Discretely tunable multi cavity FFP filter for standard WDM frequency grid

In this paper, we present theoretical results of research on a new discretely tunable multi cavity fiber Fabry-Perot (DTFFP) filter. The structure we propose assumes using at least two F-P filters with different length of resonance cavities, tuned by a shared piezoelectric transducer, e.g: the changes of all filter lengths are equal. Different speed of cavity tuning creates a set of separate frequencies of the common resonances. In this paper, we derive basic equations describing properties and allowing a design of DTFFP filter. We also carry out calculations for a standard frequency grid used in optical fiber WDM systems. The research done proves that, for the examined filters, it is possible to obtain both high selectivity and high value of tuning range at the same time.