Recent advances on all-fiber tunable filter

Abstract

A unique all-fiber tunable filter is based on the combination of a single resonant band long period grating (LPG) and an electro-optic polymer second cladding layer. The single resonant band LPG is fabricated by etching the cladding of a standard 125 µm thick fiber and using either ultraviolet (UV) illumination or electric arc discharge to write the grating. Once a single resonant band has been achieved, a polymer second cladding layer is applied to the LPG. The refractive index of the polymer cladding determines the resonant wavelength of the filter and is tuned by applying an external electric field. The grating fabrication method and type of polymer used for the second cladding affect filter performance, and both must be considered when designing an application specific all-fiber filter.