Data processing: artificial intelligence – Machine learning – Genetic algorithm and genetic programming system
Reexamination Certificate
2000-03-24
2003-04-01
Follansbee, John A. (Department: 2121)
Data processing: artificial intelligence
Machine learning
Genetic algorithm and genetic programming system
C359S896000, C382S141000
Reexamination Certificate
active
06542876
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing optical multilayered optical filters, for appropriately splitting/merging signal lights having plural wavelength convoluted, used in an optical communication system sending/receiving wavelengths multiplexed light communications, and to a method for ICE operating the genetic algorithm for extracting the most suitable combination from candidates of complex combination.
2. Description of the Prior Art
As wavelength-multiplexed light communications have been developed, there are needs for multilayered splitting/merging filters having such characteristics as a narrow passband or small para-reflex characteristics.
For methods of designing multilayered optical filters each layer of which has refractive index Ni and thickness Di based on a desired optic characteristics, in general, it has been common to use a method of thickness optimization such as described in Japanese Published Unexamined Patent Application No. 2650048, by determining in advance refractive index Ni of each layer composing the filter, to preset the thickness Di, to determine optical characteristics for each wavelength, to change the thickness Di, to optimize the thickness Di so as to have maximum in the optical characteristics.
As another method of optimization, there is only a trial and error method in which refractive index of a layer is altered, and the thickness for every layer is optimized again.
In accordance with the method as described above, since the refractive index Ni is predetermined, the degree of freedom of design is not insufficient, and furthermore the results may often fall into a local solution.
In addition, there are a huge number of combinations of Ni and Di in a multilayered optical filter so that the optimization requires very long time for selection; therefore the selection of the most optimized combination has been practically impossible.
In the Prior Art local resolution obtained by using the thickness optimization method as have been described above was needed and the only practical result.
BRIEF SUMMARY OF THE INVENTION
The present invention been made in view of the above circumstances and has an object to overcome the above problems and to provide a method of production of multilayered optical filters, used in the designing of multilayered optical filters having such complex combinations as described above, for selecting the most optimized combination of refractive index Ni and thickness Di for each of layers without falling into a local solution.
Also, the inventors of the present invention have been realized a method for selecting the most optimized solution, in order to determine the most optimized or almost optimized solution, in which a genetic algorithm (abbreviated as GA hereinafter) are used for converting the problems of optimization into the genetic sequences, such as the problems of optimization of the combinations of refractive index Ni and thickness Di in each layer in the designing of multilayered optical filters, comprising the steps of:
generating pattern groups, for generating pattern groups each comprised of a plurality of patterns;
extracting at least two patterns from within the generated group of patterns;
mutating and crossing over for generating new patterns by mutating or crossing over the extracted patterns;
evaluating for calculating the fitness of the optimization problem of the groups comprising the extracted patterns and newly generated patterns, for each of mutation and cross-over steps;
selecting to decrease the number of groups including extracted patterns and newly generated patterns to the number of extracted patterns;
substituting the selected patterns in place of the patterns extracted from the pattern groups, and
altering the contents of pattern groups by repeating between the extracting step and the selecting step.
The step of selecting in the genetic algorithm comprises either elite method, for selecting patterns of the predetermined numbers in the order of fitness among the object pattern group and removing others, or elite-roulette method, for selecting some patterns by using the elite method, and others by using the roulette method and removing the rest.
In both selection methods, there is no restriction of pattern selection, so that any duplicated patterns having the identical pattern elements were not rejected. If the selected patterns are filled with patterns having the identical elements, in some optimization problems, patterns having the same elements are inserted into the pattern group, and after repeating the genetic algorithm steps as described above, pattern group are totally filled with the patterns having the identical elements. This may result in an unexpected error in the retrieval search of the most optimized solution.
Often the search results obtained by the GA as above may be a local solution, which may or may not satisfy the goal.
Another object of the present invention is to avoid, in GA the predominance of selected pattern and of pattern group with the patterns having the same elements by preventing the patterns having the identical elements from coexisting in the selection patterns in order to retrieval search not only a local solution but also the most suitable one.
A method for producing multilayered optical filters comprises:
a generating step for generating a initial pattern comprising a matrix given by
P
=(
X
1
,
X
2
,
X
3
. . . ,
XS
) (1)
which is comprised of elemental matrices Xi, each of which comprises as element refractive index and thickness of i layers (i is an integer equal to or more than 1) of a multilayered optical filter having S layers (S is an integer equal to or more than 1);
a reproducting/mutating step for either increasing or decreasing, in an arbitrary element Xi of the initial pattern, either the refractive index or thickness of the initial pattern by a predetermined number, in terms of the initial pattern, to generate a predetermined number of mutation patterns which are mutually different one from other;
a cross over step for selecting at least one pair of patterns from the mutated patterns generated in the reproducting/mutating step and the initial patterns to cross over, in the pair of patterns selected, the matrix Xi in the pattern and/or the matrix obtained by the mutation of the matrix by the predetermined number to generate a predetermined number of crossed over patterns;
a selecting step for selecting the desired number of patterns having the most appropriate optical characteristics from the mutated pattern group generated in the reproducting/mutating step, the crossed over pattern group, and the pattern group comprised of the initial patterns; and
a repeating step for repeating a series of algorithmic process steps comprised of the reproducting/mutating step, the cross over step, and the selecting step,in terms of the predetermined number of patterns selected in the selecting step instead of the initial patterns, until the optical characteristics of the selected patterns obtained in the immediately preceding algorithmic steps may conform to the desired error range for the desired optical characteristics.
In accordance with the method of producing multilayered optical filters in accordance with the present invention, the repetition of a series of algorithmic process steps allows each layer in a multilayered optical filter to be set in such a manner as the optic characteristics may conform to a specific desired range. This may result in a better design and production of multilayered optical filters when compared with the conventional designing method.
When a series of the algorithmic process steps comprised of the reproducting and mutating step, the cross over step, and the selecting step, if the optical characteristics of the selected pattern obtained from the algorithmic process steps match with the optical characteristics of the selected pattern obtained from one of the repetitions preceding to the former, a second initial pattern, which is different from the
Hirai Toshio
Kawazoe Yoshiyuki
Kikuchi Toshihiro
Mizuseki Hiroshi
Someno Yoshihiro
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Follansbee John A.
Hirl Joseph P.
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