Improved fiber Fabry-Perot (FFP) filter configurations are provided in which
at least one of the mirror-ended fiber ends forming the FFP has a concave fiber
core end. The mirror at that fiber core end is thus concave. The invention provides
waferless FFP configurations in which the FFP cavity is an air-gap cavity formed
by two highly reflective dielectric mirrors deposited directly on optical fiber
ends. The air gap cavity can be tuned using various methods to tune the filter.
Use of a concave mirror at the fiber core enables filters with improved performance
characteristics: including very wide FSR (12000 GHz), very high finesse (5,000),
and high glitch-free dynamic range (GFDR) (40 dB). The invention also provides
improved wafer-based FFP fixed and tunable filters that incorporate a concave mirror
at a fiber core forming the FFP cavity and a fiber (SMF) waveguide within the cavity.
