CN105487169B - A kind of compensation method of the optical filter based on linear enhancing grating - Google Patents

A kind of compensation method of the optical filter based on linear enhancing grating Download PDF

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Publication number
CN105487169B
CN105487169B CN201510892077.9A CN201510892077A CN105487169B CN 105487169 B CN105487169 B CN 105487169B CN 201510892077 A CN201510892077 A CN 201510892077A CN 105487169 B CN105487169 B CN 105487169B
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duty ratio
linear
grating
function
refractive index
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CN105487169A (en
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司马朝坦
刘柏兰
余宇
杨威
杨旺
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
    • G02B2006/02166—Methods of designing the gratings, i.e. calculating the structure, e.g. algorithms, numerical methods

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)

Abstract

The invention belongs to fields of communication technology, disclose a kind of compensation method of the optical filter based on linear enhancing grating, include the following steps：In fiber grating scribing process, the duty ratio of rectangular wave and refractive index variable quantity maximum value Δ n are obtainedmaxNon-linear relation function NL；Ask for the inverse function NL of function NL‑1；Using inverse function NL‑1As compensating factor, the duty ratio of the rectangular wave is calculated；Wherein, compensating operation is performed as precompensation so that the duty ratio of the rectangular wave after compensation and refractive index variable quantity maximum value Δ nmaxRestore linear relationship.The present invention calculates compensating factor and carries out optical grating reflection deterioration in characteristics caused by compensated in advance elimination non-linear factor on this basis by obtaining nonlinear function.

Description

A kind of compensation method of the optical filter based on linear enhancing grating
Technical field
The present invention relates to field of communication technology, the compensation of more particularly to a kind of optical filter based on linear enhancing grating Method.
Background technology
Grating filter be common high-precision filter, generally use lithography process.
In the ultraviolet light directly inscription method of existing fiber grating filter, the square of control system transmitting is approximately thought It is linear relationship between shape wave duty ratio and index modulation degree, and the non-linear characteristic that can lead to grating of physical presence is bad Change.
Under common grating carving and writing method, there are certain defects for the making of grating filter.Direct based on ultraviolet light It inscribes in the filter production for making plane grating technology, is reflected by being controlled the methods of intensity modulation or phase-modulation Rate changes delta nmax, due to the nonlinear characteristic of the factors such as material itself and system of processing, the reflectance spectrum of the grating filter of inscription There is difference with target reflectance spectra, deteriorate Grating Properties.
Invention content
The present invention provides a kind of compensation method of the optical filter based on linear enhancing grating, solve in the prior art by The nonlinear system error caused by material and system of processing etc. are non-linear；The skill for promoting machining accuracy and product quality is reached Art effect.
In order to solve the above technical problems, the present invention provides a kind of compensation of the optical filter based on linear enhancing grating Method includes the following steps：
In fiber grating scribing process, the duty ratio of rectangular wave and refractive index variable quantity maximum value Δ n are obtainedmaxIt is non-thread The function NL of sexual intercourse；
Ask for the inverse function NL of function NL-1；
Using inverse function NL-1As compensating factor, the duty ratio of the rectangular wave is calculated；
Wherein, compensating operation is performed as precompensation so that the duty ratio and refractive index variable quantity of the rectangular wave after compensation are most Big value Δ nmaxRestore linear relationship.
Further, the duty ratio of rectangular wave and refractive index variable quantity maximum value Δ n are obtainedmaxNon-linear relation operation For：
Slowly change the size of duty ratio from 0 to 100%, refractive index maximum changing value is easy to get by measuring and calculating ΔnmaxWith the variation relation of duty ratio.
Further, using inverse function NL-1As compensating factor, calculate the rectangular wave duty ratio include initial portion and Compensating factor；
Wherein, function of the initial portion for the calculating duty ratio of initial setting up under the conditions of ideal linearity, the benefit The factor is repaid as inverse function NL-1。
One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages：
The compensation method of the optical filter based on linear enhancing grating provided in the embodiment of the present application, by accurately obtaining During taking actual processing, the non-linear relation function NL of duty cycle signals and grating refractive index maximum variable quantity seeks its anti-letter Number NL-1As compensating factor, the calculating of compensated in advance duty cycle control signal so that duty ratio changes with grating refractive index maximum Amount restores linear, so as to eliminate non-linear relation and as it caused by grating reflection deterioration.
Description of the drawings
Fig. 1 is that the principle of the compensation method of the optical filter provided in an embodiment of the present invention based on linear enhancing grating is shown It is intended to；
Fig. 2 is apodization and the reflection of Hilbert transform grating provided in an embodiment of the present invention and Sinc apodization gratings Spectrum.
Specific embodiment
The embodiment of the present application is solved existing by providing a kind of compensation method of the optical filter based on linear enhancing grating Have in technology due to the non-linear caused nonlinear system error such as material and system of processing；Promotion machining accuracy is reached, has disappeared Except non-linear effects and high-quality caused reflection characteristic deterioration, the technique effect of Improving The Quality of Products.
Referring to Fig. 1, in order to solve the above technical problems, the general thought that the embodiment of the present application provides technical solution is as follows：
A kind of compensation method of the optical filter based on linear enhancing grating, includes the following steps：
In fiber grating scribing process, the duty ratio of rectangular wave and refractive index variable quantity maximum value Δ n are obtainedmaxIt is non-thread The function NL of sexual intercourse；
Ask for the inverse function NL of function NL-1；
Using inverse function NL-1As compensating factor, the duty ratio of the rectangular wave is calculated；
Wherein, compensating operation is performed as precompensation so that the duty ratio and refractive index variable quantity of the rectangular wave after compensation are most Big value Δ nmaxRestore linear relationship.
Obtain the duty ratio of rectangular wave and refractive index variable quantity maximum value Δ nmaxThe operation of non-linear relation be：From 0 to 100% slowly changes the size of duty ratio, and refractive index maximum changing value Δ n is easy to get by measuring and calculatingmaxWith duty ratio Variation relation.
Using inverse function NL-1As compensating factor, the duty ratio for calculating the rectangular wave includes initial portion and compensating factor； Wherein, function of the initial portion for the calculating duty ratio of initial setting up, the compensating factor are inverse function NL-1。
Through the above as can be seen that duty ratio in control planning and the non-linear relation of refractive index maximum changing value Budget is carried out, and the inverse function for passing through nonlinear function compensates in advance, introduces linear enhancing function NL-1It compensates, makes It restores linear.By the method linearly enhanced, the characteristic of the optical filter based on grating is improved.
Referring to Fig. 2, the defects of the present embodiment is intended to caused by compensating non-linear relationship, before scheme is compensated, I First have to measure obtain specific non-linear relation.
Slowly change the size of duty ratio (Duty cycle) from 0 to 100%, refraction is easy to get by measuring and calculating Rate maximum changing value Δ nmaxWith the variation relation of duty ratio to get to non-linear relation curve NL, herein with illustration (a) in Fig. 2 For shown non-linear relation.As it can be seen that in duty ratio and the relationship of refractive index maximum value variation, there are initial threshold, and Finally there are saturated phenomenons.
In directly inscribing the method for grating in existing ultraviolet light, duty ratio and refractive index maximum changing value are by approx Think linear, so as target Δ nmaxWhen (normalization) is 0.2, control system can be by rectangular wave duty cycle adjustment It is 0.2.However the Δ n actually obtained under non-linear relation shown in Fig. 2 (a)maxBut it is 0.08, less than 0.2.Similarly, target Δ nmaxWhen being 0.8, rectangular wave duty cycle adjustment is 0.8 by control system, actually obtains Δ nmaxIt is 0.92, more than actual value.
Before the duty control waveguide index maximum changing value of square-wave signal, we first to non-linear carry out budget, And it compensates in advance.Negate to nonlinear curve NL function NL-1, as compensating factor, duty ratio is made to first pass through NL-1It calculates The dutyfactor value after corresponding compensation is obtained, as shown in Fig. 3 dashed rectangles, wherein Fig. 2 illustrations (b) represent penalty function NL-1。 That is, as target Δ nmaxWhen being 0.8, it is 0.8 according to dutyfactor value corresponding to linear approximate relationship, passes through linear compensation NL-1 (0.8) for 0.683 to get to compensating later duty ratio setting value 68.3%.By adding in NL in non-linear process-1It calculates It compensates so that duty ratio and Δ nmaxLinear relationship is restored.
Under nonlinear condition shown in Fig. 2, we have been done to the two kinds of filtering of Sinc apodization gratings and Hilbert grating Device under nonlinear condition with the simulation analysis after linear compensation, with analyze it is non-linear to filter reflection spectrum deterioration influence.
Spectral line (a) is Hilbert transform grating apodization；Spectral line (b) Hilbert transform optical grating reflection is composed；Spectral line (c) Sinc grating apodizations；Spectral line (d) Sinc optical grating reflections are composed, and wherein solid line is under nonlinear condition, during dotted line under linear conditions.
Due to nonlinear influence, Δ n in grating apodizationmaxWeak part becomes weaker, reflectance spectrum also great deterioration, in Heart flat is no longer steady, frequency spectrum edge inhibits to generate secondary lobe than reducing.Meanwhile the Hilbert transform frequency after overcompensation Spectrum and Sinc spectrum of function center are very flat, and rolloff-factor is big, and edge inhibits than high, and Grating Properties are excellent.After linear enhancing, The flat wide range and central concave of hilbert-transform filter coincide very much with preferable Hilbert transform frequency spectrum；Based on Sinc The rectangular filter of grating coincide substantially with ideal rectangle wave filter.
In conclusion by emulation and analysis, can significantly deduce the linear compensation of duty ratio and grating apodization can have The spectral characteristic of the improvement grating of effect.
Further, in the making of fiber grating filter, making grating to the light sensitivity of ultraviolet light using optical fiber is Very universal method.The square-wave signal duty ratio sent out except through changing control system changes to change refractive index maximum Except value, also changing other governing factors such as time for exposure can achieve the effect that make fiber grating.And in these controls Inevitable there is also similar non-linear relation due to material light sensitive characteristic and grating processing method in relationship, we equally can be with It is compensated by context of methods.
One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages：
The compensation method of the optical filter based on linear enhancing grating provided in the embodiment of the present application, by accurately obtaining During taking actual processing, the non-linear relation function NL of duty cycle signals and grating refractive index maximum variable quantity seeks its anti-letter Number NL-1As compensating factor, the calculating of compensated in advance duty cycle control signal so that duty ratio changes with grating refractive index maximum Amount restores linear, so as to eliminate non-linear relation and as it caused by grating reflection deterioration.
It should be noted last that more than specific embodiment is merely illustrative of the technical solution of the present invention and unrestricted, Although the present invention is described in detail with reference to example, it will be understood by those of ordinary skill in the art that, it can be to the present invention Technical solution be modified or replaced equivalently, without departing from the spirit and scope of technical solution of the present invention, should all cover In scope of the presently claimed invention.

Claims (3)

1. a kind of compensation method of the optical filter based on linear enhancing grating, which is characterized in that include the following steps：
In fiber grating scribing process, the duty ratio of rectangular wave and refractive index variable quantity maximum value Δ n are obtainedmaxNonlinear dependence The function NL of system；
Ask for the inverse function NL of function NL-1；
Using inverse function NL-1As compensating factor, the duty ratio of the rectangular wave is calculated；
Wherein, compensating operation is performed as precompensation so that the duty ratio of the rectangular wave after compensation and refractive index variable quantity maximum value ΔnmaxRestore linear relationship.
2. the compensation method of the optical filter as described in claim 1 based on linear enhancing grating, which is characterized in that obtain square The duty ratio of shape wave and refractive index variable quantity maximum value Δ nmaxThe operation of non-linear relation be：
Slowly change the size of duty ratio from 0 to 100%, refractive index maximum changing value Δ is easy to get by measuring and calculating nmaxWith the variation relation of duty ratio.
3. the compensation method of the optical filter as claimed in claim 2 based on linear enhancing grating, it is characterised in that：
Using inverse function NL-1As compensating factor, the duty ratio for calculating the rectangular wave includes initial portion and compensating factor；
Wherein, function of the initial portion for the calculating duty ratio of initial setting up under the conditions of ideal linearity, the compensation because Son is inverse function NL-1。
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20000032475A (en) * 1998-11-14 2000-06-15 박호군 Optical fiber delay line filter using fiber bragg grating
EP1037416A2 (en) * 1999-03-15 2000-09-20 Lucent Technologies Inc. Optical fibre communication system comprising means for optical pulse reshaping
CN101750671A (en) * 2009-12-23 2010-06-23 南京大学 Planar waveguide Bragg grating and laser thereof based on reconstruction-equivalent chirp and equivalent apodization
CN103576223A (en) * 2013-10-31 2014-02-12 佛山科学技术学院 RZ to NRZ code type converting fiber bragg grating designing method and device thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20000032475A (en) * 1998-11-14 2000-06-15 박호군 Optical fiber delay line filter using fiber bragg grating
EP1037416A2 (en) * 1999-03-15 2000-09-20 Lucent Technologies Inc. Optical fibre communication system comprising means for optical pulse reshaping
CN101750671A (en) * 2009-12-23 2010-06-23 南京大学 Planar waveguide Bragg grating and laser thereof based on reconstruction-equivalent chirp and equivalent apodization
CN103576223A (en) * 2013-10-31 2014-02-12 佛山科学技术学院 RZ to NRZ code type converting fiber bragg grating designing method and device thereof

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