CN101290456A - All-light analog-digital converter 2AMZSX parallel quantitative coding method - Google Patents

Abstract

The invention discloses a 2AMZSX parallel quantization coding method for an all-optical analog-to-digital converter. The method is as follows: the N-bit all-optical analog-to-digital converter is designed; stable sounding optical pulses and steering optical pulses (analog optical) are input into a splitting coupler array (2) through a wavelength division multiplexer or a polarization coupler (1); the coupler array (2) is formed by series connection of N-1 1x2 couplers, wherein, one output port of each 1x2 coupler is connected with an asymmetric Mach-Zehnder interferometer (3) and the other output port of each 1x2 coupler is connected with the next 1x2 coupler; and a band-pass filter or an analyzer (4) is arranged on a position of each asymmetric Mach-Zehnder interferometer (3) which is directly communicated with the output ports and only allows probe light to pass. The structure is combined with adequate splitting ratio of the coupler array (2) and the splitting ratio of a first coupler of each asymmetric Mach-Zehnder interferometer (3) to realize parallel output of Gray code pulses by the probe light.

Description

The all-light analog-digital converter 2AMZSX quantization coding method that walks abreast

Technical field

The present invention relates to the optical information processing technical field, it is particularly related to the parallel quantization coding method of a kind of all-light analog-digital converter 2AMZSX, promptly adopt N the asymmetric mach-Ceng Deer interferometer (Asym_MachZehnderI) and the line output of N-1 1 * 2 coupling mechanism serial connection beam splitting input array, based on realizing N position all-light analog-digital converter from the parallel quantification and the coding of phase modulation (PM) (SPM) and cross-phase modulation (XPM) principle.

Background technology

Light signal processing, optical communication and light sensing etc. are very urgent to the demand of high speed, high-precision adc (ADC), and full optical tech is the most potential method of realizing this goal.Full light ADC relates to optical sampling, optics quantizes and three elementary cells of optical encoding and gordian technique thereof.The optical sampling technology domestic and international researchist satisfactorily resolve, and the key of design all-optical ADC is to adopt which type of device to realize quantizing and coding.

Along with the continuous development that full light signal is handled, full light quantization technology has become a challenge, and the nonlinear quantization technology that is used for full light ADC little by little grows up.Proposed to adopt Waveguide interference instrument array to realize the scheme that quantizes as far back as Taylor in 1979, the people such as Konishi of Japanese Osaka University in 2002 propose to utilize the nonlinear effect of optical fiber to quantize, promptly utilize the Raman orphan self-frequency shift effect in the highly nonlinear optical fiber to realize the transfer of luminous power to optical frequency shift, utilize AWG that the gained signal is carried out apart again, thereby realize quantification treatment to sampled signal, people such as the Chris Xu of Cornell Univ USA also adopted similar method to realize the full light quantization of signal afterwards of sampling in 2003, this method adopts in full light ADC scheme in recent years in a large number, this pulsewidth that requires input optical pulse signal to be quantified based on the full light quantization method of orphan's self-frequency shift effect in the optical fiber is in the femtosecond magnitude, then needs to carry out in advance the pulsewidth compression for the light pulse signal of picosecond magnitude.The people such as Oda of Japanese OsakaUniversity in 2004 have proposed to utilize the high-order optical soliton in the optical fiber to form and have separated the scheme that realizes full light quantization, and the result of principle confirmatory experiment shows that the full light quantization of 3bits can realize.People such as Oda had proposed to utilize the cutting super continuous spectrums to realize full light quantization again in 2005, promptly utilize Dispersion Flattened Fiber to produce super continuous spectrums, its spectrum width is by the intensity decision of sampled signal, and utilize array waveguide grating to carry out demultiplexing, output to different ports, the port number and the sample signal strength that are in logical light state are closely related, thereby have realized the quantification of signal.

Coding is the important arm joint of full light ADC, has caused various countries researchist's concern in recent years, has proposed many full light Methods for Coding.The people such as Oda of Japan in 2002 have proposed to utilize pulse-shaping technique to realize quantizing the encoding scheme of back signal, its shaping pulse system is made of spatial filter and dispersion element, and has reported the experimental result that realizes full light coding by integrated AWG and adjustable optical attenuator formation shaping pulse system in 2005.People such as U.S. Chris Xu in 2003 are to the signal after utilizing orphan's self-frequency shift effect in the optical fiber and quantizing, adopt filter array as a comparison device realized optical encoding.People such as Oda in 2002 propose to realize based on nonlinear optical arm mirror the scheme of coding again, and have provided the experimental result of the full light ADC of 2bits.People such as Japanese Konishi proposed to adopt the optical interconnection mode to realize the method for Gray code in 2006, and from having verified that experimentally light signal from 8 grades of quantifications is to the 3bits Gray code conversion.They had proposed to utilize the optical delay line coding to carry out the full light ADC of corresponding 3bits again in 2007.The Ikeda of Osaka University in 2006 (sees document Kensuke Ikeda.Design considerations of alloptical A/D conversion:nonlinear fiber optic Sagnac loop interometer based optical quantizing andcoding.IEEE, J.lightwave technology, 2006,24 (7): 2618-2627), utilize the cross-phase modulation of 1/2nd beam splitting Sagnac interferometers to realize Gray code output, they obtain the experimental system of 3bitsADC.

We had applied for Chinese invention patent " all-light analog-digital converter (200710049158.8) " in 2007, the symmetrical Sagnac interferometer mode of N 1 * 2 coupling mechanism beam splitting input array of employing quantizes and encodes, realize N position all-light analog-digital converter, but the peak power of control light (simulated light) pulse does not reach best utilization factor.

Summary of the invention

The object of the invention provides the parallel quantization coding method of a kind of novel all-light analog-digital converter 2AMZSX, promptly adopt N the asymmetric mach-Ceng Deer interferometer and the line output of N-1 1 * 2 coupling mechanism serial connection beam splitting input array, based on parallel quantization encoding, make full use of the simulated light pulse peak power and realize N position all-light analog-digital converter from phase modulation (PM) and cross-phase modulation principle.

Purpose of the present invention can realize by following measure:

The present invention relates to the parallel quantization coding method of a kind of all-light analog-digital converter 2ASSX, design N position all-light analog-digital converter: stable detecting optical pulses and control light pulse (simulated light) are through wavelength division multiplexer or polarizing coupler [1] input beam-splitting coupler array [2], coupler array [2] is formed by N-1 1 * 2 coupling mechanism serial connection, wherein delivery outlet of each 1 * 2 coupling mechanism connects an asymmetric mach-Ceng Deer interferometer [3], and another delivery outlet connects next 1 * 2 coupling mechanism; Pass filter is set the straight-through equipped at outlet port of each asymmetric mach-Ceng Deer interferometer [3] or analyzer [4] only allows detection light to pass through.Above structure in conjunction with suitable coupler array [2] beam splitting when each asymmetric mach-Ceng Deer interferometer [3] first coupling mechanism splitting ratios make and survey light and line output Gray code (as shown in Figure 1).

Advantageously when surveying light and control light and be different wave length, in each asymmetric mach-Ceng Deer interferometer [3] Polarization Controller [5] is set, adjusts that to survey polarization state of light in the arm consistent with the control polarization state of light as far as possible.

Advantageously improve the contrast of surveying the output of light Gray code, pass filter or analyzer [4] are connected in series light blanking rejector [6] afterwards, and light blanking rejector is by constituting from phase modulation (PM) Sagnac interferometer.Advantageously reduce light blanking rejector number, fibre delay line is set earlier makes detection light import N * 1 coupling mechanism [7] in regular turn, after the serial output light blanking rejector (as shown in Figure 2) is set again.

The phase shift that produces Gray code is not only relevant with the time, and its shape also obviously is subjected to the influence of group velocity mismatch, when zero-dispersion wavelength of fiber is between control optical wavelength and detection optical wavelength, two ripples have same group velocity, so just can solve pulse walks from this difficult problem, when two ripples not exclusively were symmetrical in zero-dispersion wavelength, control light pulsewidth can reduce the influence of walking from phenomenon less times greater than surveying the light pulsewidth.The best solution of the problems referred to above is to utilize wavelength identical and control and detecting optical pulses cross polarization are realized, at this moment because polarization mode dispersion, still there is the group velocity mismatch problems, but it is quite little, and fast, the slow axis that alternately change polarization maintaining optical fibre in a periodic manner constitute Mach-Zehnder interferometer brachium and have more advantage, such as constituted the arm that L grows with the such part of M section.The control of cross polarization and detecting optical pulses are injected in the arm and with orphan's form and transmit.Gating pulse is along fast axle polarization and through an initial delay, and it will catch up with and surpass direct impulse at first section like this.And at second section because fast and slow axis is inverted, direct impulse transmission is faster and catch up with gating pulse.All repeat this process in each part, result two orphans will be through repeatedly collision in arm, and XPM causes phase shift and enlarges markedly (as shown in Figure 3).

The present invention is that the principle of optical fiber explanation said structure is as follows with the light propagation medium:

Wavelength X ₁, firm power P ₀Detecting optical pulses and wavelength X ₂, peak power P (t) ∈ [P _a, P _b] the control light pulse inject synchronously as shown in Figure 1 structure through wavelength division multiplexer [1], the splitting ratio of 1 * 2 coupling mechanism is followed successively by η in the coupler array [2] _i(i=1,2 ..., N-1), the one 2 * 2 coupling mechanism splitting ratio of N asymmetric mach-Ceng Deer interferometer is ρ _i(i=1,2 ..., N), the second coupling mechanism splitting ratio is 1-ρ _i(i=1,2 ..., N), Mach-Zehnder interferometer two arm effective lengths are respectively L ₁, L ₂, | L ₁-L ₂|＜survey the light coherent length, two arm transmissions are respectively β ₁, β ₂, two arm nonlinear fiber coefficients are respectively γ ₁, γ ₂Ignore fibre loss, the pass filter of Mach-Zehnder interferometer (BPF) [4] is only permitted λ ₁Pulse is passed through, and λ only is discussed below ₁Transport function, i Mach-Zehnder interferometer straight-through port λ ₁The transport function of ripple is:

P _{i_out}＝2δ _iρ _i(1-ρ _i)P ₀{1-cos(φ _l+φ _nl)} (1)

Here linear phase shift and nonlinear phase shift are respectively

${\mathrm{\&phi;}}_l={\mathrm{\&beta;}}_1{L}_1-{\mathrm{\&beta;}}_2{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A20081004460400071.png,A20081004460400073.png"\; state="\{\{state\}\}">L</figure-callout>}}_2,{\mathrm{\&phi;}}_{\mathrm{nl}}={\mathrm{\&delta;}}_i\left\{P_0\right[{\mathrm{\&rho;}}_i{\mathrm{\&gamma;}}_1{L}_1-(1-{\mathrm{\&rho;}}_i){\mathrm{\&gamma;}}_2{L}_2]+2{\mathrm{\&gamma;}}_1\underset{0}{\overset{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A20081004460400071.png,A20081004460400072.png"\; state="\{\{state\}\}">L</figure-callout>}}_1}{\&Integral;}}{\mathrm{\&rho;}}_{i}P(T-d_{w}z)\mathrm{dz}-2{\mathrm{\&gamma;}}_2\underset{0}{\overset{L_2}{\&Integral;}}(1-{\mathrm{\&rho;}}_i)P(T-d_{w}z)\mathrm{dz}\}$

${\mathrm{\&delta;}}_i=\left\{\begin{array}{cc}1-{\mathrm{\&eta;}}_1& i=1\\ {\mathrm{\&eta;}}_1{\mathrm{\&eta;}}_2...{\mathrm{\&eta;}}_{i-1}(1-{\mathrm{\&eta;}}_i)& i=\mathrm{2,3},...,N-1,\\ {\mathrm{\&eta;}}_1{\mathrm{\&eta;}}_2...{\mathrm{\&eta;}}_{N-1}{\mathrm{\&eta;}}_N& i=N\end{array}\right.$ T＝t-z/v _gs， $d_w=v_{\mathrm{gp}}^{-1}-v_{\mathrm{gs}}^{-1},$ v _Gp, v _GsBe respectively control light and the group velocity of surveying light.Can be successful in order to encode, need β ₁=β ₂, L ₁=L ₂=L, γ ₁=γ ₂=γ, need the identical optical fiber of Mach-Zehnder interferometer two arms and isometric in other words, advantageously adopt twin-core fiber, fluctuate in time domain, the active stationary mode of phase controller is set on Mach-Zehnder interferometer one arm for fear of light detecting signal.Formula (1) abbreviation is

$P_{i\_\mathrm{out}}=2{\mathrm{\&delta;}}_i{\mathrm{\&rho;}}_i(1-{\mathrm{\&rho;}}_i)P_0\{1-\cos \left(2{\mathrm{\&delta;}}_i(1-2{\mathrm{\&rho;}}_i)\mathrm{\&gamma;}(0.5P_{0}L+\underset{0}{\overset{L}{\&Integral;}}P(T-d_{w}z)\mathrm{dz})\right)\}---\left(2\right)$

Suppose i=2,3... is during N-1

${\mathrm{\&rho;}}_1(1-{\mathrm{\&rho;}}_1)(1-{\mathrm{\&eta;}}_1)={\mathrm{\&rho;}}_i(1-{\mathrm{\&rho;}}_i)\underset{m=1}{\overset{i-1}{\mathrm{\&Pi;}}}{\mathrm{\&eta;}}_m(1-{\mathrm{\&eta;}}_i)={\mathrm{\&rho;}}_N(1-{\mathrm{\&rho;}}_N)\underset{m=1}{\overset{N}{\mathrm{\&Pi;}}}{\mathrm{\&eta;}}_m=A---\left(3\right)$

The supposition of formula (3) makes formula (2) have the standard of quantification.Work as T _{I_out}〉=2AP ₀The time, regard the light pulse of " 1 " as, work as T _{I_out}＜2AP ₀The time, regard the light pulse of " 0 " as.

$(1-2{\mathrm{\&rho;}}_1)(1-{\mathrm{\&eta;}}_1)=2^{i-1}(1-2{\mathrm{\&rho;}}_i)\underset{m=1}{\overset{i-1}{\mathrm{\&Pi;}}}{\mathrm{\&eta;}}_m(1-{\mathrm{\&eta;}}_i)=2^{N-1}(1-2{\mathrm{\&rho;}}_N)\underset{m=1}{\overset{N}{\mathrm{\&Pi;}}}{\mathrm{\&eta;}}_m={\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="A20081004460400071.png,A20081004460400072.png"\; state="\{\{state\}\}">B</figure-callout>}}_1$

Or $(1-2{\mathrm{\&rho;}}_1)(1-{\mathrm{\&eta;}}_1)=2^{1-i}(1-2{\mathrm{\&rho;}}_i)\underset{m=1}{\overset{i-1}{\mathrm{\&Pi;}}}{\mathrm{\&eta;}}_m(1-{\mathrm{\&eta;}}_i)=2^{1-N}(1-2{\mathrm{\&rho;}}_N)\underset{m=1}{\overset{N}{\mathrm{\&Pi;}}}{\mathrm{\&eta;}}_m=B_2---\left(4\right)$

The supposition of formula (4) makes formula (2) have the parallel output form of Gray code.

Parameter is set ${\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="A20081004460400071.png,A20081004460400072.png"\; state="\{\{state\}\}">B</figure-callout>}}_1\mathrm{\&gamma;}(\frac{1}{2}{P}_{0}L+\underset{0}{\overset{L}{\&Integral;}}{P}_b(T-d_{w}z)\mathrm{dz})=2^{N-2}\mathrm{\&pi;}---\left(5\right)$

Or ${\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="A20081004460400071.png,A20081004460400073.png"\; state="\{\{state\}\}">B</figure-callout>}}_2\mathrm{\&gamma;}(\frac{1}{2}{P}_{0}L+\underset{0}{\overset{L}{\&Integral;}}{P}_b(T-d_{w}z)\mathrm{dz})=\frac{\mathrm{\&pi;}}{2}---\left(6\right)$

Set up.The first corresponding Mach-Zehnder interferometer of formula (5) is exported the lowest order all-light analog-digital converter so, the light pulse Gray code of N Mach-Zehnder interferometer output most significant digit all-light analog-digital converter, the first Mach-Zehnder interferometer output most significant digit all-light analog-digital converter that formula (6) is corresponding, the light pulse Gray code of N Mach-Zehnder interferometer output lowest order all-light analog-digital converter.Formula (2) illustrates that not having control light time detection light all outputs to cross-port, and when the nonlinear optical fiber that adopts medium coefficient, control light is preferably quasi-continuous light, and control light is preferably continuous light when adopting highly nonlinear optical fiber.

Advantage of the present invention:

1. the parallel quantification of all-light analog-digital converter, coding method are based on optical fiber, and the nonlinear response of optical fiber almost is instantaneous (less than 10fs), therefore the speed of analog to digital converter surpasses THz in theory, and other integrated optical waveguides cause controlling light and also are in the test exploratory stage to surveying light generation big phase shift like this.

2. the control light pulse of the parallel quantification of all-light analog-digital converter, coding method and the shared coupler array of detecting optical pulses have been stablized the synchronism of light pulse, need not to be provided with the fibre delay line in the input array.

3. relative phase shift difference and constant amplitude output power curve are determined by input array and the Mach-Zehnder interferometer first coupling mechanism splitting ratio, have determined simultaneously to quantize and coding; Avoid asymmetricly being provided with in the arm attenuator or amplifier, also do not need isolator simultaneously, simplified the all-light analog-digital converter structure.

4. based on highly nonlinear optical fiber, control light can be continuous light, present invention includes sampling section like this.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a serial export structure synoptic diagram of the present invention;

Fig. 3 is a cross polarization input structure synoptic diagram of the present invention;

Fig. 4 is one 3 all-light analog-digital converter example structure synoptic diagram;

Fig. 5 is one 3 all-light analog-digital converter emulation testing data and curves synoptic diagram.

Number in the figure is described as follows:

1-wavelength division multiplexer or polarizing coupler 2-coupler array 3-asymmetric mach-Ceng Deer interferometer 4-pass filter or analyzer 5-Polarization Controller 6-light blanking rejector 7-N * 1 coupling mechanism 8-fast and slow axis joint 9-fiber laser 10-mode-locked laser 11-light power meter

Only marked first Mach-Zehnder interferometric device or element among the figure, what use in all the other Mach-Zehnder interferometers is identical device or element, omits mark.

Concrete embodiment

For the purpose of general the present invention, this paper has described some aspect of the present invention, advantage and novel feature.Should be appreciated that, need not realize all these advantages by any one specific embodiment according to the present invention.Therefore, the invention is not restricted to disclosed any specific embodiment.

With reference to the example structure synoptic diagram of Fig. 4 for 3 all-light analog-digital converters of the present invention.High non-linearity dispersion shifted optical fiber γ=12W ^-1Km ^-1Control the only stabilized lasers of fiber laser emission, maximum peak power P _b(t)=and 10W, wavelength X ₁=1560nm.Detecting optical pulses λ ₂=1552nm, T _FWHMThe mode-locked laser of=2ps, 10GHz/s is launched does not have the hyperbolic secant pulse of warbling, pulsewidth T ₀=T _FWHM/ 1.76=1.136ps, average power P ₀=2mW.Control light incides in the device of the present invention through adjustable attenuator (VOA), establishes different class and measures, and the phase shift of this situation is

φ _i≈2 ^2-iB ₁γ[0.5P ₀+P(t)]L(i＝1，2，3)

The splitting ratio of first 1 * 2 fiber coupler is ≈ 0.467, first Mach-Zehnder interferometer effective rake 122.8m, the first coupling mechanism splitting ratio 0.1; The splitting ratio of second 1 * 2 fiber coupler is 0.294, the second Mach-Zehnder interferometer of ≈ effective rake 122m, the first coupling mechanism splitting ratio ≈ 0.1767; The 3rd Mach-Zehnder interferometer effective rake 122m, the first coupling mechanism splitting ratio ≈ 0.1118, B=0.4264.

The maximum phase shift of these three delivery outlets is respectively: φ _{1_max}≈ 4 π, φ _{2_max}≈ 2 π, φ _{3_max}≈ π.

So the parameter of the present invention that is provided with satisfies the requirement of 3 all-light analog-digital converters, the emulation output signal as shown in Figure 5.

Claims (7)

1. the parallel quantization coding method of N position all-light analog-digital converter 2AMZSX adopts N-1 1 * 2 coupling mechanism to be connected in series N the asymmetric mach-Ceng Deer interferometer and the line output of beam splitting input array, based on constant detection light P ₀, control light P (t) causes straight-through delivery outlet detection of optical power to be:

$P_{i\_\mathrm{out}}=2{\mathrm{\&rho;}}_i(1-{\mathrm{\&rho;}}_i)\underset{m=1}{\overset{i-1}{\mathrm{\&Pi;}}}{\mathrm{\&eta;}}_m(1-{\mathrm{\&eta;}}_i)P_0\{1-\cos \left(2(1-2{\mathrm{\&rho;}}_i)\underset{m=1}{\overset{i-1}{\mathrm{\&Pi;}}}{\mathrm{\&eta;}}_m(1-{\mathrm{\&eta;}}_i)\mathrm{\&gamma;}(0.5P_{0}L+\underset{0}{\overset{L}{\&Integral;}}P(T-d_{w}z)\mathrm{dz})\right)\}$

Quantitative criteria is that braces is outer partly to i=1 in the following formula, 2 ..., N equates; Coding standard be in the following formula cosine independent variable to i=1,2 ..., the adjacent ratio of N is 2 or 0.5.Wherein the splitting ratio of N-1 1 * 2 coupling mechanism is followed successively by η _i, the Mach-Zehnder interferometer first coupling mechanism splitting ratio ρ _i, the second coupling mechanism splitting ratio 1-ρ _i, brachium L, T=t-z/v _Gs, $d_w=v_{\mathrm{gp}}^{-1}-v_{\mathrm{gs}}^{-1},v_{\mathrm{gp}},v_{\mathrm{gs}}$ Be respectively control light and the group velocity of surveying light.

2. by the described method of claim 1, stable detecting optical pulses and control light pulse (simulated light) are through wavelength division multiplexer or polarizing coupler [1] input beam-splitting coupler array [2], coupler array [2] is formed by N-1 1 * 2 coupling mechanism serial connection, wherein delivery outlet of each 1 * 2 coupling mechanism connects an asymmetric mach-Ceng Deer interferometer [3], and another delivery outlet connects next 1 * 2 coupling mechanism; Pass filter is set the straight-through equipped at outlet port of each asymmetric mach-Ceng Deer interferometer [3] or analyzer [4] only allows detection light to pass through.Above structure in conjunction with suitable coupler array [2] beam splitting when each asymmetric mach-Ceng Deer interferometer [3] first coupling mechanism splitting ratios make and survey light and line output Gray code.

3. all-light analog-digital converter as claimed in claim 2 is characterized in that: Polarization Controller [5] is set in each Mach-Zehnder interferometer, the active stationary mode of phase controller is set.

4. all-light analog-digital converter as claimed in claim 2 is characterized in that: survey light and have firm power, control light is continuous or discontinuous.

5. the quantification of all-light analog-digital converter as claimed in claim 2, coding method is characterized in that: fibre delay line is set, and light signal is surveyed in serial output.

6. all-light analog-digital converter as claimed in claim 2 is characterized in that: be connected in series light blanking rejector [6] after the pass filter.

7. all-light analog-digital converter as claimed in claim 2 is characterized in that: the optical fiber of use is dispersion shifted optical fiber, and perhaps highly nonlinear optical fiber is perhaps protected bias tyre optical fiber; The integrated optical waveguide line.

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