CN1238741C - Producing method for optical fibre raster with object reflective response realized by amplitude template - Google Patents

Producing method for optical fibre raster with object reflective response realized by amplitude template Download PDF

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CN1238741C
CN1238741C CNB2004100091670A CN200410009167A CN1238741C CN 1238741 C CN1238741 C CN 1238741C CN B2004100091670 A CNB2004100091670 A CN B2004100091670A CN 200410009167 A CN200410009167 A CN 200410009167A CN 1238741 C CN1238741 C CN 1238741C
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template
amplitude
fiber grating
sampling
amplitude template
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CN1584640A (en
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戴一堂
陈向飞
谢世钟
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Tsinghua University
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Tsinghua University
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Abstract

The present invention relates to a producing method for optical fiber rasters with object reflective response realized by an amplitude template, which belongs to the technical field of an optical filter. The present invention is characterized in that an amplitude template is led in a producing method for phase templates used by the optical fiber rasters for realizing an optical fiber raster designed by a reconstruction-equivalent-chirp method; thereby, the optical fiber raster is suitable for large-scale production. The present invention comprises a vibration amplitude template, a phase template and a fiber, wherein the vibration amplitude template, the phase template and the fiber are orderly parallel and tightly placed; thereby, ultraviolet laser beam vertically emits to the core diameter of a photosensitive optical fiber orderly through the vibration amplitude template and the phase template. The present invention provides a computational formula for the central position, the period and the length of a transparent slit of the vibration amplitude template; no apodization is realized through a mode of changing the slit length, the no apodization compensation is realized through a mode of changing the period of the transparent slit, and a corresponding formula is provided. The result tallies with the design value through the certification of examples.

Description

With the firm and hard method for making that now has the fiber grating of target reflection response of amplitude mode
Technical field
The present invention relates to the field that optical fiber communication, light sensing and other relevant light signal are handled, relate in particular to optical filter wherein.
Background of invention
Fiber grating much relates in the field of light signal processing in optical fiber communication, light sensing etc., is widely used as single input, single optical filter of exporting.So-called fiber grating is to form the fiber waveguide device that the periodic refractive index modulation forms in optical fiber upper edge optical fiber direction.The method for making of phase mask-scanning that it is traditional is as shown in Figure 1: ultraviolet ray 13 is by ultraviolet laser 11 outputs, be fixed on earlier level crossing 14 on the translation stage 15 reflect, then again by 16 diffraction of phase mask, form ± 1 order diffraction light, form along the light distribution of the periodic undulations of template 16 directions at its overlapping region 18, make the refractive index of light-sensitive optical fibre 17 obtain a same periodic relief accordingly, promptly form one section fiber grating.Deserving to be called and stating the refractive index cycle fluctuating is the index modulation of fiber grating, the energy of its amplitude and laser instrument 11, light application time (for continuous wave laser) or light pulse number (paired pulses laser instrument) are relevant, and this relation can obtain by experiment repeatedly; The cycle of index modulation is half of template cycle.Thereby mobile translation stage 15 moving areas 18 are controlled energy, light application time or the number of pulses of laser instrument 11 simultaneously, just can be, obtain different index modulation amplitudes in the diverse location exposure of optical fiber 17, thus obtain the more complicated fiber grating of structure.
Utilizing fiber grating to realize the reflex response of target, is the basis that fiber grating is used, and is subjected to people's attention always.In theory, people have proposed the restructing algorithm of fiber grating: utilize the target reflection response to ask the structure of fiber grating, the i.e. distribution of index modulation
Wherein, z is the distance to the fiber grating initial end, A S(z) more than or equal to zero, the index modulation amplitude function of expression fiber grating; Λ SIt is the cycle of index modulation; S(z) be phase function, characterize warbling and phase shift of fiber grating; C.c represents last conjugation.But, the fiber grating that is obtained by restructing algorithm adopts the method for making of traditional phase mask-scanning to be difficult to realize: the fiber grating that obtains of reconstruct often requires the complicated toe of cutting on the one hand, and cuts toe and the toe of cutting that thereupon brings compensates and makes manufacturing process loaded down with trivial details or be difficult to control; The phase mask of comparative maturity comprises all phase masks of even linear chrip now on the other hand, makes the fiber grating that obtains by this phase mask and traditional phase mask-scan method and has fixing phase function
Figure C20041000916700051
Wherein, Λ is the average period of making the fiber grating that obtains, C is the rate of change of the cycle of this fiber grating to z, and the fiber grating that reconstruct obtains often has complicated warbling and phase shift, realize it or utilize special phase mask, perhaps require the control accuracy of nanometer scale, make the cost of manufacture raising or be unfavorable for large-scale production.
Two difficulties above the reconstruct-equivalent chirp method that proposes has got around recently, this method has detailed description in the middle of list of references " Dai Yitang, Chen Xiangfei, the lunar calendar, Jiang Dianjie and the clock of passing away; ' a kind of fiber grating of realizing having the arbitrary target response '; Chinese invention patent, application number: 200410007530.5 ".This theory shows, utilizes the sampling optical fiber grating and the common phase template of special construction, though the sampling optical fiber grating that obtains only has the phase function suc as formula 2 expressions, also can obtain the target reflection response.Its ultimate principle is: the sampling function of sampling optical fiber grating is carried out suitable warble and cutting toe, promptly control exposure position and exposure in the sampling optical fiber grating manufacturing process, thereby reach the cutting toe and warble of its a certain non-zero order reflection peak (normally-1 grade), make this reflection peak have the target reflection response.
Amplitude template with sub-micrometer precision has been unusual proven technique in semiconductor technology, and Fig. 2 is the synoptic diagram of an amplitude template, and wherein 21 and 22 is respectively printing opacity slit and lightproof part.Claim that below total number in printing opacity slit is N, the midpoint in k bar printing opacity slit is z to the distance of amplitude template initial end k, the length in this printing opacity slit is L k, and the cycle that defines this printing opacity slit be
P k = z 2 - z 1 k = 1 z k + 1 - z k - 1 2 2 ≤ k ≤ N - 1 z N - z N - 1 k = N - - - ( 3 )
As seen, utilize the amplitude template method can realize control accurately to exposure position.
The method of variable duty cycle is used to realize the toe of cutting of sampling optical fiber grating, and the size of the exposure spot of this method by controlling each exposure position place is come the control of the realization of equivalence to exposure intensity, thereby realizes the toe of cutting to sampling optical fiber grating.And the size of control everywhere exposure spot can be by the amplitude template control of being represented by Fig. 2.The variable duty cycle method has been avoided the toe of cutting of sampling optical fiber grating, because the exposure of each exposure station is identical, so the manufacturing process of fiber grating is reduced to Fig. 3: ultraviolet light is expanded bundle from ultraviolet laser 31 outputs by beam expander 32, covers whole optical fiber grating region; Amplitude template 33 is near phase mask 34, and the ultraviolet light that sees through the amplitude template forms fiber grating on the ad-hoc location 36 of light-sensitive optical fibre 35.As seen,, simplified the method for making of fiber grating, be fit to large-scale fiber grating and make in conjunction with the amplitude template.
Cut toe compensation and be always the important step during fiber grating is made.Cut toe and can cause fiber grating direct current index modulation difference everywhere, thereby introduce additional warbling; Cutting the toe compensation is exactly that this additional warbling is compensated.The relation of direct current index modulation D and fiber grating index modulation A is generally
D＝αA (4)
α be one more than or equal to 1 number, can estimate by experiment repeatedly.The re-expose method be use always cut the toe compensation technique, this method is removed phase mask after fiber grating is made, fiber grating is exposed once again, makes double exposure fiber grating total exposure amount unanimity everywhere afterwards.Yet this method has two shortcomings: the one, remove phase mask after light path change, the 2nd, for the second time exposure position be subjected to making the influence of platform precision may be not exclusively and primary overlapping, these two shortcomings all can cause the re-expose can not full remuneration direct current index modulation inconsistency.
Summary of the invention
Purpose of the present invention is to introduce the amplitude template in the phase mask method that fiber grating is made, and realizes the fiber grating by the design of reconstruction-equivalent chirp method, and makes it be fit to large-scale the making.For this reason, the present invention proposes a kind of method for making of fiber grating, this method is by amplitude template, phase mask and optical fiber that place successively, parallel and that press close to, and vertical incidence and see through amplitude template, phase mask successively and the UV laser beam that incides on the optical fiber is formed.
Ultimate principle of the present invention: reconstruct-equivalent chirp method shows, can realize the target reflection response by the sampling optical fiber grating with the distribution of suitable index modulation amplitude profile and sampling period in its-1 grade of reflection peak; The present invention utilizes that amplitude mode is firm and hard have been showed above-mentioned sampling period and distribute.Sampling optical fiber grating is made up of the fiber grating of a lot of sections weak points, the toe of cutting to sampling optical fiber grating is that each short fiber grating section of requirement has different reflectivity in essence, and the reflectivity of fiber grating is not only relevant with its index modulation amplitude, but also it is relevant with its length, so the length by each section of appropriate design fiber grating keeps its index modulation amplitude constant, also can reach the toe of cutting to sampling optical fiber grating; The present invention is by the firm and hard control that has showed the length of each section fiber grating of amplitude mode.Coupled-mode theory by fiber grating, the direct current index modulation of sampling optical fiber grating, be equivalent to do a phase shift in each short fiber grating section back, the equivalent phase shift theoretical proof can compensate this phase shift by the sampling period of adjusting sampling optical fiber grating; The present invention utilizes the firm and hard adjustment that shows this sampling period of amplitude mode.
Thus, the present invention proposes a kind ofly, it is characterized in that it contains following steps successively with the firm and hard method for making that now has the fiber grating of target reflection response of amplitude mode:
1) parallel successively from top to bottom and placement amplitude template, phase mask and the light-sensitive optical fibre pressed close to are regulated light path, make UV laser beam vertical incidence and being mapped on the core diameter of light-sensitive optical fibre by amplitude template, phase mask successively;
Described phase mask is common phase mask, comprises uniformly and the phase mask of linear chrip that the sampling optical fiber grating that is obtained by this phase mask and traditional phase mask-scan method has fixing phase function:
Figure C20041000916700061
Wherein z is the distance to the fiber grating initial end, and Λ is the average period of sampling optical fiber grating, and C is the rate of change of the cycle of this sampling optical fiber grating to z;
The printing opacity slit and the lightproof part of described amplitude template are determined by following formula:
Figure C20041000916700071
It is a tolerance in sampling period greater than zero number that SP is one, and it is a tolerance of sampling dutycycle greater than zero less than 1 number that γ is one, Δ (z)= S(z)-and (z), S(z) obtain by arbitrary target response reconstruct or the phase function of given fiber grating arbitrarily, (z) is the phase function of sampling optical fiber grating, the fraction part of x is asked in " { x} " expression, be that x deducts the maximum integer less than x, can obtain the distance z of the center in k printing opacity slit of amplitude template to amplitude template initiating terminal by this formula k, cycle P kAnd length L k, total number in printing opacity slit is N;
Described given fiber grating that obtained by the reconstruct of any template reflex response or any has following index modulation and distributes:
Figure C20041000916700072
A wherein S(z) 〉=the 0th, the index modulation amplitude distribution function of this fiber grating, c.c are represented last conjugation;
The index modulation amplitude A that on sampling optical fiber grating, forms in the place's exposure of k printing opacity slit of amplitude template kExpression;
2) width of adjusting UV laser beam makes its maximal value greater than the printing opacity gap length of amplitude template;
3) laser beam is moved to z kThe place, k=1 is to N, exposes and forms required index modulation amplitude A k
Described γ=0.5 o'clock, the index modulation amplitude A that on sampling optical fiber grating, forms in the place's exposure of k printing opacity slit kBe A S(z) mean value in this printing opacity slit is divided by 0.32.
In the above-mentioned method for making with the firm and hard fiber grating that now has a target reflection response of amplitude mode, the length in k printing opacity slit of described amplitude template is done according to following formula and is exempted to cut the toe correction:
L k ′ = P k π sin - 1 [ A k A Max sin ( π L k P k ) ] - - - ( 6 )
Wherein, L k, L ' kBe respectively former amplitude template and the length of revising k printing opacity slit of amplitude template, P kIt is the cycle in k printing opacity slit of former amplitude template; A kBe the index modulation amplitude of k exposure station correspondence of former sampling optical fiber grating, A MaxBe all A kIn maximal value.The index modulation amplitude that forms on sampling optical fiber grating in the place's exposure of k printing opacity slit of amplitude template is A Max
Above-mentioned cuts in the toe correction with firm and hard method for making and above-mentioned the exempting from that now has the fiber grating of target reflection response of amplitude mode, and described amplitude template is done according to following formula and exempted to cut toe compensation correction:
P k ′ = P k ( 1 + α A k L k nΛ ) - - - ( 7 )
Wherein, P k, P ' kBe respectively the cycle in k printing opacity slit of former amplitude template and correction amplitude template, L kBe the length in k printing opacity slit of former amplitude template, A kBe the index modulation amplitude of k exposure station correspondence of former sampling optical fiber grating, α is the ratio of direct current modulation amplitude and ac modulation amplitude, and n is the mean refractive index of sampling optical fiber grating, and Λ is the average period of sampling optical fiber grating.
Inventive embodiments shows, in certain physically realizable scope, this method can match the reflex response of sampling optical fiber grating and design load aspect two of power reflection spectrum and group delay spectral lines: in the three dB bandwidth power reflection of example sampling optical fiber grating compose and design load between error on average at 0.1dB, and the error of group delay is on average at 2.6ps.
The present invention introduces the amplitude template in the phase mask method that fiber grating is made, realize the fiber grating by reconstruct-equivalent chirp method design, makes reconstruct-equivalent chirp method be fit to large-scale fiber grating and makes.
Description of drawings
The phase mask that Fig. 1 is traditional-scanning synoptic diagram.
Fig. 2 amplitude template synoptic diagram.
Fig. 3 utilizes amplitude template-phase mask realization variable duty cycle to cut the sampling optical fiber grating synoptic diagram of toe.
The amplitude template that Fig. 4 is general-phase mask method realizes the making platform synoptic diagram of sampling optical fiber grating.
The structure of amplitude template among Fig. 5 inventive embodiments I:
The center in 54 printing opacity slits is with the change curve of sampling number,
The length in 55 printing opacity slits is with the change curve of sampling number.
The distribution of index modulation amplitude among Fig. 6 inventive embodiments I:
Place, 63 printing opacity slits index modulation amplitude is with the change curve of sampling number.
The reflex response of sampling optical fiber grating among Fig. 7 inventive embodiments I:
The power reflection spectrum spectral line of 74 these sampling optical fiber gratings,
The power reflection spectrum spectral line of 75 designs,
The group delay spectral line of 76 these sampling optical fiber gratings,
The group delay spectral line of 77 designs.
The length distribution in amplitude template light penetrating slit crack among Fig. 8 inventive embodiments II:
The length in 83 printing opacity slits is with the change curve of sampling number.
The reflex response of sampling optical fiber grating among Fig. 9 inventive embodiments II:
The power reflection spectrum spectral line of 94 these sampling optical fiber gratings,
The power reflection spectrum spectral line of 95 designs,
The group delay spectral line of 96 these sampling optical fiber gratings,
The group delay spectral line of 97 designs.
The distribution of center, amplitude template light penetrating slit crack among Figure 10 inventive embodiments III:
The center in 103 printing opacity slits is with the change curve of sampling number.
The reflex response of sampling optical fiber grating among Figure 11 inventive embodiments III:
The power reflection spectrum spectral line of 114 these sampling optical fiber gratings,
The power reflection spectrum spectral line of 115 designs,
The group delay spectral line of 116 these sampling optical fiber gratings,
The group delay spectral line of 117 designs.
The distribution of center, amplitude template light penetrating slit crack among Figure 12 inventive embodiments IV:
The center in 123 printing opacity slits is with the change curve of sampling number.
The reflex response of sampling optical fiber grating among Figure 13 inventive embodiments IV:
The power reflection spectrum spectral line of 134 these sampling optical fiber gratings,
The power reflection spectrum spectral line of 135 designs,
The group delay spectral line of 136 these sampling optical fiber gratings,
The group delay spectral line of 137 designs.
Embodiment
Implement device of the present invention as shown in Figure 4, concrete technological process is as follows:
I. adjust light path, make: UV laser beam impinges perpendicularly on the amplitude template 42; Phase mask 43 is near amplitude template 42; Light-sensitive optical fibre 44 stretching and be fixed on phase mask 43 after, as far as possible near but do not stick, its placement should make the ultraviolet luminous energy that sees through amplitude template 42 and phase mask 43 be radiated on its core diameter.
II. adjust the width of UV laser beam 41, make its maximal value greater than the printing opacity slit of amplitude template 42.
III. make k from 1 to N, laser beam is moved to z kPlace's exposure is to form the index modulation amplitude that needs.
The present invention proposes a kind ofly, it is characterized in that it contains following steps successively with the firm and hard method for making that now has the fiber grating of target reflection response of amplitude mode:
1) parallel successively from top to bottom and placement amplitude template, phase mask and the light-sensitive optical fibre pressed close to are regulated light path, make UV laser beam vertical incidence and being mapped on the core diameter of light-sensitive optical fibre by amplitude template, phase mask successively;
Described phase mask is common phase mask, comprises uniformly and the phase mask of linear chrip that the sampling optical fiber grating that is obtained by this phase mask and traditional phase mask-scan method has fixing phase function:
Figure C20041000916700101
Wherein z is the distance to the fiber grating initial end, and Λ is the average period of sampling optical fiber grating, and C is the rate of change of the cycle of this sampling optical fiber grating to z;
The printing opacity slit and the lightproof part of described amplitude template are determined by following formula:
It is a tolerance in sampling period greater than zero number that SP is one, and it is a tolerance of sampling dutycycle greater than zero less than 1 number that γ is one, Δ (z)= S(z)-and (z), S(z) obtain by arbitrary target response reconstruct or the phase function of given fiber grating arbitrarily, (z) is the phase function of sampling optical fiber grating, the fraction part of x is asked in " { x} " expression, be that x deducts the maximum integer less than x, can obtain the distance z of the center in k printing opacity slit of amplitude template to amplitude template initiating terminal by this formula k, cycle P kAnd length L k, total number in printing opacity slit is N;
Described given fiber grating that obtained by the reconstruct of any template reflex response or any has following index modulation and distributes:
A wherein S(z) 〉=the 0th, the index modulation amplitude distribution function of this fiber grating, c.c are represented last conjugation;
The index modulation amplitude A that on sampling optical fiber grating, forms in the place's exposure of k printing opacity slit of amplitude template kExpression;
2) width of adjusting UV laser beam makes its maximal value greater than the printing opacity gap length of amplitude template;
3) laser beam is moved to z kThe place, k=1 is to N, exposes and forms required index modulation amplitude A k
Described γ=0.5 o'clock, the index modulation amplitude A that on sampling optical fiber grating, forms in the place's exposure of k printing opacity slit kBe A S(z) mean value in this printing opacity slit is divided by 0.32.
In the above-mentioned method for making with the firm and hard fiber grating that now has a target reflection response of amplitude mode, the length in k printing opacity slit of described amplitude template is done according to following formula and is exempted to cut the toe correction:
L k ′ = P k π sin - 1 [ A k A Max sin ( π L k P k ) ] - - - ( 6 )
Wherein, L k, L ' kBe respectively former amplitude template and the length of revising k printing opacity slit of amplitude template, P kIt is the cycle in k printing opacity slit of former amplitude template; A kBe the index modulation amplitude of k exposure station correspondence of former sampling optical fiber grating, A MaxBe all A kIn maximal value.The index modulation amplitude that forms on sampling optical fiber grating in the place's exposure of k printing opacity slit of amplitude template is A Max
Above-mentioned cuts in the toe correction with firm and hard method for making and above-mentioned the exempting from that now has the fiber grating of target reflection response of amplitude mode, and described amplitude template is done according to following formula and exempted to cut toe compensation correction:
P k ′ = P k ( 1 + α A k L k nΛ ) - - - ( 7 )
Wherein, P k, P ' kBe respectively the cycle in k printing opacity slit of former amplitude template and correction amplitude template, L kBe the length in k printing opacity slit of former amplitude template, A kBe the index modulation amplitude of k exposure station correspondence of former sampling optical fiber grating, α is the ratio of direct current modulation amplitude and ac modulation amplitude, and n is the mean refractive index of sampling optical fiber grating, and Λ is the average period of sampling optical fiber grating.
Inventive embodiments I
The present invention realized a three dB bandwidth 1.5nm, have the wave filter of the chromatic dispersion that changes with frequency linearity from-500ps/nm to-100ps/nm.
Implement device such as Fig. 4 of this example represent that the wavelength of Ultra-Violet Laser is 244nm, and it is the even phase mask of 1066nm that phase mask adopts average period, and the mean refractive index of light-sensitive optical fibre is 1.4512.
Utilize Fourier transform to do fiber grating restructing algorithm and formula (5), obtain the center z of amplitude template kLength L with the printing opacity slit kDistribution, and the refractive index amplitude distribution function A of sampling optical fiber grating k, represent by Fig. 5, Fig. 6 respectively.Horizontal ordinate 51 is sampling number k among Fig. 5, and left side ordinate 52 is center z of amplitude template kUnit is mm, and right side ordinate 53 is the length L in each printing opacity slit of amplitude template k, unit is mm, curve 54 and 55 has been represented z respectively kAnd L kThe variation with k.Horizontal ordinate 61 is sampling number k among Fig. 6, and ordinate 62 is index modulation amplitude A k, curve 63 is A kCurve with sampling number k variation.
When utilizing the above-mentioned design of transfer matrix method emulation ,-1 grade of reflex response of the sampling optical fiber grating that obtains and design curve are as shown in Figure 7.Wherein horizontal ordinate 71 is wavelength, unit is nm, the power reflectance of left side ordinate 72 expression fiber gratings, unit is dB, the group delay of right side ordinate 73 expression fiber gratings, unit is ps, and curve 74 and 75 has been represented the power reflection spectrum and the group delay spectral line (in the three dB bandwidth) of this sampling optical fiber grating that emulation obtains respectively, and curve 76 and 77 has been represented the power reflection spectrum and the group delay spectral line (in the three dB bandwidth) of design respectively.As seen, utilize the reflex response of the sampling optical fiber grating that the present invention obtains and design load very identical all aspect two of power reflection spectrum and group delay responses: in the three dB bandwidth, the power reflection spectrum of the sampling optical fiber grating of example and the difference maximal value of design load are 0.65dB, and average error is 0.069dB; The group delay spectral line of example sampling optical fiber grating and the difference maximal value of design load are 2.35ps, and average error is 0.53ps.
Inventive embodiments II
The present invention realized a three dB bandwidth 1.5nm, have the wave filter of the chromatic dispersion that changes with frequency linearity from-500ps/nm to-100ps/nm.
The implement device of this example is with inventive embodiments I.
This example on the basis of example I, to the amplitude template carry out as formula (6) thus correction avoided the toe of cutting in the manufacturing process.The center z in each printing opacity slit of revised amplitude template kWith the curve among Fig. 5 54, and the length L in printing opacity slit kDistribute as shown in Figure 8.Wherein horizontal ordinate 81 is represented hits, the length L in ordinate 82 expression printing opacity slits kDistribution, unit is mm, the 83rd, L kDistribution curve with sampling number.The index modulation amplitude A that the exposure in each printing opacity slit causes in this example kBe 3.13*10 -4
When utilizing the above-mentioned design of transfer matrix method emulation ,-1 grade of reflex response of the sampling optical fiber grating that obtains and design curve are as shown in Figure 9.Wherein horizontal ordinate 91 is wavelength, unit is nm, the power reflectance of left side ordinate 92 expression fiber gratings, unit is dB, the group delay of right side ordinate 93 expression fiber gratings, unit is ps, and curve 94 and 95 has been represented the power reflection spectrum and the group delay spectral line (in the three dB bandwidth) of this sampling optical fiber grating that emulation obtains respectively, and curve 96 and 97 has been represented the power reflection spectrum and the group delay spectral line (in the three dB bandwidth) of design respectively.As seen, utilize the reflex response of the sampling optical fiber grating that the present invention obtains and design load very identical all aspect two of power reflection spectrum and group delay responses: in the three dB bandwidth, the power reflection spectrum of the sampling optical fiber grating of example and the difference maximal value of design load are 0.66dB, and average error is 0.072dB; The group delay spectral line of example sampling optical fiber grating and the difference maximal value of design load are 3.76ps, and average error is 1.13ps.
Inventive embodiments III
The present invention realized a three dB bandwidth 1.5nm, have the wave filter of the chromatic dispersion that changes with frequency linearity from-500ps/nm to-100ps/nm.
The implement device of this example is with inventive embodiments I.
This example on the basis of example I, to the amplitude template carry out as formula (7) thus correction avoided cutting the toe compensation in the manufacturing process.The length L in each printing opacity slit of revised amplitude template kDistribute as the curve among Fig. 5 55, and center z kDistribute as shown in figure 10.Wherein horizontal ordinate 101 is represented hits, the center z in ordinate 102 expression printing opacity slits kDistribution, unit is mm, the 103rd, z kDistribution curve with sampling number.The index modulation amplitude A that the exposure in each printing opacity slit causes in this example kDistribution such as Fig. 6.α＝1。
When utilizing the above-mentioned design of transfer matrix method emulation ,-1 grade of reflex response of the sampling optical fiber grating that obtains and design curve are as shown in figure 11.Wherein horizontal ordinate 111 is wavelength, unit is nm, the power reflectance of left side ordinate 112 expression fiber gratings, unit is dB, the group delay of right side ordinate 113 expression fiber gratings, unit is ps, and curve 114 and 115 has been represented the power reflection spectrum and the group delay spectral line (in the three dB bandwidth) of this sampling optical fiber grating that emulation obtains respectively, and curve 116 and 117 has been represented the power reflection spectrum and the group delay spectral line (in the three dB bandwidth) of design respectively.As seen, utilize the reflex response of the sampling optical fiber grating that the present invention obtains and design load very identical all aspect two of power reflection spectrum and group delay responses: in the three dB bandwidth, the power reflection spectrum of the sampling optical fiber grating of example and the difference maximal value of design load are 0.57dB, and average error is 0.078dB; The group delay spectral line of example sampling optical fiber grating and the difference maximal value of design load are 13.73ps, and average error is 5.12ps.
Inventive embodiments IV
The present invention realized a three dB bandwidth 1.5nm, have the wave filter of the chromatic dispersion that changes with frequency linearity from-500ps/nm to-100ps/nm.
The implement device of this example is with inventive embodiments I.
This example on the basis of example II, to the amplitude template carry out as formula (7) thus correction avoided cutting the toe compensation in the manufacturing process.The length L in each printing opacity slit of revised amplitude template kDistribute as the curve among Fig. 8, and center z kDistribute as shown in figure 12.Wherein horizontal ordinate 121 is represented hits, the center z in ordinate 122 expression printing opacity slits kDistribution, unit is mm, the 123rd, z kDistribution curve with sampling number.The index modulation amplitude A that the exposure in each printing opacity slit causes in this example kBe 3.13*10 -4α＝1。
When utilizing the above-mentioned design of transfer matrix method emulation ,-1 grade of reflex response of the sampling optical fiber grating that obtains and design curve are as shown in figure 13.Wherein horizontal ordinate 131 is wavelength, unit is nm, the power reflectance of left side ordinate 132 expression fiber gratings, unit is dB, the group delay of right side ordinate 133 expression fiber gratings, unit is ps, and curve 134 and 135 has been represented the power reflection spectrum and the group delay spectral line (in the three dB bandwidth) of this sampling optical fiber grating that emulation obtains respectively, and curve 136 and 137 has been represented the power reflection spectrum and the group delay spectral line (in the three dB bandwidth) of design respectively.As seen, utilize the reflex response of the sampling optical fiber grating that the present invention obtains and design load very identical all aspect two of power reflection spectrum and group delay responses: in the three dB bandwidth, the power reflection spectrum of the sampling optical fiber grating of example and the difference maximal value of design load are 0.46dB, and average error is 0.15dB; The group delay spectral line of example sampling optical fiber grating and the difference maximal value of design load are 10.60ps, and average error is 3.77ps.

Claims (5)

1、用振幅模板实现具有目标反射响应的采样光纤光栅的制作方法，其特征在于，它依次含有以下步骤：1. A method for making a sampling fiber grating with a target reflection response is realized with an amplitude template, which is characterized in that it contains the following steps successively: 1)自上而下依次平行且贴近的放置振幅模板、相位模板和光敏光纤，调节光路，使得紫外激光束垂直入射并依次通过振幅模板、相位模板而射到光敏光纤的芯径上；1) Place the amplitude template, phase template and photosensitive fiber in parallel and close to each other from top to bottom, adjust the optical path so that the ultraviolet laser beam is vertically incident and hits the core diameter of the photosensitive fiber through the amplitude template and phase template in turn; 所述的相位模板是普通的相位模板，包括均匀的和线性啁啾的相位模板，由该相位模板和均匀或线性啁啾相位模板-扫描方法得到的采样光纤光栅具有固定的相位函数：Described phase template is common phase template, comprises the phase template of uniform and linear chirp, the sampling fiber grating that obtains by this phase template and uniform or linear chirp phase template-scanning method has fixed phase function: 其中z是到光纤光栅初始端的距离，Λ是采样光纤光栅的平均周期，C是该采样光纤光栅的周期对z的变化率；Wherein z is the distance to the initial end of the fiber grating, Λ is the average period of the sampling fiber grating, and C is the rate of change of the period of the sampling fiber grating to z; 所述的振幅模板的透光缝隙和不透光部分由下式决定：The light-transmitting gap and the opaque part of the amplitude template are determined by the following formula:
Figure C2004100091670002C2
Figure C2004100091670002C2
 SP是一个大于零的数，是采样周期的一个度量，γ是一个大于零小于1的数，是采样占空比的一个度量，Δ(z)＝S(z)-(z)，S(z)是由任意目标响应重构得到的、或者是任意给定的光纤光栅的相位函数，(z)是采样光纤光栅的相位函数，
Figure C2004100091670002C3
表示求 的小数部分，即
Figure C2004100091670002C5
减去小于
Figure C2004100091670002C6
的最大整数，由该式可以得到振幅模板第k个透光缝隙的中心位置到振幅模板起始端的距离zk、周期Pk和长度Lk，透光缝隙的总个数为N；SP is a number greater than zero, which is a measure of the sampling period, γ is a number greater than zero and less than 1, which is a measure of the sampling duty cycle, Δ(z)=S(z)-(z) , S(z) is reconstructed from any target response, or is the phase function of any given FBG, (z) is the phase function of the sampled FBG,
Figure C2004100091670002C3
express request The fractional part of
Figure C2004100091670002C5
minus less than
Figure C2004100091670002C6
The largest integer of , the distance z k , period P k and length L k from the center position of the kth light-transmitting slit of the amplitude template to the starting end of the amplitude template can be obtained from this formula, and the total number of light-transmitting slits is N; 所述的由任意目标反射响应重构得到的、或者是任意给定的光纤光栅具有下面的折射率调制分布：Said reconstruction obtained from any target reflection response, or any given fiber grating has the following refractive index modulation distribution: 其中AS(z)≥0是该光纤光栅的折射率调制幅度分布函数，c.c表示前一项的共轭；Where A S (z)≥0 is the refractive index modulation amplitude distribution function of the fiber grating, and cc represents the conjugate of the previous term; 在振幅模板的第k个透光缝隙处曝光而在采样光纤光栅上形成的折射率调制幅度用Ak表示；The amplitude of the refractive index modulation formed on the sampling fiber grating by exposing at the kth light-transmitting slit of the amplitude template is represented by A k ; 2)调节紫外激光束的宽度，使其大于振幅模板的透光缝隙长度的最大值；2) adjusting the width of the ultraviolet laser beam so that it is greater than the maximum value of the length of the light-transmitting slit of the amplitude template; 3)把激光束移动到zk处，k＝1到N，进行曝光而形成所需的折射率调制幅度Ak。3) Move the laser beam to z k , where k=1 to N, and perform exposure to form the required refractive index modulation amplitude A k . 2、根据权利要求书1所述的用振幅模板实现具有目标反射响应的采样光纤光栅的制作方法，其特征在于，所述的γ＝0.5时，在振幅模板的第k个透光缝隙处曝光而在采样光纤光栅上形成的折射率调制幅度Ak为AS(z)在该透光缝隙内的平均值除以0.32。2. The method for fabricating a sampling fiber grating with a target reflection response using an amplitude template according to claim 1, characterized in that, when γ=0.5, exposure is performed at the kth light-transmitting slit of the amplitude template The refractive index modulation amplitude A k formed on the sampling fiber grating is the average value of A S (z) in the light-transmitting slit divided by 0.32. 3、根据权利要求书1所述的用振幅模板实现具有目标反射响应的采样光纤光栅的制作方法，其特征在于，所述的振幅模板的第k个透光缝隙的长度按照下式做免切趾修正：3. The method for making a sampling fiber grating with a target reflection response using an amplitude template according to claim 1, wherein the length of the kth light-transmitting slit of the amplitude template is cut-free according to the following formula Toe Correction: LL kk ′′ == PP kk ππ sinsin -- 11 [[ AA kk AA MaxMax sinsin (( πLπL kk PP kk )) ]] -- -- -- (( 66 )) 其中，Lk、L’k分别是原振幅模板和修正振幅模板的第k个透光缝隙的长度，Pk是原振幅模板的第k个透光缝隙的周期；Ak是原采样光纤光栅第k个曝光点对应的折射率调制幅度，AMax是所有Ak中的最大值。Among them, L k and L' k are the lengths of the kth light-transmitting slit of the original amplitude template and the modified amplitude template respectively, P k is the period of the k-th light-transmitting slit of the original amplitude template; A k is the original sampling fiber grating The refractive index modulation amplitude corresponding to the kth exposure point, A Max is the maximum value among all A k . 4、根据权利要求书3所述的用振幅模板实现具有目标反射响应的采样光纤光栅的制作方法，其特征在于，所述的在振幅模板的第k个透光缝隙处曝光而在采样光纤光栅上形成的折射率调制幅度为AMax。4. The method for making a sampling fiber grating with a target reflection response by using an amplitude template according to claim 3, wherein the exposure at the kth light-transmitting slit of the amplitude template and the sampling fiber grating The magnitude of the refractive index modulation formed above is A Max . 5、根据权利要求书1或3中任何一项权利要求所述的用振幅模板实现具有目标反射响应的采样光纤光栅的制作方法，其特征在于，所述的振幅模板按照下式做免切趾补偿修正：5. According to any one of claims 1 or 3, the method for making a sampled fiber grating with a target reflection response using an amplitude template is characterized in that the amplitude template is free of apodization according to the following formula Compensation fixes: PP kk ′′ == PP kk (( 11 ++ αα AA kk LL kk nΛnΛ )) -- -- -- (( 77 )) 其中，Pk、P’k分别为原振幅模板和修正振幅模板的第k个透光缝隙的周期，Lk是原振幅模板的第k个透光缝隙的长度，Ak是原采样光纤光栅第k个曝光点对应的折射率调制幅度，α是直流调制幅度和交流调制幅度的比例，n是采样光纤光栅的平均折射率，Λ是采样光纤光栅的平均周期。Among them, P k and P' k are the periods of the kth light-transmitting slit of the original amplitude template and the modified amplitude template respectively, L k is the length of the k-th light-transmitting slit of the original amplitude template, and A k is the original sampling fiber grating The refractive index modulation amplitude corresponding to the kth exposure point, α is the ratio of the DC modulation amplitude to the AC modulation amplitude, n is the average refractive index of the sampled FBG, and Λ is the average period of the sampled FBG.
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