Abstract

We have previously demonstrated the feasibility of using a single in-line angle-tuned Fabry-Perot etalon filter for optical channel selection in high- density wavelength division multiplexed (WDM) transmission systems.¹ However, the number of optical channels which can be simultaneously used with a single etalon is limited. First, all optical channels should be within only one free spectral range (FSR) of an etalon. Second, the spectral spacing between channels is limited due to conflicting requirements of high optical throughput which restricts the maximum reflectivity of etalon surfaces (depending on the quality of optical surfaces and coating materials) and minimum acceptable crosstalk which requires maximization of reflectivity of etalon surfaces. We propose using stacked in-line angle-tuned Fabry-Perot etalon filters as an effective way of increasing the number of multiplexed channels and decreasing the spectral separation between them [which leads to the term frequency division multiplexing (FDM) instead of WDM].

© 1988 Optical Society of America