Browsing by Author "YEH, PC"

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GENERALIZED PERCEPTRON LEARNING RULE AND ITS IMPLICATIONS FOR PHOTOREFRACTIVE NEURAL NETWORKS
(1994-09-01)
CHENG, CJ
;
YEH, PC
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HSU, KY
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交大名義發表
;
光電工程學系
We consider the properties of a generalized perceptron learning network, taking into account the decay or the gain of the weight vector during the training stages. A mathematical proof is given that shows the conditional convergence of the learning algorithm. The analytical result indicates that the upper bound of the training steps is dependent on the gain (or decay) factor. A sufficient condition of exposure time for convergence of a photorefractive perceptron network is derived. We also describe a modified learning algorithm that provides a solution to the problem of weight vector decay in an optical perceptron caused by hologram erasure. Both analytical and simulation results are presented and discussed.
HOLOGRAM ENHANCEMENT IN PHOTOREFRACTIVE MEDIA
(1995-08-01)
YEH, PC
;
GU, C
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CHENG, CJ
;
HSU, KY
;
光電工程學系
We consider the possibility of restoration and/or enhancement of decaying holograms in photorefractive media by using a simple optical readout in conjunction with a phase conjugator. The results indicate that extremely weak holograms can be enhanced provided that the two-beam coupling is sufficiently strong. Steady-state photorefractive holograms can be maintained continuously without decay by using a properly designed readout scheme. The result also provides an explanation for the formation of mutually pumped phase conjugation in terms of the amplification of initial noise gratings.
OPTICAL RESTORATION OF PHOTOREFRACTIVE HOLOGRAMS THROUGH SELF-ENHANCED DIFFRACTION
(1995-02-01)
CAMPBELL, S
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YEH, PC
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GU, C
;
LIN, SH
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CHENG, CJ
For the first time to our knowledge, we demonstrate the use of self-enhanced diffraction to optically restore weak dynamic volume holograms. This restoration process is achieved through the use of a novel beam-toggling scheme that significantly enhances the steady-state diffraction efficiency of volume index gratings stored in photorefractive media. Experiments demonstrating and confirming theory are presented and discussed.
PHASE-CONJUGATION BY 4-WAVE-MIXING IN SINGLE-MODE FIBERS
(1994-12-01)
WU, WS
;
YEH, PC
;
CHI, S
;
光電工程學系
;
Department of Photonics
We present an exact solution to the coupled-mode equations, governing four-wave mixing in single-mode fibers, under the perfect phase-matching condition. The solution accounts for pump depletion and fiber absorption. Optimum length of fiber is derived and phase conjugation efficiency is calculated and discussed. The calculated results are in good agreement with the reported experimental results.