CN201885827U - Dual-wavelength light-source self-correcting distributed optical-fiber Raman temperature sensor for optical-fiber Raman frequency shifter - Google Patents

Abstract

The utility model discloses a dual-wavelength light-source self-correcting distributed optical-fiber Raman temperature sensor for an optical-fiber Raman frequency shifter, which comprises an optical-fiber pulse laser, an optical-fiber branching device, the optical-fiber Raman frequency shifter, two optical-fiber wavelength division multiplexers, two optical-fiber switches, a sensing optical fiber, a photoelectric receiving module, a digital signal processor and an industrial control computer, wherein the optical-fiber Raman frequency shifter comprises a single-mode optical fiber and a 1660nm light filter. The Raman related dual-wavelength light source of the sensor is obtained by the sensor by using the optical-fiber pulse laser through the optical-fiber Raman frequency shifter, the nonlinear loss caused by the bending and the pressurized stretching generated by optical fibers and optical cables when temperature-measuring optical fibers and optical cables are used on the spot is self-corrected, and temperature-measuring errors caused by deviation from linearity when an anti-Stokes Raman signal channel is demodulated by a Stokes Raman reference channel in a temperature-measuring system are overcome. The temperature sensor has the advantages of low cost, long service life, simple structure, good signal-to-noise ratio and good reliability and is applicable to petrochemical pipelines, tunnels, large civil-engineering monitoring and disaster forecasting and monitoring within the range of long-distance 30 kilometers.

Description

A kind of fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor

Technical field

The utility model relates to optical fiber Raman temperature sensor, and particularly fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor belongs to technical field of optical fiber sensing.

Background technology

In recent years, utilize fiber raman scattering light Strong degree to be subjected to the effect of temperature modulation and optical time domain reflection (OTDR) principle to be developed into distributed optical fiber Raman temperature sensor, it can online in real time forecast the on-the-spot temperature and the orientation of temperature variation, the variation of on-line monitoring scene temperature, in certain temperature range alarm temperature is set, be a kind of line-type heat detector of essential safe type, successfully use in fields such as power industry, petroleum chemical enterprise, large scale civil engineering and online disaster monitorings.

Because the fibre loss of each wave band is different, be that fibre loss exists spectral effects, in distributed optical fiber Raman temperature sensor, use the anti-Stokes Raman diffused light as measuring the temperature signal passage, with the Stokes Raman diffused light as measuring the temperature reference passage, because two passages are at different-waveband, the loss difference of thermometric optical fiber, non-linear phenomena appears during with Stokes Raman reference channel demodulation anti-Stokes Raman signal passage in temp measuring system, and the temperature measurement error that causes, reduced temperature measurement accuracy, can in demodulating process, artificially proofread and correct for the fibre loss of fixing wavelength.

Zhang Zaixuan proposed " a kind of Raman related double-wavelength light source self-correction distributed optical fiber Raman temperature sensor " (Chinese patent: ZL 200920192483.4) in 2009, adopting the 1550nm laser instrument is main light source, the 1450nm laser instrument is secondary light source, utilize the relevant automatic correcting method of Raman solved in, the correction problem in the short distance 100m-15km on-line temperature monitoring.But need with main light source and two light sources of secondary light source, more complicated, the cost height, and can not satisfy the safety and Health monitoring of petroleum pipe line, transferring electric power cable in recent years fully, to active demand long-range, the very-long-range distributed optical fiber Raman temperature sensor (DOFRTS) with self-correction.

Summary of the invention

The purpose of this utility model provides that a kind of cost is low, signal to noise ratio (S/N ratio) good, and stability and good reliability can realize the self-tuning fiber Raman frequency shifter of long-range 30km double-wavelength light source self-correction distributed optical fiber Raman temperature sensor with a fiber pulse laser.

Fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor of the present utility model, comprise fiber pulse laser, optical fiber splitter is by the fiber Raman frequency shifter that single-mode fiber and 1660nm light filter are formed, first optical fibre wavelength division multiplexer, second optical fibre wavelength division multiplexer, first fiber switch, sensor fibre, second fiber switch, photoelectricity receiver module, digital signal processor and industrial computer.Fiber pulse laser sends laser pulse and is divided into two bundles by optical fiber splitter, the laser of wherein a branch of 1550nm wave band enters the fiber Raman frequency shifter, through frequency displacement 13.2THz to the 1660nm wave band as main light source, the laser of another bundle 1550nm wave band is as secondary light source, first optical fibre wavelength division multiplexer has three ports, its 1660nm input port links to each other with the main light source of fiber Raman frequency shifter output, COM port links to each other with an input end of first fiber switch, the 1550nm output port links to each other with an input end of second fiber switch, second optical fibre wavelength division multiplexer has three ports, 1550nm input port wherein links to each other with the secondary light source of optical fiber splitter beam splitting, COM port links to each other with another input end of first fiber switch, the 1660nm output port links to each other with another input end of second fiber switch, the output terminal of first fiber switch links to each other with sensor fibre, the output terminal of second fiber switch links to each other with the input end of photoelectricity receiver module, the output terminal of photoelectricity receiver module links to each other with the input end of digital signal processor, the output terminal of digital signal processor links to each other with industrial computer, first, the second two fiber switch interlocks, utilize first fiber switch that two bundle Laser Time Sharings of first optical fibre wavelength division multiplexer and the output of second optical fibre wavelength division multiplexer are alternately entered sensor fibre, utilize second fiber switch that the output terminal timesharing of first optical fibre wavelength division multiplexer and second optical fibre wavelength division multiplexer is alternately linked to each other with the photoelectricity receiver module, when first fiber switch links to each other with the 1660nm main light source by first optical fibre wavelength division multiplexer, the second fiber switch input end links to each other with the first optical fibre wavelength division multiplexer 1550nm output port, and the anti-Stokes echo of sensor fibre is sent into the photoelectricity receiver module; When first fiber switch linked to each other with the secondary light source of 1550nm by second optical fibre wavelength division multiplexer, the second fiber switch input end linked to each other with the second optical fibre wavelength division multiplexer 1660nm output port, and the Stokes echo of sensor fibre is sent into the photoelectricity receiver module.

In the utility model, the centre wavelength of said pulsed laser is 1550nm, and spectral width is 0.1nm, and laser pulse width is 10ns, and peak power is that 1-1kW is adjustable, and repetition frequency is that 500Hz-20KHz is adjustable.

The centre wavelength of 1660nm light filter is 1660nm in the above-mentioned fiber Raman frequency shifter, spectral bandwidth 28nm, and transmitance 98% is to the isolation＞45dB of 1550nm laser.

In the utility model, said sensor fibre is that length is the G652 communication unit mode fiber of 30km.Sensor fibre be transmission medium be again sensor information, it is not charged to be laid on the thermometric scene, anti-electromagnetic interference (EMI), radiation hardness, corrosion-resistant.

During work, the laser pulse that fiber pulse laser sends is respectively in turn by first, second optical fibre wavelength division multiplexer is injected sensor fibre, the anti-Stokes Raman light wavelet of the main laser that produces on sensor fibre is through the first optical fibre wavelength division multiplexer beam splitting, convert analog electrical signal and amplification to by the photoelectricity receiver module, the Stokes Raman light wavelet of secondary laser is through the second optical fibre wavelength division multiplexer beam splitting, convert analog electrical signal and amplification to by the photoelectricity receiver module, the anti-Stokes Raman light dorsad and the strength ratio of Stokes Raman light, obtain the temperature information of each section of optical fiber, provide the temperature of each point on the sensor fibre (segment), utilize optical time domain reflection Raman photon temperature sensing detection point location on the temperature-sensitive optical fiber (optical fibre radar location).By the digital signal processor demodulation, through Temperature Scaling, in 60 seconds, obtain the temperature and the temperature variation of each section on the 30km sensor fibre, temperature measurement accuracy ± 1 ℃, in 0 ℃ of-300 ℃ of scope, carry out on-line temperature monitoring, carry out the telecommunication network transmission by communication interface, communications protocol by industrial computer.

The principle of work of fiber Raman frequency shifter:

The fiber Raman frequency shifter is made up of single-mode fiber and broadband 1660nm light filter.When laser incides single-mode fiber, the nonlinear interaction of laser and optical fiber molecule, incident photon is become another Stokes photon or anti-Stokes photon by an optical fiber molecular scattering, corresponding molecule is finished two transition between the vibrational state, emit a phonon and be called the Stokes Raman scattering photon, absorb a phonon and be called the anti-Stokes Raman scattering photon, the phonon frequency of optical fiber molecule is 13.2THz.After the 1550nm of incident laser power reaches certain threshold value, the Stokes Raman diffused light that produce to amplify, optical frequency shift 13.2THz, obtained wide band 1660nm light, behind the 1660nm light filter as the main light source of Raman relevant source.

The temperature-measurement principle of fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor:

Fiber pulse laser sends laser pulse and injects sensor fibre by optical fibre wavelength division multiplexer, the nonlinear interaction of laser and optical fiber molecule, incident photon is become another Stokes photon or anti-Stokes photon by an optical fiber molecular scattering, corresponding molecule is finished two transition between the vibrational state, emit a phonon and be called the Stokes Raman scattering photon, absorb a phonon and be called the anti-Stokes Raman scattering photon, the phonon frequency of optical fiber molecule is 13.2THz.Boltzmann (Boltzmann) law is obeyed in population heat distribution on the optical fiber molecular entergy level, the strength ratio R (T) of anti-Stokes Raman diffused light and Stokes Raman diffused light:

$R\left(T\right)=\frac{I_{\mathrm{AS}}}{I_S}={\left(\frac{{\mathrm{\λ}}_S}{{\mathrm{\λ}}_{\mathrm{AS}}}\right)}^4\exp (-\frac{\mathrm{hcv}}{\mathrm{kT}})---\left(1\right)$

I wherein _AS, I _SBe respectively the Strong degree λ of anti-Stokes Raman scattering photon and Stokes Raman diffused light _AS, λ _SBe respectively anti-Stokes Raman diffused light and Stokes Raman scattering light wavelength, h is Bo Langke (Planck) constant, and cv is that the Raman phonon frequency of optical fiber molecule is 13.2THz, and k is a Boltzmann constant, and T is Kai Erwen (Kelvin) absolute temperature.By both strength ratios, obtain the temperature information of each section of optical fiber.Must consider in the practical application that the anti-Stokes Raman diffused light is different with the place's fibre loss of Stokes Raman scattering light wavelength, then (1) changes (2) formula into

Because the loss of the optical fiber of each wave band is different, be that fibre loss exists spectral effects, in distributed optical fiber Raman temperature sensor, use the anti-Stokes Raman diffused light as measuring the temperature signal passage, with the Stokes Raman diffused light as measuring the temperature reference passage, because two passages are at different-waveband, the loss difference of thermometric optical fiber, with reference channel demodulation temperature signal passage the time, fiber optic temperature after the demodulation is with the distribution curve meeting departs from linear of fiber lengths, cause temperature measurement error, reduce temperature measurement accuracy, can in demodulating process, artificially proofread and correct for the fibre loss of fixing wavelength.

But thermometric optical fiber, the optical cable of Shi Yonging at the scene, the loss that causes is different because the optical fiber of each wave band, optical cable bending and pressurized stretch, and all there is randomness the bending that produces of optical fiber, optical cable and pressurized stretching size and position, is difficult to artificial correction, needs to adopt self-tuning way.

Fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor of the present utility model, non-linear loss that bending that produces owing to optical fiber, optical cable when can self-correcting using the thermometric optical fiber cable at the scene and pressurized stretch and cause, departs from linear when having overcome in the temp measuring system and the temperature measurement error that causes with Stokes Raman reference channel demodulation anti-Stokes Raman signal passage.

The Raman light of the Stokes dorsad strength ratio of the Raman light of anti-Stokes dorsad of main laser and secondary laser instrument

Wherein, λ _{2, S}=λ ₁, λ _{1, AS}=λ ₂,

Then all has offset with the fibre loss relative section on (3) formula the right.

$R\left(T\right)=\frac{I_1}{I_2}{\left(\frac{{\mathrm{\λ}}_1}{{\mathrm{\λ}}_2}\right)}^4\exp (-\frac{\mathrm{hcv}}{\mathrm{kT}})---\left(4\right)$

The utility model has adopted the main laser λ of the relevant dual wavelength of Raman frequency shift ₁=1660nm, secondary laser instrument λ ₂=1550nm.

If the temperature T=T of the one section optical fiber in known thermometric optical fiber front ₀, then obtain the temperature of any segment on the thermometric optical fiber by (5) formula by known Raman light strength ratio.

$T=[\frac{1}{T_0}-\frac{k}{\mathrm{hcv}}\ln \left(\frac{R\left(T\right)}{R\left(T_0\right)}\right)]---\left(5\right)$

The beneficial effects of the utility model are:

The fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor that the utility model provides, based on the fiber raman scattering frequency shift effect, utilize a 1550nm fiber pulse laser to produce Raman related double-wavelength, through Raman frequency shift 1660nm laser instrument as main light source, 1550nm forms a long-range 30km Raman related double-wavelength light source self-correction distributed optical fiber Raman temperature sensor system as secondary light source.Non-linear loss that bending that produces owing to optical fiber, optical cable when can self-correcting using the thermometric optical fiber cable at the scene and pressurized stretch and cause, departs from linear when having overcome in the temp measuring system and the temperature measurement error that causes with Stokes Raman reference channel demodulation anti-Stokes Raman signal passage.

Owing to adopt a fiber laser to obtain the Raman relevant wavelength, and the 2X1 fiber switch of two simple optical fibre wavelength division multiplexers and two interlocks and photoelectricity receiver module, amplifying circuit have been adopted, be that a kind of cost is low, signal to noise ratio (S/N ratio) good, the distributed optical fiber Raman temperature sensor (DOFRTS) with self-correction of stability and good reliability.Being laid on the on-the-spot thermometric optical fiber of monitoring insulate, uncharged, anti-electromagnetic interference (EMI), radiation hardness, corrosion resistant, be essential safe type, optical fiber be transmission medium be again sensor information, be the thermometric optical fiber of Intrinsical, and have the long-life that the utility model is applicable to long-range 30 kilometers distributed optical fiber Raman temperature sensors.Can be used for pipelines and petrochemical pipelines, tunnel, large scale civil engineering monitoring and hazard forecasting monitoring.

Description of drawings

Fig. 1 is a fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor.

Embodiment

With reference to Fig. 1, fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor comprises fiber pulse laser 10, optical fiber splitter 11, the fiber Raman frequency shifter of forming by single-mode fiber 12 and 1660nm light filter 13, first optical fibre wavelength division multiplexer, 14, the second optical fibre wavelength division multiplexers, 15, the first fiber switchs 16, sensor fibre 17, second fiber switch 18, photoelectricity receiver module 19, digital signal processor 20 and industrial computer 21.Fiber pulse laser 10 sends laser pulse and is divided into two bundles by optical fiber splitter 11, the laser of wherein a branch of 1550nm wave band enters the fiber Raman frequency shifter, through frequency displacement 13.2THz to the 1660nm wave band as main light source, the laser of another bundle 1550nm wave band is as secondary light source, first optical fibre wavelength division multiplexer 14 has three ports, its 1660nm input port links to each other with the main light source of fiber Raman frequency shifter output, COM port links to each other with an input end of first fiber switch 16, the 1550nm output port links to each other with an input end of second fiber switch 18, second optical fibre wavelength division multiplexer 15 has three ports, 1550nm input port wherein links to each other with the secondary light source of optical fiber splitter 11 beam splitting, COM port links to each other with another input end of first fiber switch 16, the 1660nm output port links to each other with another input end of second fiber switch 18, the output terminal of first fiber switch 16 links to each other with sensor fibre 17, the output terminal of second fiber switch 18 links to each other with the input end of photoelectricity receiver module 19, the output terminal of photoelectricity receiver module 19 links to each other with the input end of digital signal processor 20, the output terminal of digital signal processor 20 links to each other with industrial computer 21, first, the second two fiber switch interlocks, utilize first fiber switch 16 that two bundle Laser Time Sharings of first optical fibre wavelength division multiplexer 14 and 15 outputs of second optical fibre wavelength division multiplexer are alternately entered sensor fibre 17, utilize second fiber switch 18 that the output terminal timesharing of first optical fibre wavelength division multiplexer 14 and second optical fibre wavelength division multiplexer 15 is alternately linked to each other with photoelectricity receiver module 19, when first fiber switch 16 links to each other with the 1660nm main light source by first optical fibre wavelength division multiplexer 14, second fiber switch, 18 input ends link to each other with the 1550nm output port of first optical fibre wavelength division multiplexer 14, and the anti-Stokes echo of sensor fibre is sent into photoelectricity receiver module 19; When first fiber switch 16 links to each other with the secondary light source of 1550nm by second optical fibre wavelength division multiplexer 15, second fiber switch, 18 input ends link to each other with the 1660nm output port of second optical fibre wavelength division multiplexer 15, and the Stokes echo of sensor fibre is sent into photoelectricity receiver module 19.

The centre wavelength of above-mentioned pulsed laser is 1550nm, and spectral width is 0.1nm, and laser pulse width is 10ns, and peak power is that 1-1kW is adjustable, and repetition frequency is that 500Hz-20KHz is adjustable.

First above-mentioned fiber switch 16 and 18 interlocks of second fiber switch, the time of switching can be provided with, and the time that is provided with is 60s usually.

Above-mentioned photoelectricity receiver module adopts HZOE-GDJM-2 type photoelectricity receiver module.

Above-mentioned sensor fibre is that length is the G652 communication unit mode fiber of 30km.

Above-mentioned digital signal processor can adopt the 100MHz bandwidth of Hangzhou OE Technology Co., Ltd., the HZOE-SP01 type signal processing card of 250MS/s acquisition rate.

Claims (4)

1. fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor, it is characterized in that comprising fiber pulse laser (10), optical fiber splitter (11), the fiber Raman frequency shifter of forming by single-mode fiber (12) and 1660nm light filter (13), first optical fibre wavelength division multiplexer (14), second optical fibre wavelength division multiplexer (15), first fiber switch (16), sensor fibre (17), second fiber switch (18), photoelectricity receiver module (19), digital signal processor (20) and industrial computer (21), fiber pulse laser (10) sends laser pulse and is divided into two bundles by optical fiber splitter (11), the laser of wherein a branch of 1550nm wave band enters the fiber Raman frequency shifter, through frequency displacement 13.2THz to the 1660nm wave band as main light source, the laser of another bundle 1550nm wave band is as secondary light source, first optical fibre wavelength division multiplexer (14) has three ports, its 1660nm input port links to each other with the main light source of fiber Raman frequency shifter output, COM port links to each other with an input end of first fiber switch (16), the 1550nm output port links to each other with an input end of second fiber switch (18), second optical fibre wavelength division multiplexer (15) has three ports, 1550nm input port wherein links to each other with the secondary light source of optical fiber splitter (11) beam splitting, COM port links to each other with another input end of first fiber switch (16), the 1660nm output port links to each other with another input end of second fiber switch (18), the output terminal of first fiber switch (16) links to each other with sensor fibre (17), the output terminal of second fiber switch (18) links to each other with the input end of photoelectricity receiver module (19), the output terminal of photoelectricity receiver module (19) links to each other with the input end of digital signal processor (20), the output terminal of digital signal processor (20) links to each other with industrial computer (21), first, the second two fiber switch interlocks, utilize first fiber switch (16) that two bundle Laser Time Sharings of first optical fibre wavelength division multiplexer (14) and second optical fibre wavelength division multiplexer (15) output are alternately entered sensor fibre (17), utilize second fiber switch (18) that the output terminal timesharing of first optical fibre wavelength division multiplexer (14) and second optical fibre wavelength division multiplexer (15) is alternately linked to each other with photoelectricity receiver module (19), when first fiber switch (16) links to each other with the 1660nm main light source by first optical fibre wavelength division multiplexer (14), second fiber switch (18) input end links to each other with first optical fibre wavelength division multiplexer (14) 1550nm output port, and the anti-Stokes echo of sensor fibre is sent into photoelectricity receiver module (19); When first fiber switch (16) links to each other with the secondary light source of 1550nm by second optical fibre wavelength division multiplexer (15), second fiber switch (18) input end links to each other with second optical fibre wavelength division multiplexer (15) 1660nm output port, and the Stokes echo of sensor fibre is sent into photoelectricity receiver module (19).

2. fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor according to claim 1, the centre wavelength that it is characterized in that pulsed laser (10) is 1550nm, spectral width is 0.1nm, laser pulse width is 10ns, peak power is that 1-1kW is adjustable, and repetition frequency is that 500Hz-20KHz is adjustable.

3. fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor according to claim 1, the centre wavelength that it is characterized in that 1660nm light filter (13) in the fiber Raman frequency shifter is 1660nm, spectral bandwidth 28nm, transmitance 98% is to the isolation＞45dB of 1550nm laser.

4. fiber Raman frequency shifter double-wavelength light source self-correction distributed optical fiber Raman temperature sensor according to claim 1 is characterized in that sensor fibre (17) is that length is the G652 communication unit mode fiber of 30km.

Images