Tunable double-cavity solid-spaced bandpass filter.

In this paper, we introduce the principle and demonstrate the feasibility of a tunable multiple-cavity solid-spaced bandpass filter for WDM (Wavelength Division Multiplexing) applications, which uses a vernier effect since the two cavities have different thermal sensitivities. A set of specific wavelengths can be addressed in the whole C-Band by using temperature changes less than 100 degrees C. This result corresponds to a gain factor in sensitivity about 5 with respect to alternative standard thin-film configurations.