CN104101447B - Distributed optical fiber temperature sensor and method for removing nonlinear error of same - Google Patents

Abstract

The invention discloses a distributed optical fiber temperature sensor which mainly comprises a machine casing and a pulse laser source, a wavelength division multiplexer and an optical switch which are arranged in the machine casing. The optical switch is further connected with an optical fiber box, a reference optical fiber ring is arranged in the optical fiber box, a temperature probe is further arranged on the optical fiber box, and the tail end of the optical fiber ring is connected with an external sensing optical fiber through an optical terminal arranged on the machine casing. The wavelength division multiplexer is further sequentially connected with a photoelectric detection module, a high speed collection card and an industrial personal computer board card. The sensor is low in cost, simple in structure, good in signal to noise ratio, good in stability, reliable and high in temperature resolution. A method for removing a nonlinear error of the distributed optical fiber temperature sensor by utilizing a subsection loss difference compensation method to remove the nonlinear error caused by Raman Stokes and anti-Strokes optical loss difference is further provided. By means of the method, a temperature curve demodulated by the system accords with the actual condition, and temperature measuring accuracy and reliability of the system are improved.

Description

Distributed optical fiber temperature sensor and the method eliminating this Nonlinear Error of Transducer

Technical field

The invention discloses a kind of fibre optic temperature sensor and its method eliminating this Nonlinear Error of Transducer, specifically relate to And a kind of distributed optical fiber temperature sensor and the method eliminating this Nonlinear Error of Transducer, belong to sensory field of optic fibre.

Background technology

Since j.p.dakin in 1985 et al. is successfully realized first based on the distributed temperature measuring technology of Raman scattering, People the various technology realizing distributed fiber temperature sensing have been carried out widely studied, wherein distributed based on Raman scattering Sensing technology has obtained most commonly used practical application.Compared with traditional sensor, distributed optical fiber temperature sensor has Many remarkable advantages: using optical fiber itself as sensing media, one-shot measurement can be obtained by the thousands of point temperature along fiber distribution Degree information, it is achieved that the measurement of continuous distribution formula, reduces uncertainty of measurement；Far measuring distance, time of measuring is short, is suitable for long-range Monitor in real time；Sensitivity is high, and certainty of measurement is high, and rate of false alarm, rate of failing to report are low；Corrosion-resistant, water-fast, fire resisting, electromagnetic interference immunity, can High by property, maintenance cost is low.

The ultimate principle of the distributed optical fiber temperature sensor based on Raman scattering is: the injection in one end of sensor fibre swashs Light pulse, occurs energy to hand over when laser pulse is propagated in a fiber because the thermal vibration of fibre core molecule is interacted with photon Change, create Raman scattering.Specifically, when the part energy of photon passes to the thermal vibration of molecule, then will send The photon of wavelength ratio original optical maser wavelength length, referred to as Raman Stokes (raman stokes) light；When molecule thermal vibration one Portion of energy passes to the light period of the day from 11 p.m. to 1 a.m, then will send the photon of wavelength ratio original laser wave length, referred to as Raman anti-Stokess (raman anti-stokes) light.Wherein, Raman anti-Stokes light is very sensitive to temperature, and Raman stokes light is to temperature Degree is insensitive, so people generally demodulate temperature information with Raman anti-Stokes light；And, in order to eliminate light source power The impact of fluctuation, generally adopts Raman stokes light as reference light.Raman scattering techniques combine optical time domain reflection technology (otdr, optical time domain reflectometer) it becomes possible to positioning temperature information, it is achieved thereby that distributed Optical fiber sensing.Commonly referred to as this sensing technology is raman-dts (raman distributed temperature sensing).

Chinese invention patent (publication number: cn101696896a) discloses a kind of light of distributed optical fiber temperature sensing system Electric installation, as shown in Figure 2, including laser instrument 21, optical fiber raman-wdm bonder 22, the first Optical Receivers 31, the second light Receiver module 41, the first amplification matching circuit 32, the second amplification matching circuit 42, reference optical fiber ring 26, sensor fibre.Laser instrument The signal of telecommunication that the synchronizing signal 27,32 to capture card exports anti-Stokes light conversion, 42 output stokes lights can be produced The signal of telecommunication of conversion.This is a kind of typical raman-dts scheme.

It is known that the loss size of optical fiber is related to optical wavelength, due to Raman anti-Stokes light and Raman stoke The wavelength of this light differs greatly (for example in the raman-dts system of 1550nm light source, both wavelength difference about 200nm), institute With both in a fiber loss also different.And, in actual applications, the loop of sensor fibre is by some sometimes Section fused fiber splice, the loss of every section of optical fiber is likely to different.Especially, increase with measurement distance, loss difference The different impact to the measuring precision is bigger.During solution temperature regulating, the impact being lost discounting for these, will result in system Nonlinearity erron, demodulating the temperature curve obtaining is distortion, and system, by cisco unity malfunction, researches and develops a kind of distribution type fiber-optic temperature The degree sensor and method of this Nonlinear Error of Transducer can be eliminated become those skilled in the art's technical problem urgently to be resolved hurrily.

Content of the invention

The technical problem to be solved is, for the shortcoming of above prior art presence, proposes a kind of distributed Fibre optic temperature sensor and the method eliminating this Nonlinear Error of Transducer, this distributed optical fiber temperature sensor low cost, knot Structure is simple, and signal to noise ratio is good, good stability during work, reliability and temperature resolution is high；Method using segmented compensation differential loss Eliminate the nonlinearity erron that Stokes and anti-Stokes light differential loss bring thus eliminating distributed fiber temperature sensing The method of device nonlinearity erron, is enabled to raman-dts Demodulation Systems temperature curve out and is consistent with practical situation, thus Improve temperature measurement accuracy and the reliability of system.

The technical scheme that the present invention solves above technical problem is:

A kind of distributed optical fiber temperature sensor, the main pulse including casing and being arranged in casing and be sequentially connected with swashs Light source, wavelength division multiplexer and photoswitch, photoswitch is also connected with a fiber termination box, is provided with reference optical fiber ring, fiber termination box in fiber termination box On be additionally provided with a temperature probe integrated with reference optical fiber ring, the tail end of reference optical fiber ring passes through setting light on the housing Fine terminal is connected with outside sensor fibre；

Also it is connected with turn on wavelength division multiplexer and Raman stokes light and anti-Stokes light are converted to corresponding simulation The photoelectric detection module of the signal of telecommunication, high-speed collection card analog electrical signal being converted to digital electric signal and card for industrial computer, its In:

Wavelength division multiplexer has four ports, and the outfan of pulsed laser source connects the input of wavelength division multiplexer, and pulse swashs The light of light source passes through to positive outfan from the input of wavelength division multiplexer, the stokes light in reverse Raman diffused light and anti- Stokes light is separated by wavelength division multiplexer, exports and is sent to light electrical resistivity survey from two inverse output terminals of wavelength division multiplexer respectively Survey module, the positive outfan of wavelength division multiplexer connects the main side of photoswitch, an end connection for photoswitch is positioned in fiber termination box The reference optical fiber ring in portion, the temperature probe on fiber termination box measures the temperature of reference optical fiber ring, and the tail end of reference optical fiber ring connects machine Optic fibre connector on shell externally exports, and outside sensor fibre is connected on optic fibre connector, using photoswitch by wavelength division multiplexer The laser of output is ultimately delivered to sensor fibre, and it is right that Raman stokes light and anti-Stokes light are converted to by photoelectric detection module The analog electrical signal answered simultaneously exports to high-speed collection card, and analog electrical signal is converted to digital electric signal by high-speed collection card, output To card for industrial computer, the software system that card for industrial computer runs carries out calculating process to digital electric signal, thus demodulating temperature The curve of degree distribution.

Further, the further technical scheme of the present invention is:

In aforementioned distributed optical fiber temperature sensor, pulsed laser source is directly modulated laser or optical-fiber laser Device, and the centre wavelength of pulsed laser source is 1550.12nm, pulse width is 10ns, and peak power is 15w, and the repetition period is 152us, the repetition period of pulsed laser source is more than transmission time in sensor fibre for the light pulse.

Pulsed laser source in the present invention is directly modulated laser or optical fiber laser, pulsed laser source Peak power is 15 watts of levels, on the premise of not producing the nonlinear optical phenomenas such as stimulated Raman scattering, the peak of pulsed laser source The higher the better for value power, can improve the signal to noise ratio of system, and the pulse width of pulsed laser source is 10 nanosecond, narrow pulse width Degree is conducive to the spatial resolution of raising system, but nor the too narrow signal to noise ratio that otherwise can reduce be unfavorable for temperature resolution, Parameter in the present invention is compromised high and low between the two through what experiment repeatedly obtained, plays a role to greatest extent.

In aforementioned distributed optical fiber temperature sensor, the length of reference optical fiber ring is 20-50m, a diameter of 8-15cm of coiling, Sensor fibre length is 15km, and sensor fibre is transmission medium and sensor information, and it is not charged to be laid on thermometric scene, anti-electricity Magnetic disturbance, radiation hardness, corrosion-resistant；Described in coiling, the fiber type of reference optical fiber ring is identical with sensor fibre and is single-mode fiber Or multimode fibre.

Sensor fibre in the present invention is 15km, and shorter length is convenient to eliminate distributed optical fiber temperature sensor non-thread Property error approach in sensor fibre carried out with segmented compensation loss, the longer error rate of length of sensor fibre is higher, reduces error May just reduce.

In aforementioned distributed optical fiber temperature sensor, the material of fiber termination box and casing is metal material: aluminum, aluminium alloy, copper Or any one in rustless steel, box body is made using metal material and housing is not easy corrosion, increase the service life, fall Low cost.

In aforementioned distributed optical fiber temperature sensor, temperature probe be thermocouple, platinum resistance, critesistor, diode or It is Special temperature measurement chip；Optic fibre connector is one of fc, sc ring flange or e2000 terminal.

The present invention adopts the thermometry of contact, simple to operate, and certainty of measurement is high, is conducive to follow-up data and reality The plyability of border situation, such as has structure simply using thermocouple, response is fast, realizes telemeasurement and the spy automatically controlling Point, is widely used；This utility model is effectively linked together sensor fibre and photoswitch it is ensured that transmitting using optic fibre connector Parameter and practical situation meet the phenomenons such as minimizing error.

In aforementioned distributed optical fiber temperature sensor, the circuit bandwidth of photoelectric detection module is 100-150mhz, described height The picking rate of fast capture card is 500-503ms/s.

In aforementioned distributed optical fiber temperature sensor, the interface of high-speed collection card and card for industrial computer be pci interface or Usb interface.

The present invention have also been devised the method eliminating above-mentioned distributed optical fiber temperature sensor nonlinearity erron, is mended using segmentation The method repaying differential loss eliminates the nonlinearity erron that Raman Stokes and anti-Stokes light differential loss bring, concrete step Suddenly as follows:

(1) photoelectric detection module in distributed temperature sensor is utilized to detect the work(of stokes light and anti-Stokes light Rate is simultaneously recorded, and lentor light and anti-Stokes light power expression are as follows:

$p_s=p_0\·k_s\·s_b\·v_s^4\·r_s\left(t\right)\·e^{-({\mathrm{\α}}_0+{\mathrm{\α}}_s)x}---\left(1\right)$

$p_{\mathrm{as}}=p_0\·k_{\mathrm{as}}\·s_b\·v_{\mathrm{as}}^4\·r_{\mathrm{as}}\left(t\right)\·e^{-({\mathrm{\α}}_0+{\mathrm{\α}}_{\mathrm{as}})x}---\left(2\right)$

Wherein, p_s、p_asRepresent stokes light and anti-Stokess luminous power, p respectively₀For light source power, k_s、k_asRespectively For the scattering boundary coefficient of stokes light and anti-Stokes light, s_bFor optical fiber backscattering coefficient, v_s、v_asIt is respectively this support Ke Si light and the frequency of anti-Stokes light, α₀、α_s、α_asIt is respectively light source, stokes light and anti-Stokes light in optical fiber The loss factor of middle transmission, x is the position in sensor fibre；r_s(t)、r_asT () is the Raman scattering coefficient of optical fiber (with temperature phase Close) expression formula is as follows:

$r_s\left(t\right)=\frac{1}{1-e^{-\frac{h\·\mathrm{\δv}}{k\·t}}}---\left(3\right)$

$r_{\mathrm{as}}\left(t\right)=\frac{1}{e^{\frac{h\·\mathrm{\δv}}{k\·t}}-1}---\left(4\right)$

Wherein, h is planck constant, and δ v is Raman frequency shift, and k is Boltzmann constant, and t is absolute temperature；

(2) with stokes light as reference light, by formula (3), formula (4) respectively correspondence bring formula (1) into, in formula (2) and with walking Suddenly the formula (2) in (1) is divided by formula (1), that is, obtain the function with regard to Temperature Distribution:

$f(t,x)=\frac{k_{\mathrm{as}}\·v_{\mathrm{as}}^4}{k_s\·v_s^4}\·e^{-\frac{h\·\mathrm{\δv}}{k\·t}}\·e^{-({\mathrm{\α}}_{\mathrm{as}}-{\mathrm{\α}}_s)\·x}---\left(5\right)$

So, the temperature profile function of reference optical fiber ring present position is:

$f{(t}_{\mathrm{ref}},x_{\mathrm{ref}})=\frac{k_{\mathrm{as}}\·v_{\mathrm{as}}^4}{k_s\·v_s^4}\·e^{-\frac{h\·\mathrm{\δv}}{k\·t_{\mathrm{ref}}}}\·e^{-({\mathrm{\α}}_{\mathrm{as}}-{\mathrm{\α}}_s)\·x_{\mathrm{ref}}}---\left(6\right)$

Demodulated temperature distribution information and be by formula (5), formula (6):

$\frac{1}{t}=\frac{1}{t_{\mathrm{ref}}}-\frac{k}{h\·\mathrm{\δv}}[\ln \left(\frac{f(t,x)}{f(t_{\mathrm{ref}},x_{\mathrm{ref}})}\right)+({\mathrm{\α}}_{\mathrm{as}}-{\mathrm{\α}}_s)\·(x-x_{\mathrm{ref}})]---\left(7\right),$

Wherein, (α_as-α_s)·(x-x_ref) in item the loss of Raman anti-Stokes light and Raman stokes light is described Difference can affect temperature demodulation, (α_as-α_s) it is not constant, such as sensor fibre is by different fused fiber splices, then Demodulation temperature information out will be distributed in broken line with x position change, and result has nonlinearity erron；

(3) sensor fibre is divided into n section, and calculates each section of differential loss and add in formula (7) and carry out segmentation loss Disparity compensation, specific as follows:

(α in the formula (7) of step (2)_as-α_s) for the differential loss of anti-Stokes light and stokes light, to make it be δ α,

(0 arrives x to the 1st section of sensor fibre₁) differential loss be δ α₁, the 2nd section of (x₁To x₂) differential loss be δ α₂..., N-th section of (x_n-1To x_n) differential loss be δ α_n；During the 1st section of temperature of calculating sensor fibre, by formula (7) plus the next item upCarry out differential loss compensation；In the same manner, during the 2nd section of temperature of calculating sensor fibre, formula (7) is added one ?During n-th section of temperature of calculating sensor fibre, by formula (7) plus the next item up

(4) row operation is entered for the computing formula in step (3) to integrate, obtain one and eliminate the straight of differential loss impact Sensor fibre temperature curve as follows:

$\frac{1}{t}=\frac{1}{t_{\mathrm{ref}}}-\frac{k}{h\·\mathrm{\δv}}\·\ln \left(\frac{f(t,x)}{f(t_{\mathrm{ref}},x_{\mathrm{ref}})}\right)---\left(8\right)$

Effectively eliminate the nonlinearity erron of distributed optical fiber temperature sensor, will not be because of anti-Stokes light and stoke The loss difference of this light and on temperature curve demodulation produce impact.

Each device in the present invention is existing commercially available, combined can run together.

The operation principle of distributed optical fiber temperature sensor in the present invention: sensing is injected by high-power pulsed laser source In optical fiber, return wavelength division multiplexer along the produced reverse anti-Stokes scattering light with temperature information of sensor fibre transmission And eventually arrive at photoelectric detection module, then be converted to analog electrical signal through photoelectric detection module, simulation is gathered by high-speed collection card Signal of telecommunication reconvert becomes digital electric signal, is ultimately transmitted card for industrial computer and is contrasted and related to the parameter of stokes light Process, finally obtain the temperature signal of each point on sensor fibre, draw temperature curve.

The invention has the beneficial effects as follows:

The invention provides a kind of structure is more simple, low cost, signal to noise ratio are good, the high distributed fiber optic temperature of reliability Sensor, this sensor only needs a pulse laser, wavelength-division recombiner, photoswitch, a photodetection mould Block just can realize temperature monitoring；

Wavelength division multiplexer is adopted by the Si Tuo in reverse Raman diffused light in the distributed optical fiber temperature sensor of the present invention Ke Si light separates with tired stokes light, respectively from two inverse output terminal outputs of wavelength division multiplexer, reduces stokes light The impact to the temperature curve finally demodulating for the differential loss and tired stokes light between；

Adopt sensor fibre segmentation in the method for elimination distributed optical fiber temperature sensor nonlinearity erron of the present invention, The method carrying out segmented compensation differential loss eliminates nonlinearity erron, applies this side in distributed optical fiber temperature sensor Method, can eliminate the impact that the differential loss of stokes light and anti-Stokes light demodulates to temperature curve, eliminate non-linear Error is so that the temperature curve of measurement is straight, thus improve system temperature measurement accuracy.

Brief description

Fig. 1 is the structural principle block diagram of distributed optical fiber temperature sensor in the embodiment of the present invention；

Fig. 2 is a kind of theory diagram of the electrooptical device of distributed optical fiber temperature sensing system of the prior art；

Fig. 3 is that the embodiment of the present invention is not obtained using the method eliminating distributed optical fiber temperature sensor nonlinearity erron Temperature distribution history；

Fig. 4 is the temperature that the embodiment of the present invention is obtained using the method eliminating distributed optical fiber temperature sensor nonlinearity erron Degree distribution curve；

In figure: 1, pulsed laser source, 2, wavelength division multiplexer, 3, photoswitch, 4, fiber termination box, 5, reference optical fiber ring, 6, temperature Probe, 7, optic fibre connector, 8, sensor fibre, 9, photoelectric detection module, 10, high-speed collection card, 11, card for industrial computer, 12, machine Shell.

Specific embodiment

The present invention is further detailed explanation for 1-4 below in conjunction with the accompanying drawings.

Embodiment 1

The present embodiment provides a kind of distributed optical fiber temperature sensor, and structure is as shown in figure 1, mainly including casing 12 and setting The wavelength put in casing 12 and be sequentially connected with is 1550.12nm, and pulse width is 10ns, and peak power is 15w, the repetition period For 152us as the optical fiber laser of the mopa structure of pulsed laser source 1, wavelength division multiplexer 2 and photoswitch 3, on photoswitch 3 also Connect the fiber termination box 4 of an aluminum alloy material, being provided with length in fiber termination box 4 is 20m, the reference optical fiber ring 5 of a diameter of 15m of coiling, The one Special temperature measurement chip ds18b20 as temperature probe 6 integrated with reference optical fiber ring 5, reference light are additionally provided with fiber termination box 4 The 50/125um's that the tail end of fine ring 5 is 15km by the e2000 terminal that is arranged in stainless steel casing 12 with outside length Multimode fibre connects；

Also it is connected with turn on wavelength division multiplexer 2 and Raman stokes light and anti-Stokes light are converted to corresponding simulation The circuit bandwidth of the signal of telecommunication be 125mhz photoelectric detection module 9, analog electrical signal is converted to digital electric signal collection speed Spend ads5474 type high-speed collection card 10 and the card for industrial computer 11 for 500ms/s, high-speed collection card 10 and card for industrial computer 11 Interface is pci interface, wherein:

Wavelength division multiplexer 2 has four ports, and the outfan of pulsed laser source 1 connects the input of wavelength division multiplexer 2, pulse The light of lasing light emitter 1 passes through to positive outfan from the input of wavelength division multiplexer 2, the stokes light in reverse Raman diffused light Separated by wavelength division multiplexer 2 with anti-Stokes light, export and be sent to from two inverse output terminals of wavelength division multiplexer 2 respectively Photoelectric detection module 9, the positive outfan of wavelength division multiplexer 2 connects the main side of photoswitch 3, and an end for photoswitch 3 connects places Reference optical fiber ring 5 within fiber termination box 4, the temperature probe 6 on fiber termination box 4 measures the temperature of reference optical fiber ring 5, reference optical fiber The optic fibre connector 7 that the tail end of ring 5 connects in casing 12 externally exports, and outside sensor fibre 8 is connected on optic fibre connector 7, profit With photoswitch 3, the laser that wavelength division multiplexer 2 exports is ultimately delivered to sensor fibre 8, photoelectric detection module is by Raman Stokes Light and anti-Stokes light are converted to corresponding analog electrical signal and export to high-speed collection card 10, and high-speed collection card 10 will be simulated The signal of telecommunication is converted to digital electric signal, exports and carries out calculating process to card for industrial computer 11, thus demodulating the song of Temperature Distribution Line.

Embodiment 2

The present embodiment provides a kind of side for eliminating distributed optical fiber temperature sensor nonlinearity erron in embodiment 1 Method, eliminates, using the method for segmented compensation differential loss, the non-thread that Raman Stokes and anti-Stokes light differential loss bring Property error, specifically comprises the following steps that

(1) photoelectric detection module 9 in distributed temperature sensor is utilized to detect stokes light and anti-Stokes light Power is simultaneously recorded, and lentor light and anti-Stokes light power expression are as follows:

$p_s=p_0\·k_s\·s_b\·v_s^4\·r_s\left(t\right)\·e^{-({\mathrm{\α}}_0+{\mathrm{\α}}_s)x}---\left(1\right)$

$p_{\mathrm{as}}=p_0\·k_{\mathrm{as}}\·s_b\·v_{\mathrm{as}}^4\·r_{\mathrm{as}}\left(t\right)\·e^{-({\mathrm{\α}}_0+{\mathrm{\α}}_{\mathrm{as}})x}---\left(2\right)$

Wherein, p_s、p_asRepresent stokes light and anti-Stokess luminous power, p respectively₀For light source power, k_s、k_asRespectively For the scattering boundary coefficient of stokes light and anti-Stokes light, s_bFor optical fiber backscattering coefficient, v_s、v_asIt is respectively this support Ke Si light and the frequency of anti-Stokes light, α₀、α_s、α_asIt is respectively light source, stokes light and anti-Stokes light in optical fiber The loss factor of middle transmission, x is the position in sensor fibre；r_s(t)、r_asT () is the Raman scattering coefficient of optical fiber (with temperature phase Close) expression formula is as follows:

$r_s\left(t\right)=\frac{1}{1-e^{-\frac{h\·\mathrm{\δv}}{k\·t}}}---\left(3\right)$

$r_{\mathrm{as}}\left(t\right)=\frac{1}{e^{\frac{h\·\mathrm{\δv}}{k\·t}}-1}---\left(4\right)$

Wherein, h is planck constant, and δ v is Raman frequency shift, and k is Boltzmann constant, and t is absolute temperature；

(2) with stokes light as reference light, by formula (3), formula (4) respectively correspondence bring formula (1) into, in formula (2) and with walking Suddenly the formula (2) in (1) is divided by formula (1), that is, obtain the function with regard to Temperature Distribution:

$f(t,x)=\frac{k_{\mathrm{as}}\·v_{\mathrm{as}}^4}{k_s\·v_s^4}\·e^{-\frac{h\·\mathrm{\δv}}{k\·t}}\·e^{-({\mathrm{\α}}_{\mathrm{as}}-{\mathrm{\α}}_s)\·x}---\left(5\right)$

So, the temperature profile function of reference optical fiber ring present position is:

$f{(t}_{\mathrm{ref}},x_{\mathrm{ref}})=\frac{k_{\mathrm{as}}\·v_{\mathrm{as}}^4}{k_s\·v_s^4}\·e^{-\frac{h\·\mathrm{\δv}}{k\·t_{\mathrm{ref}}}}\·e^{-({\mathrm{\α}}_{\mathrm{as}}-{\mathrm{\α}}_s)\·x_{\mathrm{ref}}}---\left(6\right)$

Demodulated temperature distribution information and be by formula (5), formula (6):

$\frac{1}{t}=\frac{1}{t_{\mathrm{ref}}}-\frac{k}{h\·\mathrm{\δv}}[\ln \left(\frac{f(t,x)}{f(t_{\mathrm{ref}},x_{\mathrm{ref}})}\right)+({\mathrm{\α}}_{\mathrm{as}}-{\mathrm{\α}}_s)\·(x-x_{\mathrm{ref}})]---\left(7\right),$

Wherein, (α_as-α_s)·(x-x_ref) in item the loss of Raman anti-Stokes light and Raman stokes light is described Difference can affect temperature demodulation, (α_as-α_s) it is not constant, such as sensor fibre is by different fused fiber splices, then Demodulation temperature information out will be distributed in broken line with x position change, and result has nonlinearity erron；

(3) sensor fibre is divided into n section, and calculates each section of differential loss and add in formula (7) and carry out segmentation loss Disparity compensation, specific as follows:

(α in the formula (7) of step (2)_as-α_s) for the differential loss of anti-Stokes light and stokes light, to make it be δ α,

(0 arrives x to the 1st section of sensor fibre₁) differential loss be δ α₁, the 2nd section of (x₁To x₂) differential loss be δ α₂..., N-th section of (x_n-1To x_n) differential loss be δ α_n；During the 1st section of temperature of calculating sensor fibre, by formula (7) plus the next item upCarry out differential loss compensation；In the same manner, during the 2nd section of temperature of calculating sensor fibre, formula (7) is added one ?During n-th section of temperature of calculating sensor fibre, by formula (7) plus the next item up

(4) row operation is entered for the computing formula in step (3) to integrate, obtain one and eliminate the straight of differential loss impact Sensor fibre temperature curve as follows:

$\frac{1}{t}=\frac{1}{t_{\mathrm{ref}}}-\frac{k}{h\·\mathrm{\δv}}\·\ln \left(\frac{f(t,x)}{f(t_{\mathrm{ref}},x_{\mathrm{ref}})}\right)---\left(8\right)$

Effectively eliminate the nonlinearity erron of distributed optical fiber temperature sensor, will not be because of anti-Stokes light and stoke The loss difference of this light and on temperature curve demodulation produce impact.

Raman anti-Stokes light and Raman stokes light are eliminated by the method for the electrode compensation difference of stagewise The impact to temperature demodulation for the differential loss, thus obtaining a straight sensor fibre temperature curve as shown in Figure 4 so that being The temperature curve that demodulates out of uniting is consistent with practical situation, and error is maximum to be less than 1 degree Celsius, improve system temperature measurement accuracy with can By property, do not adopt the method for the present invention to be under conditions of the same using the distributed optical fiber temperature sensor in the present invention simultaneously Obtain demodulating temperature distribution information: $\frac{1}{t}=\frac{1}{t_{\mathrm{ref}}}-\frac{k}{h\·\mathrm{\δv}}[\ln \left(\frac{f(t,x)}{f(t_{\mathrm{ref}},x_{\mathrm{ref}})}\right)+({\mathrm{\α}}_{\mathrm{as}}-{\mathrm{\α}}_s)\·(x-x_{\mathrm{ref}})]$ Do not damaged afterwards The compensation of consumption difference, when sensor fibre is to be formed by different fused fiber splices, (α_as-α_s)·(x-x_ref) in (α_as-α_s) no It is constant, then demodulation temperature information out will be distributed in broken line with x position change, and result has nonlinearity erron, obtains To temperature logs as shown in figure 3, can be clearly visible temperature curve is in that polyline shaped distorts, exceed with actual temperature error maximum 4 degrees Celsius.

Method using eliminating distributed optical fiber temperature sensor nonlinearity erron in the present invention, can eliminate stokes light And the impact that the differential loss of anti-Stokes light demodulates to temperature curve, eliminate nonlinearity erron so that measurement temperature Curve is straight, thus improve system temperature measurement accuracy and reliability.

In addition to the implementation, the present invention can also have other embodiment.All employing equivalents or equivalent transformation shape The technical scheme becoming, all falls within the protection domain of application claims.

Claims (9)

1. a kind of method eliminating distributed optical fiber temperature sensor nonlinearity erron, this distributed optical fiber temperature sensor is main Including casing (12) and the pulsed laser source (1), wavelength division multiplexer (2) and the photoswitch that are arranged in casing (12) and are sequentially connected with (3), described photoswitch (3) is also connected with a fiber termination box (4), in described fiber termination box (4), is provided with reference optical fiber ring (5), described light It is additionally provided with one with the integrated temperature probe (6) of reference optical fiber ring (5), the tail end of described reference optical fiber ring (5) passes through on fine box (4) The optic fibre connector (7) being arranged in described casing (12) is connected with outside sensor fibre (8)；

Also it is connected with turn on described wavelength division multiplexer (2) and Raman stokes light and anti-Stokes light are converted to correspondence The photoelectric detection module (9) of analog electrical signal, the high-speed collection card (10) analog electrical signal being converted to digital electric signal and work Control machine board (11), wherein:

Described wavelength division multiplexer (2) has four ports, and the outfan of described pulsed laser source (1) connects wavelength division multiplexer (2) Input, the light of pulsed laser source (1) passes through to positive outfan from the input of wavelength division multiplexer (2), and reverse Raman dissipates Penetrate the stokes light in light and anti-Stokes light is separated by wavelength division multiplexer (2), respectively from two of wavelength division multiplexer (2) Inverse output terminal exports and is sent to photoelectric detection module (9), and the positive outfan of described wavelength division multiplexer (2) connects photoswitch (3) main side, an end connection for described photoswitch (3) is positioned over the internal reference optical fiber ring (5) of fiber termination box (4), fiber termination box (4) On temperature probe (6) measure the temperature of reference optical fiber ring (5), the tail end of reference optical fiber ring (5) connects the light in casing (12) Fine terminal (7) externally exports, and outside sensor fibre (8) is connected on optic fibre connector (7), using photoswitch (3), wavelength-division is multiple Be ultimately delivered to sensor fibre (8) with the laser that device (2) exports, described photoelectric detection module (9) by Raman stokes light and Anti-Stokes light is converted to corresponding analog electrical signal and exports to high-speed collection card (10), described high-speed collection card (10) Analog electrical signal is converted to digital electric signal, exports and carry out calculating process to card for industrial computer (11), thus demodulating temperature Distribution curve it is characterised in that:

The method of this elimination distributed optical fiber temperature sensor nonlinearity erron is to be disappeared using the method for segmented compensation differential loss The nonlinearity erron bringing except Raman Stokes and anti-Stokes light differential loss, specifically comprises the following steps that

(1) photoelectric detection module (9) described in distributed temperature sensor is utilized to detect stokes light and anti-Stokess The power of light is simultaneously recorded, and lentor light and anti-Stokes light power expression are as follows:

$p_s=p_0\·k_s\·s_b\·v_s^4\·r_s\left(t\right)\·e^{-({\mathrm{\α}}_0+{\mathrm{\α}}_s)x}---\left(1\right)$

$p_{as}=p_0\·k_{as}\·s_b\·v_{as}^4\·r_{as}\left(t\right)\·e^{-({\mathrm{\α}}_0+{\mathrm{\α}}_{as})x}---\left(2\right)$

Wherein, p_s、p_asRepresent stokes light and anti-Stokess luminous power, p respectively₀For light source power, k_s、k_asIt is respectively this The scattering boundary coefficient of lentor light and anti-Stokes light, s_bFor optical fiber backscattering coefficient, v_s、v_asIt is respectively Stokes Light and the frequency of anti-Stokes light, α₀、α_s、α_asIt is respectively light source, stokes light and anti-Stokes light to pass in a fiber Defeated loss factor, x is the position in sensor fibre；r_s(t)、r_asT () is the Raman scattering coefficient of optical fiber, it embodies public affairs Formula is as follows:

$r_s\left(t\right)=\frac{1}{1-e^{-\frac{h\·\mathrm{\δ}v}{k\·t}}}---\left(3\right)$

$r_{as}\left(t\right)=\frac{1}{e^{\frac{h\·\mathrm{\δ}v}{k\·t}}-1}---\left(4\right)$

Wherein, h is planck constant, and δ v is Raman frequency shift, and k is Boltzmann constant, and t is absolute temperature；

(2) with stokes light as reference light, by formula (3), formula (4) respectively correspondence bring formula (1) into, in formula (2) and with step (1) In formula (2) divided by formula (1), that is, obtain the function with regard to Temperature Distribution:

$f(t,x)=\frac{k_{as}\·v_{as}^4}{k_s\·v_s^4}\·e^{-\frac{h\·\mathrm{\δ}v}{k\·t}}\·e^{-({\mathrm{\α}}_{as}-{\mathrm{\α}}_s)\·x}---\left(5\right)$

So, the temperature profile function of reference optical fiber ring present position is:

$f(t_{ref},x_{ref})=\frac{k_{as}\·v_{as}^4}{k_s\·v_s^4}\·e^{-\frac{h\·\mathrm{\δ}v}{k\·t_{ref}}}\·e^{-({\mathrm{\α}}_{as}-{\mathrm{\α}}_s)\·x_{ref}}---\left(6\right)$

Demodulated temperature distribution information and be by formula (5), formula (6):

$\frac{1}{t}=\frac{1}{t_{ref}}-\frac{k}{h\·\mathrm{\δ}v}\[ln\left(\frac{f(t,x)}{f(t_{ref},x_{ref})}\right)+({\mathrm{\α}}_{as}-{\mathrm{\α}}_s)\·(x-x_{ref})\]---\left(7\right);$

(3) sensor fibre is divided into n section, and calculates each section of differential loss and add in formula (7) and carry out segmentation differential loss Compensate, specific as follows:

(α in the formula (7) of step (2)_as-α_s) for anti-Stokes light and stokes light loss difference, and be expressed as δ α,

(0 arrives x to the 1st section of sensor fibre₁) differential loss be δ α₁, the 2nd section of (x₁To x₂) differential loss be δ α₂..., n-th section (x_n-1To x_n) differential loss be δ α_n；During the 1st section of temperature of calculating sensor fibre, by formula (7) plus the next item upCarry out differential loss compensation；In the same manner, during the 2nd section of temperature of calculating sensor fibre, formula (7) is added one ?During n-th section of temperature of calculating sensor fibre, by formula (7) plus the next item up

(4) row operation is entered for the computing formula in step (3) to integrate, obtain a straight biography eliminating differential loss impact Photosensitive fibre temperature curve is as follows:

$\frac{1}{t}=\frac{1}{t_{ref}}-\frac{k}{h\·\mathrm{\δ}v}\·\ln \left(\frac{f(t,x)}{f(t_{ref},x_{ref})}\right)---\left(8\right)$

Effectively eliminate the nonlinearity erron of distributed optical fiber temperature sensor, will not be because of anti-Stokes light and stokes light Loss difference and on temperature curve demodulation produce impact.

2. according to claim 1 eliminate distributed optical fiber temperature sensor nonlinearity erron method it is characterised in that Described pulsed laser source (1) is directly modulated laser or optical fiber laser, and the middle cardiac wave of pulsed laser source (1) A length of 1550.12nm, pulse width is 10ns, and peak power is 15w, and the repetition period is 152us.

3. according to claim 1 eliminate distributed optical fiber temperature sensor nonlinearity erron method it is characterised in that The length of described reference optical fiber ring (5) is 20-50m, a diameter of 8-15cm of coiling, and sensor fibre (8) length is 15km.

4. according to claim 1 eliminate distributed optical fiber temperature sensor nonlinearity erron method it is characterised in that: Described in coiling, the fiber type of reference optical fiber ring (5) is identical with sensor fibre (8) and is single-mode fiber or multimode fibre.

5. according to claim 1 eliminate distributed optical fiber temperature sensor nonlinearity erron method it is characterised in that: The material of described fiber termination box (4) and casing (12) is metal material: any one in aluminum, aluminium alloy, copper or rustless steel.

6. according to claim 1 eliminate distributed optical fiber temperature sensor nonlinearity erron method it is characterised in that: Described temperature probe (6) is thermocouple, platinum resistance, critesistor, diode or Special temperature measurement chip.

7. according to claim 1 eliminate distributed optical fiber temperature sensor nonlinearity erron method it is characterised in that: Described optic fibre connector (7) is one of fc, sc ring flange or e2000 terminal.

8. according to claim 1 eliminate distributed optical fiber temperature sensor nonlinearity erron method it is characterised in that: The circuit bandwidth of described photoelectric detection module (9) is 100-150mhz, and the picking rate of described high-speed collection card (10) is 500-503ms/s.

9. according to claim 1 eliminate distributed optical fiber temperature sensor nonlinearity erron method it is characterised in that: Described high-speed collection card (10) is pci interface or usb interface with the interface of card for industrial computer (12).