CN105651399A - Time domain phase recovery all-fiber laser pulse weak phase measuring device and method - Google Patents

Abstract

The invention provides a time domain phase recovery all-fiber laser pulse weak phase measuring device and method. The device comprises a fiber splitter arranged long the laser pulse input direction. The fiber splitter divides laser pulses to be measured into a high beam of light and a weak beam of light. An adjustable optical fiber delayer, a high speed optical fiber phase modulator, a dispersion optical fiber and an oscilloscope are successively arranged long the direction of the high light beam. A high speed PIN photoelectric tube, an arbitrary waveform generator and an electric signal amplifier are successively arranged long the direction of the weak light beam. An output end of the electric signal amplifier is connected with a modulation input end of the high speed optical fiber phase modulator. According to the invention, the all-fiber structure is utilized to carry out phase modulation and dispersion transmission on the laser pulses, the structure is compact, simple and flexible, and the measuring method is different from other laser pulse phase measuring modes; in addition, by adopting the measuring device and method, the weak phase picoseconds or nanosecond laser pulses can be measured, and the measuring device and method are applicable to the conditions of a high repetition frequency and a low repetition frequency.

Description

The time domain phase recovery weak phase measurement device of full optical fiber laser pulse and measuring method

Technical field

The present invention relates to weak phase place laser pulse, particularly a kind of time domain phase recovery weak phase measurement device of full optical fiber laser pulse and measuring method. The present invention adopts fibre-optic waveguide phase-modulator that laser pulse is carried out phase-modulation, obtains waveform and the phase place of laser pulse again through the method for time domain phase recovery. The present invention is applicable to have weak phase place, the weak psec warbled or nanosecond laser pulses, it is possible to be operated in high repetition frequency or low-repetition-frequency situation. This device adopts the structure of all-fiber can increase device stability and compactedness, thus obtaining reliable and stable laser pulse PHASE DISTRIBUTION.

Background technology

Since First laser instrument manufacture so far, the application of laser and laser instrument penetrated into gradually society all trades and professions in, especially for precision machining industry, the application of laser is greatly improved machining accuracy. Wherein high-energy nanosecond or Ps Laser Pulse are widely used at multiple fields such as laser physics research (inertial confinement fusion), laser precision machining, cut, laser radar, Ultrafast spectrum, medical science, high-energy physics. Such as, high-energy nanosecond laser pulses can apply to inertial confinement fusion so that pellet reaches nuclear fusion condition, discharges substantial amounts of energy, and inertial confinement fusion is expected to realize controllable nuclear fusion in future, fundamentally solves energy problem. High-energy picopulse can apply to Laser Processing and Laser Surface Treatment, fast laser pulse and material mechanism substantially increase, without heat deposition and contactless characteristic, processing characteristics such as processing the controllability of pattern, machining accuracy and surface smoothness, the processing cutting of the multiple materials such as metal, crystal, gem, glass, high molecular polymer even explosive shows excellent characteristic, presents wide application prospect in Precision Machining fields such as auto industry, medical apparatus and instruments, industrial safeties. Current high-energy ps pulsed laser and ns pulsed laser and picosecond pulse laser all adopt the structure of king oiscillator+multistage amplifier.But in amplification process, due to the existence of nonlinear effect such as Self-phase modulation, laser pulse can accumulation nonlinear phase shift, produce impact thus rear class is amplified. But unlike that the situation of ultrashort pulse, the nonlinear phase shift that nanosecond or picopulse are accumulated in transmitting procedure is typically small, from spectrally, spectrum widening is inconspicuous, but these little nonlinear phase shifts can produce large effect in follow-up amplification process. Additionally, due to there is the compensation way of some nonlinear phase shifts, for instance the precompensation method of Direct Phase modulation, it is possible to when its nonlinear phase shift size known, utilize precompensation means that nonlinear phase shift is compensated. This is accomplished by the phase place of the laser pulse that these have weak phase place is accurately measured. The mode that current burst length phase place (spectrum phase measurement) is measured has a variety of, the mode such as including FROG (frequency resolution optical switch), SPIDER (self-reference spectral interference) and time auto-correlation, but these modes are all based on the principle of auto-correlation/cross-correlation, carry out related operation by pulse itself or carry out related operation with reference pulse. It is that non-linear process carries out related operation that FROG utilizes, and SPIDER scheduling algorithm is to carry out related operation by the mode interfered. But the structure of these modes is general all more complicated, the intensity of measured pulse be there are certain requirements (FROG) by related operation simultaneously, or resolution relatively low (SPIDER etc.), and these methods for weak phase place nanosecond or Ps Laser Pulse in the case of, often helpless.

Therefore the present invention proposes to utilize the method for time domain phase recovery to realize the high-precision phase measurement for weak phase place nanosecond or Ps Laser Pulse in conjunction with the device that Direct Phase is modulated. This method is suitable for measuring the narrow spectral laser pulse with weak PHASE DISTRIBUTION, and the data calculation process of Simultaneous Iteration process can realize high-precision phase measurement.

Summary of the invention

It is an object of the invention to the shortcoming overcoming measuring method time phase of above-mentioned existing laser pulse can not measure weak phase place nanosecond or Ps Laser Pulse, a kind of time domain phase recovery weak phase measurement device of full optical fiber laser pulse and measuring method are proposed, the method adopts the mode of time domain phase place Iterative restoration, utilize Direct Phase modulating device that laser pulse is carried out phase-modulation, calculated the waveform and the PHASE DISTRIBUTION that obtain primary laser pulse by the time waveform of the laser pulse through phase-modulation after dispersive medium as known conditions. The structure adopting all-fiber can improve device motility and compactedness, it is achieved the high-acruracy survey that time phase of weak phase place laser pulse is distributed.

The technical solution of the present invention is as follows:

A kind of time domain phase recovery weak phase measurement device of full optical fiber laser pulse, it is characterized in that its composition includes: be fiber optic splitter along testing laser pulse input direction, testing laser pulse is divided into by force by this fiber optic splitter, weak two-beam, it is adjustable optic fibre chronotron successively along strong beam direction, high speed fibre phase-modulator, dispersive optical fiber and oscillograph, it is high speed PIN photocell successively along weak beam direction, AWG (Arbitrary Waveform Generator), electric signal amplifier, the modulation input of the high speed fibre phase-modulator described in output termination of this electric signal amplifier, the delay adjustment precision of described adjustable optic fibre chronotron is 1ps, the length of described dispersive optical fiber meets the following conditions:

${\mathrm{\β}}_{2}L>>\frac{4{\mathrm{\π}}^2}{{\left(\mathrm{\Δ}\mathrm{\ν}\right)}^2}---\left(1\right)$

Wherein, ��₂For the 2nd order chromatic dispersion of described dispersive optical fiber, L is the length of dispersive optical fiber, and �� �� is the spectral width of testing laser pulse after the phase-modulation of high speed fibre phase-modulator;

The modulation signal that described AWG (Arbitrary Waveform Generator) produces is single order Gaussian pulse, and the pulse width �� of this single order Gaussian pulse to meet �ӡܦ� T, �� T be the pulsewidth of testing laser pulse.

Utilize the above-mentioned time domain phase recovery weak phase measurement device of the full optical fiber laser pulse measuring method to the weak phase place of laser pulse to be measured, it is characterised in that the method comprises the following steps:

1. t is set₀Amplify, through described electric signal amplifier, the initial relative time delay that the center of modulation signal of output reaches the moment of described high speed fibre phase-modulator and reaches the moment of described high speed fibre phase-modulator relative to testing laser pulse for what described AWG (Arbitrary Waveform Generator) produced, the time delay of the delay time every time regulating described adjustable optic fibre chronotron increases to �� t, often adjust a time delay, one testing laser pulse strength I of described oscillograph recording_m, obtain I successively₁��I₂������I_m����I_2n+1, the time delay that adjustable optic fibre chronotron described after regulating for the m time produces is t₀+ m �� t, after regulating for the m time, testing laser pulse is collected this delay time (t by described oscillograph after described high speed fibre phase-modulator and dispersive optical fiber₀Laser pulse intensity I under+m �� t)_mFor:

I_m=| A_m|²(2)

Wherein, m=1,2,3 ... 2n+1, n are any positive integer and meet 2n+1 >=�� T/ �� t, A_mFor testing laser pulse light field complex amplitude after dispersive optical fiber (7);

2. utilize time domain Phase Retrieve Algorithm to described laser pulse intensity I_mCarry out data process, calculate the PHASE DISTRIBUTION of testing laser pulse, specifically comprise the following steps that

1) data initialization is arranged: i is current iteration number of times, and m is the sequence number of the m time adjustment adjustable optic fibre chronotron, and the maximum making i=0, m is 2n+1; N_0,2n+1The COMPLEX AMPLITUDE of t testing laser pulse that () generates for computer random, �� is minimum of computation error, and K is maximum iteration time;

2) i=i+1 is made, m=0, the initial testing laser pulsed reset amplitude N that current iteration calculates_i,mT light field complex amplitude that () calculates for m=2n+1 correspondence in i-1 iteration, i.e. N_i,m(t)=N_i-1,2n+1(t);

3) m=m+1 is made, currently to testing laser pulsed reset amplitude E initial in the iterative computation of m_i,mT () is the light field complex amplitude calculated corresponding in m-1 iteration, i.e. E_i,m(t)=N_i,m-1(t);

4) the light field complex amplitude after high speed fibre phase-modulator it is calculated as follows

$P_{i,m}^{in}\left(t\right)=E_{i,m}\left(t\right)\exp \left(j\mathrm{\π}\frac{V}{V_{\mathrm{\π}}}B\right(t-m\mathrm{\Δ}t\left)\right)---\left(3\right)$

Wherein, V is the voltage magnitude of modulation signal, V_��For the half-wave voltage of high speed fibre phase-modulator,

B (t-m �� t) is the modulation signal of the time delays with m �� t;

5) it is calculated as follows againLight field complex amplitude A after dispersive optical fiber_i,m(t) and light field PHASE DISTRIBUTIONIt is respectively as follows:

Wherein: F is Fourier transformation, F^-1For inverse Fourier transform, �� is light field angular frequency;

6) the laser pulse intensity I through high speed fibre phase-modulator and dispersive optical fiber that oscillograph records for the m time is utilized_m, replace the calculated light field complex amplitude of (4) formula, and retain phase invariant, the complex amplitude after being updated

7) by described light field complex amplitudeReverse propagation is to the input of dispersive optical fiber, the incident field complex amplitude after being updated

$P_{i,m}^{out}\left(t\right)=F^{-1}\left\{F\right\{A_{i,m}^o\left\}\exp \right(-j\frac{{\mathrm{\β}}_{2}L}{2}{\mathrm{\ω}}^2\left)\right\}---\left(6\right)$

8) the complex amplitude N of high speed fibre phase-modulator input testing laser pulse is calculated according to following formula_i,m(t):

$\begin{array}{c}{N}_{i,m}\left(t\right)=E_{i,m}\left(t\right)+\frac{\left|\mathrm{\φ}\left(t-m\mathrm{\Δ}t\right)\right|}{{\left|\mathrm{\φ}\left(t-m\mathrm{\Δ}t\right)\right|}_{\max }}\frac{conj\left(\mathrm{\φ}\left(t-m\mathrm{\Δ}t\right)\right)}{{\left|\mathrm{\φ}\left(t-m\mathrm{\Δ}t\right)\right|}^2+\mathrm{\α}}\left(P_{i,m}^{out}\left(t\right)-P_{i,m}^{in}\left(t\right)\right)\\ \mathrm{\φ}\left(t-m\mathrm{\Δ}t\right)=\exp \left(j\mathrm{\π}\frac{V}{V_{\mathrm{\π}}}B\left(t-m\mathrm{\Δ}t\right)\right)\end{array}---\left(7\right)$

Wherein, | �� (t-m �� t) |_maxThe phase-modulation being carried on high speed fibre phase-modulator for modulation signal to produce, conj (*) is function complex conjugate, and �� is for preventing except null divisor;

9) when m < during 2n+1, return step 3); As m=2n+1, the error E rror being calculated as follows the calculating of current ith iteration is:

$Error=\&Integral;dt\underset{m}{\&Sigma;}\frac{\left|\right|A_{i,m}\left(t\right){|}^2-I_m\left(t\right)|}{|I_m\left(t\right){|}_{max}}/(2n+1)---\left(8\right)$

10) if Error<��, then stop iterative computation, carry out next step 11); If Error>=��, and i<K, then return step 2), if i=K, then enter step 12);

11)N_i,2n+1T () is the light field complex amplitude of testing laser pulse, its PHASE DISTRIBUTION is according to light field complex amplitude N_i,2n+1T () utilizes conventional phase unwrapping algorithm to obtain testing laser pulse PHASE DISTRIBUTION in time is N_i,2n+1(t)/|N_i,2n+1(t) |;

12) as i=K, it was shown that the maximum occurrences 2n+1 of current m can not meet the requirement of computational accuracy, then make n=n+1, increase laser pulse intensity I_mMeasurement number, return step 1), proceed calculate.

The invention has the advantages that:

1. apparatus of the present invention adopt the structure of all-fiber, apparatus of the present invention compact conformation, it is simple to adjust.

2. adopt the method recovered time phase, it is possible to the phase place of weak phase place laser pulse is measured.

3. utilize the method that Direct Phase is modulated can control modulation signal flexibly.

4. can be operated in Gao Zhongying and low repetition situation.

Accompanying drawing explanation

Fig. 1 is the structured flowchart of the time domain phase recovery weak phase measurement device of full optical fiber laser pulse of the present invention.

Fig. 2 is restoration methods flow chart time phase of the weak phase place laser pulse of the present invention.

Detailed description of the invention

Below in conjunction with embodiment and accompanying drawing, the present invention will be further described, but should not limit the scope of the invention with this.

First refer to the structured flowchart that Fig. 1, Fig. 1 are the time domain phase recovery weak phase measurement devices of full optical fiber laser pulse of the present invention. as seen from the figure, the composition of the time domain phase recovery weak phase measurement device of full optical fiber laser pulse of the present invention includes: be fiber optic splitter 1 along testing laser pulse In input direction, testing laser pulse In is divided into by force by this fiber optic splitter 1, weak two-beam, it is adjustable optic fibre chronotron 5 successively along strong beam direction, high speed fibre phase-modulator 6, dispersive optical fiber 7 and oscillograph 8, it is high speed PIN photocell 2 successively along weak beam direction, AWG (Arbitrary Waveform Generator) 3, electric signal amplifier 4, the modulation input of the high speed fibre phase-modulator 6 described in output termination of this electric signal amplifier 4, the delay adjustment precision of described adjustable optic fibre chronotron 5 is 1ps, the length of described dispersive optical fiber 7 meets the following conditions:

${\mathrm{\&beta;}}_{2}L>>\frac{4{\mathrm{\&pi;}}^2}{{\left(\mathrm{\&Delta;}\mathrm{\&nu;}\right)}^2}---\left(1\right)$

Wherein, ��₂For the 2nd order chromatic dispersion of dispersive optical fiber 7, L is the length of dispersive optical fiber 7, and �� �� is the spectral width of the testing laser pulse after high speed fibre phase-modulator 6 phase-modulation;

The modulation signal that described AWG (Arbitrary Waveform Generator) 3 produces is single order Gaussian pulse, is somebody's turn to do and the pulse width of single order Gaussian pulse meets �ӡܦ� T, and wherein �� is the pulse width of modulation signal, and �� T is the pulsewidth of testing laser pulse.

It is two parts that incident laser pulse first passes around fiber optic splitter 1 beam splitting, and wherein splitting ratio is 10% and 90%. 10% end laser pulse is converted into the signal of telecommunication triggering signal as AWG (Arbitrary Waveform Generator) 3 through high-speed photodetector PIN pipe 2. The AWG (Arbitrary Waveform Generator) 3 being triggered exports the pulse width electric impulse signal less than or equal to testing laser pulse width, this electric impulse signal after high-gain high-speed electric amplifier 4 amplifies as the modulation signal of fibre optic phase modulator 6. 90% end testing laser pulse then through the effect of optical fiber adjustable light delay 5, changes the relative time time delay between itself and electrical modulation signal.Laser pulse after elapsed time time delay enters fibre optic phase modulator 6, obtains phase-modulation, laser pulse light spectrum generation broadening in time. Laser pulse after phase-modulation then enters the dispersive optical fiber 7 with relatively large dispersion, broadened through the laser pulse of phase-modulation in time, the waveform of laser pulse is detected by oscillograph 8, and its time waveforms stands spectral signature of laser pulse.

The Laser pulse time Wave data collected through apparatus of the present invention oscillograph 8 can utilize time phase restoration methods to obtain the PHASE DISTRIBUTION of laser pulse, time phase restoration methods flow chart referring to Fig. 2, its detailed process is as follows:

Assume t₀Amplify, through described electric signal amplifier 4, the initial relative time delay that the center of modulation signal of output reaches the moment on high speed fibre phase-modulator 6 and reaches the moment of described high speed fibre phase-modulator 6 relative to testing laser pulse for what described AWG (Arbitrary Waveform Generator) 3 produced, the time delay of the delay time every time regulating described adjustable optic fibre chronotron 5 increases to �� t, then the time delay that the m time regulates described adjustable optic fibre chronotron 5 is t₀+ m �� t, the m time testing laser pulse is collected this delay time (t by described oscillograph 8 after described high speed fibre phase-modulator 6 and dispersive optical fiber 7₀Laser pulse intensity I under+m �� t)_mFor:

I_m=| A_m|²(9)

Wherein, m=1,2,3 ... 2n+1, n are any positive integer, A_mFor testing laser pulse light field complex amplitude after dispersive optical fiber 7.

1) first carrying out data initialization, making i is current iteration number of times, and m regulates adjustable optic fibre chronotron 5, i=0, m=2n+1 the m time; Make N_0,2n+1T () is the complex amplitude of the testing laser pulse in current iteration calculating, N_0,2n+1The COMPLEX AMPLITUDE of t testing laser pulse that () is stochastic generation;

2) i=i+1, m=0 are made, initial testing laser pulsed reset amplitude N in current iteration calculating simultaneously_i,mT light field complex amplitude that () calculates for m=2n+1 correspondence in i-1 iteration, i.e. N_i,m(t)=N_i-1,2n+1(t);

3) m=m+1 is made, simultaneously current to testing laser pulsed reset amplitude E initial in the iterative computation of m_i,mT () is the light field complex amplitude calculated corresponding in m-1 iteration, i.e. E_i,m(t)=N_i,m-1(t);

4) the light field complex amplitude after high speed fibre phase-modulator 6 is calculatedFor:

$P_{i,m}^{in}\left(t\right)=E_{i,m}\left(t\right)\exp \left(j\mathrm{\&pi;}\frac{V}{V_{\mathrm{\&pi;}}}B\right(t-m\mathrm{\&Delta;}t\left)\right)---\left(10\right)$

Wherein V is the voltage magnitude of modulation signal, V_��For the half-wave voltage of high speed fibre phase-modulator (6),

B (t-m �� t) is the modulation signal of the time delays with m �� t;

5) calculate againLight field complex amplitude A after dispersive optical fiber 7_i,m(t) and light field PHASE DISTRIBUTIONIt is respectively as follows:

Wherein: F is Fourier transformation, F^-1For inverse Fourier transform, �� is light field angular frequency;

6) the laser pulse intensity I through high speed fibre phase-modulator 6 and dispersive optical fiber 7 obtained is measured according to oscillograph 8_m, replace the calculated light field complex amplitude of (11) formula, and retain phase invariant, the complex amplitude after being updatedIts process is as follows:

7) by the light field complex amplitude after renewalReverse propagation is to the input of dispersive optical fiber 7, the incident field complex amplitude after being updated

$P_{i,m}^{out}\left(t\right)=F^{-1}\left\{F\right\{A_{i,m}^o\left\}\exp \right(-j\frac{{\mathrm{\&beta;}}_{2}L}{2}{\mathrm{\&omega;}}^2\left)\right\}---\left(13\right)$

8) the complex amplitude N of high speed fibre phase-modulator 6 input testing laser pulse is calculated according to following formula_i,m(t):

$\begin{array}{c}{N}_{i,m}\left(t\right)=E_{i,m}\left(t\right)+\frac{\left|\mathrm{\&phi;}\left(t-m\mathrm{\&Delta;}t\right)\right|}{{\left|\mathrm{\&phi;}\left(t-m\mathrm{\&Delta;}t\right)\right|}_{\max }}\frac{conj\left(\mathrm{\&phi;}\left(t-m\mathrm{\&Delta;}t\right)\right)}{{\left|\mathrm{\&phi;}\left(t-m\mathrm{\&Delta;}t\right)\right|}^2+\mathrm{\&alpha;}}\left(P_{i,m}^{out}\left(t\right)-P_{i,m}^{in}\left(t\right)\right)\\ \mathrm{\&phi;}\left(t-m\mathrm{\&Delta;}t\right)=\exp \left(j\mathrm{\&pi;}\frac{V}{V_{\mathrm{\&pi;}}}B\left(t-m\mathrm{\&Delta;}t\right)\right)\end{array}---\left(14\right)$

Wherein: | �� (t-m �� t) |_maxThe phase-modulation being carried on high speed fibre phase-modulator 6 for modulation signal to produce, conj (*) is function complex conjugate, and �� is for preventing except null divisor;

9) when m < during 2n+1, return step 3); Otherwise as m=2n+1, the error E rror calculating the calculating of current ith iteration is:

$Error=\&Integral;dt\underset{m}{\&Sigma;}\frac{\left|\right|A_{i,m}\left(t\right){|}^2-I_m\left(t\right)|}{|I_m\left(t\right){|}_{max}}/(2n+1)---\left(15\right)$

10) if Error<��, then stop iterative computation, carry out next step 11); If otherwise Error>=��, and i<K, then return step 2), wherein �� is minimum of computation error, and K is maximum iteration time; If i=K, then carry out step (12);

11) when iterative computation terminates, the light field complex amplitude of testing laser pulse is N when last iterative computation terminates_i,2n+1T (), its PHASE DISTRIBUTION is according to light field complex amplitude N_i,2n+1T () utilizes conventional phase unwrapping algorithm to obtain testing laser pulse PHASE DISTRIBUTION in time is N_i,2n+1(t)/|N_i,2n+1(t) |;

12) as i=K, it was shown that the maximum occurrences 2n+1 of current m can not meet the requirement of computational accuracy, then make n=n+1 increase laser pulse intensity I_mMeasurement number, return step 1), proceed calculate.

Practice have shown that, the present invention adopts the structure of all-fiber, apparatus of the present invention compact conformation, it is simple to adjust. Adopt the method that time phase recovers, it is possible to the phase place of weak phase place laser pulse is measured. Utilize the method that Direct Phase is modulated can control modulation signal flexibly. Can be operated in Gao Zhongying and low repetition situation.

Claims (2)

1. the time domain phase recovery weak phase measurement device of full optical fiber laser pulse, it is characterized in that its composition includes: be fiber optic splitter (1) along testing laser pulse input direction, testing laser pulse is divided into by force by this fiber optic splitter (1), weak two-beam, it is adjustable optic fibre chronotron (5) successively along strong beam direction, high speed fibre phase-modulator (6), dispersive optical fiber (7) and oscillograph (8), it is high speed PIN photocell (2) successively along weak beam direction, AWG (Arbitrary Waveform Generator) (3), electric signal amplifier (4), the modulation input of the high speed fibre phase-modulator (6) described in output termination of this electric signal amplifier (4), the delay adjustment precision of described adjustable optic fibre chronotron (5) is 1ps, the length of described dispersive optical fiber (7) meets the following conditions:

${\mathrm{\&beta;}}_{2}L>>\frac{4{\mathrm{\&pi;}}^2}{{\left(\mathrm{\&Delta;}\mathrm{\&nu;}\right)}^2}---\left(1\right)$

Wherein, ��₂For the 2nd order chromatic dispersion of described dispersive optical fiber (7), L is the length of dispersive optical fiber (7), and �� �� is the spectral width of testing laser pulse after the phase-modulation of high speed fibre phase-modulator (6);

The modulation signal that described AWG (Arbitrary Waveform Generator) (3) produces is single order Gaussian pulse, and the pulse width �� of this single order Gaussian pulse to meet �ӡܦ� T, �� T be the pulsewidth of testing laser pulse.

2. utilize the measuring method to the weak phase place of laser pulse to be measured of the time domain phase recovery weak phase measurement device of full optical fiber laser pulse described in claim 1, it is characterised in that the method comprises the following steps:

1. t is set₀Amplify, through described electric signal amplifier (4), the initial relative time delay that the center of modulation signal of output reaches the moment of described high speed fibre phase-modulator (6) and reaches the moment of described high speed fibre phase-modulator (6) relative to testing laser pulse for what described AWG (Arbitrary Waveform Generator) (3) produced, the time delay of the delay time every time regulating described adjustable optic fibre chronotron (5) increases to �� t, often adjust a time delay, described oscillograph (8) one testing laser pulse strength I of record_m, obtain I successively₁��I₂������I_m����I_2n+1, the time delay that after regulating for the m time, described adjustable optic fibre chronotron (5) produces is t₀+ m �� t, after regulating for the m time, testing laser pulse is collected this delay time (t by described oscillograph (8) after described high speed fibre phase-modulator (6) and dispersive optical fiber (7)₀Laser pulse intensity I under+m �� t)_mFor:

I_m=| A_m|²(2)

Wherein, m=1,2,3 ... 2n+1, n are any positive integer and meet 2n+1 >=�� T/ �� t, A_mFor testing laser pulse light field complex amplitude after dispersive optical fiber (7);

2. 3. utilize time domain Phase Retrieve Algorithm to described laser pulse intensity I_mCarry out data process, calculate the PHASE DISTRIBUTION of testing laser pulse, specifically comprise the following steps that

1) data initialization is arranged: i is current iteration number of times, and m is the sequence number of the m time adjustment adjustable optic fibre chronotron (5), and the maximum making i=0, m is 2n+1; N_0,2n+1The COMPLEX AMPLITUDE of t testing laser pulse that () generates for computer random, �� is minimum of computation error, and K is maximum iteration time;

2) i=i+1 is made, m=0, the initial testing laser pulsed reset amplitude N that current iteration calculates_i,mT light field complex amplitude that () calculates for m=2n+1 correspondence in i-1 iteration, i.e. N_i,m(t)=N_i-1,2n+1(t);

3) m=m+1 is made, currently to testing laser pulsed reset amplitude E initial in the iterative computation of m_i,mT () is the light field complex amplitude calculated corresponding in m-1 iteration, i.e. E_i,m(t)=N_i,m-1(t);

4) the light field complex amplitude after high speed fibre phase-modulator (6) it is calculated as follows

$P_{i,m}^{in}\left(t\right)=E_{i,m}\left(t\right)\exp \left(j\mathrm{\&pi;}\frac{V}{V_{\mathrm{\&pi;}}}B\right(t-m\mathrm{\&Delta;}t\left)\right)---\left(3\right)$

Wherein, V is the voltage magnitude of modulation signal, V_��For the half-wave voltage of high speed fibre phase-modulator (6), B (t-m �� t) is the modulation signal of the time delays with m �� t;

5) it is calculated as follows againLight field complex amplitude A after dispersive optical fiber (7)_i,m(t) and light field PHASE DISTRIBUTIONIt is respectively as follows:

$A_{i,m}\left(t\right)=F^{-1}\left\{F\right\{P_{i,m}^{in}\left(t\right)\left\}\exp \left(j\frac{{\mathrm{\&beta;}}_{2}L}{2}{\mathrm{\&omega;}}^2\right)\right\}---\left(4\right)$

Wherein: F is Fourier transformation, F^-1For inverse Fourier transform, �� is light field angular frequency;

6) the laser pulse intensity I through high speed fibre phase-modulator (6) and dispersive optical fiber (7) that oscillograph (8) records for the m time is utilized_m, replace the calculated light field complex amplitude of (4) formula, and retain phase invariant, the complex amplitude after being updated

7) by described light field complex amplitudeReverse propagation is to the input of dispersive optical fiber (7), the incident field complex amplitude after being updated

$P_{i,m}^{out}\left(t\right)=F^{-1}\left\{F\right\{A_{i,m}^o\left\}\exp (-j\frac{{\mathrm{\&beta;}}_{2}L}{2}{\mathrm{\&omega;}}^2)\right\}---\left(6\right)$

8) the complex amplitude N of high speed fibre phase-modulator (6) input testing laser pulse is calculated according to following formula_i,m(t):

$\begin{array}{c}{N}_{i,m}\left(t\right)=E_{i,m}\left(t\right)+\frac{\left|\mathrm{\&phi;}(t-m\mathrm{\&Delta;}t)\right|}{{\left|\mathrm{\&phi;}(t-m\mathrm{\&Delta;}t)\right|}_{\max }}\frac{conj\left(\mathrm{\&phi;}\right(t-m\mathrm{\&Delta;}t\left)\right)}{{\left|\mathrm{\&phi;}(t-m\mathrm{\&Delta;}t)\right|}^2+\mathrm{\&alpha;}}\left(P_{i,m}^{out}\right(t)-P_{i,m}^{in}(t\left)\right)\\ \mathrm{\&phi;}(t-m\mathrm{\&Delta;}t)=\exp \left(j\mathrm{\&pi;}\frac{V}{V_{\mathrm{\&pi;}}}B\right(t-m\mathrm{\&Delta;}t\left)\right)\end{array}---\left(7\right)$

Wherein, | �� (t-m �� t) |_maxBeing carried in the upper phase-modulation produced of high speed fibre phase-modulator (6) for modulation signal, conj (*) is function complex conjugate, and �� is for preventing from removing null divisor;

9) when m < during 2n+1, return step 3); As m=2n+1, the error E rror being calculated as follows the calculating of current ith iteration is:

$Error=\&Integral;dt\underset{m}{\&Sigma;}\frac{|{\left|A_{i,m}\left(t\right)\right|}^2-I_m\left(t\right)|}{{\left|I_m\left(t\right)\right|}_{max}}/(2n+1)---\left(8\right)$

10) if Error<��, then stop iterative computation, carry out next step 11); If Error>=��, and i<K, then return step 2), if i=K, then enter step 12);

11)N_i,2n+1T () is the light field complex amplitude of testing laser pulse, its PHASE DISTRIBUTION is according to light field complex amplitude N_i,2n+1T () utilizes conventional phase unwrapping algorithm to obtain testing laser pulse PHASE DISTRIBUTION in time is N_i,2n+1(t)/|N_i,2n+1(t) |;

12) as i=K, it was shown that the maximum occurrences 2n+1 of current m can not meet the requirement of computational accuracy, then make n=n+1, increase laser pulse intensity I_mMeasurement number, return step 1), proceed calculate.