CN101231367A - High resolution wavelength demodulation system and demodulation method thereof - Google Patents

Abstract

A wavelength demodulation system with high resolution comprises a wavelength modulation sensor; a first 1 is multiplied by 2 coupler with the input end connected with the output end of the wavelength modulation sensor; a second 1 is multiplied by 2 coupler with the input end connected with the output end of the first 1 is multiplied by 2 coupler; a phase modulator with the input end connected with the output end of the first 1 is multiplied by 2 coupler and the output end connected with the input end of the second 1 is multiplied by 2 coupler; a photoelectric detector; a signal processing module connected between the second 1 is multiplied by 2 coupler and the photoelectric detector in series and used for demodulating a detected signal from an interference signal; and a sinusoidal signal generator with the output end connected with the phase modulator and the input end connected with the signal processing module and used for providing sinusoidal modulation signal from the phase modulator and the signal processing module.

Description

High resolution wavelength demodulation system and demodulation method thereof

Technical field

The present invention is a kind of high resolution wavelength demodulation system and demodulation method thereof, is mainly used in the Wavelength demodulation of wavelength-modulated type sensor, belongs to technical field of optical fiber sensing.

Background technology

Optical fiber sensing technology is to be that carrier, optical fiber are medium with light, the novel sensing technology of perception and transmission outer signals.According to the light wave characteristic parameter difference of transmitting external information, Fibre Optical Sensor can be divided into types such as wavelength-modulated, Modulation and Amplitude Modulation, phase modulation (PM) and polarization state modulation.Compare with other Fibre Optical Sensors based on wavelength-modulated type Fibre Optical Sensor, have that antijamming capability is strong, sensing probe is simple in structure, size is little and be convenient to advantages such as networking is multiplexing, so wavelength-modulated type sensor is most widely used in Fibre Optical Sensor.Most typical wavelength-modulated type Fibre Optical Sensor is fiber grating (FBG) sensor.

Occurred in recent years with the new generation sensor of fiber-grating laser as sensing element, it utilizes the reflection characteristic and the frequency-selecting effect of fiber grating, forms optical fiber laser structure by write fiber grating at one section high-gain Active Optical Fiber.It is as a kind of novel wavelength-modulated type sensor, except advantage with ordinary passive fiber grating, the signal of its output has extremely narrow live width (can reach the KHz magnitude), and variation to external world is very responsive, therefore Wavelength demodulation is had higher requirement.

For wavelength-modulated type Fibre Optical Sensor a lot of demodulation methods is arranged, the chromatic dispersion method of in actual engineering, using at present that mainly contains, F-P wave filter method, coupling raster method, boundary filter method etc., the highest wavelength resolution of these methods is about 0.1pm.Reach higher resolution, must adopt the method for interfering, the sensing head wavelength change is converted into phase change through behind the non-equilibrium interferometer, by high-resolution phase demodulating technology reduction wavelength change, can reach 10-6pm even higher wavelength resolution.

Wavelength demodulation method based on interfere type mainly contains Phase Tracking method and 3 * 3 coupling mechanism methods.

The Phase Tracking method is to introduce phase-modulator on an arm of interferometer, interferometer output signal carries out FEEDBACK CONTROL through behind the phase compensating circuit to it, produce phase compensation, make that the phase differential of two arms of interferometer is a pi/2, be interferometer work under quadrature, this moment, the change in voltage exported of variable quantity and detector of sensor wavelength was directly proportional.The structure of Phase Tracking method is simpler, demodulation speed is fast, its shortcoming is that distortion is serious when detecting large-signal, demodulation result is relevant with light intensity, and in networking is multiplexing, because the drift of the interference signal initial phase of each road sensor is different, so each road sensor needs independent interferometer and compensating circuit, networking structure more complicated.

3 * 3 coupling mechanism methods change 2 * 2 coupling mechanisms of interferometer output terminal into 3 * 3 coupling mechanisms, according to the performance of 3 * 3 coupling mechanisms, will have 120 ° between three road signals of output this moment as can be known and differ.Survey processing simultaneously by three road signals, can make system keep constant phse sensitivity, demodulation result will be linear with sensor wavelength.3 * 3 coupling mechanism methods of employing realize Wavelength demodulation, do not need active device in its interferometer, and are simple in structure, can adopt digitized scheme to carry out signal Processing, and algorithm operation quantity is little.Its shortcoming is that the splitting ratio and the stability of 3 * 3 coupling mechanisms self will exert an influence to demodulation result, and because the every passage of 3 * 3 coupling mechanism schemes of employing needs 3 detectors to receive simultaneously, has increased the multiplexing networking complexity of system.

Summary of the invention

In order to overcome the shortcoming of above-mentioned prior art, the object of the present invention is to provide a kind of high resolution wavelength demodulation system and demodulation method, the present invention has the resolution height, dynamic range is big, response speed is fast, working stability is reliable and be easy to the advantage of multiplexing networking.

A kind of high resolution wavelength demodulation system of the present invention is characterized in that, comprising:

One wavelength-modulated type sensor;

One the one 1 * 2 coupling mechanism, the input end of the one 1 * 2 coupling mechanism is connected with the output terminal of wavelength-modulated type sensor, as the input end of non-equilibrium fibre optic interferometer;

One the 21 * 2 coupling mechanism, the input end of the 21 * 2 coupling mechanism is connected with the output terminal of the one 1 * 2 coupling mechanism, as the output terminal of non-equilibrium fibre optic interferometer;

One phase-modulator, the input end of this phase-modulator is connected with the output terminal of the one 1 * 2 coupling mechanism, and the output terminal of this phase-modulator is connected with the input end of the 21 * 2 coupling mechanism, is used to provide the phase carrier signal;

One photodetector is exported light signal with interferometer and is converted into electric signal;

Be connected in series photodetector between one signal processing module, this signal processing module and the 21 * 2 coupling mechanism, be used for measured signal is come out from the interference signal demodulation;

One sinusoidal signal generator, the output terminal of this sinusoidal signal generator is connected with phase-modulator, and the input end of this sinusoidal signal generator is connected with signal processing module, for phase-modulator and signal processing module provide sinusoidal modulation signal.

Wherein the splitting ratio of the one 1 * 2 coupling mechanism and the 21 * 2 coupling mechanism is 50: 50.

Wherein phase-modulator is selected the piezoelectric transducer that is wound with optical fiber for use.

Wherein signal processing module selects for use mimic channel to realize, perhaps selects for use the method for software or flush bonding processor to realize.

The invention provides a kind of high resolution wavelength demodulation method, adopt the described high resolution wavelength demodulation system of claim 1, it is characterized in that, comprising following steps:

Step 1: the light that wavelength-modulated type sensor sends enters non-equilibrium fibre optic interferometer, and the variation of sensor wavelength is converted into the variation of interference signal phase place;

Step 2: use phase-modulator that the phase place of interferometer is carried out the high frequency phase modulation (PM), overcome because initial phase drifts about to the influence of input sensitivity;

Step 3: use photodetector that interferometer output intensity signal is converted into electric signal;

Step 4: adopt phase place generation carrier wave algorithm that sensor wavelength is changed demodulation and come out.

Wherein non-equilibrium fibre optic interferometer is selected Mach-Zehnder interferometer or Michelson interferometer.

Wherein the amplitude of phase modulation (PM) is 2.64rad, and modulation frequency range is 5-20KHz.

Wherein the flow process of phase place generation carrier wave algorithm is: photodetector 4 detection signals input multiplier module, output two-way mixed frequency signal, enter low-pass filtering module filtering radio-frequency component again, enter the normalization module then and carry out normalization operation, next enter differential multiplication cross module and obtain differential signal, enter integration high-pass filtering module at last and obtain demodulation result.

Wherein multiplier module comprises two multipliers, and input signal multiplies each other with phase modulated signal and phase modulation (PM) two frequency-doubled signals respectively, output two-way mixed frequency signal.

Wherein low-pass filtering module comprises two low-pass filters, respectively the radio-frequency component of filtering two-way mixed frequency signal.

Wherein normalization module comprises a quadratic sum computing, square root calculation and two dividers, carry out square root calculation after the two paths of signals process quadratic sum computing of input and obtain normalization coefficient, then Shu Ru two paths of signals respectively by divider divided by this coefficient, output two-way normalized signal.

Wherein differential multiplication cross module comprises two differentiators, two multipliers and a subtracter, and the two paths of signals of input enters multiplier after through two differentiators and carries out multiplication cross, after the two paths of signals that obtains enters subtracter, exports one road differential signal.

Wherein also comprise an integrator and a Hi-pass filter, one road signal of input enters Hi-pass filter again through behind the integrator, the output demodulation result.

The high resolution wavelength demodulation system and the demodulation method that the present invention is based on phase place generation carrier wave (PGC) have following advantage: because system is based on the demodulation principle of interfere type, wavelength variations is converted into phase change detects again, so system wavelength resolution height, dynamic range is big, response speed is fast; Because this method can be eliminated the factor of sensing head luminous power, so system works is reliable and stable; And because system adopts the method for the interferometer initial phase being carried out the active modulation, make the sensitivity of interferometer be in more stable working point, therefore only need the single interference instrument just can simply realize the multiple spot wavelength-division multiplex of sensor, simultaneously, each road sensor only needs a photodetector to detect, so the present invention has the advantage that is easy to multiplexing networking.

Description of drawings

For further specifying concrete technology contents of the present invention, below in conjunction with embodiment and accompanying drawing describes in detail as after, wherein:

Fig. 1 is based on the high-resolution Wavelength demodulation system structural representation of Mach-Zehnder interferometer;

Fig. 2 is based on the high resolution wavelength demodulation system structural representation of Michelson interferometer;

Fig. 3 is the block scheme that phase place produces carrier wave (PGC) demodulating algorithm.

Embodiment

In conjunction with the drawings most preferred embodiment according to the present invention is described in detail, of the present invention and/or others and advantage will become clear and be more readily understood.

See also shown in Figure 1ly, a kind of high resolution wavelength demodulation system of the present invention is characterized in that, comprising:

One wavelength-modulated type sensor 1;

The input end of one the one 1 * 2 coupling mechanism 2, the one 1 * 2 coupling mechanisms 2 is connected with the output terminal of wavelength-modulated type sensor 1, as the input end of non-equilibrium fibre optic interferometer;

The input end of one the 21 * 2 coupling mechanism 3, the 21 * 2 coupling mechanisms 3 is connected with the output terminal of the one 1 * 2 coupling mechanism 2, as the output terminal of non-equilibrium fibre optic interferometer;

Wherein the splitting ratio of the one 1 * 2 coupling mechanism 2 and the 21 * 2 coupling mechanism 3 is 50: 50;

One phase-modulator 6, the input end of this phase-modulator 6 is connected with the output terminal of the one 1 * 2 coupling mechanism 2, and the output terminal of this phase-modulator 6 is connected with the input end of the 21 * 2 coupling mechanism 3, is used to provide the phase carrier signal; This phase-modulator 6 is selected the piezoelectric transducer that is wound with optical fiber for use;

One photodetector 4 is exported light signal with interferometer and is converted into electric signal;

Be connected in series photodetector 4 between one signal processing module 5, this signal processing module 5 and the 21 * 2 coupling mechanism 3, be used for measured signal is come out from the interference signal demodulation; This signal processing module 5 selects for use mimic channel to realize, perhaps selects for use the method for software or flush bonding processor to realize;

One sinusoidal signal generator 7, the output terminal of this sinusoidal signal generator 7 is connected with phase-modulator 6, and the input end of this sinusoidal signal generator 7 is connected with signal processing module 5, for phase-modulator 6 and signal processing module 5 provide sinusoidal modulation signal.

Please continue to consult shown in Figure 1, a kind of high resolution wavelength demodulation method of the present invention, it is to adopt aforesaid high resolution wavelength demodulation system, comprising following steps:

Step 1: the light that wavelength-modulated type sensor 1 sends enters non-equilibrium fibre optic interferometer, and the variation of sensor wavelength is converted into the variation of interference signal phase place; This non-equilibrium fibre optic interferometer is selected Mach-Zehnder interferometer or Michelson interferometer;

Step 2: use the phase place of 6 pairs of interferometers of phase-modulator to carry out the high frequency phase modulation (PM), overcome because initial phase drifts about to the influence of input sensitivity; The amplitude of this phase modulation (PM) is 2.64rad, and modulation frequency range is 5-20KHz;

Step 3: use photodetector 4 that interferometer output intensity signal is converted into electric signal;

Step 4: adopt phase place generation carrier wave algorithm that sensor wavelength is changed demodulation and come out, the flow process that this phase place produces the carrier wave algorithm is: photodetector 4 detection signals input multiplier module, output two-way mixed frequency signal, enter low-pass filtering module filtering radio-frequency component again, enter the normalization module then and carry out normalization operation, next enter differential multiplication cross module and obtain differential signal, enter integration high-pass filtering module at last and obtain demodulation result; Wherein multiplier module comprises two multipliers, and input signal multiplies each other with phase modulated signal and phase modulation (PM) two frequency-doubled signals respectively, output two-way mixed frequency signal; This low-pass filtering module comprises two low-pass filters, respectively the radio-frequency component of filtering two-way mixed frequency signal; This normalization module comprises a quadratic sum computing, square root calculation and two dividers, carry out square root calculation after the two paths of signals process quadratic sum computing of input and obtain normalization coefficient, then Shu Ru two paths of signals respectively by divider divided by this coefficient, output two-way normalized signal; This differential multiplication cross module comprises two differentiators, two multipliers and a subtracter, and the two paths of signals of input enters multiplier after through two differentiators and carries out multiplication cross, after the two paths of signals that obtains enters subtracter, exports one road differential signal; This also comprises an integrator and a Hi-pass filter, and one road signal of input enters Hi-pass filter again through behind the integrator, the output demodulation result.

Please in conjunction with consulting the embodiment based on Mach-Zehnder interferometer structure of Fig. 1 for high resolution wavelength demodulation system of the present invention.This embodiment is made up of the one 1 * 2 coupling mechanism 2, phase-modulator the 6, the 21 * 2 coupling mechanism 3, photodetector 4, sinusoidal signal generator 7, signal processing module 5, its syndeton is: the input end of the one 1 * 2 coupling mechanism 2 connects wavelength-modulated type sensor 1, two output terminals connect an input end of phase-modulator 6 optic fibre input ends and the 21 * 2 coupling mechanism 3 respectively, the fiber-optic output of phase-modulator 6 is connected with another input end of the 21 * 2 coupling mechanism 3, and the output terminal of the 21 * 2 coupling mechanism 3 connects photodetector 4; Detector is converted into light intensity and enters signal processing module 5 behind the electric signal and carry out demodulation; The modulation signal that sinusoidal signal generator 7 produces is divided into two-way, one tunnel control phase modulator 6, another road entering signal processing module 5.

Fig. 2 is the embodiment based on the Michelson interferometer structure of high resolution wavelength demodulation system of the present invention.This embodiment is made up of with photodetector 18 1 * 2 coupling mechanism 12, first catoptron 13, second catoptron 14, phase-modulator 15, sinusoidal signal generator 16, signal processing module 17, its syndeton is: the input end of 1 * 2 coupling mechanism 12 connects wavelength-modulated type sensor 11, two output terminals connect the optic fibre input end of phase-modulator 15 optic fibre input ends and catoptron 13 respectively, the fiber-optic output of phase-modulator 15 is connected with the optic fibre input end of second catoptron 14, and another input end of 1 * 2 coupling mechanism 12 connects photodetector 18; Detector is converted into light intensity and enters signal processing module 17 behind the electric signal and carry out demodulation; The modulation signal that sinusoidal signal generator 16 produces is divided into two-way, one tunnel control phase modulator 5, another road entering signal processing module 7.

The principle of work of high-resolution Wavelength demodulation system is: the light signal that wavelength-modulated type sensor sends enters non-equilibrium fibre optic interferometer, the changes delta λ of sensor wavelength is converted into the changes delta φ s of phase place, is converted into voltage signal entering signal processing module through behind the photodetector.Owing to be subjected to the interference of external environment, slowly drift will take place in the initial phase of interferometer, in order to overcome owing to of the influence of phase place random drift to input sensitivity, produce away from the phase-modulator on the high frequency sinusoidal modulation signal driving interferometer arm of measured signal frequency band by signal generator, interference signal is produced phase modulation (PM), adopt phase place to produce carrier wave (PGC) algorithm at last the demodulation of sensing head wavelength variations is come out.

The high resolution wavelength demodulating algorithm principle that produces carrier wave (PGC) based on phase place is as follows:

Interference signal after ovennodulation is write as:

I＝A+Bcos(Ccosω ₀t+φ(t)) (1)

Wherein, C is the phase carrier amplitude that modulation signal produces, ω ₀Be the modulation signal angular frequency, A is the average intensity after interfering, and B is the coefficient relevant with light intensity and visibility of interference fringes, φ (t)=Δ φ _s(t)+φ ₀(t), Δ φ _s(t) phase change to be measured that causes for the sensing head wavelength change, φ ₀(t) be initial phase.

(1) formula with the Bessel's function formal expansion, is obtained:

$I=A+B\left\{\right[J_0\left(C\right)+2\underset{K=1}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k}\left(C\right)\cos 2k{\mathrm{\ω}}_{0}t]\cos \mathrm{\φ}\left(t\right)$

$-2\left[\underset{K=0}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k+1}\left(C\right)\cos (2k+1){\mathrm{\ω}}_{0}t\right]\sin \mathrm{\φ}\left(t\right)\}$ (2)

J wherein _k(C) be k rank Bessel's function, following formula be multiply by cos ω respectively ₀T and cos2 ω ₀T obtains:

$A\cos {\mathrm{\ω}}_{0}t+B{J}_0\left(C\right)\cos {\mathrm{\ω}}_{0}t\cos \mathrm{\φ}\left(t\right)+B\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k}\left(C\right)[\cos (2k+1){\mathrm{\ω}}_{0}t+$

$\cos (2k-1){\mathrm{\ω}}_{0}t]\cos \mathrm{\φ}\left(t\right)-B\underset{k=0}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k+1}\left(C\right)[\cos 2(k+1){\mathrm{\ω}}_{0}t+\cos 2k{\mathrm{\ω}}_{0}t]\sin \mathrm{\φ}\left(t\right)$

(3)

$A\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20071006299500241.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_{0}t+B{J}_0\left(C\right)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20071006299500241.png"\; state="\{\{state\}\}">cos</figure-callout>}2{\mathrm{\&omega;}}_{0}t\cos \mathrm{\&phi;}\left(t\right)+B\underset{k=1}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^k{J}_{2k}\left(C\right)[\cos (2k+2){\mathrm{\&omega;}}_{0}t+$

$\cos (2k-2){\mathrm{\&omega;}}_{0}t]\cos \mathrm{\&phi;}\left(t\right)-B\underset{k=0}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{(-1)}^k{J}_{2k+1}\left(C\right)[\cos (2k+3){\mathrm{\&omega;}}_{0}t+\cos (2k-1){\mathrm{\&omega;}}_{0}t]\sin \mathrm{\&phi;}\left(t\right)$

(4)

Because modulating frequency ω 0 is higher than the measured signal frequency range far away, therefore above-mentioned two formulas through contain after the low-pass filtering ω 0 with and frequency multiplication Xiang Jun by elimination, can get:

-BJ ₁(C)sinφ(t) (5)

-BJ ₂(C)cosφ(t) (6)

The amplitude of adjusting phase carrier gets J ₁(C)=J ₂(C), this moment, C got 2.64, (6) formula that square adds of (5) formula square and open radical sign again and can obtain:

$\sqrt{B^2{\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="A20071006299500241.png,A20071006299500251.png"\; state="\{\{state\}\}">J</figure-callout>}}_1^2\left(C\right){\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A20071006299500241.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\mathrm{\&phi;}\left(t\right)+B^2{\mathrm{<figure-callout\; id="2"\; label="J"\; filenames="A20071006299500241.png"\; state="\{\{state\}\}">J</figure-callout>}}_2^2\left(C\right){\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20071006299500241.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\mathrm{\&phi;}\left(t\right)}={\mathrm{BJ}}_1\left(C\right)$ (7)

(5) formula obtains divided by (7) formula respectively with (6) formula:

-sinφ(t) (8)

-cosφ(t) (9)

Obtain through differential:

$-\cos \mathrm{\&phi;}\left(t\right)\frac{\mathrm{d\&phi;}\left(t\right)}{\mathrm{dt}}$ (10)

$\sin \mathrm{\&phi;}\left(t\right)\frac{\mathrm{d\&phi;}\left(t\right)}{\mathrm{dt}}$ (11)

Multiply by (11) formula by (8) formula gets:

${-\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A20071006299500241.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\mathrm{\&phi;}\left(t\right)\frac{\mathrm{d\&phi;}\left(t\right)}{\mathrm{dt}}$ (12)

Multiply by (10) formula by (9) formula gets:

${\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20071006299500241.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\mathrm{\&phi;}\left(t\right)\frac{\mathrm{d\&phi;}\left(t\right)}{\mathrm{dt}}$ (13)

Deducting (12) formula by (13) formula obtains:

$\frac{\mathrm{d\&phi;}\left(t\right)}{\mathrm{dt}}$ (14)

Obtain through integration:

φ(t)＝Δφ _s(t)+φ ₀(t) (15)

Because interferometer initial phase φ ₀(t) be tempolabile signal, obtain Δ φ through after the high-pass filtering at last _s(t).Can obtain phase change Δ φ according to the principle of interfering _s(t) with wavelength variations Δ λ _s(t) pass is:

$\mathrm{\&Delta;}{\mathrm{\&phi;}}_s\left(t\right)=\frac{2\mathrm{\&pi;nL}}{{\mathrm{\&lambda;}}^2}\mathrm{\&Delta;}{\mathrm{\&lambda;}}_s\left(t\right)$ (16)

Wherein n is an optical fibre refractivity, and L is that the interferometer brachium is poor.Thereby sensor wavelength variation demodulation is come out the most at last.

Fig. 3 produces carrier wave (PGC) demodulation method process flow diagram for the phase place of high resolution wavelength demodulation of the present invention.This method flow process comprises multiplier module 10, low-pass filtering module 20, normalization module 30, differential multiplication cross module 40 and integration high-pass filtering module 50 successively.

Interferometer output signal at first enters multiplier module 10 after receiving through detector, obtain two paths of signals after signal that produces with sinusoidal signal generator and two frequency-doubled signals thereof multiply each other respectively, this two paths of signals enters low-pass filtering module 20 simultaneously, enter normalized mode piece 30 through behind the low-pass filter, after eliminating the influence of luminous power, enter differential multiplication cross module 40, and the two paths of signals after the multiplication cross passed through subtracter, the difference that obtains enters integration high-pass filtering module 50, finally exports demodulation result.

Aforesaid multiplier module 10, it is characterized in that comprising two multipliers, the signal b1 that first multiplier 101 produces input signal a and sinusoidal signal generator multiplies each other and obtains signal c1, and second multiplier 102 multiplies each other two frequency-doubled signal b2 of input signal a and sinusoidal signal generator generation signal and obtains signal c2.

Aforesaid low-pass filtering module 20 is characterized in that comprising two low-pass filters, and signal c1 obtains signal d1 through behind the low-pass filter 201, and signal c2 obtains signal d2 through behind the low-pass filter 202.

Aforesaid normalization module 30, it is characterized in that signal d1 and d2 respectively tell one the road and carry out quadratic sum operation 301 earlier and obtain signal e, carry out square root functions 302 again and obtain signal f, use then divider 303 and divider 304 respectively with signal d1 and d2 divided by signal f, obtain signal g1 and g2.

Aforesaid differential multiplication cross module 40 is characterized in that comprising two differentiators, two multipliers and a subtracter.Signal g1 and g2 are respectively through obtaining signal h1 and h2 behind differentiator 401 and the differentiator 402, multiplier 403 multiplies each other signal g2 and h1 and obtains signal i1, multiplier 404 multiplies each other signal g1 and h2 and obtains signal i2, uses subtracter 405 to obtain the difference signal j of signal i1 and i2.

Aforesaid integration high-pass filtering module 50 is characterized in that comprising an integrator and a Hi-pass filter.Signal j obtains signal k through behind the integrator 501, obtains final demodulation result through behind the Hi-pass filter 502 again.

Although the present invention specifically shows in conjunction with its exemplary embodiment and describes, it should be appreciated by those skilled in the art, under the situation that does not break away from the spirit and scope of the present invention that are defined by the following claims, can carry out the modification of form and details to it.

Claims (13)

1. a high resolution wavelength demodulation system is characterized in that, comprising:

One wavelength-modulated type sensor;

One the one 1 * 2 coupling mechanism, the input end of the one 1 * 2 coupling mechanism is connected with the output terminal of wavelength-modulated type sensor, as the input end of non-equilibrium fibre optic interferometer;

One the 21 * 2 coupling mechanism, the input end of the 21 * 2 coupling mechanism is connected with the output terminal of the one 1 * 2 coupling mechanism, as the output terminal of non-equilibrium fibre optic interferometer;

One phase-modulator, the input end of this phase-modulator is connected with the output terminal of the one 1 * 2 coupling mechanism, and the output terminal of this phase-modulator is connected with the input end of the 21 * 2 coupling mechanism, is used to provide the phase carrier signal;

One photodetector is exported light signal with interferometer and is converted into electric signal;

Be connected in series photodetector between one signal processing module, this signal processing module and the 21 * 2 coupling mechanism, be used for measured signal is come out from the interference signal demodulation;

One sinusoidal signal generator, the output terminal of this sinusoidal signal generator is connected with phase-modulator, and the input end of this sinusoidal signal generator is connected with signal processing module, for phase-modulator and signal processing module provide sinusoidal modulation signal.

2. high resolution wavelength demodulation system as claimed in claim 1 is characterized in that wherein the splitting ratio of the one 1 * 2 coupling mechanism and the 21 * 2 coupling mechanism is 50: 50.

3. high resolution wavelength demodulation system as claimed in claim 1 is characterized in that wherein phase-modulator is selected the piezoelectric transducer that is wound with optical fiber for use.

4. high resolution wavelength demodulation system as claimed in claim 1 is characterized in that, wherein signal processing module selects for use mimic channel to realize, perhaps selects for use the method for software or flush bonding processor to realize.

5. high resolution wavelength demodulation method adopts the described high resolution wavelength demodulation system of claim 1, it is characterized in that, comprising following steps:

Step 1: the light that wavelength-modulated type sensor sends enters non-equilibrium fibre optic interferometer, and the variation of sensor wavelength is converted into the variation of interference signal phase place;

Step 2: use phase-modulator that the phase place of interferometer is carried out the high frequency phase modulation (PM), overcome because initial phase drifts about to the influence of input sensitivity;

Step 3: use photodetector that interferometer output intensity signal is converted into electric signal;

Step 4: adopt phase place generation carrier wave algorithm that sensor wavelength is changed demodulation and come out.

6. high resolution wavelength demodulation method as claimed in claim 5 is characterized in that, wherein non-equilibrium fibre optic interferometer is selected Mach-Zehnder interferometer or Michelson interferometer.

7. high resolution wavelength demodulation method as claimed in claim 5 is characterized in that, wherein the amplitude of phase modulation (PM) is 2.64rad, and modulation frequency range is 5-20KHz.

8. high resolution wavelength demodulation method as claimed in claim 5, it is characterized in that, wherein the flow process of phase place generation carrier wave algorithm is: photodetector 4 detection signals input multiplier module, output two-way mixed frequency signal, enter low-pass filtering module filtering radio-frequency component again, enter the normalization module then and carry out normalization operation, next enter differential multiplication cross module and obtain differential signal, enter integration high-pass filtering module at last and obtain demodulation result.

9. high resolution wavelength demodulation method as claimed in claim 8 is characterized in that, wherein multiplier module comprises two multipliers, and input signal multiplies each other with phase modulated signal and phase modulation (PM) two frequency-doubled signals respectively, output two-way mixed frequency signal.

10. high resolution wavelength demodulation method as claimed in claim 8 is characterized in that, wherein low-pass filtering module comprises two low-pass filters, respectively the radio-frequency component of filtering two-way mixed frequency signal.

11. high resolution wavelength demodulation method as claimed in claim 8, it is characterized in that, wherein normalization module comprises a quadratic sum computing, square root calculation and two dividers, carry out square root calculation after the two paths of signals process quadratic sum computing of input and obtain normalization coefficient, then Shu Ru two paths of signals respectively by divider divided by this coefficient, output two-way normalized signal.

12. high resolution wavelength demodulation method as claimed in claim 8, it is characterized in that, wherein differential multiplication cross module comprises two differentiators, two multipliers and a subtracter, the two paths of signals of input enters multiplier after through two differentiators and carries out multiplication cross, after the two paths of signals that obtains enters subtracter, export one road differential signal.

13. high resolution wavelength demodulation method as claimed in claim 8 is characterized in that, wherein also comprises an integrator and a Hi-pass filter, one road signal of input enters Hi-pass filter again through behind the integrator, the output demodulation result.

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