Optical fiber anemometer using silver-coated fiber Bragg grating and bitaper

• We demonstrate an anemometer based on a fiber bitaper and a silver-coated FBG.
• The waist-enlarged fiber bitaper couples light from a pump laser to the fiber cladding.
• The silver coating absorbs the pump laser to heat up the FBG.
• Bragg wavelength of the FBG changes with velocity of air flow.
• Experimental results show that a large measurement range up to 13.7 m/s is realized.

An optical fiber hot-wire anemometer based on an optical fiber bitaper and a silver-coated fiber Bragg grating (FBG) is demonstrated for airflow velocity measurement. The specially-fabricated fiber bitaper with an enlarged waist diameter couples light from a high-power pump laser into cladding area of the fiber and the silver coating absorbs the light to generate heat that increases temperature of the FBG to a certain level. In measurement, air flow takes away some heat and reduces temperature, thus Bragg wavelength of the FBG changes with velocity of air flow according to a certain relationship. Experimental results show that a large measurement range up to 13.7 m/s is realized.