| Summary: | 碩士 === 國立中正大學 === 機械系 === 92 === A methodology based on shape optimization technique to design EDFA gain flattening filters (GFF) is developed. The GFF is made by one or two FBG-bonded substrates that are designed to be strained and then the bonded FBG can be tuned to have designated spectra. Numerical simulations show that the ripple is approximately ± 1.1 dB for the GFF made by one substrate and ± 0.4 dB for that by two substrates. However the refractive index modulation of FBG, the pos-sibility of buckling of the substrate while tuning the FBG and the glue that is used to bond the FBG on the substrate affect the performance of the GFF. Therefore it is suggested that the parameters of FBG should be determined before the substrate is designed. Two semi-experimental methods to measure the parameters of FBG have been developed. In the first method, the reflective spectrum and the stain distribution of a FBG bonded on a deformed cantilever beam are measured first and then the associate seven parameters are obtained using the optimization technique. The second method is to measure five instead of seven parameters of FBG but without bonding the FBG on a substrate. Numerical simulations show that the accuracy of the first method is better than that of the second. However the second method provides a easy and a fast way to measure five parameters of FBG within an acceptable accuracy. The experimental errors were verified to be insufficient refractive index modulation of FBG﹑substrates bulking while tuning and stain reducing from glue to fiber. Due to the simulate and experimental spectrum turn into approached while the values of errors were considered.
The fine results have been demonstrated both on simulation and ex-periment, but the convergence and accuracy became worse while measuring 5 parameters without bonding on a cantilever beam. How-ever, it still satisfies the errors tolerance and acceptable operating time.
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