Research On Designing Of Optic Film Narrow Bandpass Filters

Along with the higher demand of the optics communications with the optcal film bandpass filters, bringing forward new challenge to the design of film coatings.The narrow bandpass filters require to have extremely low insertion loss-extremely low ripple-broad pass bandwidth-high isolation-excellent and so on.. The research on design methods are discussed. Several type of coatings are designed,and a good optimize design methods are discussed also.The main contents are as follows:First, the development of the optcal film bandpass filters is introduced.The film coatings design methods in nation and abroad and the developing trend are discussed. The influence factors and key techniques of spectrum are analyzed. The basic principle of optic film design is given . the formula of reflectivity and Transmittance are educed,the characteristic matrixs are educed also. Thus, the basic principle of optcal film bandpass filters design is given.Secondly, Two analytic design methods of bandpass filters are researched. The two design methods stand or fall are compared.Using the two methods, the one-cavity,two-cavities and several-cavities bandpass filters are designed. Along with the increasing difficulty of design, the two methods have some shortages.Finally, The configurable characteristic of 3-skip-1 filter for 100 GHz using in Optical Add-Drop Multiplexing(OADM)was analyzed. several factors influence the spectrum was analyzed aslo. A optimal arithmetic based on combinating simulated annealing and genetic algorithm was provided. By calculating the characteristic matrix , the fitness function which sensitivity to the films structure was builded.To minish the ripple-broad pass, Reflective coatings were added also.By the genetic operator ,the multilayer optimized has extremely low insertion loss;extremely low ripple,broad pass bandwidth;high isolation,and meets the 3-skip-1 filter for 100 GHz design demand.