CN201417140Y - Distributed optical-fiber Rayleigh/Raman-scattering-photon strain/temperature sensor - Google Patents

Abstract

The utility model discloses a distributed optical-fiber Rayleigh/Raman-scattering-photon strain/temperature sensor, which is a sensor based on integrated optical-fiber wavelength division multiplexingtechnology, adopting the Rayleigh/Raman scattering and sensing principles and utilizing the optical time domain reflection principle to position the points to be tested. The sensor includes a pulse laser, an integrated optical fiber wavelength division multiplexer, a sensing optical fiber, three photoelectric receiving modules, a digital signal processor, a display and an alarm. The deformation,the cracks and the temperature can be simultaneously measured and the measuring does not interfere with each other; and as conveying media and sensing media, the optical fibers laid on the filer do not carry electricity and resist electromagnetic interference, radiation and corrosion. The sensor has the advantages of low cost, long service life, simple structure, and good SNR (signal-to-noise ratio) and reliability. The sensor is applicable to the monitoring of medium/short range production process (100 m to 15 km), large-scale civil engineering monitoring and hazard forecasting monitoring.

Description

A kind of fully distributed fiber Rayleigh and Raman scattering photon strain, temperature sensor

Technical field

The utility model relates to optical strain, temperature sensor, especially fully distributed fiber Rayleigh and Raman scattering photon strain, temperature sensor.

Background technology

For a long time, both at home and abroad in the engineering field, large-scale civil construction, bridge fine strain of millet, tunnel, pipelines and petrochemical pipelines, storage tank and power cable mainly use electricity foil gauge and temperature-sensitive electricity group as strain and temperature sensor, each sensor all need connect electric wire, form large-scale detection network, structure is very complicated, this class sensor itself is charged, be unsafe in essence, be subject to electromagnetic interference (EMI), not corrosion-resistant, can not locate, be not suitable for using in the rugged surroundings, more be not suitable for the scene of applied geology disaster and fire.

The Fibre Optical Sensor net that development in recent years is got up can be realized large scale civil engineering, power engineering, petrochemical industry, traffic bridge, tunnel, subway station, the forecast and the monitoring of monitoring of safety and Health such as dam, embankment and Mineral Engineering and disaster.Fibre Optical Sensor has two big classes: a class be with the white point sensors " extension " (laying) such as (F-P) of fiber grating (FBG) and optical Fiber Method on optical fiber, the quasi-distributed optical fiber sensor network that adopts the light time field technique to form, the subject matter of quasi-distributed optical fiber sensor network is that the optical fiber between point sensor only is transmission medium, thereby has detection " blind area "; The another kind of intrinsic property that utilizes optical fiber, fiber Rayleigh, Raman and Brillouin scattering effect, the full distribution optical fiber sensor net that adopts light time territory (OTDR) technology to form is measured strain and temperature.Optical fiber in the full distribution optical fiber sensor net be transmission medium be again sensor information, do not exist and detect the blind area.

The development optical fiber sensing technology is built novel optical fiber sensing monitoring network, is to ensure China's electric power, petrochemical industry, colliery, large bridge, the important measures of the safety in tunnel.Adopt Intrinsical fully distributed fiber Rayleigh, Raman and Brillouin scattering sensor network can predict the variation in structural stress field, stratum, temperature field, monitoring stratal configuration, earthquake, landslide and big face journey landslide are had prediction effect; Adopt full distributed sensor network can prevent great disaster to power engineering, large scale civil engineering, the influence of petrochemical industry project is implemented the safety and Health monitoring and is taked corresponding emergency preplan and measure.

What development in recent years was got up utilizes distributed optical fiber temperature sensor as line style fire monitoring heat fire detector, it can online in real time forecast variation of temperature, can alarm temperature be set in very big temperature range, be the line-type heat detector of essential safe type, on power industry, traffic tunnel and underground works, successfully use.

But, not only need to measure temperature field but also big strain field (deformation) even the crackle of needs measurement to the prediction and the monitoring of large scale civil engineering, tunnel and geologic hazard.Though fully distributed fiber Brillouin Time Domain Analyzer is detected temperatures and strain simultaneously, has cross effect, influence testing result, and instrument costs an arm and a leg.

Summary of the invention

The purpose of this utility model provides that a kind of cost is low, simple in structure, signal to noise ratio (S/N ratio) is good, the fully distributed fiber Rayleigh of good reliability and Raman scattering photon strain, temperature sensor.

The fully distributed fiber Rayleigh and the Raman scattering photon strain of invention, temperature sensor comprises pulsed laser, the integrated-type optical fibre wavelength division multiplexer, sensor fibre, three photoelectricity receiver modules, digital signal processor, display and alarm, the integrated-type optical fibre wavelength division multiplexer has five ports, wherein the 1550nm input port links to each other with pulsed laser, the COM output port links to each other with sensor fibre, the 1450nm output port links to each other with the input end of the first photoelectricity receiver module, the 1660nm output port links to each other with the input end of the second photoelectricity receiver module, the 1550nm output port links to each other with the input end of the 3rd photoelectricity receiver module, and the output terminal of three photoelectricity receiver modules links to each other with digital signal processor respectively, and the signal output part of digital signal processor connects display and alarm.

It is 1550nm that above-mentioned pulsed laser adopts centre wavelength, and spectral width is 0.1nm, and laser pulse width is 18ns, and peak power is 20W, and repetition frequency is the pulsed laser of 4kHz.

Said integrated-type optical fibre wavelength division multiplexer adopts SZMX-WDM-3 type integrated-type optical fibre wavelength division multiplexer.This integrated-type optical fibre wavelength division multiplexer comprises discrete optical fiber bidirectional coupler, the optical fiber parallel light path, Stokes and anti-Stokes Raman diffused light broad band pass filter, has 1550nm laser input port, the COM output port, the 1450nm output port, five ports such as 1660nm output port and 1550nm output port, optical fiber bidirectional coupler 1550nm laser input port links to each other with pulsed laser, the COM output terminal links to each other with sensor fibre, the Rayleigh scattering of 1550nm dorsad that the other end by optical fiber bidirectional coupler is collected, Raman scattering of 1450nm anti-Stokes and the Raman scattering of 1660nm Stokes, by the first optical fiber parallel light path and 1450nm broad band pass filter, the optical fiber anti-Stokes Raman diffused light in the 1450nm broadband that sees through is exported by 1450 fiber ports, 1550nm Rayleigh scattering light that reflects and the Stokes Raman scattering of 1660nm broadband, again by the second optical fiber parallel light path and 1660nm broad band pass filter, the 1660nm broadband Stokes Raman diffused light that sees through is by the output of 1660nm fiber port, and the 1550nm Rayleigh scattering light of reflection is exported by optical fiber 1550nm output port.

In the utility model, said three photoelectricity receiver modules are all by InGaAs photoelectricity avalanche diode and low noise broadband prime amplifier integrated chip MAX4107 and three grades of HZOE-GDJM-2 type photoelectricity receiver modules that main amplifier is formed of low noise.

Said sensor fibre is that carbon applies multimode optical fiber, and sensor fibre is that carbon coating multimode optical fiber is a kind of in drawing process, the special fiber of deposition one deck agraphitic carbon on the bare fibre surface.The technology that this carbon sealing applies has solved optical fiber because the physical strength that static fatigue causes descends, and because hydrogen diffuses into the long-term integrity problems such as loss increase that cause in the quartz glass body.This carbon coated fiber can be in the medium-term and long-term work reliably of harsh rugged environment.The carbon coated fiber is that the cladding surface at optical fiber adds the thick fine and close carbon film of one deck 35～70nm; and then coating one deck ultra-violet curing organic coating; fine and close carbon film can strengthen under rugged surroundings greatly to the protection of bare fibre, ensures its permanance, and sensor fibre length is 100m～15km.Sensor fibre is laid on the scene, and this optical fiber is not charged, anti-electromagnetic interference (EMI), radiation hardness, corrosion-resistant, good reliability, optical fiber be transmission medium be again sensor information.

Pulsed laser sends laser pulse and injects sensor fibre by the integrated-type optical fibre wavelength division multiplexer, the Rayleigh scattering dorsad that in sensor fibre, produces, Stokes and anti-Stokes Raman diffused light wavelet are through the beam splitting of integrated-type optical fibre wavelength division multiplexer, respectively through three photoelectricity receiver modules, convert light signal to analog electrical signal and amplification, obtain the information of strain by the strength ratio of Rayleigh scattering, provide the strain of each strain sensing point on the sensor fibre, strain variation speed and direction; Strength ratio by anti-Stokes and Stokes Raman diffused light, obtain the temperature information of each section of optical fiber, the temperature of each heat detection point, temperature changing speed and direction, there is not cross effect in the detection of strain and temperature, utilizes optical time domain reflection to the location of the check point on the sensor fibre (optical fibre radar location).By the digital signal processor demodulation, process is to strain and thermometric calibration, in 30 seconds, obtain each point strain and temperature variation on the sensor fibre, temperature measurement accuracy ± 1 ℃, carry out the telecommunication network transmission by display or by communication interface, communications protocol, when check point on the sensor fibre reaches the strain of setting or temperature alarming setting value, send alerting signal to alarm controller.

The principle of distributed fiber Rayleigh scattered photon sensor measurement deformation:

Fiber pulse laser sends laser pulse and injects sensor fibre by the integrated-type optical fibre wavelength division multiplexer, the interaction of laser and optical fiber molecule, produce Rayleigh scattering light with the incident photon same frequency, Rayleigh scattering light transmits in optical fiber deposits loss, the exponential decay with fiber lengths, hold sharp scattered light intensity to represent dorsad with following formula:

I＝I ₀exp(-2α ₀L) (1)

I in the following formula ₀For inciding the light intensity at optical fiber place, L is a fiber lengths, I be dorsad Rayleigh scattering light at the light intensity at fiber lengths L place, α ₀Fiber transmission attenuation for the incident light wave strong point.

Because optical fiber is laid on the scene of detection with sensor fibre, when site environment produces deformation or crackle, cause the optical fiber at the scene of being laid on to bend, optical fiber produces local loss, forms the added losses Δ α of optical fiber, then total losses α=α ₀+ Δ α, the light intensity at local place has one to fall, and light intensity is reduced to I ' (l) by I (l), and the added losses that deformation causes are measured by the change of light intensity.

$\mathrm{\Δ\α}=\frac{1}{2l}\log \frac{I\left(l\right)}{I^{\′}\left(l\right)}---\left(2\right)$

The relation of deformation or crackle size and fibre loss adopts realistic model to calculate and carries out the simulation test measurement in the laboratory and obtains.

The principle of distributed fiber Raman scattered photon sensor measurement temperature:

When incident laser and optical fiber molecule generation nonlinear interaction scattering, 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, the strength ratio R (T) of anti-Stokes Raman diffused light and Stokes Raman diffused light are obeyed in population heat distribution on the optical fiber molecular entergy level

$R\left(T\right)={\left[\frac{v_{\mathrm{as}}}{v_s}\right]}^4{e}^{-\left(\frac{\mathrm{h\Δ}{v}_r}{\mathrm{kT}}\right)}---\left(3\right)$

V wherein _As, v _sBe respectively the frequency of anti-Stokes Raman scattering photon and Stokes Raman scattering photon, h is Bo Langke (Planck) constant, Δ v _rBe the phonon frequency of an optical fiber molecule, be 13.2THz, k is a Boltzmann constant, and T is Kai Erwen (Kelvin) absolute temperature.By the strength ratio of fiber Raman optical time domain reflection (OTDR) curve, obtain the temperature information of each section of optical fiber at the optical fiber check point.

The beneficial effects of the utility model are:

Fully distributed fiber Rayleigh of the present utility model and Raman scattering photon strain, temperature sensor, simultaneously deformation, crack and the temperature of measure field and do not intersect mutually.Adopt integrated wavelength division multiplexer, improved the signal to noise ratio (S/N ratio) of sensing system, reliability and spatial resolution have reduced cost; On cost performance, be better than distribution type fiber-optic Brillouin temperature, strain transducer.Being laid on the on-the-spot sensor fibre of taking precautions against natural calamities 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 sensor fibre of Intrinsical, and have the long-life more than 50 years, during the utility model is applicable to, the monitoring of short distance 100m～15km production run and large scale civil engineering and hazard forecasting monitoring.

Description of drawings

Fig. 1 is the synoptic diagram of fully distributed fiber Rayleigh and Raman scattering photon strain, temperature sensor.

Embodiment

With reference to Fig. 1, fully distributed fiber Rayleigh and Raman scattering photon strain, temperature sensor, comprise pulsed laser 10, integrated-type optical fibre wavelength division multiplexer 11, sensor fibre 12, three photoelectricity receiver modules 13,14,15, digital signal processor 16, display 17 and alarm 18, integrated-type optical fibre wavelength division multiplexer 11 has five ports, wherein the 1550nm input port links to each other with pulsed laser 10, the COM output port links to each other with sensor fibre 12, the 1450nm output port links to each other with the input end of the first photoelectricity receiver module 14, the 1660nm output port links to each other with the input end of the second photoelectricity receiver module 13, the 1550nm output port links to each other with the input end of the 3rd photoelectricity receiver module 13, three photoelectricity receiver modules 13,14,15 output terminal links to each other with digital signal processor 16 respectively, and the signal output part of digital signal processor 16 connects display 17 and alarm 18.

Wherein, it is 1550nm that pulsed laser adopts centre wavelength, and spectral width is 0.1nm, and laser pulse width is 18ns, and peak power is 20W, and repetition frequency is the pulsed laser of 4kHz.Be laid on on-the-spot sensor fibre and be 15 kilometers long be coated with carbon optical fiber, spatial resolution is 3 meters, has 1,5000 check point.The integrated-type optical fibre wavelength division multiplexer is a SZMX-WDM-3 type integrated-type optical fibre wavelength division multiplexer.Digital signal processor adopts general signal processing card, is inserted in the industrial control computer.

Signal processor can adopt the 100MHz bandwidth of America NI company, the NI 5112 type signal processing cards of 100MS/s acquisition rate, or adopt Canadian GaGe company, the CS21GB-1GHz type signal processing card of 500MS/s acquisition rate.

Claims (5)

1. fully distributed fiber Rayleigh and Raman scattering photon strain, temperature sensor, it is characterized in that comprising pulsed laser (10), integrated-type optical fibre wavelength division multiplexer (11), sensor fibre (12), three photoelectricity receiver modules (13,14,15), digital signal processor (16), display (17) and alarm (18), integrated-type optical fibre wavelength division multiplexer (11) has five ports, wherein the 1550nm input port links to each other with pulsed laser (10), the COM output port links to each other with sensor fibre (12), the 1450nm output port links to each other with the input end of the first photoelectricity receiver module (14), the 1660nm output port links to each other with the input end of the second photoelectricity receiver module (13), the 1550nm output port links to each other with the input end of the 3rd photoelectricity receiver module (13), three photoelectricity receiver modules (13,14,15) output terminal links to each other with digital signal processor (16) respectively, and the signal output part of digital signal processor (16) connects display (17) and alarm (18).

2. fully distributed fiber Rayleigh according to claim 1 and Raman scattering photon strain, temperature sensor, the centre wavelength that it is characterized in that pulsed laser (10) is 1550nm, and spectral width is 0.1nm, and laser pulse width is 16ns, peak power is 20W, and repetition frequency is 4kHz.

3. fully distributed fiber Rayleigh according to claim 1 and Raman scattering photon strain, temperature sensor, it is characterized in that said integrated-type optical fibre wavelength division multiplexer (11) is for having 1550nm laser input port, the COM output port, the 1450nm output port, the SZMX-WDM-3 type integrated-type optical fibre wavelength division multiplexer of 1660nm output port and 1550nm output port.

4. fully distributed fiber Rayleigh according to claim 1 and Raman scattering photon strain, temperature sensor is characterized in that said three photoelectricity receiver modules (13,14,15) are HZOE-GDJM-2 type photoelectricity receiver module.

5. fully distributed fiber Rayleigh according to claim 1 and Raman scattering photon strain, temperature sensor is characterized in that sensor fibre (12) applies multimode optical fiber for carbon.

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