Fiber-Optic Anemometer Based on Bragg Grating Inscribed in Metal-Filled Microstructured Optical Fiber

A compact all-fiber optical anemometer based on a fiber Bragg grating (FBG) inscribed in a metal-filled microstructured optical fiber (MOF) is presented. Six-hole MOF (SHMOF) with a suspended core is fabricated to engineer the evanescent field of the fundamental guided mode, and low-melting-point alloy is filled in the micro-holes to achieve highly efficient light-heat conversion. Such a metal-filled SHMOF can strongly absorb pumping light at 1450 nm to generate heat and forms a fiber-optic "hot wire". The Bragg grating at 850 nm is inscribed in the core of SHMOF and acts as an in-fiber sensor for monitoring wind-speed dependent temperature of the "hot wire". Experimental results show the sensitivity of the fiber-optic anemometer is as high as ~0.091 nm (m/s) at wind speed of around 2 m/s. Such a compact anemometer is promising as a low-power-consumption optical flow-meter for remote sensing and on-chip integration.