Enhanced Thermally Tunable Optical Filter and its Applications in Erbium-Doped Fiber Lasers

In this letter, an enhanced thermally tunable filter design based on a stack of three layers and a long external sleeve at the tip of a single mode fiber is presented. Here, two of these layers and the sleeve are thermo-sensitive. Moreover, it is shown that by using the sleeve with a large length compared with the thicknesses of the layers, the thermal tuning mechanism can be considerably enhanced. Furthermore, the mathematical model of the enhanced filter is presented and it is experimentally supported. Finally, a tunable single-wavelength erbium doped fiber laser based on this filter was implemented. This laser can be tuned ~19 nm by applying a temperature change of just 2.7°C achieving a resolution of 6.89 nm/°C.