CN101713901B - Nonlinear fiber based generating device of high-frequency ultrashort optical pulse and working method thereof - Google Patents

Abstract

The invention relates to a nonlinear fiber based generating device of a high-frequency ultrashort optical pulse and a working method thereof. The generating device of the high-frequency ultrashort optical pulse is characterized by comprising a device based on an unstably modulated ultrahigh repetition frequency optical pulse, a double-frequency beat-frequency optical source, a high-power fiber amplifier and nonlinear fiber, wherein the output end of the double-frequency beat-frequency optical source is connected with the high-power fiber amplifier; the output end of the high-power fiber amplifier is connected with the nonlinear fiber; and the output end of the nonlinear fiber outputs a high-frequency ultrashort optical pulse sequence. The invention mainly utilizes the high nonlinear effect and the dispersion effect of the nonlinear fiber and converts a double-frequency beat-frequency signal into a high repetition frequency ultrashort optical pulse sequence through the high nonlinear fiber; in addition, optical pulse equipment has simple device, and the method can conveniently and quickly realize the signal conversion.

Description

Generation device and method of work based on the high frequency ultrashort light pulse of nonlinear optical fiber

(1) technical field:

The present invention relates to the optical pulse instrument, particularly a kind of based on the controlled high frequency of highly nonlinear optical fiber generation repetition frequency, the device and the method for work thereof of ultrashort light pulse.

(2) background technology:

In recent years, the optical fiber communication fast development, people are also increasingly high to the demand of network capacity.Will further improve the capacity of Networks of Fiber Communications, except utilizing multiplexing means such as wavelength-division multiplex (WDM) or Time Division Multiplexing, the transfer rate that improves single channel also is to improve the effective ways of network capacity.(＞high-quality ultrashort light pulse 40GHz) becomes an important research direction of raising optical communication system transfer rate to the research and development high repetition frequency.

Up to the present, realize that the main method of high repetition frequency ultrashort light pulse has: utilize initiatively or laser with active-passive lock mould generation ultrashort light pulse sequence, utilize modulational instability that beat frequency coherent source shaping compression is realized high repetition frequency light pulse sequence etc.Obtain the light pulse of repetition frequency, just need avoid the use of the device of rate-constrained system as far as possible, like electrooptic modulator etc. greater than 40GHz.Nonlinear effect is very fast owing to its response speed, and does not receive the restriction of electrooptic modulator, becomes a kind of very effective method that produces the high repetition frequency light pulse.Therefore utilize the method for the ultrashort light pulse that modulational instability produces to have the superiority that other method institute can not compare, as be easy to obtain repetition frequency above 40GHz.

An obvious characteristic of modulational instability is that on time domain, quasi c. w. is changed into periodic pulse train.Small sample perturbations on the time domain finally can be converted into the light pulse of high repetition frequency.In the world, modulational instability is applied to the generation of ultrashort light pulse very early.Wherein, the disturbance that utilizes double frequency beat frequency light wave to form on the initial time domain becomes the research focus.The repetition frequency of the high repetition frequency light pulse sequence that double frequency beat frequency light wave produces is identical with the frequency interval of beat frequency light wave, is easy to obtain big beat frequency at interval through two the continuous light waves that are coupled.For example, obtain the light pulse of the high repetition frequency of 1THz, corresponding beat frequency is spaced apart 1THz, and it can obtain through two laser instruments that coupled wavelength is spaced apart 8nm, and this is easy to realize at optical field.Modulational instability is nonlinear effect and the result of chromatic dispersion combined action in the nonlinear medium, utilizes different nonlinear medium (different nonlinear factors and chromatic dispersion) can obtain the light pulse of different high repetition frequencies.For example; Double frequency beat frequency light wave can be produced the 32GHz light pulse sequence through a nonlinear fiber loop mirror (NFLM); It can be produced 59.1GHz optical soliton pulse train through one section optical fiber with pectination dispersion profile; It can be produced 114GHz optical soliton pulse train through one section chromatic dispersion optical fiber (DDF) that successively decreases,, can produce the light pulse sequence of 160GHz its optical fiber through one section chromatic dispersion particular design.But obtain the optical fiber of chromatic dispersion special distribution and be not easy, use conventional fiber (nonlinear optical fiber that promptly has constant chromatic dispersion) also can obtain the light pulse of high repetition frequency.As utilize standard single-mode fiber can obtain the light pulse sequence of the high repetition frequency of 20GHz, 80GHz; Utilize the dispersion flattene highly nonlinear optical fiber can obtain 320GHz, 640GHz, even the light pulse sequence of the high repetition frequency of 1THz.

But, in order to suppress the stimulated Brillouin scattering in the optical fiber, need the live width that electrooptic modulator comes broadening double frequency beat frequency light wave usually, thereby improve the threshold value of stimulated Brillouin scattering.Because the threshold value of stimulated Brillouin scattering (SBS) is relevant with the live width of incoming signal.The introducing of phase-modulator has increased the complexity of structure, has improved cost.

(3) summary of the invention:

The object of the present invention is to provide a kind of generation device and method of work of the high frequency ultrashort light pulse based on nonlinear optical fiber; It has mainly utilized the high non-linearity effect and the effect of dispersion of nonlinear optical fiber; Convert the double frequency beat signal to high repetition frequency ultrashort light pulse sequence through highly nonlinear optical fiber; Be that a kind of device is simple, signal transforms the optical pulse equipment easily of realizing.

Technical scheme of the present invention: a kind of generation device of the high frequency ultrashort light pulse based on nonlinear optical fiber; It is characterized in that it is to be made up of the device based on the superelevation repetition frequency light pulse of modulational instability; Comprise: double frequency beat frequency light source, high-power fiber amplifier and nonlinear optical fiber; The output terminal of double frequency beat frequency light source links to each other with high-power fiber amplifier; The output terminal of high-power fiber amplifier connects nonlinear optical fiber, the output terminal output high frequency ultrashort light pulse sequence of nonlinear optical fiber.

Above-mentioned said double frequency beat frequency light source has two kinds of frame modes, and a mode is to connect Polarization Controller by a laser instrument, is parallel to coupling mechanism with another laser instrument more afterwards, and the output terminal of coupling mechanism connects high-power fiber amplifier; Other type is for directly to connect high-power fiber amplifier by dual laser.

The coupling mechanism of above-mentioned said parallelly connected dual-laser device adopts three-dB coupler, promptly 50: 50 coupling mechanism.

Above-mentioned said high-power fiber amplifier can be selected Erbium-Doped Fiber Amplifier (EDFA) or erbium-ytterbium co-doped fiber amplifier.

Above-mentioned said nonlinear optical fiber adopts dispersion shifted optical fiber, ignore the highly nonlinear optical fiber of loss, ignore loss non-linear photon crystal optical fiber, consider that (photonic crystal fiber of loss factor α=0.2dB/km) comprises bismuthate glass optical fiber (bismuth fiber), sulfide optical fiber or other highly nonlinear optical fibers in loss.

A kind of method of work of generation device of above-mentioned high frequency ultrashort light pulse based on nonlinear optical fiber is characterized in that being made up of following steps:

(1) at first will be input to the double frequency beat frequency light source with same magnitude in the high-power fiber amplifier (EDFA) and carry out power amplification, wherein the frequency of beat frequency light source is represented with f, and the output power of power amplifier is represented with P;

(2) the beat frequency light source through the high-power fiber amplifier power amplification is γ at nonlinear factor; Abbe number is to receive chromatic dispersion and nonlinear acting in conjunction in the nonlinear optical fiber of β; In the process that acts on, chromatic dispersion can and finally produce light pulse sequence identical with beat frequency light repetition frequency but that the width pressure is narrow to the compression of beat frequency polishing shape with nonlinear effect;

(3) general power P, the CHROMATIC DISPERSION IN FIBER OPTICS factor beta of the frequency interval f of the beat frequency light source in above-mentioned said step (1) and the step (2), fiber amplifier output ₂, optical fiber nonlinear factor γ and length of fiber L all influential to the pulse train of final output: promptly

Order $N^{}$ ${}^2=\frac{\mathrm{\&gamma;\; P}}{8{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="H2009100705887E00012.png,H2009100705887E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}^2\left|{\mathrm{\&beta;}}_2\right|},$ When N is positioned within the span of following relational expression (1),

${1.45}^2<{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="H2009100705887E00012.png,H2009100705887E00021.png"\; state="\{\{state\}\}">N</figure-callout>}}^2=\frac{\mathrm{\&gamma;P}}{8{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="H2009100705887E00012.png,H2009100705887E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}^2\left|{\mathrm{\&beta;}}_2\right|}<{1.9}^2---\left(1\right)$

The pulse width that then proves the output pulse sequence that obtains is narrow, and the pedestal of pulse is little;

Prove that simultaneously fiber lengths L satisfies following relational expression

$L\&ap;\frac{1}{16{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="H2009100705887E00012.png,H2009100705887E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}^2\left|{\mathrm{\&beta;}}_2\right|}\&ap;\frac{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="H2009100705887E00012.png,H2009100705887E00021.png"\; state="\{\{state\}\}">N</figure-callout>}}^2}{2\mathrm{\&gamma;P}}---\left(3\right),$

Wherein whether ignoring of fibre loss can be influential to the N value in the formula (1);

N in the above-mentioned said step (3) chooses with the loss of optical fiber when irrelevant, i.e. fibre loss is ignored, and N obtains best value according to formula (1) and is positioned near 1.49, promptly

N ≈ 1.49 (2), then clap

Frequently signal compression is to optimum condition.

Fibre loss is ignored when obtaining beat signal and being compressed to optimum condition in the above-mentioned said step (3), then chooses the optical fiber of definite abbe number and nonlinear factor and confirms to be input to the luminous power P in the nonlinear optical fiber.

N in the above-mentioned said step (3) chooses when relevant with the loss of optical fiber; Be that fibre loss is not ignored; Obtain the numerical value of N according to formula (1) with reference to " three-dimensional plot that parameter N changes with abbe number and loss " (seeing accompanying drawing 11), when abbe number one timing, best N value increases with the increase of loss; When loss one timing, best N value reduces with the increase of abbe number.

Fibre loss is not ignored when obtaining beat signal and being compressed to optimum condition in the above-mentioned said step (3), chooses the optical fiber of definite abbe number and nonlinear factor and confirms to be input to the luminous power P in the nonlinear optical fiber.

Double frequency beat frequency light source in the above-mentioned said step (1) adopts two output wavelength different laser devices of coupling to obtain or adopts a tunable dual laser to obtain.

Nonlinear optical fiber used in the above-mentioned said step (2) can have multiple choices; Comprise dispersion shifted optical fiber; Non-linear photon crystal optical fiber; Bismuthate glass optical fiber (bismuth fiber), sulfide optical fiber or other highly nonlinear optical fibers, compression effectiveness has difference when being applicable to the different fiber of step (2).

Nonlinear factor in the above-mentioned said step (2) in the used photonic crystal fiber and the abbe number all spacing and the size of the airport through regulating photonic crystal fiber are chosen.

When selecting for use nonlinear factor high, chromatic dispersion is little in the above-mentioned said step (2), during the high nonlinear optical fiber of excited Brillouin threshold value, then in whole device, need not use electrooptic modulator.

The light pulse sequence that produces in the above-mentioned said step (2) is the ultrashort light pulse greater than the high-repetition-rate of 40GHz, and the repetition frequency of the light pulse sequence of generation can reach 1THz.

The adjustable repetitive frequency of the light pulse sequence that produces in the above-mentioned said step (2) or non-adjustable; Wherein, The adjustable repetitive frequency characteristic of the light pulse sequence that produces is adjustable decision of frequency interval by the double frequency beat frequency light source in the step (1), and the non-adjustable characteristic of the repetition frequency of the light pulse sequence of generation is that the fixed frequency interval by the double frequency beat frequency light source in the step (1) determines.

Principle of work of the present invention is: utilize modulational instability (chromatic dispersion and nonlinear acting in conjunction) that the beat frequency coherent source is carried out the shaping compression; Make beat frequency coherent source through nonlinear optical fiber, produce and the identical light pulse sequence of beat frequency light source repetition frequency with same magnitude.Wavelength interval through regulating dual laser is regulated the repetition frequency of output optical pulse sequence.The output of the high repetition frequency light pulse that the method realizes has very strong dirigibility, can realize the output of different repetition frequency light pulses.Non-linear Schrodinger equation below the process that develops of in whole nonlinear optical fiber, transmitting light wave satisfies:

$i\frac{\&PartialD;U}{\&PartialD;\mathrm{\&zeta;}}+\frac{1}{2}\frac{{\&PartialD;}^{2}U}{\&PartialD;{\mathrm{\&tau;}}^2}+{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="H2009100705887E00012.png,H2009100705887E00021.png"\; state="\{\{state\}\}">N</figure-callout>}}^2{\left|U\right|}^{2}U+\mathrm{i\&Gamma;U}=0$

Superiority of the present invention and beneficial effect are: 1, produce the technological deficiency of high frequency light pulse to existing modulational instability, proposed to use the nonlinear optical fiber that nonlinear factor is high, the stimulated Brillouin scattering threshold value is high to realize the apparatus and method that high-frequency impulse produces; 2, because the stimulated Brillouin scattering threshold value of this nonlinear optical fiber is higher; In the generation device of high frequency ultrashort light pulse sequence, need not to dispose electrooptic modulator; This method reduces the cost of system greatly; Realize the generation of cost-effective high frequency light pulse, solved the superelevation speed light source problem of following superelevation speed optical fiber telecommunications system; 3, apparatus structure is simple, the method easy operating, and cost is low, is convenient to promote.

(4) description of drawings:

Accompanying drawing 1 is the generation device theory diagram of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention.

Accompanying drawing 2 is embodiment 1 structural representation of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention.

Accompanying drawing 3 is embodiment 2 structural representations of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention.

Accompanying drawing 4 is embodiment 3 structural representations of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention.

Accompanying drawing 5 is embodiment 4 structural representations of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention.

Accompanying drawing 6 is the embodiment 1 work figure of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention, i.e. the pulse train waveform of the initial input of repetition frequency 100GHz and output.

Accompanying drawing 7 is the embodiment 2 work figure of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention; Be under the adjustable situation of frequency interval of dual laser, obtain the initial input of repetition frequency 200GHz and the pulse train waveform of output when selecting repetition frequency 200GHz.

Accompanying drawing 8 is the embodiment 2 work figure of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention; Be under the adjustable situation of frequency interval of dual laser, obtain the initial input of repetition frequency 300GHz and the pulse train waveform of output when selecting repetition frequency 300GHz.

Accompanying drawing 9 is the embodiment 3 work figure of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention, i.e. the pulse train waveform of the initial input of repetition frequency 500GHz and output.

Accompanying drawing 10 is the embodiment 4 work figure of the generation device of the related a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of the present invention, i.e. the pulse train waveform of the initial input of repetition frequency 500GHz and output.

Accompanying drawing 11 for the parameter N of the best of step (3) institute reference in the method for work of the related a kind of high frequency ultrashort light pulse generation device based on nonlinear optical fiber of the present invention with the three-dimensional plot of abbe number with the loss variation.

Wherein: 1 is laser instrument, and 2 is laser instrument, and 3 is dual laser; 4 is Polarization Controller, and 5 is three-dB coupler, and 6 is Erbium-Doped Fiber Amplifier (EDFA) (EDFA); 7 for ignoring the dispersion shifted optical fiber of loss, and 8 for ignoring the highly nonlinear optical fiber of loss, and 9 is erbium-ytterbium co-doped fiber amplifier; 10 for ignoring the photonic crystal fiber of loss, and 11 is the photonic crystal fiber of loss factor α=0.2dB/km.

(5) embodiment:

The present invention is the modulational instability effect of utilizing in the nonlinear optical fiber; With double frequency beat frequency light wave as primary light source; As nonlinear medium, produce a kind of be applied to high speed optical fiber communication, high-quality, high repetition frequency, ultra-short pulse source efficiently with nonlinear optical fiber.

Embodiment 1: consult accompanying drawing 2, accompanying drawing 2 is a kind of models of this experiment structure, and double frequency beat frequency light source adopts the continuous light laser instrument of two different wave lengths of coupling to obtain.Obtain by laser instrument 1 and laser instrument 2 these two laser instruments respectively, and the frequency interval of laser instrument 1 and laser instrument 2 is 100GHz.Polarization Controller 4 is used for regulating the polarization state of one of them laser instrument, thereby the light that makes two laser instruments is through among dispersion shifted optical fiber 7, having same polarization state during transmission after the three-dB coupler 5, to strengthen the nonlinear interaction between them.The beat frequency light source amplifies through Erbium-Doped Fiber Amplifier (EDFA) 6 (EDFA), in the dispersion shifted optical fiber that is input to then.High repetition frequency ultrashort light pulse sequence is by its output terminal output.The nonlinear factor of the dispersion shifted optical fiber 7 that we adopt is γ=1.7W ^-1Km ^-1, abbe number is β ₂=0.48ps ²/ km.The output power of Erbium-Doped Fiber Amplifier (EDFA) 6 (EDFA) is adjusted to 50.6mW, and obtaining repetition frequency at the output terminal of dispersion shifted optical fiber 7 is 100GHz, and pulse width is the pulse train of 1.56ps, shown in accompanying drawing 6.

Embodiment 2: consult accompanying drawing 3, accompanying drawing 3 is another kind of models of this experiment structure, replaces two laser instruments in the accompanying drawing 2 to produce double frequency beat frequency light source with adjustable dual laser 3, realizes the adjustable of output optical pulse repetition frequency.The beat frequency light source is input in the highly nonlinear optical fiber 8 after Erbium-Doped Fiber Amplifier (EDFA) 6 (EDFA) amplifies, and high repetition frequency ultrashort light pulse sequence is by its output terminal output.The nonlinear factor of the highly nonlinear optical fiber 8 that we adopt is γ=10.5W ^-1Km ^-1, abbe number is β ₂=0.97ps ²/ km.When the frequency interval of dual laser is adjusted to 200GHz; Output power with Erbium-Doped Fiber Amplifier (EDFA) 6 (EDFA) is adjusted to 83.7mW simultaneously; It is 200GHz that output terminal obtains repetition frequency, and pulse width is the ultrashort light pulse sequence of 781fs, shown in accompanying drawing 7; When the frequency interval of dual laser is adjusted to 300GHz; Output power with Erbium-Doped Fiber Amplifier (EDFA) 6 (EDFA) is adjusted to 188.2mW simultaneously; It is 300GHz that output terminal obtains repetition frequency, and pulse width is the light pulse sequence of 520.8fs, shown in accompanying drawing 8.

Embodiment 3: consult accompanying drawing 4; Accompanying drawing 4 is another kind of models of this experiment structure, and the frequency interval of dual laser 3 is 500GHz, after amplifying through erbium-ytterbium co-doped fiber amplifier 9; Be input in the photonic crystal fiber 10, high repetition frequency ultrashort light pulse sequence is by its output terminal output.The nonlinear factor of the photonic crystal fiber of ignoring loss 10 that we adopt is γ=11W ^-1Km ^-1, abbe number is β ₂=0.48ps ²/ km.The output power of erbium-ytterbium co-doped fiber amplifier 9 is adjusted to 195.5mW, has obtained repetition frequency to 500GHz at the output terminal of photonic crystal fiber 10, pulse width is the light pulse sequence of 312fs, shown in accompanying drawing 9.

Embodiment 4: consult accompanying drawing 5; Accompanying drawing 5 is another kind of models of this experiment structure, and the frequency interval of dual laser 3 is 500GHz, after amplifying through erbium-ytterbium co-doped fiber amplifier 9; Be input in the photonic crystal fiber 11, high repetition frequency ultrashort light pulse sequence is by its output terminal output.The nonlinear factor of the photonic crystal fiber 11 of the consideration loss that we adopt is γ=11W ^-1Km ^-1, abbe number is β ₂=0.48ps ²/ km, loss factor α=0.2dB/km.The output power of erbium-ytterbium co-doped fiber amplifier 9 is adjusted to 195.5mW, has obtained repetition frequency to 500GHz at the output terminal of photonic crystal fiber 11, pulse width is the light pulse sequence of 312fs, shown in accompanying drawing 10.

Table 1 is the summary to above-mentioned four embodiment, and P is the output power of amplifier, and L is a fiber lengths, and f is the repetition frequency of output pulse sequence, and Δ t is the pulse width of output pulse sequence.

Table 1

Fiber type	β 2 ps 2/km	?γ?(w -1km -1)	P (mW)	L (m)	f (GHz)	Δt (fs)	The embodiment design sketch
								Dispersion shifted optical fiber	0.48	1.7	50.6	13369	100	1560	Embodiment 1 effect such as accompanying drawing 6
Highly nonlinear optical fiber	0.97	10.5	83.7	1671	200	781	Embodiment 2 effects such as accompanying drawing 7
								Highly nonlinear optical fiber	0.97	10.5	188.2	742.7	300	520.8	Embodiment 2 effects such as accompanying drawing 8
Photonic crystal fiber	0.48	11	195.5	534.7	500	312	Embodiment 3 effects such as accompanying drawing 9
								Photonic crystal fiber	0.48	11	195.5	534.7	500	330.1	Embodiment 4 effects such as accompanying drawing 10

Sum up; This case is to utilize the chromatic dispersion of nonlinear optical fiber and high non-linearity effect; Through the effect of modulational instability, produce the generation device and the method for work of the repetition frequency high frequency ultrashort light pulse sequence identical, and this apparatus structure is simple with the initial input beat frequency rate to beat signal; Cost is low, therefore is convenient to promote.

Claims (7)

1. method of work based on the generation device of the high frequency ultrashort light pulse of nonlinear optical fiber is characterized in that being made up of following steps:

(1) make up generation device based on the high frequency ultrashort light pulse of nonlinear optical fiber: it is based on the device of the superelevation repetition frequency light pulse of modulational instability; Comprise: double frequency beat frequency light source, high-power fiber amplifier and nonlinear optical fiber; The output terminal of double frequency beat frequency light source links to each other with high-power fiber amplifier; The output terminal of high-power fiber amplifier connects nonlinear optical fiber, the output terminal output high frequency ultrashort light pulse sequence of nonlinear optical fiber; Said double frequency beat frequency light source has two kinds of frame modes, and a mode is to connect Polarization Controller by a laser instrument, is parallel to coupling mechanism with another laser instrument more afterwards, and the output terminal of coupling mechanism connects high-power fiber amplifier; Other type is for directly to connect high-power fiber amplifier by dual laser; Said high-power fiber amplifier is selected Erbium-Doped Fiber Amplifier (EDFA) or erbium-ytterbium co-doped fiber amplifier; Said nonlinear optical fiber adopts dispersion shifted optical fiber, photonic crystal fiber or sulfide optical fiber;

(2) be input to the double frequency beat frequency light source with same magnitude in the high-power fiber amplifier of step (1) construction device and carry out power amplification, wherein the frequency interval of beat frequency light source is represented with f, and the output power of high-power fiber amplifier is represented with P;

(3) the beat frequency light source through the high-power fiber amplifier power amplification is γ at nonlinear factor, and abbe number is β ₂Nonlinear optical fiber in receive chromatic dispersion and nonlinear acting in conjunction, in the process of effect, chromatic dispersion and nonlinear effect can produce light pulse sequence identical with beat frequency light repetition frequency but that the width pressure is narrow to beat frequency polishing shape compression and final;

(4) the frequency interval f of the beat frequency light source in above-mentioned said step (2) and the step (3), the output power P of high-power fiber amplifier, the abbe number β of nonlinear optical fiber ₂, nonlinear optical fiber the length L of nonlinear factor γ and nonlinear optical fiber all influential to the pulse train of final output: promptly

Make

when N is positioned within the span of following relational expression (1)

${1.45}^2<N^2=\frac{\mathrm{\&gamma;P}}{8f^2\left|{\mathrm{\&beta;}}_2\right|}<{1.9}^2---\left(1\right)$

The pulse width that then proves the output pulse sequence that obtains is narrow, and the pedestal of pulse is little;

Prove that simultaneously fiber lengths L satisfies following relational expression

$L\&ap;\frac{1}{16f^2\left|{\mathrm{\&beta;}}_2\right|}\&ap;\frac{N^2}{2\mathrm{\&gamma;P}}---\left(3\right),$

Wherein whether ignoring of fibre loss can be influential to the N value in the formula (1).

2. according to the method for work of the generation device of the said a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of claim 1; It is characterized in that in the said step (4) N choose with the loss of optical fiber when irrelevant; Be that fibre loss is ignored, N obtains best value according to formula (1) and is positioned near 1.49, promptly

N≈1.49 (2)，

Then beat signal is compressed to optimum condition; Choose simultaneously the optical fiber of definite abbe number and nonlinear factor again and confirm to be input to the luminous power P in the nonlinear optical fiber.

3. according to the method for work of the generation device of the said a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of claim 1, it is characterized in that double frequency beat frequency light source in the said step (2) adopts two output wavelength different laser devices of coupling to obtain or adopts a tunable dual laser to obtain.

4. according to the method for work of the generation device of the said a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of claim 1; When it is characterized in that adopting photonic crystal fiber in the said step (3), the nonlinear factor in the used photonic crystal fiber and the abbe number all spacing and the size of the airport through the adjusting photonic crystal fiber are chosen.

5. according to the method for work of the generation device of the said a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of claim 1; It is characterized in that in the said step (3) when selecting for use nonlinear factor high; Chromatic dispersion is little; During the high nonlinear optical fiber of excited Brillouin threshold value, then in whole device, need not use electrooptic modulator.

6. according to the method for work of the generation device of the said a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of claim 1; The adjustable repetitive frequency of the light pulse sequence that it is characterized in that producing in the said step (3) or non-adjustable; Wherein, The adjustable repetitive frequency characteristic of the light pulse sequence that produces is adjustable decision of frequency interval by the double frequency beat frequency light source in the step (2), and the non-adjustable characteristic of the repetition frequency of the light pulse sequence of generation is that the fixed frequency interval by the double frequency beat frequency light source in the step (2) determines.

7. according to the method for work of the generation device of the said a kind of high frequency ultrashort light pulse based on nonlinear optical fiber of claim 1; It is characterized in that the light pulse sequence that produces in the said step (3) is the ultrashort light pulse greater than the high-repetition-rate of 40GHz, the repetition frequency of the light pulse sequence of generation can reach 1THz.

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