An athermal design on LPG-based tunable filter

Abstract

In this paper, a unique all-fiber tunable filter based on the combination ofsingle resonant band long period grating (LPG) and harsh environment electro-optic polymer second cladding layer is presented. The single resonant band LPG is used to select the resonant wavelength and the tuning of resonant wavelength is realized by changing the refractive index of electro-optic polymer cladding layer via external electric field. Although the basic operational principle and implementation of this unique tunable filter have been previously reported by authors, this paper is focused on athermal operation design and synthesis of harsh environment electro-optic polymer, which enhances the practicability of proposed tunable filter.

Recent advances on all-fiber tunable filter

“…Although the refractive index of each polymer can be tuned by an applied electric field, the material characteristics of each polymer may cause one polymer to be better suited for a particular application than another. For instance, a polymer that can be synthesized with the proper thermal characteristics could potentially cancel out the intrinsic thermal dependence of the LPG, thereby rendering the filter thermally independent [14][15]. On the other hand, applications that require a very high degree of resolution in a temperature controlled environment may require a polymer that is very sensitive to changes in the applied field, in which case the thermal characteristics are no longer as high a priority.…”