CN201935670U - Ultra long-range 100km full-distributed optical fiber Rayleigh and Raman scattering sensor - Google Patents

Abstract

The utility model discloses an ultra long-range 100km full-distributed optical fiber Rayleigh and Raman scattering sensor, which comprises an optical fiber impulse laser, an integrated optical fiber wavelength division multiplexer, an optical fiber narrow-band reflection filter, an optical fiber channel subdivider, an optical fiber Raman laser, a 100km sensing optical fiber, a photoelectric receiving module, a digital signal processor and an industrial personal computer. The sensor adopts a distributed optical fiber Raman amplifier, the backward Rayleigh scattering signal which is generated by the probing laser light with strain information in the sensing optical fiber is amplified, and the backward anti-Stokes scattering signal with temperature information is amplified, so the signal to noise ratio of a sensor system is improved, the measuring length of the sensor is increased, the reliability and spatial resolution of the sensor are improved, the field temperature can be measured while the filed deformation, cracks and temperature can also be measured at the same time, and the measurement are not intersected with one another. The utility model has the characteristics of low cost, long service life, simple structure, good signal to noise ratio and the like, and is applicable to monitor petrifaction pipelines, tunnels and large civil engineering within the ultra long range of 100km and hazard forecast.

Description

A kind of very-long-range 100km fully distributed fiber Rayleigh and Raman scattering sensor

Technical field

The utility model relates to the Fibre Optical Sensor field, especially distributed fiber Rayleigh and Raman scattering strain, temperature sensor.

Background technology

For a long time, both at home and abroad in the engineering field, large-scale civil construction, bridge, 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.

" fully distributed fiber Rayleigh and Raman scattering photon strain, the temperature sensor " that Zhang Zaixuan proposes (Chinese patent: ZL200910099463.7) provide that a kind of cost is low, simple in structure, signal to noise ratio (S/N ratio) is good, the distributed fiber Rayleigh of good reliability and Raman scattering photon strain, temperature sensor are in being applicable to, the sensing range of short distance 0-15km fully distributed fiber sensing net.But can not satisfy the safety and Health monitoring of petroleum pipe line, transferring electric power cable in recent years fully, to the active demand of long-range, very-long-range fully distributed fiber Rayleigh, Raman and Brillouin scattering strain, temperature sensing net.

Summary of the invention

The purpose of this utility model provide a kind of low cost that adopts the fiber Raman amplifying technique, simple in structure, signal to noise ratio (S/N ratio) good, the very-long-range 100km fully distributed fiber Rayleigh of good reliability and Raman scattering sensor.

Very-long-range 100km fully distributed fiber Rayleigh of the present utility model and Raman scattering sensor, comprise fiber pulse laser, the integrated-type optical fibre wavelength division multiplexer, the optical fiber narrowband reflection filter, optical fiber splitter, fibre optic Raman laser, 100km sensor fibre, photoelectricity receiver module, digital signal processor and industrial computer.The integrated-type optical fibre wavelength division multiplexer has four ports, wherein the 1550nm input port links to each other with fiber pulse laser, the COM output port links to each other with the input end of optical fiber splitter by the optical fiber optical filter, the 1450nm output port links to each other with two input ends of photoelectricity receiver module respectively with the 1550nm output port, an output terminal of optical fiber splitter links to each other with fibre optic Raman laser, another output termination sensor fibre of optical fiber splitter, two output terminals of photoelectricity receiver module link to each other with two input ports of digital signal processor respectively, digital signal processor will be gathered, the signal that adds up is through the industrial computer demodulation process, obtain the 100km sensor fibre strain at the scene, temperature information also sends the remote monitoring net to.

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 1-100W is adjustable, and repetition frequency is that 500Hz-20KHz is adjustable.

Above-mentioned fibre optic Raman laser is a continuous wave laser, and its centre wavelength is 1465nm, and spectral width is 0.1nm, and power 0-1.5W is adjustable.Fibre optic Raman laser and 100km sensor fibre constitute the C-band fiber Raman amplifier of a forward direction pumping.

The centre wavelength of above-mentioned optical fiber optical filter is 1465nm, and spectral width is 0.3nm, to the isolation＞45dB of 1465nm Rayleigh scattering light.The optical fiber narrowband reflection filter suppresses the dorsad Rayleigh scattering of 1465nm fibre optic Raman laser in sensor fibre, avoids Rayleigh scattering light to disturb the influence of the anti-Stokes Raman scattering of 1450nm wave band in the sensor fibre.

Above-mentioned sensor fibre is a 100km G652 communication unit mode fiber.

The light pulse laser instrument sends laser pulse and enters sensor fibre, the Rayleigh scattering dorsad that in sensor fibre, produces, Stokes and anti-Stokes Raman diffused light wavelet, Rayleigh scattering dorsad, Stokes and anti-Stokes Raman diffused light wavelet, constitute the C-band fiber Raman amplifier amplification of forward direction pumping via fibre optic Raman laser and 100km sensor fibre after, by the beam splitting of integrated-type optical fibre wavelength division multiplexer, have the Rayleigh scattering light dorsad of strain information and have the anti-Stokes Raman diffused light wavelength-division of temperature information not through the photoelectricity receiver module, convert light signal to analog electrical signal and amplification, obtain the information of strain by the strength ratio of Rayleigh scattering light, provide the strain of each strain sensing point on the sensor fibre, strain variation speed and direction; Strength ratio by anti-Stokes Raman diffused light and Rayleigh scattering light, the influence of deduction strain obtains 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).Survey by digital signal processor and strain, the demodulation of temperature demodulation software and to strain and temperature and to calibrate, in 60 seconds, obtain each point strain and temperature variation on the 100km sensor fibre, temperature measurement accuracy ± 2 ℃, carry out the telecommunication network transmission by computing machine 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 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 distributed optical fiber Raman amplifier principle

As incident laser v ₀Produce the nonlinear interaction scattering with the optical fiber molecule, emit a phonon and be called the Stokes Raman scattering photon, absorb a phonon and be called anti-Stokes Raman scattering photon Δ v, the phonon frequency of optical fiber molecule is 13.2THz.

v＝v ₀±Δv (1)

The turn off gain of amplifier is

G _A＝exp(g _RP ₀L _eff/A _eff) (2)

P wherein ₀=I ₀A _EffBe the pump light power input of amplifier, g _RBe Raman gain coefficienct A _EffBe the free area of optical fiber, L _EffBe the effective interaction length (having considered the absorption loss of optical fiber to pumping) of optical fiber, its expression formula is as follows:

$L_{\mathrm{eff}}=\frac{1}{{\mathrm{\α}}_p}[1-\exp (-{\mathrm{\α}}_{p}L)]---\left(3\right)$

For fiber Raman amplifier, pump power has only when surpassing a certain threshold value, just might produce excited Raman to signal and amplify the stokes wave v=v in optical fiber ₀-Δ v increases in fiber medium fast, the power of most of pump light can convert stokes light to, and Raman amplification arranged, gain can suppress the loss of optical fiber, improve the operating distance of fully distributed fiber strain, temperature sensor, this stimulated Raman scattering phenomenon is used for increasing the operating distance of fully distributed fiber sensor.

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 _Ray＝I ₀·v ₀ ⁴exp(-2α ₀L) (4)

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.

$\mathrm{\Δ\α}=\frac{1}{2l}\log \frac{I\left(l\right)}{I^{\′}\left(l\right)}---\left(5\right)$

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 is obeyed in population heat distribution on the optical fiber molecular entergy level, and anti-Stokes Raman scattering light intensity dorsad is in optical fiber

I _a＝I ₀·v _a ⁴R _a(T)exp[-(α ₀+α _a)·L] (6)

It is subjected to the modulation of fiber optic temperature, temperature modulation function R a

R _a(T)＝[exp(hΔv/kT)-1] ^-1 (7)

H is Bo Langke (Planck) constant, and Δ v is the phonon frequency of an optical fiber molecule, is 13.2THz, and k is a Boltzmann constant, and T is Kai Erwen (Kelvin) absolute temperature.

In the utility model, adopt the fiber Rayleigh passage to do reference signal, come detected temperatures with the ratio of anti-Stokes Raman diffused light and auspicious scattered light profit light intensity

$\frac{I_a\left(T\right)}{I_R\left(T\right)}={\left(\frac{v_a}{v_0}\right)}^4\·\exp {[(\mathrm{h\Δv}/\mathrm{kT})-1]}^{-1}\·\exp [-({\mathrm{\α}}_a-{\mathrm{\α}}_0)\·L]---\left(8\right)$

By anti-Stokes Raman diffused light and the auspicious scattered light sharp light strength ratio of fiber Raman optical time domain reflection (OTDR) curve at the optical fiber check point, the influence of deduction strain obtains the temperature information of each section of optical fiber.

The beneficial effects of the utility model are:

Very-long-range 100km fully distributed fiber Rayleigh of the present utility model and Raman scattering sensor, adopt distributed optical fiber Raman amplifier, the exploring laser light that will have strain information produces dorsad in sensor fibre, and Rayleigh scattering signal amplifies, and amplified the signal of anti Stokes scattering dorsad that has temperature information, improved the signal to noise ratio (S/N ratio) of sensing system, increased the measurement length of sensor, the reliability and the spatial resolution of sensor have been improved, the deformation at energy measurement scene, crack and temperature and do not intersect mutually in the measure field temperature.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 the life-span is long, the utility model is applicable to the strain of very-long-range 100km fully distributed fiber, temperature sensing net.Can be used for pipelines and petrochemical pipelines in very-long-range 100 kilometer range, tunnel, large scale civil engineering monitoring and hazard forecasting monitoring.

Description of drawings

Fig. 1 is the synoptic diagram of very-long-range 100km fully distributed fiber Rayleigh and Raman scattering sensor.

Embodiment

With reference to Fig. 1, very-long-range 100km fully distributed fiber Rayleigh and Raman scattering sensor, comprise fiber pulse laser 10, integrated-type optical fibre wavelength division multiplexer 11, optical fiber narrowband reflection filter 12, optical fiber splitter 13, fibre optic Raman laser 14,100km sensor fibre 15, photoelectricity receiver module 16, digital signal processor 17 and industrial computer 18.Integrated-type optical fibre wavelength division multiplexer 11 has four ports, wherein the 1550nm input port links to each other with fiber pulse laser 10, the COM output port links to each other with the input end of optical fiber splitter 13 by optical fiber optical filter 12, the 1450nm output port links to each other with two input ends of photoelectricity receiver module 16 respectively with the 1550nm output port, an output terminal of optical fiber splitter 13 links to each other with fibre optic Raman laser 14, another output termination sensor fibre 15 of optical fiber splitter 13, two output terminals of photoelectricity receiver module 16 link to each other with 17 two input ports of digital signal processor respectively, digital signal processor 17 will be gathered, the signal that adds up obtains 15 strains at the scene of 100km sensor fibre through industrial computer 18 demodulation process, temperature information also sends the remote monitoring net to.

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 1-100W is adjustable, and repetition frequency is that 500Hz-20KHz is adjustable.

Above-mentioned fibre optic Raman laser is a continuous wave laser, and its centre wavelength is 1465nm, and spectral width is 0.1nm, and power 0-1.5W is adjustable.

The centre wavelength of above-mentioned optical fiber filter narrowband reflection filter is 1465nm, and spectral width is 0.3nm, the 1465nm Raman laser is produced the isolation＞45dB of Rayleigh scattering light in optical fiber.The optical fiber narrowband reflection filter suppresses the dorsad Rayleigh scattering of 1465nm fibre optic Raman laser in sensor fibre, avoids Rayleigh scattering light to disturb the influence of the anti-Stokes Raman scattering of 1450nm wave band in the sensor fibre.

Above-mentioned photoelectricity receiver module adopts HZOE-GDJM-2 type photoelectricity receiver module.Above-mentioned sensor fibre adopts 100km G652 communication unit mode fiber.Signal processor adopts the 100MHz bandwidth of Hangzhou OE Technology Co., Ltd., the HZOE-SP01 type signal processing card of 250MS/s acquisition rate.

Claims (5)

1. very-long-range 100km fully distributed fiber Rayleigh and Raman scattering sensor, it is characterized in that comprising fiber pulse laser (10), integrated-type optical fibre wavelength division multiplexer (11), optical fiber narrowband reflection filter (12), optical fiber splitter (13), fibre optic Raman laser (14), 100km sensor fibre (15), photoelectricity receiver module (16), digital signal processor (17) and industrial computer (18), integrated-type optical fibre wavelength division multiplexer (11) has four ports, wherein the 1550nm input port links to each other with fiber pulse laser (10), the COM output port links to each other with the input end of optical fiber splitter (13) by optical fiber optical filter (12), the 1450nm output port links to each other with two input ends of photoelectricity receiver module (16) respectively with the 1550nm output port, an output terminal of optical fiber splitter (13) links to each other with fibre optic Raman laser (14), another output termination sensor fibre (15) of optical fiber splitter (13), two output terminals of photoelectricity receiver module (16) link to each other with (17) two input ports of digital signal processor respectively, digital signal processor (17) will be gathered, the signal that adds up is through industrial computer (18) demodulation process, obtain 100km sensor fibre (15) strain at the scene, temperature information also sends the remote monitoring net to.

2. very-long-range 100km fully distributed fiber Rayleigh according to claim 1 and Raman scattering sensor, the centre wavelength that it is characterized in that pulsed laser (11) is 1550nm, spectral width is 0.1nm, laser pulse width is 10ns, peak power is that 1-100W is adjustable, and repetition frequency is that 500Hz-20KHz is adjustable.

3. very-long-range 100km fully distributed fiber Rayleigh according to claim 1 and Raman scattering sensor is characterized in that fibre optic Raman laser (14) is a continuous wave laser, and its centre wavelength is 1465nm, and spectral width is 0.1nm, and power 0-1.5W is adjustable.

4. very-long-range 100km fully distributed fiber Rayleigh according to claim 1 and Raman scattering sensor, the centre wavelength that it is characterized in that optical fiber narrowband reflection filter (12) is 1465nm, spectral width is 0.3nm, to the isolation＞45dB of 1465nm Rayleigh scattering light.

5. very-long-range 100km fully distributed fiber Rayleigh according to claim 1 and Raman scattering sensor is characterized in that sensor fibre (15) is a 100km G652 communication unit mode fiber.

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