CN102798612B - A kind of device and method utilizing ofdm signal to carry out refractometry - Google Patents

Abstract

Propose a kind of device and method utilizing light ofdm signal to carry out refractometry, this device comprises light ofdm signal generator, DI probe, detection module and display module, light ofdm signal generator is for generation of light ofdm signal, DI probe is exactly the interference time delay structure comprising reference arm and signal arm, detection module is the device of the parameter measurement to be measured for completing testing liquid, and display module is used for measured result to be shown to user; The light ofdm signal wherein generated by light ofdm signal generator is sent to after module to be detected carries out respective handling after being popped one's head in by a DI and obtains parameter to be measured, and the parameter described to be measured obtained is shown test results by display module; The light path of described signal arm will be coupled into testing liquid.Use device and method of the present invention can realize the measuring refractive indexes of liquid of ultrafast speed and superhigh precision, the dynamic realtime monitoring of refractive index change can also be realized, for the subject experiments such as biological chemistry provide the method for a kind of monitoring completely newly solution refractive index to be measured parameter.

Description

A kind of device and method utilizing ofdm signal to carry out refractometry

Technical field

The invention belongs to refractometry technical field, relate to a kind of apparatus and method utilizing light ofdm signal to carry out refractometry, this technology can realize the measuring refractive indexes of liquid of ultrafast speed and superhigh precision, the dynamic monitoring of refractive index change can be realized, for the subject experiments such as biological chemistry provide a kind of monitoring completely newly solution refractive index to be measured parametric technique simultaneously.

Background technology

The refractive index of liquid is a basic physical parameters of liquid.The change of a lot of Important Parameters (as density, concentration etc.) of liquid all can cause liquid refractivity to change, and can calculate these parameters of liquid by measuring refractive index.Relate to the industry of national economy in food processing, medical treatment and pharmacy etc., have higher requirement to the concentration, density etc. of liquid, therefore, to the Measurement accuracy of liquid refractivity, there is considerable realistic meaning.

The method summary of existing measurement liquid refractivity gets up to mainly contain geometrical optics approach and wave optics method.But they also exist corresponding shortcoming.It is utilize light beam to arrive liquid medium surface to reflect or phenomenon such as permeate body medium generation refraction etc. that geometrical optics approach measures liquid refractivity.Experimental principle is the reflection or the refraction law that utilize light, and the refractive index of testing liquid is measured in the change of the incident angle of measuring beam after liquid medium or refraction angle.

The experimental technique that liquid refractivity is measured by existing geometrical optics side has a variety of:

The first: measure liquid refractivity by glancing incidence method.This glancing incidence method is the total reflection principle according to light, measures the critical ray emergence angle after refraction, obtains testing liquid refractive index; (set its refractive index as n testing liquid _x) to drip be n (n in refractive index _x> n) right-angle prism on.As shown in Figure 1,1 and 2 is two glancing light lines, and incident light is plunderred and penetrated on the interface of testing liquid and glass prism, and light beam arrives the refraction of O point through testing liquid and glass prism interface and penetrates from BC face.And the incident ray 2 being parallel to AB face enters prism with critical angle a, then with angle β from the outgoing of BC face, the refractive index expression formula of testing liquid is: n _x=sin γ (n ²-sin ²β) ^1/2-cos γ sin β

The second, measures liquid refractivity with laser irradiation.Utilize during experiment laser be irradiated to liquid lamella surface occur reflection and refraction, then measure reflection, reflect side-play amount to measure liquid refractivity.Experimental provision as shown in Figure 2.Horizontal positioned one flat plate glass in the glass flume of sky, laser beam is mapped on glass plate so that θ angle is oblique, and incident beam arrives blank sheet of paper D place, right side through the reflection of glass plate upper surface and forms hot spot.Testing liquid is injected in tank, at this moment on the blank sheet of paper of right side, two specks are formed, that hot spot is comparatively the hot spot A reflected to form by the liquid lamella on glass, and the hot spot B followed closely under it is formed by the refraction of optical beam entering testing liquid and Air Interface.Laser beam incident angle tangent value tan θ=OC/OD, as long as measure spot separation AD, AB and OC above blank sheet of paper, OD just can try to achieve testing liquid refractive index, its expression formula is:

$n=\frac{\mathrm{sim\θ}}{\sin \mathrm{\β}}=\frac{\sin \left(\arctan \frac{\mathrm{OC}}{\mathrm{OD}}\right)}{\sin \left[\arctan (\frac{\mathrm{AB}}{\mathrm{AD}}\·\frac{\mathrm{OC}}{\mathrm{OD}})\right]}$

Existing geometrical optics side measures liquid refractivity and there is following defect:

(1) experimental provision is simple and crude, and measuring accuracy is low;

(2) Measuring Time is very long, can only measuring point refractive index value;

(3) poor stability, the factors such as liquid sloshing can bring error to experimental result.

Wave optics method mainly comprises Diffraction grating, optical fiber Mechanical Study On Young Interference method and wedge fringes method.Measure the experimental principle of liquid refractivity as shown in Figure 3 with Diffraction grating, before glass guide channel, place a diffraction grating during experiment, laser beam vertical irradiation on the diffraction grating.After there is diffraction phenomena, zero-order terms and twin-image impinges upon glass guide channel rear wall C place, and one order diffracted spots impinges upon A place.Add testing liquid in groove after, one order diffracted spots originally impinges upon B place due to the impact being subject to testing liquid refraction effect.Have according to Bragg's law: first-order diffraction dsina=λ, d are grating parameters, λ is lambda1-wavelength, ignores the impact of the beam deviation that flume wall thickness produces.Air refraction is 1.00, has n=sina/sin β according to Snell's law, sina=CA/OA, sin β=CB/OB.Utilize geometric triangulation shape knowledge, can 0A and OB be obtained.Then testing liquid refractive index can be expressed as:

$n=\frac{\sin \mathrm{\α}}{\sin \mathrm{\β}}=\frac{\mathrm{CA}}{\mathrm{OA}}\·\frac{\mathrm{OB}}{\mathrm{CB}}=\frac{\mathrm{CA}}{\mathrm{CB}}\·\frac{{({\mathrm{CB}}^2+L^2)}^{\frac{1}{2}}}{{({\mathrm{CA}}^2+L^2)}^{\frac{1}{2}}}$

With optical fiber Mechanical Study On Young Interference method measure liquid refractivity experimental principle as shown in Figure 4, during experiment with two single-mode fibers as coherent point light sources, realize Mechanical Study On Young Interference and obtain interference pattern; By measuring related streak width, ask the refractive index of testing liquid.Experimental provision as shown in Figure 4.Two single-mode fibers are fixed on the side of container, and are close to one block of frosted glass in the another side of chamber wall.By laser beam irradiation in two single-mode fibers, the fiber end face making two length identical is in same plane, and two single-mode fibers receive the laser in same wave front simultaneously, thus N bring out penetrate with angle of divergence θ ₀the polarization direction of two-beam is consistent, phase place is identical.Therefore be easy to observe light and dark interference fringe on frosted glass.If optical fiber pitch is 2a, optical fiber N holds the distance of frosted glass to be d, and the width of interference fringe is Δ x, then testing liquid refractive index is:

$n=\frac{\mathrm{\λd}}{2\mathrm{a\Δx}}$

Add testing liquid front and rear width of fringe and be respectively Δ x ₀with Δ x ₁, therefore have air refraction n in formula ₀be 1.00.Then testing liquid refractive index expression formula is

In wave optics method is equal thickness interference principle by the experiment principle used that wedge fringes method is measured in liquid refractivity.First two pieces of sheet glass one end are overlapping, an other end filament separates, and forms minimum air splitter.Again testing liquid is injected air splitter.Finally irradiate glass plate by laser vertical, the surface of glass plate will there will be light and dark interference fringe.The optical path difference of two light beams is γ=2nd _i+ λ/2, in formula, λ is lambda1-wavelength, and λ/2 are that two light beams always have half-wave loss when surface reflections, therefore should add half-wave loss in the optical path difference expression formula of two light beams.D _ithe thickness of testing liquid film.When γ is the odd-multiple of λ/2, there is dark fringe, adjacent dark stripe span △ l=d _i+l-d _i=λ/2n.Measure M dark stripe span △ L respectively before and after testing liquid and be followed successively by △ L adding _air=M △ l=N λ/2n, △ L _liquid=N △ l=N λ/2n.Then the refractive index of testing liquid can be expressed as:

N=Δ L _air/ Δ L _liquid

Wave optics method is measured liquid refractivity and be there is following defect:

(1) higher, complicated operation is required to experiment equipment;

(2) measuring speed is slow, can not obtain dynamic variations in refractive index situation;

(3) stability influence by light source fluctuation and interference system is comparatively large, and Measurement sensibility is poor.

In sum, no matter use geometrical optics approach or use wave optics method all to there is various defect, cannot realize in real time, rapidly to the problem that liquid refractivity detects.

Summary of the invention

The invention provides a kind of apparatus and method utilizing light ofdm signal to carry out refractometry, not only overcome the defect of prior art, achieve the measuring refractive indexes of liquid of ultrafast speed and superhigh precision, the dynamic monitoring of refractive index change can also be realized, for the subject experiments such as biological chemistry provide the method for a kind of monitoring completely newly solution refractive index to be measured parameter; Compared with prior art, there is higher precision.

According to a first aspect of the present invention, a kind of device utilizing light ofdm signal to carry out refractometry is provided, comprising light ofdm signal generator, DI probe, detection module and display module, light OFDM generator is for generation of light ofdm signal, DI probe is exactly the interference time delay structure comprising reference arm and signal arm, detection module is the device of the parameter measurement to be measured for completing testing liquid, and display module is used for measured result to be shown to user; The ofdm signal wherein produced by ofdm signal generator carries out respective handling by feeding detection module after a DI probe and obtains parameter to be measured, and the parameter described to be measured obtained is shown test results by display module; The light path of described signal arm will be coupled into testing liquid.

Wherein, it is relevant that the algorithm that detection module is used and light ofdm signal generator produce the algorithm that light ofdm signal adopts.

Preferably, OFDM electric signal generator, electrooptic modulator and lasing light emitter is adopted to form light ofdm signal generator.

Further, the OFDM electric signal generated by OFDM electric signal generator, is modulated on the corresponding light carrier wave that lasing light emitter sends through electrooptic modulator, is popped one's head in, carried out the detection of parameter to be measured by relevant detection module by DI; The road laser that lasing light emitter sends is as the light source of modulator, and another road laser that lasing light emitter sends provides local oscillation signal for detection module.

Preferably, described relevant detection module refers to and utilizes the coherence of light to detect the information entrained by light carrier and process.

Preferably, realize DI probe with optical fiber MZ interference structure or pop one's head in realize DI with space MZ interference structure.

Preferably, the function of described modulator is realized with editable processors such as FPGA/ASIC/DSP, or realize the function of described modulator based on the real-time system measurement of the softwares such as Labview, or carry out the specific implementation of finishing device based on the off-line measurement of the softwares such as Matlab/C/C++.

According to a second aspect of the present invention, a kind of method utilizing light ofdm signal to carry out refractometry is provided, wherein, in OFDM algorithm, PRBS code is after serioparallel exchange, and modulation maps, IFFT, add CP, parallel-serial conversion step forms required digital OFDM signal and sends into AWG (Arbitrary Waveform Generator) (AWG), and the effect of AWG is main is that digital signal is converted to simulating signal.The simulating signal that OFDM electric signal generator generates is loaded into after on the light carrier that lasing light emitter sends through MZM photomodulator and enters DI probe.Need synchronous, serioparallel exchange in receiving end, remove CP, FFT after channel estimating and phase estimation, repetitive measurement obtains interference pattern phase pushing figure.

Preferably, PRBS code need not add CP after serioparallel exchange, modulation mapping, IFFT, only compile a frame, then send with same frame signal circulation, parallel-serial conversion step forms required digital OFDM signal, sends into simulating signal that AWG generates and is loaded into after the light carrier that lasing light emitter sends through MZM electrooptic modulator and enters DI probe.Receiving end needs serioparallel exchange, FFT, channel estimating and phase estimation.

The technical scheme using embodiment of the present invention to provide, has following beneficial effect:

(1) restriction of prior art measuring speed is solved, the change of more difficult Quick Measurement refractive index.

(2) problem that supper-fast variations in refractive index cannot be measured is solved.

(3) solve the restriction of Fluctuation Method due to light source stability, measurement result is more reliable and more stable.

(4) solve the problem of geometric method measuring accuracy, very high measuring accuracy can be obtained.

Accompanying drawing explanation

Fig. 1 is the principle schematic that glancing incidence method of the prior art measures liquid refractivity;

Fig. 2 is that laser irradiation of the prior art measures liquid refractivity principle schematic;

Fig. 3 is that Diffraction grating of the prior art measures liquid refractivity principle schematic;

Fig. 4 is that optical fiber Mechanical Study On Young Interference method of the prior art measures liquid refractivity principle schematic;

Fig. 5 is ofdm signal spectrogram;

Fig. 6 is according to the device schematic diagram utilizing ofdm signal to carry out refractometry of the present invention;

Fig. 7 adopts relevant detection algorithm to realize utilizing ofdm signal to carry out the device schematic diagram of refractometry;

Fig. 8 be according to realization of the present invention be concerned with detect algorithm first schematic diagram;

Fig. 9 be according to realization of the present invention be concerned with detect algorithm second schematic diagram;

Figure 10 is the device schematic diagram according to optical-fiber type MZ interference structure probe of the present invention;

Figure 11 is the device schematic diagram according to spatial mode MZ interference structure probe of the present invention;

Figure 12 is according to the real time algorithm measuring system block diagram realizing this concrete implement device with FPGA/ASIC/DSP processor of the present invention;

Figure 13 is according to the schematic block diagram realizing this concrete implement device function based on the measurement of Labview software real-time system of the present invention;

Figure 14 carries out according to Matlab/C/C++ software of the present invention the schematic block diagram that off-line measurement realizes this concrete implement device function;

Original English text and the Chinese translation of the dummy suffix notation related in the description are as follows:

AWG Arbitrary Waveform Generator AWG (Arbitrary Waveform Generator)

MZM Mach-Zehnder Modulator MZ Mach-Zehnder

DAC Digital-to-Analog Converter digital analog converter

ADC Analog-to-Digital Converter analog-digital converter

OFDM Orthogonal Frequency Division Multiplexing orthogonal frequency division multiplexi

FPGA Field-Programmable Gate Array field programmable gate array

GPIB General-Purpose Interface Bus general purpose interface bus

DI delay interferometrer interferes time delay structure

MZ Mach-zehnder Mach Zeng De

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only a part of embodiment of the present invention, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

Light OFDM channel estimation method and Mach-zehnder interference structure are combined the measurement of refractive index by technical scheme of the present invention, this technology can be used for detecting variations in refractive index very fast, reach a very high measuring accuracy, overall plan implements relatively simple simultaneously.Ofdm signal is a kind of broadband signal containing multiple subcarrier, and as shown in Figure 5, be a light ofdm signal containing 5 subcarriers, the frequency of its center light carrier is f0.Suppose that the bandwidth of subcarrier is fixed, namely frequency interval is fixed, and by increasing the number of subcarrier, the bandwidth of light ofdm signal is increased, then the bandwidth of a frequency sweep scanning is larger, and measuring speed is higher.By regulating the bandwidth of subcarrier, adjustable frequency interval, thus measuring accuracy can be improved.

The principle of Mach-zehnder time delay interference structure is similar to Mach-zehnder interferometer, can as the probe of sensor; When carrying out sensing, its signal arm puts into environment to be measured.Due to the impact of environment to be measured, main manifestations is the change of refractive index; Light in the light relative reference arm now transmitted in signal arm produces new phase differential, utilizes OFDM channel estimation method to observe the interference spectum of this structure, observes simultaneously and changes phase place change corresponding to its interference spectum in time, be i.e. the movement of interference fringe; By the analysis changed interference fringe, the refractive index of testing liquid just can be obtained.

Provide structural drawing and the concrete steps of the method and device below.As shown in Figure 6, the device utilizing light ofdm signal to carry out refractometry comprises light ofdm signal generator, DI probe, detection module and display module, the light ofdm signal produced by light ofdm signal generator interferes time delay structure by one, be sent to detection module to carry out after respective handling obtains parameter to be measured, being shown test results by display module.Wherein, light ofdm signal generator is for generation of light ofdm signal, and DI probe is exactly interfere time delay structure, and it comprises reference arm and signal arm, and the light path of signal arm will be coupled into testing liquid.Detection module has referred to the device of parameter measurement to be measured, and it is relevant that its algorithm used and light ofdm signal produce the algorithm adopted.Display module is used for measured result to be shown to user.

Fig. 7 adopts relevant detection algorithm to realize utilizing light ofdm signal to carry out refractometry schematic diagram, it carries out refinement to light ofdm signal generator part on the device basic shown in Fig. 6, and employing OFDM electric signal generator, electrooptic modulator and lasing light emitter form a new light ofdm signal generator.This technology schematic diagram as shown in Figure 7, the OFDM electric signal generated by OFDM electric signal generator, be loaded on the corresponding light carrier wave that lasing light emitter sends through electrooptic modulator, popped one's head in by DI, carried out the detection of parameter to be measured by detection module (being preferably relevant detection module); Laser one tunnel sent by lasing light emitter is as the light source of modulator, and another road is that detection module (being preferably relevant detection module) provides local oscillation signal.Local oscillation signal the form of being not limited thereto is provided, also can select in detection module, use independently local oscillator lasing light emitter.Finally by relevant detection module, signal is processed, obtain the phase place change information of interference spectum structure and its correspondence.The measurement result obtained can be shown by display device.Wherein OFDM electric signal generator is for generating the ofdm signal of electricity, and its specific algorithm can use the relevant algorithm detected to do corresponding adjustment according to detection module.The effect of electrooptic modulator is loaded on light carrier by the ofdm signal of electricity, thus generate light ofdm signal.Use relevant detection module that the accuracy of systematic survey can be made to be greatly improved; Relevant detection refers to and utilizes the coherence of light to detect the information entrained by light carrier and process.Fig. 8 and Fig. 9 gives two kinds of specific algorithms and the step of light ofdm signal generator under coherent detection scheme and relevant detection module.

As shown in Figure 8, and coherent communication is similar, and in electric ofdm signal generator, PRBS code is through serioparallel exchange, and modulation maps, and IFFT, adds CP, and the steps such as parallel-serial conversion form required digital OFDM signal; Enter AWG again, the effect of AWG is main is that digital signal is converted to simulating signal.The simulating signal that OFDM electric signal generator generates is loaded into after the light carrier that lasing light emitter sends through MZM electrooptic modulator and enters DI probe again.It is to be noted that the effect of lasing light emitter provides carrier wave to MZM electrooptic modulator and provides local oscillation signal to the coherent receiver in relevant detection module.In relevant detection module, signal just enters oscillograph after the process of coherent receiver, and its effect converts simulating signal to digital signal.Then just enter corresponding algorithm process part, comprise synchronous, serioparallel exchange, removes CP, FFT, and the signal transacting such as channel estimating obtain phase response and amplitude response.If testing liquid variations in refractive index is within an OFDM frame signal duration, process with variations in refractive index matches by that the phase response that obtains, if variations in refractive index is a slow change process, we can according to the corresponding phase place change of amplitude, and namely the movement of interference fringe simulates the phase place change procedure corresponding with refractive index.

As shown in Figure 9, Fig. 9 is that another kind that we propose is concerned with detection algorithm, this method is saved the modulation added CP and load different PRBS on different frame and is mapped, only need the ofdm signal launching same frame in transmitting terminal circulation, owing to not considering the PRBS that demodulation maps, add CP process so economize to omit, the algorithm complex of transmitting terminal can be simplified like this.The simulating signal that the circulation ofdm signal modulated through this shortcut calculation is generated by AWG is loaded into after the light carrier that lasing light emitter sends through MZM modulator and enters DI probe.Adopt same laser instrument as flashlight and local oscillator light.In relevant detection module, signal just enters oscillograph after the process of coherent receiver, and its effect converts simulating signal to digital signal.Then just enter corresponding algorithm process part, comprise synchronous, serioparallel exchange, FFT, the operation such as channel estimating obtains phase response and amplitude response.If testing liquid variations in refractive index is within an OFDM frame signal duration, so obtain phase response the process with variations in refractive index is matched, if variations in refractive index is a slow change process, we can according to the corresponding phase place change of amplitude, and namely the movement of interference fringe simulates the phase place change procedure corresponding with refractive index.

Below several ways of realization of DI probe are described in detail.

The first way of realization of DI probe, namely realizes with optical fiber MZ interference structure.As shown in Figure 10, Figure 10 is the probe of the MZ interference structure based on optical fiber structure making, and utilize two optical fiber 3dB attenuators and a pair GRIN Lens to form, reference arm and signal arm have certain optical path difference, form interference spectum.Light path in optical fiber is coupled in free space by the effect of GRIN Lens, then by another lens by light again coupled into optical fibres.In aerial this section of light path, put into cuvette container, this container has fine light transmission.Light can reach through the liquid held in this container on another lens.GRIN Lens is placed on signal arm, and on another reference arm, we introduce adjustable light power attenuator and Polarization Controller simultaneously, makes the power on two arms and polarization state trim, makes the extinction ratio of interference spectum the highest.Because MZ structure is very sensitive, so need extraordinary encapsulation, to avoid the interference of external environment.

The second way of realization of DI probe, namely realizes with space MZ interference structure.As shown in figure 11, Figure 11 is the probe of the MZ interference structure based on space structure making, and utilize spectroscope to close light microscopic and some catoptrons formation, relative to optical-fiber type MZ interference structure, space structure is much relatively stable, and ambient temperature is very little on the impact of space light path.But the more difficult debugging of space structure light path, needs integration, otherwise vibrations are very large on the impact of system.Similar with optical-fiber type MZ interference structure, reference arm and signal arm have certain optical path difference, form interference spectum.Light path in optical fiber diffuses on the two-way of free space by spectroscope, catoptron act as adjustment optical path direction.In the light path of signal arm, put into colorimetric container, this container has fine light transmission.Light can reach through the liquid held in this container and close on light microscopic, and the effect of closing light microscopic is sent back in optical fiber on two-way light compositing one tunnel again.On reference arm, we introduce adjustable light power attenuator and Polarization Controller simultaneously, make the power on two arms and polarization state trim, make the extinction ratio of interference spectum the highest.

Several ways of realization below for concrete implement device make elaboration:

The first way of realization of implement device: realize with editable processors such as FPGA/ASIC/DSP.

Figure 12 shows the real time algorithm measuring system block diagram realizing this implement device function, and wherein, MZM modulator is a kind of electrooptic modulator, and its effect is that electric ofdm signal is modulated into light ofdm signal; Use pole narrow linewidth laser greatly to reduce the impact of phase noise, coherent receiver utilizes the homodyne criterion of light the change of light phase can be detected accurately; DI probe is the target of native system; The effect of DAC is the ofdm signal ofdm signal of numeral being converted to simulation; Utilize the processors such as FPGA/DSP/ASIC to produce ofdm signal, make digital signal be converted into simulating signal through ADC module; Utilize embedded system to process signal with man-machine interaction mode, obtain the refractive index of testing liquid; Finally the measurement result obtained is shown to user by LCD.Certain display device is not limited to LCD.

The second way of realization of implement device: the real-time system measurement based on softwares such as Labview realizes.As shown in figure 13, Figure 13 is according to the schematic block diagram realizing this implement device function based on the measurement of Labview software real-time system of the present invention; The solution principle of the first way of realization of the program and implement device is close.Unlike, the second way of realization of modulator adopts the softwares such as Labview to carry out real-time system measurement.

In the second way of realization of implement device, total three parts: (1) ofdm signal generating portion.It is the ofdm signal of simulating that the digital OFDM signal produced by softwares such as Labview exports through AWG, and AWG achieves the function of digital-to-analog conversion.(2) main part is measured.Main part comprises modulator, and DI pops one's head in, coherent receiver.Its effect is similar to scheme one with working method, repeats no more here; (3) Real-Time Monitoring and operation part.Comprise computing machine, Labview and oscillograph.Wherein oscillograph plays the function of ADC, and the digital signal obtained by oscillograph is sent into Labview and detected.The effect of this part makes whole system detect in real time and to operate by Labview software and network.The advantage of the present embodiment: computer interactive formula is easy to operate, utilize the Labview construction cycle short, observation effect is good.

The third way of realization of implement device: the off-line measurement based on softwares such as Matlab/C/C++ realizes.As shown in figure 14, Figure 14 carries out according to Matlab/C/C++ software of the present invention the schematic block diagram that off-line measurement realizes this modulator function; The solution principle of the second way of realization of the program and modulator is close.Unlike, the third way of realization of modulator adopts the softwares such as Matlab/C/C++ to carry out the mode of off-line measurement, and realizes systemic-function by control AWG and oscillograph.Particularly, this programme adopts the software replacements such as Matlab/C/C++ Labview to carry out processed offline.Wherein, AWG and oscillograph also play the effect of DAC and ADC.The advantage of this programme is: be utilize the softwares such as Matlab/C/C++ to produce ofdm signal and process the signal after transmission, it can utilize more complicated algorithm to improve system performance.

Performing step

The simple performing step introducing lower this programme below:

The first step, obtains OFDM digital signal by FPGA/DSP/ASIC processor, is simulating signal by ADC module converts;

Second step, utilizes extremely narrow limit for width laser instrument the simulation ofdm signal produced in the first step to be modulated to the ofdm signal of light by MZM electrooptic modulator;

3rd step, the signal through coherent receiver process carries out data acquisition by ADC;

4th step, the sample signal that obtains of ADC sends into FPGA/DSP/ASIC processor and embedded system processs and displays, and finally obtains refractive index dynamic change value;

5th step, the measured value obtained is shown to user by LCD display.

Use technical scheme of the present invention, relative to prior art, there is obviously advantage, specific as follows:

(1) coherent light OFDM method is incorporated in refractometry by the present invention first, and the ultrafast speed that it brings and high precision are not available for conventional physical method and optical means.

(2) the present invention realizes simply, and probe can be diversified, is easy to realize.

(3) can change by real-time dynamic monitoring liquid refractivity after utilizing normal fluid to calibrate, trickle biological or chemical change fast can be monitored out thus.

(4) this programme adopts light ofdm signal to replace single beam laser, and it can increase sweep velocity greatly, and the disposable scanning completing multiple frequency, obtains interference pattern fast, thus reaches a kind of high measuring speed.

(5) be modulated on light carrier through electrooptic modulator after the present invention can adopt electric OFDM generation device to produce electric ofdm signal and form light ofdm signal, to light source without special requirement.

(6) the present invention adopts Coherent processing algorithm, make accurate results, and sensitivity is very high.

(7) this programme utilizes LabVIEW to carry out equivalence process in real time, user is used more convenient.

(8) this programme can utilize the processors such as FPGA/DSP/ASIC to the real-time process realizing data, system to be processed in real time, provides more sound assurance for this patent is generalized to commercial market.

(9) the present invention can utilize the softwares such as Matlab/C/C++ to carry out off-line measurement, can select suitable algorithm as required, improves measuring accuracy.

The above; be only the present invention's preferably embodiment; but protection scope of the present invention is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the embodiment of the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.

Claims (1)

1. the device utilizing light ofdm signal to carry out refractometry, it is characterized in that, comprise light ofdm signal generator, DI probe, relevant detection module and display module, light ofdm signal generator is for generation of light ofdm signal, DI probe is exactly the interference time delay structure comprising reference arm and signal arm, relevant detection module is the device of the parameter measurement to be measured for completing testing liquid, and display module is used for measured result to be shown to user;

The light ofdm signal wherein produced by light ofdm signal generator carries out respective handling by the relevant detection module of feeding after a DI probe and obtains parameter to be measured, and the parameter described to be measured obtained is shown test results by display module; The light of described signal arm will be coupled into testing liquid;

Wherein, it is relevant that the algorithm that relevant detection module is used and light ofdm signal generator produce the algorithm that light ofdm signal adopts; Electric ofdm signal generator, electrooptic modulator and lasing light emitter is adopted to form light ofdm signal generator; The electric ofdm signal generated by OFDM electric signal generator, is modulated on the corresponding light carrier wave that lasing light emitter sends through electrooptic modulator, is popped one's head in, carried out the detection of parameter to be measured by relevant detection module by DI; The road laser that lasing light emitter sends is as the light source of modulator, and another road laser that lasing light emitter sends provides local oscillation signal for relevant detection module; Described relevant detection module refers to and utilizes the coherence of light to detect the information entrained by light carrier and process;

Realize DI probe with optical fiber MZ interference structure, wherein utilize two optical fiber 3dB attenuators and a pair GRIN Lens to form, reference arm and signal arm have certain optical path difference, form interference spectum; Light in optical fiber is coupled in free space by the first GRIN Lens by the effect of GRIN Lens, in aerial this section of light path, put into cuvette container, this container has fine light transmission, light can reach through the liquid held in this container in the second GRIN Lens, then by the second GRIN Lens by light again coupled into optical fibres;

With the editable processor of FPGA/ASIC/DSP or measure based on the real-time system of Labview software or realize the described light ofdm signal that utilizes based on the off-line measurement of Matlab/C/C++ software and carry out refractometry;

In OFDM algorithm, PRBS code is after serioparallel exchange, and modulation maps, and IFFT, adds CP, and digital signal is mainly converted to simulating signal by the effect that parallel-serial conversion step forms required digital OFDM signal feeding AWG (Arbitrary Waveform Generator) AWG, AWG; OFDM electric signal generator generate simulating signal on the light carrier that MZM light modulator modulates sends to lasing light emitter after enter DI probe; Need synchronous, serioparallel exchange in receiving end, remove CP, FFT after channel estimating and phase estimation, finally obtain interference pattern phase pushing figure.