The invention relates to Fabry-Perot interferometers (FFPI) comprising two or more optically coupled tunable all-fiber Fabry-Perot component filters, wherein the Fabry-Perot cavity of the filter is formed within a bare section of optical fiber held within a fiber ferrule. The wavelength transmitted by the interferometer can be tuned thermally or electromechanically for a fiber containing the Fabry-Perot cavity bonded into a groove of a metal substrate. The interferometer can be tuned by changing the length of Fabry-Perot cavity, including by the use of a piezoelectric transducer.