Optical fiber interferometric anemometer using a cobalt-doped fiber hot wire

An optical fiber interferometric anemometer using a short length of cobalt-doped fiber (CDF) as the hot wire is demonstrated. The CDF is inserted in the sensing arm of a dual-arm optical fiber Mach-Zehnder interferometer (MZI) and heated optically with a 1480 nm laser. Optical path difference and hence fringe wavelength of the MZI change with wind speed via temperature variation of the CDF, resulting in a certain relationship between fringe wavelength of the MZI and wind speed. Experimental results show that high sensitivity up to -5.13 and -2.44 nm/(m/s) is achieved at 0.1 and 0.5 m/s, respectively, which are ∼4.9 and 3.3 times that of the hot-wire anemometer based on a fiber grating Fabry-Perot interferometer. Since the CDF absorbs the laser energy by itself, the conventional requirements for metal coating and laser coupling device in optical fiber hot-wire anemometers are eliminated. The simple structure, easy fabrication, and high sensitivity make the proposed optical fiber interferometric anemometer a promising solution for wind speed measurement in a wide range of industry applications.