CN201289462Y - Device for detecting liquor refractive index using plasma resonance fiber optic sensor - Google Patents

Abstract

The utility model discloses a device which utilizes a plasma resonance optical fiber sensor to detect index of refraction. The device comprises a light source, the plasma resonance optical fiber sensor, a tunable LCD light filter, a photoelectric detector and a control and processing circuit. A light emitted from the light source travels through the plasma resonance optical fiber sensor, travels through the tunable LCD light filter controlled by the control and processing circuit after the effective information is acquired, is detected by the photoelectric detector, enters the control and processing circuit, and is scanned, and finally the index of refraction of the liquid to be detected is acquired. The device of the utility model has the advantages of simple structure, small volume, favorable miniaturization, portability, high response speed, use in real-time on-line detection circumstance, wide detection dynamic range, and wide application in the detection of the index of refraction of various liquids.

Description

Utilize the device of plasma resonance optical fiber sensor tracer liquid refractive index

Technical field

The utility model relates to a kind of device of tracer liquid refractive index, especially utilizes the device of plasma resonance optical fiber sensor tracer liquid refractive index.

Background technology

Surface plasma resonance (SPR, Surface Plasmon Resonance) sensing technology is a kind of physical optics phenomenon that occurs on thin metal layer and the dielectric interphase, occur in thin metal layer surface physical quantity variation and biochemical reaction and the transfer process relevant because of it can be used for real-time follow-up, and be subjected to increasing environmentalist's attention with the medium refraction index variation.Spr sensor detects the variations in refractive index of sensing interface place sample by excitating surface plasma resonance wave (SPW, Surface Plasmon Wave).When satisfying resonant condition,,, thereby obtain the physical quantity of sample effects refractive index by resonance angle θ SPR or resonant wavelength λ SPR working sample refractive index because attenuated total reflection (ATR, Attenuated Total Reflection) produces resonance absorbing peak.Spr sensor has prism-type; optical-fiber type; grating types etc. are several; wherein the optical-fiber type spr sensor is that the covering of the optical fiber about a segment length 5mm is peelled off; then at the metal film about deposition or evaporation one deck 50nm on this section fibre core; for the phase place that makes waveguide guided mode and SPW is mated better, also between metal level and fibre core ducting layer, add the suitable cushion of one deck usually.

Utilize plasma resonance optical fiber sensor tracer liquid refractive index at present, mainly contain the resonance angle probe method, resonant wavelength probe method etc.It mainly is to adopt wideband light source or tunable optical source that resonant wavelength detects, and uses spectral detection, and principle is simple.The key component that resonant wavelength detects is that spectrum is analyzed, normally utilize a spectrometer to carry out length scanning, then data upload to host computer is carried out data analysis, this implementation method need be purchased a spectrometer, cost is too high, use dumbly, also need special software kit to carry out data acquisition and processing (DAP); Also can utilize the method for other spectral scan, detect such as utilizing grating or prism etc. to carry out beam split, this requirement to light path is relatively stricter, still needs to utilize host computer to carry out data processing.

Utilize tunable filter can also be used for spectral scan.The tunable filter utilization is very extensive, as optical-fibre communications, astronomy, remote sensing survey etc.The tunable filter that often uses has at present: tunable LCD filters, Mach-Zehnder fibre optic interferometer, Fiber Bragg Grating FBG, acoustooptic modulation optical filter etc.Advantages such as tunable LCD filters is the birefringent phenomenon that has utilized liquid crystal, by the voltage modulated to liquid crystal molecule, changes its effective refractive index, thereby makes it have wavelength selectivity, and it is little to have a volume, is easy to control, and dynamic range is big.The optical axis of the nematic crystal molecule in the tunable LCD filters will redirect along the direction of electric field under the driving of voltage, changes its effective refractive index, and along with the voltage difference that applies, the effective refractive index of liquid crystal is also with difference.Not during making alive, after light beam enters tunable LCD filters, O light and E light all will produce Fa-Po effect in the chamber of the Fa-Po of device inside, because liquid crystal molecule is to the refractive index difference of two light, the centre wavelength that sees through is also with difference, still, after adding voltage, the centre wavelength that sees through of O light does not change, E light see through wavelength just along with the voltage change, thereby realize tuning effect.

Summary of the invention

The purpose of this utility model provides a kind of device that utilizes plasma resonance optical fiber sensor tracer liquid refractive index fast, in real time, easily.

The device of plasma resonance optical fiber sensor tracer liquid refractive index that utilizes of the present utility model comprises light source, plasma resonance optical fiber sensor, tunable LCD filters, photodetector and control and treatment circuit, the input end of plasma resonance optical fiber sensor links to each other with light source through optical fiber, the output terminal of plasma resonance optical fiber sensor links to each other with the input end of tunable LCD filters through optical fiber, the output terminal of tunable LCD filters links to each other with the input end of photodetector through optical fiber, the control end of tunable LCD filters links to each other with the sweep signal output terminal of control and treatment circuit, and control links to each other with the optical power signals input end of treatment circuit and the output terminal of photodetector.

In the utility model, light source can be wideband light source or tunable optical fiber laser.

In the utility model, the plasma resonance Fibre Optical Sensor can be single-mode fiber plasma resonance sensor or photonic crystal fiber plasma resonance sensor.

In the utility model, photodetector is the photoelectric tube that light signal is converted to electric signal, photomultiplier, photodiode, avalanche photodide, devices such as PIN pipe or phototransistor.

In the utility model, control and treatment circuit comprise CPU, the D/A modular converter, and the A/D modular converter, signal amplification module and display module in order to realize and the data transmission of host computer, can add communication module.

Principle of work is as follows:

Plasma resonance optical fiber sensor is put into fluid to be measured, sweep signal output terminal output scanning voltage by control and treatment circuit, control the transmission peak wavelength of tunable LCD filters, at this moment the component of signal that tunable LCD filters only allows the wavelength in the input optical signal to equal transmission peak wavelength sees through, photodetector is surveyed the luminous power of this transmission peak wavelength, convert optical power signals to electric signal and be defeated by control and treatment circuit, after single pass is finished, control and treatment circuit are according to transmission peak wavelength that is obtained and luminous power numerical value, analyze and obtain the plasma resonance wavelength, calculate the refractive index of fluid to be measured.

The beneficial effects of the utility model are:

The apparatus structure of plasma resonance optical fiber sensor tracer liquid refractive index that utilizes of the present utility model is simple, and lightweight and portable in volume is beneficial to miniaturization, is easy to carry.This device response speed is fast, can be applied to real-time online and detect occasion.The detection dynamic range is big, can be widely used in the detection of various liquid refractivities.

Description of drawings

Fig. 1 is the formation synoptic diagram that utilizes the device of plasma resonance optical fiber sensor tracer liquid refractive index, and 1 is light source, and 2 is plasma resonance optical fiber sensor, and 3 is tunable LCD filters, and 4 is photodetector, and 5 are control and treatment circuit;

Fig. 2 is a kind of enforcement circuit diagram of control and treatment circuit, and 6 is the D/A modular converter, and 7 is CPU, and 8 is the A/D modular converter, and 9 is the signal amplification module, and 10 is display module, and 11 is communication module.

Embodiment

The utility model is described in further detail below in conjunction with accompanying drawing.

With reference to Fig. 1, utilize the device of plasma resonance optical fiber sensor tracer liquid refractive index to comprise light source 1, plasma resonance optical fiber sensor 2, tunable LCD filters 3, photodetector 4 and control processing circuit 5.The input end of plasma resonance optical fiber sensor 2 links to each other with light source 1 through optical fiber, the output terminal of plasma resonance optical fiber sensor 2 links to each other through the input end of optical fiber with tunable LCD filters 3, the output terminal of tunable LCD filters 3 links to each other through the input end of optical fiber with photodetector 4, the control end of tunable LCD filters 3 links to each other with the sweep signal output terminal of control processing circuit 5, and the optical power signals input end of control processing circuit 5 links to each other with the output terminal of photodetector 4.

When plasma resonance optical fiber sensor places fluid to be measured, because the plasma resonance effect has taken place, the parallel component Kx of incident light wave wave vector equates that with plasma wave wave vector KSPW the multiple dielectricity according to Maxwell equation and metal has when plasma resonance takes place:

$K_{\mathrm{SPW}}=K_0\sqrt{\frac{{\mathrm{\ϵ}}_m{\mathrm{\ϵ}}_s}{{\mathrm{\ϵ}}_m+{\mathrm{\ϵ}}_s}}=K_x=\frac{{2\mathrm{\πn}}_0}{\mathrm{\λ}}\sin {\mathrm{\θ}}_0$

In the formula: K ₀=ω/c is the free space wave vector, and c and ω are respectively light speed and angular frequency in a vacuum; ε _mAnd ε _sComplex permittivity for metal film and sample; n ₀Be waveguide index, θ ₀Be the light wave incident angle; λ is an incident light wave length.Change lambda1-wavelength and can make K _SPW=K _xThereby, satisfy the plasma resonance condition.When a certain light wavelength lambda _SPRThe SPR effect takes place in incident, and surface plasma-wave (SPW) is excited, and its feature is exactly significantly weakening of reflective light intensity.

Control and treatment circuit are as shown in Figure 3, it comprises D/A modular converter 6, CPU 7, A/D modular converter 8, signal amplification module 9, display module 10 and communication module 11, the input end of signal amplification module 9 is as the optical power signals input end of control and treatment circuit 5, the output terminal of signal amplification module 9 is connected with the input end of A/D modular converter 8, the output terminal of A/D modular converter 8 connects the IO mouth of CPU 7, the output terminal of D/A modular converter 6 is as the output terminal of the sweep signal of control and treatment circuit 5, the 2nd IO mouth of the input end of D/A modular converter 6 and CPU 7 is connected, display module 10 is connected to the 3rd IO mouth of CPU7, and communication module 11 is connected to serial or the parallel communications port of CPU.Wherein CPU can be the MSP430F149 single-chip microcomputer, and the A/D modular converter can be the AD5531 chip, and the D/A modular converter can be the ICL7315 chip, is shown as seven segment digital tubes.

After system starts working, CPU according to a wavelength coverage (spectral ranges) such as 400 to 750nm with certain step-length, scan the wavelength value λ in this scope, calculate corresponding control signal amount, and send control signal, convert simulating signal to through the D/A modular converter, be defeated by the control end of tunable LCD filters, make that the transmission peak wavelength of tunable LCD filters is λ, photodetector is surveyed the optical power value of tunable LCD filters output light, and with result of detection input signal amplification module 9, the signal amplification module is with this optical power signals amplification and export the A/D modular converter to.The A/D modular converter converts the optical power signals of amplifying to digital signal input CPU.CPU stores the optical power signals value of transmission peak wavelength and input, carries out next length scanning then.After scanning is finished, CPU analyzes transmission peak wavelength and the optical power value of being stored, and analyzes the resonant wavelength numerical value that plasma takes place, and calculates corresponding refractive index, show by display module at last, can be uploaded to host computer by communication module 11 if needed.

In order correctly to detect resonant wavelength, the wavelength coverage of contingent plasma resonance when the spectral response range of the spectrum width of light source, the wavelength tuning range of tunable LCD filters, photodetector need cover plasma resonance optical fiber sensor and places testing liquid.

In order to improve the Device Testing precision, can select the tunable LCD filters of narrow bandwidth, or the wavelength step-length that reduces to scan, or the figure place of raising D/A modular converter and A/D modular converter.

Claims (6)

1, utilize the device of plasma resonance optical fiber sensor tracer liquid refractive index, it is characterized in that comprising light source (1), plasma resonance optical fiber sensor (2), tunable LCD filters (3), photodetector (4) and control and treatment circuit (5), the input end of plasma resonance optical fiber sensor (2) links to each other with light source (1) through optical fiber, the output terminal of plasma resonance optical fiber sensor (2) links to each other through the input end of optical fiber with tunable LCD filters (3), the output terminal of tunable LCD filters (3) links to each other through the input end of optical fiber with photodetector (4), the control end of tunable LCD filters (3) links to each other with the sweep signal output terminal of control with treatment circuit (5), and control links to each other with the optical power signals input end of treatment circuit (5) and the output terminal of photodetector (4).

2, the device of tracer liquid refractive index according to claim 1 is characterized in that, light source (1) is wideband light source or tunable optical fiber laser.

3, the device of tracer liquid refractive index according to claim 1 is characterized in that, plasma resonance Fibre Optical Sensor (2) is single-mode fiber plasma resonance sensor or photonic crystal fiber plasma resonance sensor.

4, the device of tracer liquid refractive index according to claim 1 is characterized in that, photodetector (4) is the photoelectric tube that light signal is converted to electric signal, photomultiplier, photodiode, avalanche photodide, PIN pipe or phototransistor.

5, the device of tracer liquid refractive index according to claim 1, it is characterized in that, control and treatment circuit (5) comprise D/A modular converter (6), CPU (7), A/D modular converter (8), signal amplification module (9), display module (10) and communication module (11), the input end of signal amplification module (9) is as the optical power signals input end of control and treatment circuit (5), the output terminal of signal amplification module (9) is connected with the input end of A/D modular converter (8), the output terminal of A/D modular converter (8) connects the IO mouth of CPU (7), the output terminal of D/A modular converter (6) is as the output terminal of the sweep signal of control and treatment circuit (5), the 2nd IO mouth of the input end of D/A modular converter (6) and CPU (7) is connected, display module (10) is connected to the 3rd IO mouth of CPU (7), and communication module (11) is connected to serial or the parallel communications port of CPU.

6, the device of tracer liquid refractive index according to claim 5 is characterized in that, CPU is the MSP430F149 single-chip microcomputer, and the A/D modular converter is the AD5531 chip, and the D/A modular converter is the ICL7315 chip, is shown as seven segment digital tubes.

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