point by the size of surveying these two signals, and in the optical fiber which point by calculating the mistiming between backscatter signals and the incident light pulse, just can go out this temperature data by the speed calculation that backscatter signals is propagated in optical fiber is corresponding to.
Because the refractive index of light wave changes with wavelength change in the silica fibre, thereby causes different wavelengths of light phase velocity of wave difference.The wavelength of the wavelength ratio anti-Stokes AS light wave of Stokes S light wave is bigger, and its refractive index is less, thereby its phase velocity is bigger than AS.If not the difference of two kinds of signal phase velocities is not compensated or becomes calibration, the time of the AS signal return detector of same position will be than S signal evening, increase along with fiber lengths, the inconsistent phenomenon of S and AS signal can be more serious, can cause the reduction of system accuracy like this.
Usually compensate or calibrate by time domain up-sampling point is set at different sampling lengths at interval for this phenomenon.In the mechanism or system of this calibration, thereby generally be that the alignment that S signal and AS signal are carried out in saltus step decay by optical fiber tail end light signal realizes this two inconsistent compensation of signal phase velocity.
But in the application of reality, often have some phenomenons and cause effectively operate as normal of above-mentioned mechanism.Wherein a kind of phenomenon is exactly the reflection of light tail end, if do not have special processing or handle bad meeting to cause bigger reflected impulse peak at the optical fiber tail end, to such an extent as to such pulse meeting can't be differentiated the real tail end position of optical fiber than broad usually, thereby to influencing the alignment of S and AS signal.In addition, if the distance of surveying less than the length of optical fiber itself, the optical fiber tail end is sightless, also can't carry out the calibration of original signal data by said method in this case.If actual fiber is long, because the decay of light signal in optical fiber, signal at the optical fiber tail end is smaller, there is not the situation of scattered signal to compare all tangible without comparison difference with the optical fiber outside even, in this case, can't judge real tail end position, also can't carry out alignment S and AS signal.
The double-end measurement that needs DTS in some occasions, double-end measurement is not both him and all is connected to the two ends of detection optical fiber on the DTS with traditional single-ended measurement, all obtain the distributed temperature data from the two ends of detection optical fiber, by specific algorithm, the temperature data that will obtain at two ends is integrated into distributed temperature data then.The length calibration also is very important in double-end measurement, if lacked accurate length calibration, can all there be error in the distributed temperature data in location positioning and two dimensions of temperature data.
Summary of the invention
The objective of the invention is to overcome the deficiency of method in the above-mentioned prior art, provide a kind of data in the distributed optical fiber temperature sensing system are carried out Calibration Method and device, it is used for automatically and/or accurately aliging and calibrating the method and apparatus of DTS system raw data.Method and apparatus based on mark on the raw data of the present invention can provide more accurate calibration and configuration result, can improve the bearing accuracy and the spatial resolution of DTS system, and improves the overall performance of system.
In order to reach the foregoing invention purpose, technical scheme of the present invention is as follows:
A kind of temperature-measuring system of distributed fibers raw data Calibration Method that is used for, it is characterized in that, this method utilizes DTS self or additional laser instrument to produce a kind of calibration light pulse, after this calibration is distributed the reception of formula optical fiber temperature measurement system with light pulse, stack is a kind of on its raw data can be used for the pinpoint position pulse of DTS, by the position pulse on Stokes in the raw data and the anti-Stokes signal is carried out alignment operation, the DTS raw data is carried out the length calibration.
In the present invention, described calibration light pulse is DTS self or the laser pulse of another additional laser instrument generation and/or the Raman scattering composition that produces in optical fiber.
In the present invention, described alignment operation includes: the position pulse that superposes on Stokes in the judgement raw data and the anti-Stokes composition is the position at place separately; Come two kinds of signal framing pulses to be alignd on the position according to the difference of two pulse positions to the demarcation again that two kinds of signals in the raw data carry out length.
The above-mentioned temperature-measuring system of distributed fibers raw data Calibration Method that is used for specifically comprises the steps:
Receive simultaneously among the first step, the DTS from the raw data in the optical fiber, include Stokes signal and anti-Stokes signal in this raw data, all contain a position pulse in each signal data;
Second the step, calculate respective pulses residing position in optical fiber in Stokes signal and the anti-Stokes signal respectively with the initial value of setting among the DTS;
The 3rd step, two kinds of signals of raw data are carried out the demarcation again of length,, finish the data calibration of distributed optical fiber temperature sensing system until this two pulses alignment.
Optical fiber in the described first step carries out thermometric that root optical fiber for the application distribution fiber temperature sensing system, and the sampling length data of calibrating distributed fiber temperature sensing system are measured with the Temperature Distribution formula that is applied to this root optical fiber.
As a kind of scheme that realizes said method, this device includes distributed optical fiber temperature sensor main frame, optical module and the detection optical fiber of transmitter, receiver, described transmitter connects optical module with the emission laser pulse, and described detection optical fiber head end and tail end all directly or by additional optical fiber are connected to described optical module.
As another kind of design proposal, this device that is used for the distributed optical fiber temperature sensing system data calibration includes distributed optical fiber temperature sensor main frame, optical module and the detection optical fiber of transmitter, receiver, described transmitter connects optical module with the emission laser pulse, the head end of described detection optical fiber is connected to described optical module, an additional laser uses the optical fiber identical with testing fiber to be connected to optical module with the emission laser pulse, and the transmitter of this additional laser and distributed optical fiber temperature sensor main frame has synchronization mechanism.
Be provided with attenuator between above-mentioned additional laser and the optical module.
Above-mentioned optical module is a photoswitch or coupling mechanism.
Based on technique scheme, the present invention has following technique effect:
Method based on mark on the raw data of the present invention can provide more accurate calibration and configuration result, thereby improves the bearing accuracy and the spatial resolution of DTS system, and improves the overall performance of system.
Description of drawings
Fig. 1 is the present invention carries out Calibration Method to the data in the distributed optical fiber temperature sensing system a schematic flow sheet.
The structural representation of Fig. 2 device that to be the present invention calibrate the data in the distributed optical fiber temperature sensing system.
The structural representation of embodiment 1 in Fig. 3 device that to be the present invention calibrate the data in the distributed optical fiber temperature sensing system.
The structural representation of embodiment 2 in Fig. 4 device that to be the present invention calibrate the data in the distributed optical fiber temperature sensing system.
The structural representation of embodiment 3 in Fig. 5 device that to be the present invention calibrate the data in the distributed optical fiber temperature sensing system.
The view that raw data shows on oscillograph in Fig. 6 device that to be the present invention calibrate the data in the distributed optical fiber temperature sensing system.
The view that raw data shows on oscillograph during double-end measurement in Fig. 7 device that to be the present invention calibrate the data in the distributed optical fiber temperature sensing system.
Embodiment
Come the high voltage power cable of composite fiber of the present invention is described in further detail below in conjunction with accompanying drawing and specific embodiment, but can not therefore limit protection scope of the present invention.
It is to utilize DTS self or additional laser instrument to produce a kind of calibration light pulse that the present invention is used for temperature-measuring system of distributed fibers raw data Calibration Method, after this calibration is distributed the reception of formula optical fiber temperature measurement system with light pulse, stack is a kind of on its raw data can be used for the pinpoint position pulse of DTS, by the position pulse on Stokes in the raw data and the anti-Stokes signal is carried out alignment operation, with to the data calibration in the DTS raw data, generally we come the sampling length among the DTS is calibrated in this way.
In the present invention, described calibration light pulse is DTS self or the laser pulse of another additional laser instrument generation and/or the Raman scattering composition that produces in optical fiber.
In the present invention, described alignment operation includes: the position pulse that superposes on Stokes in the judgement raw data and the anti-Stokes signal content is the position at place separately; Come again two kinds of signal framing pulses to be alignd on the position according to the difference of two pulse positions to the demarcation again that two kinds of signals in the raw data carry out sampling length.
Fig. 1 is the present invention carries out Calibration Method to the data in the distributed optical fiber temperature sensing system a schematic flow sheet.As seen from the figure, we illustrate method of the present invention with the demarcation again to the sampling length among the DTS this system is calibrated adopt, and the method that the present invention is used for the distributed optical fiber temperature sensing system data calibration comprises the steps:
The first step, receive simultaneously among the DTS from containing the raw data of calibration in the optical fiber with pulse, include Stokes signal and anti-Stokes signal in this raw data, all contain a position pulse in each signal data, optical fiber wherein carries out thermometric that root optical fiber for the application distribution fiber temperature sensing system, the sampling length data of calibrating distributed fiber temperature sensing system are measured with the Temperature Distribution formula that is applied to this optical fiber, in the raw data that distributed optical fiber temperature sensing system DTS receives, just include forward scattering signal and backscatter signals, include Stokes signal and anti-Stokes signal in the forward scattering signal, also include Stokes signal and anti-Stokes signal in the backscatter signals;
Second the step, calculate respective pulses residing position in optical fiber in Stokes signal and the anti-Stokes signal respectively with the initial value of setting among the DTS, this initial value is generally the initial value of sampling length;
The 3rd step, two kinds of signals of raw data are carried out the demarcation again of length,, finish the calibration of the sampling length data of distributed optical fiber temperature sensing system until this two pulses alignment.
The raw data that containing in the first step calibrates with pulse is to utilize DTS self or additional laser instrument to produce the calibration light pulse, after this calibration is distributed the reception of formula optical fiber temperature measurement system with light pulse, stack is a kind of on its raw data can be used for the pinpoint position pulse of DTS
Be the several structure embodiment that adopted the calibrating installation of said method below, elaborate below:
The present invention is used for the device of distributed optical fiber temperature sensing system data calibration, this device is provided with distributed optical fiber temperature sensor main frame, optical module and the detection optical fiber that includes transmitter, receiver, described transmitter connects optical module with the emission laser pulse, and described detection optical fiber head end and tail end all are connected to described optical module.
The above-mentioned DTS main frame 1 that includes transmitter, receiver is launched laser pulse and is incided in the optical module 2, propagate from port emitting laser pulse edge optical fiber 3, in the process that optical fiber 3 is propagated, the backscatter signals that laser pulse produced turns back to DTS main frame 1 via optical module 2, and by the detection that receiver receives of DTS main frame 1 inside, through becoming the raw data of DTS system after the data processing.Laser pulse also produces the scattered signal of forward direction when optical fiber 3 is propagated, forward scattering signal and laser pulse itself incides in the optical module 2 by the far-end 4 of optical fiber 3.
The backscatter signals that produces when laser pulse is propagated in optical fiber 3 includes S, AS and Rayleigh scattering signal, the same forward scattering signal that produces also comprises S, AS and Rayleigh scattering signal, and the corresponding in twos forward scattering optical wavelength that reaches dorsad is identical and speed that propagate in optical fiber is identical.Because raw data distal-most end that backscatter signals produced is a laser pulse to be transferred to the backscattering light signal that the optical fiber far-end produced and to return DTS1 inside, the optics distance of process be the fiber lengths of twice; And corresponding laser pulse and forward scattering signal are surveyed by the DTS1 reception via the far-end 4 and the optical module 2 of optical fiber 3, and on the raw data of DTS system, be shown as a pulse, the optics distance of its process is the length of optical fiber 3, just in time be half of raw data length, so the pulse that the fl transmission signal forms is at the point midway of DTS raw data.
According to the different demands of practical application, the optical fiber in this DTS system can adopt the non-standard special fiber of single-mode fiber or multimode optical fiber or other.
Embodiment 1
In some actual application scenario, can't reconnect to the far-end of detection optical fiber on the DTS by optical module, we can realize same function by an additional pulsed laser like this.Fig. 2 is exactly an embodiment of corresponding this kind situation.The far-end 9 of detection optical fiber be because field condition can't connect light echo learns on the assembly 10, so we have introduced an additional laser instrument 7, and this additional laser 7 can produce the fl transmission pulse of same purpose together with optical fiber 8.In an embodiment, additional laser 7 must be undertaken synchronously to produce laser pulse simultaneously by synchronization mechanism 6 with DTS 5; Optical fiber 8 must be to want long enough so that the pulse of fl transmission is attached on the raw data with detection optical fiber 3 optical fiber and length of the same type; The extra-pulse laser instrument be connected between the optical module 10 can the additional attenuation device saturated with the data that prevent DTS and accept.
Embodiment 2
Fig. 3 is an another embodiment of the present invention, because promptly the Raman scattering signal is less dorsad for the original optical signalling of DTS itself, if therefore direct laser pulse with fl transmission incides in the optical module, may cause the saturated of DTS raw data, in order to prevent the saturated of DTS data, can before optical module is incided in the fl transmission pulse, pass through an attenuator, reach level, thereby prevent the saturated of DTS original signal with backscattering light signal isodose level with its strength retrogression.
Embodiment 3
Accompanying drawing 4 uses the embodiment of photoswitch as optical module for the present invention.In the practical application of DTS, often can use the effect that photoswitch plays the hyperchannel expansion.Having the optical module that multichannel photoswitch can be used as among the present invention simultaneously uses.As Fig. 4, the shoot laser pulse of photoswitch is incided in the detection optical fiber, produce the original signal of backscatter signals as DTS, the laser pulse and the forward scattering signal of fl transmission incide in another passage of photoswitch again by optical fiber simultaneously, because photoswitch itself has certain channel isolation, so the signal of fl transmission produces a pulse labeling on the raw data of DTS.Present embodiment also can incide between the photoswitch additional attenuation device to guarantee that the DTS signal is not by saturated at the fl transmission signal.
Fig. 5 is the diagram of DTS raw data of the present invention.The raw data of DTS comprises 12 two kinds of Stokes signal 11 and anti-Stokes signals, and they distinguish the scattering of corresponding detection optical fiber diverse location.The pulse labeling that the signal of fl transmission produces respectively on them is 13,14.If the detection optical fiber far-end takes back the DTS situation by certain optical module, this pulse labeling can appear at the point midway of DTS raw data.Thereby we can determine the position of pulse and mark or calibrate two kinds of raw data so that they mate again by the size of amplitude, reach the purpose of obtaining accurate temperature data and locator data.
The raw data diagram that Fig. 6 uses in double-end measurement for the present invention.Under the situation of double-end measurement, raw data is obtained from the two ends of detection optical fiber, equally also can carry out mark or calibration to raw data by the method for pulse labeling.Raw data 12 is the data of detection optical fiber one end, and 13 is the raw data that gets access to from the other end.Under normal conditions, the precise length of detection optical fiber is unknown.We can use the same method, and the paired pulses mark carries out manually or automatic the alignment realized the accurate calibration of raw data.