A novel inline tunable Fabry-Perot filter for WDM fiber systems

A novel Optical Fabry-Perot Interferometer (FPI) which consists of a couple of GRIN lenses is presented. The GRIN lenses are used not only as a collimating lens and a focus lens respectively, but also as a Fabry-Perot resonator which is piezoelectrically tuned. Compared with other types of FPI for optical filter this device has a much simple structure, lower insertion loss. It is compatible with fibers and useful for different WDM's wavelength spans.