CN101290455A - All-light analog-digital converter NSX parallel quantitative coding method - Google Patents

Abstract

The invention discloses an NSX parallel quantizing encoding 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 probe light is respectively input into N symmetrical Sagnac interferometers (2) through uniform splitting of a 1xN coupler (1) and then quantitative standards are generated; an input port in a clockwise ring or an anticlockwise ring of any symmetrical Sagnac interferometer is provided with a wavelength division multiplexer or a polarization coupler (3); steering optical (analog optical) pulses are input into each symmetrical Sagnac interferometer through the wavelength division multiplexer or the polarization coupler (3) after splitting of a 1xN coupler (4); an optical fiber microwave circulator or an isolator (5) is arranged on the front of a reflecting port of each symmetrical Sagnac interferometer for preventing the probe light from being affected by back light; and an output port of each symmetrical Sagnac interferometer can be a transmission port and also can be a reflecting port and is provided with a band-pass filter or an analyzer (7) which only allows the probe light to pass. The structure is combined with adequate splitting ratio of the 1xN coupler (4) to realize parallel output of Gray code pulses by the probe light.

Description

All-light analog-digital converter NSX parallel quantitative coding method

Technical field

The present invention relates to the optical information processing technical field, it is particularly related to a kind of all-light analog-digital converter NSX parallel quantitative coding method, promptly adopt other N symmetrical Sagnac interferometer (SagnacI) and the line output of connecing of 1 * N coupling mechanism beam splitting serial connection wavelength division multiplexer, realize the parallel quantization coding method of N position all-light analog-digital converter based on 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 technological means 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 3 bits 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 step 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 the non-linear ring of light mirror scheme of coding again, and have provided the experimental result of the full light ADC of 2 bits.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 3 bits Gray code conversion.They had proposed to utilize the optical delay line coding to carry out the full light ADC of corresponding 3 bits 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 a kind of novel all-light analog-digital converter NSX parallel quantitative coding method, promptly adopt other N symmetrical Sagnac interferometer and the line output of connecing of 1 * N coupling mechanism beam splitting serial connection wavelength division multiplexer, realize parallel quantification of N position all-light analog-digital converter and coding method based on the cross-phase modulation principle, made full use of the simulated light pulse peak power.

Purpose of the present invention can realize by following measure:

The present invention relates to a kind of parallel quantification, coding method of all-light analog-digital converter, design N position all-light analog-digital converter: stable detection light is imported N symmetrical Sagnac interferometer [2] by the average beam splitting of 1 * N coupling mechanism [1] respectively through optical fiber, produces quantitative criteria.The input port is provided with a wavelength division multiplexer or polarizing coupler [3] in the clockwise or inverse time needle ring of any symmetrical Sagnac interferometer, the pulse of control light (simulated light) is imported in each symmetrical Sagnac interferometer through wavelength division multiplexer or polarizing coupler [3] by 1 * N coupling mechanism [4] beam splitting, control light is in each symmetrical Sagnac interferometer during only along the transmission of a certain direction, can restraint certain a branch of generation nonlinear phase shift of surveying in the light to two of reverse transfer, and another Shu Guang is also unaffected.Fiber optical circulator or isolator [5] are set before the reflex port of each symmetrical Sagnac interferometer stops the backlight influence to survey light.Each symmetrical Sagnac interferometer delivery outlet can be the transmission mouth, also can be reflex port, and pass filter is set delivery outlet or analyzer [7] only allows detection light to pass through.Above structure makes in conjunction with suitable 1 * N coupling mechanism [4] splitting ratio and surveys light generation and line output Gray code pulse (as shown in Figure 1).

Advantageously in each symmetrical Sagnac interferometer Polarization Controller [6] is set, the polarization state when adjusting the two-beam pulse interference of transmitting in the other direction.Advantageously on the optical fiber before each wavelength division multiplexer Polarization Controller [7] is set, it is consistent with overlapping detection polarization state as far as possible to adjust the control polarization state of light.

Advantageously improve the contrast of surveying the output of light Gray radix-minus-one complement, pass filter [6] is connected in series light blanking rejector [8] 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 [9] in regular turn, after the serial output light blanking rejector (as shown in Figure 2) is set again.

The phase shift that produces the light pulse 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 Sagnac interferometer ring length and have more advantage, such as constituted the ring that L grows with the such part of M section.The control of cross polarization and detecting optical pulses are injected in the ring 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 ring, and XPM causes phase shift and enlarges markedly (as shown in Figure 3).

Principle of the present invention is as follows:

Wavelength X ₁, firm power P ₀Detection light and wavelength X ₂, peak power P (t) ∈ [P _a, P _b] the synchronous structure of injecting as shown in Figure 1 of control light pulse, 1 * N coupling mechanism [4] is to λ ₂Splitting ratio is η _i(i=1,2 ..., N), Sagnac interferometer non-linearity coefficient gamma, the effectively long L of ring.The pass filter of Sagnac interferometer (BPF) is only permitted λ ₁Pulse is passed through, and λ only is discussed below ₁Transport function, i Sagnac interferometer λ ₁Pulse transmission oral instructions delivery function is:

$P_{i\_\mathrm{out}}=\frac{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="A20081004460300082.png,A20081004460300091.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}{2N}[1-\cos \left({2\mathrm{\&eta;}}_i\mathrm{\&gamma;}(\underset{0}{\overset{L}{\&Integral;}}P(T-d_{w}z)\mathrm{dz}-\underset{0}{\overset{L}{\&Integral;}}\stackrel{\&OverBar;}{P(T-d_{w}z)}\mathrm{dz})\right)]---\left(1\right)$

Here T=t-z/v _Gs, $d_w=v_{\mathrm{gp}}^{-1}-v_{\mathrm{gs}}^{-1},$ v _Gp, v _GsBe respectively control light pulse and the group velocity of surveying light.

By the phase shift of other thousands of control light pulse cross-phase modulation, P (t) is the average power of control light when propagating for reverse detection light.

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

η _i=2 η _I+1Or η _i=0.5 η _I+1(2)

The supposition of formula (2) has the Gray code output form.When $T_{\mathrm{io}}\&GreaterEqual;\frac{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="A20081004460300082.png,A20081004460300091.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}{2N}$ The time, regard the light pulse of " 1 " as, when $T_{\mathrm{io}}<\frac{{\mathrm{<figure-callout\; id="0"\; label="P"\; filenames="A20081004460300082.png,A20081004460300091.png"\; state="\{\{state\}\}">P</figure-callout>}}_0}{2N}$ The time, regard the light pulse of " 0 " as.

When $\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&eta;}}_i=1$ The time, control light pulse power obtains optimum utilization, and formula (2) is found the solution:

${\mathrm{\&eta;}}_i=\frac{2^{i-1}}{2^N-1}$ Or ${\mathrm{\&eta;}}_i=\frac{2^{N-i}}{2^N-1}$ i＝1，2，...，N (3)

Parameter is set

$\mathrm{\&gamma;}\underset{0}{\overset{L}{\&Integral;}}{P}_b(T-d_{w}z)\mathrm{dz}-\mathrm{\&gamma;}\underset{0}{\overset{L}{\&Integral;}}\stackrel{\&OverBar;}{P(T-d_{w}z)}\mathrm{dz}=\frac{2^N-1}{2}\mathrm{\&pi;}---\left(4\right)$

Set up.Formula (4) illustrates the high-order analog to digital converter of design, and advantageously under the not high situation of incident control light pulse peak power, adopting highly nonlinear optical fiber is better approach.When controlling only continuous laser, the modulated average XPM of reverse detection light produces that phase shift is serious offsets positive phase shift, and therefore the dutycycle of control light pulse should be greater than 90% usually.When surveying only continuous laser, uncontrolled pulse, the Sagnac interferometer is equivalent to an ideal mirror, continuous light can be reflected back; Each gating pulse applies phase shift and guides continuous light into output terminal to continuous light by cross-phase modulation (XPM), produce the pulse train that wavelength equals the continuous wave wavelength, from cost performance, survey the preferred continuous light of light, at this moment can avoid because the generation from phenomenon is walked in the pulse that the wavelength difference between control light pulse and the detecting optical pulses causes, but this situation only in the Sagnac interferometer control light pulse number seldom just effective.

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 power optimum utilization of the parallel quantification of all-light analog-digital converter, coding method can realize the high bit all-light analog-digital converter.Do not have and survey the interference of light, can realize the whole full optical mode number conversion of figure place from phase modulation (PM).Adopt highly nonlinear optical fiber, Sagnac interferometer ring is long shorter, surveys the preferred continuous laser of light.

3. know that by formula (4) the present invention only needs minimum simulated light power just can obtain the high bit all-light analog-digital converter, the control gloss is imported its more compact structure with the beam splitting of 1 * N coupling mechanism.

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 the structural representation of cross polarization input;

Fig. 4 is the structural representation of one 3 light ADC embodiment;

Fig. 5 is the light modulated power of 3 light ADC and quantification, coding synoptic diagram;

Fig. 6 is the emulation experiment output map of embodiment.

Number in the figure is described as follows:

1,4-1 * N coupling mechanism 2-Sagnac interferometer 3-wavelength division multiplexer 5-circulator or isolator

6-Polarization Controller 7-pass filter 8-light blanking rejector 9-N * 1 coupling mechanism

10-fiber laser 11-mode-locked laser 12-light power meter

Only marked the device or the element of first Sagnac interferometer among the figure, what use in all the other Sagnac 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, dutycycle B=(100-1.136)/100=0.98864, 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≈2ε _iγBP(t)L i＝1，2，3 (7)

The splitting ratio of 1 * 3 fiber coupler is ≈ 4/7,2/7,1/7, first Sagnac interferometer effectively encircles long 93m, second Sagnac interferometer effectively encircles long 91m, the 3rd Sagnac interferometer effectively encircles long 94m, and three parallel delivery outlets are provided with fibre delay line, and to compensate these three rings inequality long, and the maximum phase shift of these three delivery outlets is respectively:

φ _{1_max}≈4π，φ _{2_max}≈2π，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 6.

Claims (7)

1. N position all-light analog-digital converter NSX parallel quantitative coding method is based on constant detection of optical power P ₀, adopt other N symmetrical Sagnac interferometer and the line output of connecing of 1 * N coupling mechanism beam splitting serial connection wavelength division multiplexer, quantize and coding the quantization encoding standard based on cross-phase modulation principle realization N position all-light analog-digital converter is parallel:

${\mathrm{\&eta;}}_i=\frac{2^{i-1}}{2^N-1}$ Or ${\mathrm{\&eta;}}_i=\frac{2^{N-i}}{2^N-1}$ i＝1，2，...，N

Wherein 1 * N coupling mechanism is η to the simulated light splitting ratio _i

2. by the described method of claim 1, stable detection light is imported N symmetrical Sagnac interferometer [2] by the average beam splitting of 1 * N coupling mechanism [1] respectively through optical fiber, the generation quantitative criteria.The input port is provided with a wavelength division multiplexer or polarizing coupler [3] in the clockwise or inverse time needle ring of any symmetrical Sagnac interferometer, the pulse of control light (simulated light) is imported in each symmetrical Sagnac interferometer through wavelength division multiplexer or polarizing coupler [3] by 1 * N coupling mechanism [4] beam splitting, control light is in each symmetrical Sagnac interferometer during only along the transmission of a certain direction, can restraint certain a branch of generation nonlinear phase shift of surveying in the light to two of reverse transfer, and another Shu Guang is also unaffected.Fiber optical circulator or isolator [5] are set before the reflex port of each symmetrical Sagnac interferometer stops the backlight influence to survey light.Each symmetrical Sagnac interferometer delivery outlet can be the transmission mouth, also can be reflex port, and pass filter is set delivery outlet or analyzer [6] only allows detection light to pass through.Above structure makes in conjunction with suitable 1 * N coupling mechanism [4] splitting ratio and surveys light generation and the pulse of line output Gray code.

3. all-light analog-digital converter as claimed in claim 2 is characterized in that: Polarization Controller [6] is set in each Sagnac interferometer.

4. all-light analog-digital converter as claimed in claim 2 is characterized in that: survey light and have firm power, the control light pulse has big space rate.

5. all-light analog-digital converter as claimed in claim 2 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 [7] 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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