Rare-earth doped optical fibers for temperature sensing

The feasibility of using a variety of rare-earth doped optical fibers for measuring spatially averaged temperatures from ~0 to ~100°C over distances of 10 to 20 m is discussed. Such distributed temperature sensors would be particularly well-suited for building climate control systems and industrial processing applications. The temperature-dependent absorption spectra of 6 MCVD processed fibers containing different concentrations of Nd³⁺, Pr³⁺, and Yb³⁺ rare-earth ions were characterized and used to determine thermally active dopant species, optimal dopant concentrations, and most sensitive operating wavelengths for use as dual wavelength distributed temperature sensors