CN101686087A - Wavelength demodulation system and method based on two outputs of a 3 x 3 coupler - Google Patents

Abstract

The present invention discloses a wavelength demodulation system and method based on two outputs of a 3 x 3 coupler. The system comprises a high-pass filtering module for performing high-pass filtering to interference fringes from any two outputs received from the 3 x 3 coupler and obtaining signals of two outputs after filtering out a DC component; cross-multiplication subtraction module for performing cross-multiplication subtraction to the signals of the two outputs to obtain a sine component and a cosine component containing signals; a differentiation square addition module for eliminatingthe sine component and the cosine component containing signals from the signals to obtain a square component of the differentiation of the signals; an evolution positive and negative judging modulefor performing evolution to the square component of the differentiation of the signals, judging that the obtained result is negative or positive and obtaining a differentiation component of the signals; a median filtering integral module for performing median filtering to the differentiation component of the signals to filter out bad points, performing an integral process by an integrator and obtaining a final demodulation result. The present invention has advantages of high precision, big dynamic range, low cost, simple algorithm and easy realization of networking.

Description

Wavelength demodulation system and method based on the output of 3 * 3 coupler two-way

Technical field

The present invention relates to technical field of optical fiber sensing, relate in particular to a kind of Wavelength demodulation system and method, be mainly used in the demodulation of wavelength-modulated type sensor wavelength based on the output of 3 * 3 coupler two-way.

Background technology

Optical fiber sensing technology is to be carrier with light, and optical fiber is media, the novel sensing technology of perception and transmission outer signals.Utilize the modulation of external physical quantity to the different parameters of light wave, Fibre Optical Sensor can be divided into: types such as wavelength-modulated type, intensity modulation type, phase modulation-type and polarization state modulation type.Wavelength-modulated type Fibre Optical Sensor has that antijamming capability is strong, sensing probe is simple in structure, size is little and is convenient to advantages such as networking is multiplexing, therefore wavelength-modulated type transducer is widely used in civil engineering in Fibre Optical Sensor, Aero-Space, petroleum industry, numerous areas such as national defense safety.

Demodulation method based on wavelength-modulated type Fibre Optical Sensor has a lot, for example chromatic dispersion method, F-P filter method, coupling raster method, boundary filter method etc., and 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, then by phase demodulating technology reduction wavelength change, method based on the interfere type Wavelength demodulation mainly comprises the Phase Tracking method, the phase carrier method, 3 * 3 coupler approach or the like.

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 difference 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 transducer is different, so each road transducer needs independent interferometer and compensating circuit, networking structure more complicated.

With respect to other phase demodulating technology, the Wavelength demodulation system cost of realizing based on 3 * 3 coupler methods is low, algorithm is simple, and the realization of system light path is relatively easy, but demodulating algorithm need depend on three tunnel outputs of 3 * 3 couplers usually, and need the phase unwrapping technology, so not only increased the difficulty of system group network but also strengthened the difficulty of algorithm.

Summary of the invention

(1) technical problem that will solve

In order to overcome the shortcoming of above-mentioned prior art, main purpose of the present invention is to provide a kind of Wavelength demodulation system and method based on the output of 3 * 3 coupler two-way, to reduce algorithm complex, increases the demodulation dynamic range, reduce the demodulating system cost, be convenient to realize networking.

(2) technical scheme

For achieving the above object, the technical solution used in the present invention is as follows:

A kind of Wavelength demodulation system based on the output of 3 * 3 coupler two-way, this system comprises:

High-pass filtering module 10 is used for any two-way interference fringe that is received from 3 * 3 couplers is carried out high-pass filtering, obtains the two-way output signal after the elimination DC terms, exports to multiplication intersection subtraction module 20;

Multiplication intersection subtraction module 20 is used for that the two paths of signals that high-pass filtering module 10 is imported is carried out the multiplication intersection and subtracts each other, and obtains comprising the sine term and the cosine term of signal, exports to differential summed square module 30;

Differential summed square module 30 is used for the signal of multiplication intersection subtraction module 20 inputs is carried out sine and the cosine term that cancellation comprises signal, obtains the quadratic term of signal differentiation, exports to evolution and judges positive and negative module 40;

Evolution is judged positive and negative module 40, is used for the quadratic term of the signal differentiation of differential summed square module 30 input is opened the radical sign computing, and then the result who obtains is carried out positive and negative judgement, obtains the differential term of signal, exports to medium filtering integration module 50;

Medium filtering integration module 50 is used for evolution is judged that the differential term of the signal of positive and negative module 40 inputs carries out medium filtering, passes through the integrator integration again behind the bad point of elimination, gets demodulation result to the end.

In the such scheme, described high-pass filtering module 10 comprises:

First high pass filter 101 is used for that the interference fringe a1 that imports is carried out high-pass filtering and obtains signal b1, exports to multiplication intersection subtraction module 20;

Second high pass filter 102 is used for that the interference fringe a2 that imports is carried out high-pass filtering and obtains signal b2, exports to multiplication intersection subtraction module 20.

In the such scheme, described multiplication intersects subtraction module 20 and comprises four multipliers and two subtracters, first multiplier 201 and second multiplier 202 respectively with signal b1 respectively with (B ₂/ B ₁) cos β ₂(B ₂/ B ₁) sin β ₂Multiplying each other obtains signal c1 and c2, the 3rd multiplier 203 and the 4th multiplier 204 respectively with signal b2 respectively with cos β ₁With sin β ₁Multiplying each other obtains signal c3 and c4, and first subtracter 205 subtracts each other signal c1 and c3 and obtains signal d1, and second subtracter 206 subtracts each other signal c2 and c4 and obtains signal d2.

In the such scheme, described differential summed square module 30 comprises two differentiators, two squarers and an adder, wherein, 301 couples of signal d1 of first differentiator differential obtains signal e1,302 couples of signal d2 of second differentiator differential obtains signal e2,303 couples of signal e1 of first squarer squares obtain signal f1, and 304 couples of signal e2 of second squarer squares obtain signal f2, and adder 305 obtains signal g with signal f1 and signal f2 addition.

In the such scheme, described evolution judges that positive and negative module 40 comprises a square root extractor and the positive and negative module of judgement, and square root extractor 401 obtains signal h with signal g evolution, judges that positive and negative module 402 obtains signal i according to the symbol of the value judgement signal h of signal d1 and e2.

In the such scheme, described medium filtering integration module 50 comprises a median filter and an integrator, and 501 couples of signal i of median filter carry out medium filtering and obtain signal j, and 502 couples of signal j of integrator carry out integration and get demodulation result to the end.

A kind of Wavelength demodulation method based on the output of 3 * 3 coupler two-way is applied to the described system of claim 1, and this method specifically comprises:

10 pairs of high-pass filtering modules are received from any two-way interference fringe of 3 * 3 couplers and carry out high-pass filtering, obtain the two-way output signal after the elimination DC terms, export to multiplication intersection subtraction module 20;

The two paths of signals of 20 pairs of high-pass filtering modules of multiplication intersection subtraction module, 10 inputs carries out the multiplication intersection and subtracts each other, and obtains comprising the sine term and the cosine term of signal, exports to differential summed square module 30;

The signal of 30 pairs of multiplication intersections of differential summed square module subtraction module, 20 inputs carries out sine and the cosine term that cancellation comprises signal, obtains the quadratic term of signal differentiation, exports to evolution and judges positive and negative module 40;

Evolution judges that the quadratic term of the signal differentiation of 40 pairs of differential summed square of positive and negative module module, 30 inputs carries out evolution and judges positive and negative processing, obtains the differential term of signal, exports to medium filtering integration module 50;

50 pairs of evolutions of medium filtering integration module judge that the differential term of the signal of positive and negative module 40 inputs carries out the medium filtering integration, gets demodulation result to the end.

In the such scheme, the two paths of signals of 20 pairs of high-pass filtering modules of described multiplication intersection subtraction module, 10 inputs carries out the multiplication intersection and subtracts each other, and obtains comprising the sine term and the cosine term of signal, exports to the step of differential summed square module 30, specifically comprises:

The first via signal of high-pass filtering module 10 inputs at first multiply by a ratio, this ratio is to be obtained by the product term of light intensity and fringe visibility in the interference fringe the second tunnel of 3 * 3 couplers output product term divided by light intensity and fringe visibility in the interference fringe first via of 3 * 3 couplers output, and then multiply by the cosine value of the second road phase difference that 3 * 3 couplers introduce; The first via signal of high-pass filtering module 10 inputs then multiply by a ratio again, this ratio is to be obtained by the product term of light intensity and fringe visibility in the interference fringe the second tunnel of 3 * 3 couplers output product term divided by light intensity and fringe visibility in the interference fringe first via of 3 * 3 couplers output, and then multiply by the sine value of the second road phase difference that 3 * 3 couplers introduce;

The second road signal of high-pass filtering module 10 inputs at first multiply by the cosine value of the first via phase difference of 3 * 3 couplers introducing; The second road signal of high-pass filtering module 10 input multiply by the sine value of the first via phase difference that 3 * 3 couplers introduce then, obtains four road signals and intersects by two subtracters and subtract each other the output that the two-way that obtains comprises the institute's signal of asking sine and cosine respectively.

(3) beneficial effect

From technique scheme as can be seen, the present invention has following beneficial effect:

1, this Wavelength demodulation system and method based on the output of 3 * 3 coupler two-way provided by the invention, owing to be based on the demodulation principle of interfere type, the variation that wavelength change is changed into phase place detects again, has high accuracy, the characteristics that dynamic range is big.

2, this Wavelength demodulation system and method based on the output of 3 * 3 coupler two-way provided by the invention, because this demodulation method carries out Wavelength demodulation based on 3 * 3 couplers, its algorithm is simple, and does not need active device, and the demodulating system cost is reduced.

3, this Wavelength demodulation system and method based on the output of 3 * 3 coupler two-way provided by the invention are because this demodulation method utilizes the more convenient realization networking of algorithm of 3 * 3 couplers, three tunnel outputs based on the two-way output of 3 * 3 couplers.

Description of drawings

Fig. 1 is the structural representation of the Wavelength demodulation system based on 3 * 3 coupler two-way output provided by the invention;

Fig. 2 is the method flow diagram of the Wavelength demodulation based on 3 * 3 coupler two-way output provided by the invention.

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.

Demodulating algorithm principle based on the output of 3 * 3 coupler two-way is as follows:

Can be write as following formula through the interference fringe after the interference of 3 * 3 couplers:

I _n＝A _n+B _ncos(S+β _n) (1)

Wherein, A _n(n=1,2,3) are the average intensity after interfering, B _n(n=1,2,3) are relevant with light intensity and visibility of interference fringes, β _n(n=1,2,3) are the phase difference that three tunnel outputs of 3 * 3 couplers cause, S is a measured signal, can be expressed as S=Dcos (ω t), and D is the amplitude of measured signal, and ω is the frequency of measured signal.

Can obtain Lissajou's figure because 3 * 3 couplers three tunnel are exported any two-way mapping, can obtain the value of 3 * 3 coupler parameters at last, comprise A by it is carried out curve fitting _n, B _n, β _n(n=1,2,3).

(1) formula is carried out Bessel function to be launched and can obtain:

$I_n\left(t\right)=A_n+B_n\left\{\right[J_0\left(D\right)+2\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k}\left(D\right)\cos 2\mathrm{k\ωt}]\cos {\mathrm{\β}}_n$

(2)

$-2\left[\underset{k=0}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k+1}\left(D\right)\cos (2k+1)\mathrm{\ωt}\right]\sin {\mathrm{\β}}_n\}$

J wherein _k(D) be k rank Bessel function, can utilize any two-way output of 3 * 3 couplers to carry out, select I here ₁And I ₂Carry out demodulation, it by after the high pass filter filtering DC terms, can be obtained following result:

$I_{11}\left(t\right)=B_1\left\{\right[2\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k}\left(D\right)\cos 2\mathrm{k\ωt}]\cos {\mathrm{\β}}_1$

$-2\left[\underset{k=0}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k+1}\left(D\right)\cos (2k+1)\mathrm{\ωt}\right]\sin {\mathrm{\β}}_1\}---\left(3\right)$

$=-B_1{J}_0\left(D\right)\cos {\mathrm{\β}}_1+B_1\cos (S+{\mathrm{\β}}_1)$

$=-B_1{J}_0\left(D\right)\cos {\mathrm{\β}}_1+B_1[\cos S\cos {\mathrm{\β}}_1-\sin S\sin {\mathrm{\β}}_1]$

$I_{22}\left(t\right)=B_2\left\{\right[2\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k}\left(D\right)\cos 2\mathrm{k\ωt}]\cos {\mathrm{\β}}_2$

$-2\left[\underset{k=0}{\overset{\∞}{\mathrm{\Σ}}}{(-1)}^k{J}_{2k+1}\left(D\right)\cos (2k+1)\mathrm{\ωt}\right]\sin {\mathrm{\β}}_2\}---\left(4\right)$

$=-B_2{J}_0\left(D\right)\cos {\mathrm{\β}}_2+B_2\cos (S+{\mathrm{\β}}_2)$

$=-B_2{J}_0\left(D\right)\cos {\mathrm{\β}}_2+B_2[\cos S\cos {\mathrm{\β}}_2-\sin S\sin {\mathrm{\β}}_2]$

In order to obtain containing the expression formula of sinS and cosS, (3) formula and (4) formula are done following processing:

$K_1\left(t\right)=I_{11}\left(t\right)\×\frac{B_2}{B_1}\cos {\mathrm{\β}}_2-I_{22}\left(t\right)\×\cos {\mathrm{\β}}_1$ (5)

$=-B_2[\sin {\mathrm{\β}}_1\cos {\mathrm{\β}}_2-\sin {\mathrm{\β}}_2\cos {\mathrm{\β}}_1]\sin S$

$=-B_2\sin ({\mathrm{\β}}_1-{\mathrm{\β}}_2)\sin S$

$K_2\left(t\right)=I_{11}\left(t\right)\×\frac{B_2}{B_1}\sin {\mathrm{\β}}_2-I_{22}\left(t\right)\×\sin {\mathrm{\β}}_1$

$=-B_2{J}_0\left(D\right)[\sin {\mathrm{\β}}_2\cos {\mathrm{\β}}_1-\sin {\mathrm{\β}}_1\cos {\mathrm{\β}}_2]---\left(6\right)$

${+B}_2[\sin {\mathrm{\β}}_2\cos {\mathrm{\β}}_1-\sin {\mathrm{\β}}_1\cos {\mathrm{\β}}_2]\cos S$

$=B_2{J}_0\left(D\right)\sin ({\mathrm{\β}}_1-{\mathrm{\β}}_2)-B_2\sin ({\mathrm{\β}}_1-{\mathrm{\β}}_2)\cos S$

(5) formula and (6) formula are carried out differential to be obtained:

K′ ₁(t)＝-B ₂sin(β ₁-β ₂)cosS×S′ (7)

K′ ₂(t)＝B ₂sin(β ₁-β ₂)sinS×S′(8)

In order to disappear S, (7) formula and (8) formula are carried out summed square obtain:

[K′ ₁(t)] ²+[K′ ₂(t)] ²＝[B ₂sin(β ₁-β ₂)S′] ²＝(HS′) ² (9)

H=B wherein ₂Sin (β ₁-β ₂) be constant.

By (7) formula and (8) formula, can obtain following result:

K′ ₂(t)＝B ₂sin(β ₁-β ₂)sinS×S′＝-K ₁(t)×S′ (10)

So according to K ' ₂(t) and K ₁(t) value, can judge | the symbol of H|S '.

Can elimination by median filter | the bad point of H|S ', by right | H|S ' integration can obtain:

|H|S＝∫|H|S′dt (11)

Can see that by (11) formula signal restores the most at last, wherein | H| is a constant.

Fig. 1 is the structural representation of the Wavelength demodulation system based on 3 * 3 coupler two-way output provided by the invention, and this system comprises that high-pass filtering module 10, multiplication intersect subtraction module 20, differential summed square module 30, evolution and judge positive and negative module 40 and medium filtering integration module 50.

Wherein, high-pass filtering module 10 is used for any two-way interference fringe that is received from 3 * 3 couplers is carried out high-pass filtering, obtains the two-way output signal after the elimination DC terms, exports to multiplication intersection subtraction module 20.Multiplication intersection subtraction module 20 is used for that the two paths of signals that high-pass filtering module 10 is imported is carried out the multiplication intersection subtracts each other, and obtains comprising the sine term and the cosine term of signal, exports to differential summed square module 30.Differential summed square module 30 is used for the signal of multiplication intersection subtraction module 20 inputs is carried out sine and the cosine term that cancellation comprises signal, obtains the quadratic term of signal differentiation, exports to evolution and judges positive and negative module 40.Evolution is judged positive and negative module 40, is used for the quadratic term of the signal differentiation of differential summed square module 30 input is opened the radical sign computing, and then the result who obtains is carried out positive and negative judgement, obtains the differential term of signal, exports to medium filtering integration module 50.Medium filtering integration module 50 is used for evolution is judged that the differential term of the signal of positive and negative module 40 inputs carries out medium filtering, passes through the integrator integration again behind the bad point of elimination, gets demodulation result to the end.

High-pass filtering module 10 comprises first high pass filter 101 and second high pass filter 102, and wherein, first high pass filter 101 is used for that the interference fringe a1 that imports is carried out high-pass filtering and obtains signal b1, exports to multiplication intersection subtraction module 20; Second high pass filter 102 is used for that the interference fringe a2 that imports is carried out high-pass filtering and obtains signal b2, exports to multiplication intersection subtraction module 20.

Multiplication intersects subtraction module 20 and comprises four multipliers and two subtracters, first multiplier 201 and second multiplier 202 respectively with signal b1 respectively with (B ₂/ B ₁) cos β ₂(B ₁/ B ₁) sin β ₂Multiplying each other obtains signal c1 and c2, the 3rd multiplier 203 and the 4th multiplier 204 respectively with signal b2 respectively with cos β ₁With sin β ₁Multiplying each other obtains signal c3 and c4, and first subtracter 205 subtracts each other signal c1 and c3 and obtains signal d1, and second subtracter 206 subtracts each other signal c2 and c4 and obtains signal d2.

Differential summed square module 30 comprises two differentiators, two squarers and an adder, wherein, 301 couples of signal d1 of first differentiator differential obtains signal e1,302 couples of signal d2 of second differentiator differential obtains signal e2,303 couples of signal e1 of first squarer squares obtain signal f1,304 couples of signal e2 of second squarer squares obtain signal f2, and adder 305 obtains signal g with signal f1 and signal f2 addition.

Evolution judges that positive and negative module 40 comprises a square root extractor and the positive and negative module of judgement, and square root extractor 401 obtains signal h with signal g evolution, judges that positive and negative module 402 obtains signal i according to the symbol of the value judgement signal h of signal d1 and e2.

Medium filtering integration module 50 comprises a median filter and an integrator, and 501 couples of signal i of median filter carry out medium filtering and obtain signal j, and 502 couples of signal j of integrator carry out integration and get demodulation result to the end.

Structural representation based on Wavelength demodulation system based on the output of 3 * 3 coupler two-way provided by the invention shown in Figure 1, Fig. 2 shows the method flow diagram of the Wavelength demodulation based on 3 * 3 coupler two-way output provided by the invention, and this method specifically may further comprise the steps:

Step 201: 10 pairs of high-pass filtering modules are received from any two-way interference fringe of 3 * 3 couplers and carry out high-pass filtering, obtain the two-way output signal after the elimination DC terms, export to multiplication intersection subtraction module 20;

Step 202: the two paths of signals of 20 pairs of high-pass filtering modules of multiplication intersection subtraction module, 10 inputs carries out the multiplication intersection and subtracts each other, and obtains comprising the sine term and the cosine term of signal, exports to differential summed square module 30;

Step 203: the signal of 30 pairs of multiplication intersections of differential summed square module subtraction module, 20 inputs carries out sine and the cosine term that cancellation comprises signal, obtains the quadratic term of signal differentiation, exports to evolution and judges positive and negative module 40;

Step 204: evolution judges that the quadratic term of the signal differentiation of 40 pairs of differential summed square of positive and negative module module, 30 inputs carries out evolution and judges positive and negative processing, obtains the differential term of signal, exports to medium filtering integration module 50;

Step 205: 50 pairs of evolutions of medium filtering integration module judge that the differential term of the signal of positive and negative module 40 inputs carries out the medium filtering integration, gets demodulation result to the end.

In the above-mentioned steps 202, the two paths of signals of 20 pairs of high-pass filtering modules of described multiplication intersection subtraction module, 10 inputs carries out the multiplication intersection and subtracts each other, obtain comprising the sine term and the cosine term of signal, export to the step of differential summed square module 30, specifically comprise: the first via signal of high-pass filtering module 10 inputs at first multiply by a ratio, this ratio is to be obtained by the product term of light intensity and fringe visibility in the interference fringe the second tunnel of 3 * 3 couplers output product term divided by light intensity and fringe visibility in the interference fringe first via of 3 * 3 couplers output, and then multiply by the cosine value of the second road phase difference that 3 * 3 couplers introduce; The first via signal of high-pass filtering module 10 inputs then multiply by a ratio again, this ratio is to be obtained by the product term of light intensity and fringe visibility in the interference fringe the second tunnel of 3 * 3 couplers output product term divided by light intensity and fringe visibility in the interference fringe first via of 3 * 3 couplers output, and then multiply by the sine value of the second road phase difference that 3 * 3 couplers introduce; The second road signal of high-pass filtering module 10 inputs at first multiply by the cosine value of the first via phase difference of 3 * 3 couplers introducing; The second road signal of high-pass filtering module 10 input multiply by the sine value of the first via phase difference that 3 * 3 couplers introduce then, obtains four road signals and intersects by two subtracters and subtract each other the output that the two-way that obtains comprises the institute's signal of asking sine and cosine respectively.

The method of the Wavelength demodulation based on 3 * 3 coupler two-way output provided by the invention, the wherein two-way interference fringe of 3 * 3 couplers output at first enters high-pass filtering module 10, enter multiplication intersection subtraction module 20 through obtaining two-way output after the high pass filter elimination DC terms, obtain comprising the sine term and the cosine term of signal, enter differential summed square module 30 then, cancellation comprises the sine and the cosine term of signal, obtain the quadratic term of signal differentiation, enter evolution and judge 40 differential terms that obtain signal of positive and negative module, can get to the end demodulation result by medium filtering integration module 50 at last.

Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (8)

1, a kind of Wavelength demodulation system based on the output of 3 * 3 coupler two-way is characterized in that this system comprises:

High-pass filtering module (10) is used for any two-way interference fringe that is received from 3 * 3 couplers is carried out high-pass filtering, obtains the two-way output signal after the elimination DC terms, exports to multiplication intersection subtraction module (20);

Multiplication intersection subtraction module (20) is used for that the two paths of signals that high-pass filtering module (10) is imported is carried out the multiplication intersection and subtracts each other, and obtains comprising the sine term and the cosine term of signal, exports to differential summed square module (30);

Differential summed square module (30) is used for the signal of multiplication intersection subtraction module (20) input is carried out sine and the cosine term that cancellation comprises signal, obtains the quadratic term of signal differentiation, exports to evolution and judges positive and negative module (40);

Evolution is judged positive and negative module (40), be used for the quadratic term of the signal differentiation of differential summed square module (30) input is opened the radical sign computing, and then the result who obtains carried out positive and negative judgement, and obtain the differential term of signal, export to medium filtering integration module (50);

Medium filtering integration module (50) is used for evolution is judged that the differential term of the signal of positive and negative module (40) input carries out medium filtering, passes through the integrator integration again behind the bad point of elimination, gets demodulation result to the end.

2, the Wavelength demodulation system based on the output of 3 * 3 coupler two-way according to claim 1 is characterized in that described high-pass filtering module (10) comprises:

First high pass filter (101) is used for that the interference fringe a1 that imports is carried out high-pass filtering and obtains signal b1, exports to multiplication intersection subtraction module (20);

Second high pass filter (102) is used for that the interference fringe a2 that imports is carried out high-pass filtering and obtains signal b2, exports to multiplication intersection subtraction module (20).

3, the Wavelength demodulation system based on the output of 3 * 3 coupler two-way according to claim 2, it is characterized in that, described multiplication intersects subtraction module (20) and comprises four multipliers and two subtracters, first multiplier (201) and second multiplier (202) respectively with signal b1 respectively with (B ₂/ B ₁) cos β ₂(B ₂/ B ₁) sin β ₂Multiplying each other obtains signal c1 and c2, the 3rd multiplier (203) and the 4th multiplier (204) respectively with signal b2 respectively with cos β ₁With sin β ₁Multiplying each other obtains signal c3 and c4, and first subtracter (205) subtracts each other signal c1 and c3 and obtains signal d1, and second subtracter (206) subtracts each other signal c2 and c4 and obtains signal d2.

4, the Wavelength demodulation system based on the output of 3 * 3 coupler two-way according to claim 3, it is characterized in that, described differential summed square module (30) comprises two differentiators, two squarers and an adder, wherein, first differentiator (301) obtains signal e1 to signal d1 differential, second differentiator (302) obtains signal e2 to signal d2 differential, first squarer (303) obtains signal f1 to signal e1 square, second squarer (304) obtains signal f2 to signal e2 square, and adder (305) obtains signal g with signal f1 and signal f2 addition.

5, the Wavelength demodulation system based on the output of 3 * 3 coupler two-way according to claim 4, it is characterized in that, described evolution judges that positive and negative module (40) comprises a square root extractor and the positive and negative module of judgement, square root extractor (401) obtains signal h with signal g evolution, judges that positive and negative module (402) obtains signal i according to the symbol of the value judgement signal h of signal d1 and e2.

6, the Wavelength demodulation system based on the output of 3 * 3 coupler two-way according to claim 5, it is characterized in that, described medium filtering integration module (50) comprises a median filter and an integrator, median filter (501) carries out medium filtering to signal i and obtains signal j, and integrator (502) carries out integration to signal j and gets demodulation result to the end.

7, a kind of Wavelength demodulation method based on the output of 3 * 3 coupler two-way is applied to the described system of claim 1, it is characterized in that this method specifically comprises:

High-pass filtering module (10) is carried out high-pass filtering to any two-way interference fringe that is received from 3 * 3 couplers, obtains the two-way output signal after the elimination DC terms, exports to multiplication intersection subtraction module (20);

The two paths of signals that multiplication intersection subtraction module (20) is imported high-pass filtering module (10) carries out the multiplication intersection and subtracts each other, and obtains comprising the sine term and the cosine term of signal, exports to differential summed square module (30);

Differential summed square module (30) is carried out sine and the cosine term that cancellation comprises signal to the signal of multiplication intersection subtraction module (20) input, obtains the quadratic term of signal differentiation, exports to evolution and judges positive and negative module (40);

Evolution judges that positive and negative module (40) carries out evolution to the quadratic term of the signal differentiation of differential summed square module (30) input and judge positive and negative processing, obtains the differential term of signal, exports to medium filtering integration module (50);

Medium filtering integration module (50) judges that to evolution the differential term of the signal of positive and negative module (40) input carries out the medium filtering integration, gets demodulation result to the end.

8, the Wavelength demodulation method based on the output of 3 * 3 coupler two-way according to claim 7, it is characterized in that, the two paths of signals that described multiplication intersection subtraction module (20) is imported high-pass filtering module (10) carries out the multiplication intersection and subtracts each other, obtain comprising the sine term and the cosine term of signal, export to the step of differential summed square module (30), specifically comprise:

The first via signal of high-pass filtering module (10) input at first multiply by a ratio, this ratio is to be obtained by the product term of light intensity and fringe visibility in the interference fringe the second tunnel of 3 * 3 couplers output product term divided by light intensity and fringe visibility in the interference fringe first via of 3 * 3 couplers output, and then multiply by the cosine value of the second road phase difference that 3 * 3 couplers introduce; The first via signal of high-pass filtering module (10) input then multiply by a ratio again, this ratio is to be obtained by the product term of light intensity and fringe visibility in the interference fringe the second tunnel of 3 * 3 couplers output product term divided by light intensity and fringe visibility in the interference fringe first via of 3 * 3 couplers output, and then multiply by the sine value of the second road phase difference that 3 * 3 couplers introduce;

The second road signal of high-pass filtering module (10) input at first multiply by the cosine value of the first via phase difference of 3 * 3 couplers introducing; The second road signal of high-pass filtering module (10) input multiply by the sine value of the first via phase difference that 3 * 3 couplers introduce then, obtains four road signals and intersects by two subtracters and subtract each other the output that the two-way that obtains comprises the institute's signal of asking sine and cosine respectively.

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