The film structure of a multiple-cavity narrow-band interference filer is always used as DEMUX in WDM optical fiber communication system. To ensure the repeat of the film coating results, the optical thickness of every layer in this film structure is designed to be the integer multiple of the quarter of the monitor wavelength. But such design, which is only composed of regular layers, cannot meet the desire. Therefore, a design method, in which the film structure of a few irregular layers is added to the multiple-layer standard film structure, is introduced in this paper. Thus, the design desire can be basically satisfied. In the design, the optical thickness of the irregular layers is obtained by the optimal method with computer. An estimate function of the optimizing is made in this paper. A program is built in MATLAB programming language. By using the program, the thickness of the irregular compensates film on whatever multiple-layer regular film structure can be optimized.
The design and deposition of the optical thin film, which have high-transmittance nearby 1550 nm wavelength for the desire of such components in the modern optical fiber communication, is systematically studied in this paper. Using the optimum-seek method of Monte Carlo experiment and POWELL least square method, we built optimization program. Based on anti- reflecting film structure, the optimum design of the BK7 glass and the GaAs is gotten. Several methods to deposit such irregular film structure are searched. The results indicate that using the double wavelength method or the various over- shoot quantities methods can accurately monitor the optical thickness of each layer. The optical thin-film components with high-transmittance nearby 1550 nm wavelength are gotten.