CN202229855U - Super long distance optical fiber temperature measuring sensor combining with multiple Raman scattering effects - Google Patents

Abstract

The utility model discloses a super long distance temperature measuring sensor combining with multiple Raman scattering effects. A wide spectral laser with a wave band of 1,660nm is generated by a Raman frequency shifter and taken as a light source for the measurement of a system; combining with a Raman scattering effect amplification system light source, the length of the sensing optical fiber for measuring temperature is lengthened; and after an anti-Stokes light containing temperature information and generated by the sensing optical fiber is amplified by a C-band Raman amplifier, the Rayleigh scattering light is separated by a matched narrow band light filter, and further the temperature information of the sensing optical fiber is obtained through demodulating the anti-Stokes light. The utility model has the advantages that the temperature measuring length of the sensing optical fiber can be lengthened after a system light source with a wave band of 1,660nm is amplified by the Raman amplifier, and the anti-Stokes light provided with the temperature information is transformed to a 1,550nm optical fiber low loss region and then combined with the C-bank amplifier to improve the signal-to-noise ratio of the system; in addition, the system is applicable to petrochemical pipelines or tunnels with a range above 100km, and other disaster forecast monitoring occasions.

Description

The very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola merges

Technical field

The utility model belongs to distributing optical fiber sensing thermometric field, relates to the very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola merges.This system is suitable for long-range 100km and the real-time disaster monitoring occasion of above need.

Technical background

In recent years, utilize optical fibre distribution type sensor realize online real-time prediction field temperature and variation tendency thereof based on simple to operate, can be applicable to advantages such as rugged surroundings and obtained to pay close attention to widely and study.Such sensor utilizes the fiber raman scattering luminous intensity to be subjected to the effect of temperature modulation and the monitoring that the optical time domain reflection principle realizes temperature, can be to petrochemical industry, and traffic bridge, tunnel etc. carry out the forecast and the monitoring of safety and Health monitoring and disaster.Zhang Zaixuan proposed " fully distributed fiber Rayleigh and Raman scattering photon strain, temperature sensor " patent of invention in 2009; Utilize the temperature information of acquisition recently of thermally sensitive anti Stokes scattering light intensity and Rayleigh scattering light intensity or stokes scattering light intensity; This method can overcome the measuring error that causes owing to light source fluctuation; But in being only applicable to, short distance 100m-15km on-line temperature monitoring, can not satisfy in recent years petroleum pipe line, transferring electric power cable etc. fully to active demand long-range, very-long-range distributed fiber Raman temperature probe.

The utility model adopt Raman frequency shift device based on the stimulated Raman scattering effect testing light source from traditional arrowband 1550nm wave band frequency displacement to wide range 1660nm wave band; When having suppressed coherent noise with the anti Stokes scattering light that has temperature information in the sensor fibre; Move on to the 1550nm low-loss band of optical fibers, improved the signal to noise ratio (S/N ratio) of system.Be fused to wide range 1660nm wave band to the Raman enlarge-effect, make system testing luminous energy highest-gain reach 17dB, be equal to and improved the about 40km of sensor fibre length.Merged the C-band fiber Raman amplifier, amplified the anti-Stokes Raman light of 1550nm wave band, highest-gain can reach 25dB, has improved system signal noise ratio, has reduced the difficulty of weak signal inspection.This temp measuring system possesses advantages such as far measuring distance, temperature measurement accuracy is high, system's demodulation is simple, is applicable to very-long-range 100km fully distributed fiber TEMP net, is used for preventing pipeline, various possible disasters such as tunnel.

Summary of the invention

The purpose of the utility model provides the very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of a kind of Duola merges, and can realize the very-long-range 100km distributed optical fiber temperature measurement function that signal to noise ratio (S/N ratio) is good, resolution is high.

The technical solution of the utility model is following:

The very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola merges comprises fiber pulse laser, optical fiber splitter, the fiber Raman frequency shifter of being made up of single-mode fiber and fiber filter; Time delay optical fiber, optical fiber wave multiplexer, optical fibre wavelength division multiplexer; Fiber coupler, Raman laser, sensor fibre; Two fiber reflection light filters, photoelectricity receiver module, digital signal processor and industrial computer.The input port of optical fiber splitter links to each other with fiber pulse laser, and two output ports link to each other with single-mode fiber, time delay optical fiber respectively; Two input ports of optical fiber wave multiplexer link to each other with time delay optical fiber, fiber filter, and output port links to each other with the input port of optical fibre wavelength division multiplexer; Optical fibre wavelength division multiplexer has three output ports; COM output port and centre wavelength are that the fiber reflection light filter input port of 1450nm links to each other; The 1660nm output port links to each other with an input port of photoelectricity receiver module (22), and the output port of 1550nm and centre wavelength are that the input port of 1550nm fiber reflection light filter links to each other; Two input ports of fiber coupler and centre wavelength are that fiber reflection light filter, the Raman laser of 1450nm links to each other, and output port links to each other with sensor fibre.

In the utility model, the centre wavelength of mentioned pulsed laser is 1550nm, and spectral width is 0.2nm, and laser pulse width is that 10-30ns is adjustable, and peak power is that 1-100W is adjustable, and repetition frequency is that 500-800Hz is adjustable; The branching ratio of mentioned optical fiber splitter is 80/20, and the branching ratio of optical fiber wave multiplexer is 60/40; Mentioned fiber Raman frequency shifter is made up of 800 meters single-mode fibers and fiber filter, and wherein the centre wavelength of light filter is 1660nm, spectral bandwidth 28nm, and transmitance 98% is to the isolation＞45dB of 1550nm laser; Mentioned time delay optical fiber length is the general single mode fiber of 805-820 rice; The centre wavelength of mentioned fiber reflection light filter (20) is 1450nm, and spectral width is 0.5nm, and reflectivity 95% is to the isolation＞45dB of 1450nm laser; The centre wavelength of fiber reflection light filter (21) is 1550nm, and spectral width is 0.5nm, and reflectivity 95% is to the isolation＞45dB of 1550nm laser.

The beneficial effect of the utility model is:

The very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of the Duola of the utility model merges adopts the stimulated Raman scattering principle to realize the raman amplifier effect of Raman frequency shift device, two wave bands, adopts the spontaneous Raman scattering effect to realize the fully distributed fiber thermometric.The raman amplifier of different-waveband plays two effects: the one, amplified the energy of system source, and increased the thermometric fiber lengths; The 2nd, amplified the anti-Stokes light intensity, improved system signal noise ratio, reduced the difficulty of Testing of Feeble Signals.Compare with traditional optical fiber temperature-measurement sensor, this system's thermometric distance, measuring accuracy height, simple in structure.The utility model is applicable to that very-long-range needs the occasion of continuous temperature measurement, prevents pipeline, various possible disasters such as tunnel.

Description of drawings

Fig. 1 is the very-long-range optical fiber temperature-measurement sensor construction synoptic diagram that the graceful scattering effect of Duola merges.

Embodiment

Below in conjunction with accompanying drawing the utility model is further described.

Referring to shown in Figure 1, the very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola merges comprises fiber pulse laser 10, optical fiber splitter 11; By the fiber Raman frequency shifter that single-mode fiber 12 and fiber filter 13 are formed, time delay optical fiber 14, optical fiber wave multiplexer 15, optical fibre wavelength division multiplexer 16; Fiber coupler 17, Raman laser 18, sensor fibre 19, fiber reflection light filter 20; Fiber reflection light filter 21, photoelectricity receiver module 22, digital signal processor 23 and industrial computer 24.

The input port of optical fiber splitter 11 links to each other with fiber pulse laser 10, and two output ports link to each other with single-mode fiber 12, time delay optical fiber 14 respectively; Two input ports of optical fiber wave multiplexer 15 link to each other with time delay optical fiber 14, fiber filter 13, and output port links to each other with the input port of optical fibre wavelength division multiplexer 16; Optical fibre wavelength division multiplexer 16 has three output ports; The COM output port links to each other with the input port of fiber reflection light filter 20; The 1660nm output port links to each other with an input port of photoelectricity receiver module 22, and the output port of 1550nm links to each other with the input port of fiber reflection light filter 21; Two input ports of fiber coupler 17 link to each other with fiber reflection light filter 20, Raman laser 18, and output port links to each other with sensor fibre 19.

The centre wavelength of above-mentioned pulsed laser is 1550nm, and spectral width is 0.2nm, and laser pulse width is that 10-30ns is adjustable, and peak power is that 1-100W is adjustable, and repetition frequency is that 500-800Hz is adjustable.

The branching ratio of above-mentioned optical fiber splitter is 80/20, and the branching ratio of optical fiber wave multiplexer is 60/40.

Above-mentioned fiber Raman frequency shifter, it is made up of 800 meters single-mode fibers and fiber filter.Wherein the centre wavelength of light filter is 1660nm, spectral bandwidth 28nm, and transmitance 98% is to the isolation＞45dB of 1550nm laser.

Above-mentioned time delay optical fiber length is the general single mode fiber of 805-820 rice.

The centre wavelength of above-mentioned fiber reflection light filter 20 is 1450nm, and spectral width is 0.5nm, and reflectivity 95% is to the isolation＞45dB of 1450nm laser; The centre wavelength of fiber reflection light filter 21 is 1550nm, and spectral width is 0.5nm, and reflectivity 95% is to the isolation＞45dB of 1550nm laser.

The utility model is based on following three principles:

(1) based on the principle of work of the fiber Raman frequency shifter of stimulated Raman scattering effect

The fiber Raman frequency shifter is made up of single-mode fiber and broadband 1660nm light filter.When a branch of 1550nm pulse laser incides single-mode fiber; Laser and optical fiber molecule generation nonlinear interaction; Incident photon is become another Stokes photon or anti-Stokes photon by an optical fiber molecular scattering, emits a phonon and is called the stokes scattering photon, in sensor fibre, has produced the 1660nm stokes light of frequency displacement 13.2THz; After the 1550nm of incident laser power reached certain threshold value, most of incident light was converted into stokes light (excited state).When another bundle 1550nm laser and 1660nm Stokes Raman light of being told by the incident laser source incide same sensor fibre; Two-beam produces nonlinear interaction at the place of meeting; Produce the stokes light (enlargement factor is relevant with the ratio of two-beam power) that amplifies, obtained to merge the wide range 1660nm wave band of laser of Raman enlarge-effect, as the system testing light source; Highest-gain can reach 17dB, is equivalent to prolong thermometric fiber lengths 40km.

(2) distributed optical fiber Raman amplifier principle of work

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 in the optical fiber is increased in fiber medium fast, the power of most of pump light can convert stokes light to; Possess Raman amplification, the turn off gain of its amplification does

G _A＝exp(g _RP ₀L _eff/A _eff) (1)

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 _EffEffective interaction length (having considered the absorption loss of optical fiber) for optical fiber to pumping.

Gain can suppress the loss of optical fiber, improves the signal to noise ratio (S/N ratio) of system, reduces the difficulty of weak signal check system.

(3) based on the fully distributed fiber temperature probe principle of spontaneous Raman scattering effect

When incident laser and optical fiber molecule generation nonlinear interaction, emit a phonon and be called the Stokes Raman scattering photon, absorb a phonon and be called the anti-Stokes Raman scattering photon.Boltzmann's law is obeyed in population heat distribution on the optical fiber molecular entergy level, and anti-Stokes Raman scattering light intensity dorsad does in optical fiber

I _a＝I ₀·v _a ⁴R _a(T)exp[-(α ₀+α _a)·L] (2)

It receives the modulation of fiber optic temperature, temperature modulation function R a

R _a(T)＝[exp(hΔv/kT)-1] ^-1 (3)

H is the Bo Langke 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 a Kai Erwen 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

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

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

Claims (6)

1. the very-long-range optical fiber temperature-measurement sensor of the graceful scattering effect fusion of Duola is characterized in that comprising fiber pulse laser (10), optical fiber splitter (11); By the fiber Raman frequency shifter that single-mode fiber (12) and fiber filter (13) are formed, time delay optical fiber (14), optical fiber wave multiplexer (15); Optical fibre wavelength division multiplexer (16), fiber coupler (17), Raman laser (18); Sensor fibre (19), fiber reflection light filter (20), fiber reflection light filter (21); Photoelectricity receiver module (22), digital signal processor (23) and industrial computer (24).The input port of optical fiber splitter (11) links to each other with fiber pulse laser (10), and two output ports link to each other with single-mode fiber (12), time delay optical fiber (14) respectively; Two input ports of optical fiber wave multiplexer (15) link to each other with time delay optical fiber (14), fiber filter (13), and output port links to each other with the input port of optical fibre wavelength division multiplexer (16); Optical fibre wavelength division multiplexer (16) has three output ports; The COM output port links to each other with the input port of fiber reflection light filter (20); The 1660nm output port links to each other with an input port of photoelectricity receiver module (22), and the output port of 1550nm links to each other with the input port of fiber reflection light filter (21); Two input ports of fiber coupler (17) link to each other with fiber reflection light filter (20), Raman laser (18), and output port links to each other with sensor fibre (19).

2. the very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola according to claim 1 merges; The centre wavelength that it is characterized in that pulsed laser (10) is 1550nm; Spectral width is 0.2nm; Laser pulse width is that 10-30ns is adjustable, and peak power is that 1-100W is adjustable, and repetition frequency is that 500-800Hz is adjustable.

3. the very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola according to claim 1 merges, the branching ratio that it is characterized in that optical fiber splitter (11) is 80/20, the branching ratio of optical fiber wave multiplexer (15) is 60/40.

4. the very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola according to claim 1 merges; It is characterized in that the fiber Raman frequency shifter; It is characterized in that single-mode fiber (12) is 800 meters, the centre wavelength of fiber filter (13) is 1660nm, spectral bandwidth 28nm; Transmitance 98% is to the isolation＞45dB of 1550nm laser.

5. the very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola according to claim 1 merges, the length that it is characterized in that time delay optical fiber (14) is the general single mode fiber of 805-820 rice.

6. the very-long-range optical fiber temperature-measurement sensor that the graceful scattering effect of Duola according to claim 1 merges; The centre wavelength that it is characterized in that fiber reflection light filter (20) is 1450nm; Spectral width is 0.5nm, and reflectivity 95% is to the isolation＞45dB of 1450nm laser; The centre wavelength of fiber reflection light filter (21) is 1550nm, and spectral width is 0.5nm, and reflectivity 95% is to the isolation＞45dB of 1550nm laser.

Images