Thermally tunable extrinsic Fabry-Perot filter

This letter describes a thermally tunable filter of extremely low cost, suitable for optical sensing, spectrometry, and video distribution. The filter utilizes a high-finesse extrinsic fiber Fabry-Pe´rot interferometer formed by fusion bonding of two mirror-coated single-mode fibers to a short piece of borosilicate tubing. Continuous wavelength tuning is achieved using a Peltier device. We demonstrate a prototype filter operating at 1550 nm with a tuning range of 90.8 nm and a temperature sensitivity of 1.63 nm/°C. The filter features polarization independence, high repeatability, and inherently low drift and low insertion loss.