Hot-wire anemometer using cobalt-doped fiber based grating Fabry-Perot interferometer

An optically-heated hot-wire anemometer using a cobalt-doped fiber based grating Fabry-Perot interferometer (FPI) is proposed. The 800 $\mu \mathrm{m}$-long cobalt-doped fiber sandwiched between two fiber Bragg gratings absorbs the heating laser and increases the cavity length of the FPI due to temperature increase. Its temperature drops with airflow velocity that shifts the fringe wavelength of the FPI. Experimental results show a measurement range of 0-4 m/s with a sensitivity of -867 pm/(m/s) at airflow velocity of 0.1 m/s.