Research On DWDM Solid Cavity Narrow Bandpass Filters

Narrow bandpass filter is one of the key components that used in DWDM optical fiber transmission system, currently its cavity and reflecting layer are all made from coating films, producing difficulties are high, finished product ratio is low and cost is high. For the solid cavity narrow bandpass filters, because its interference grade is higher than all medium film filters, so producing difficulties and cost are reduced quitely, and temperature stability is better.On the basis of analysing narrow bandpass filters structures, presented to employ the solid material to be filter's cavity layer. Then deeply theoretical analysis and experiment research have been carried out from optical thin film spectral character, optimization design, tolerance error analysis, monitoring method and real deposition technics processes.On the side of theories study, maxwell equitation of electrical magnet promulgation is first introduced, then optical characters of thin films have been comprehensive analyzed. Based on the analysis of single solid cavity filter's spectral characters, cavity layer thickness and reflectivity of reflecting layer affecting filter spectral characters is discussed. The design of single solid cavity filter is presented. On the basis of multi-solid cavity filter's bandpass charaters analysing, constructed filter's evaluation function. Multi-cavity bandpass filter auto optimizing design software is programmed based on multi-cavity compounding theory, and found out that FSR can be extended if the interference grades of solid cavity layer are difference. At last, suitable DWDM system 100GHz multi-solid-cavity narrow bandpass filters have been designed out.On the side of experimentation study, Introduced producing processes of solid cavity narrow bandpass filters. Analyzed monitoring precision of transmission turn point method, the methods of improving monitoring precision are presented. The effects of several leading technological parameters for the thin films performance during films depositing is analyzed, and the primary technological parameters and processes are established on ZZS700-6/G coating machine. Tested spectral characters of produced solid cavity narrow bandpass filters, the results are consistented with design.