Tunable single phase shifted and superstructure gratings using microfabricated on fiber thin film heaters

Tunable optical filters have applications in wavelength division multiplexing, optical sensing, and fiber lasers. Optical filters that are tuned by resistive Joule heating of a thin metal film deposited onto the fiber are presently considered. The small thermal diffusion length of such films allows one to create complex heating profiles by simply controlling the local film thickness. Devices with single and multiple thermally actuated phase-shifted elements are demonstrated. The measured reflection spectra of these devices compare favorably with simulations based on a 1-D model of heat flow.