Flow sensor using fiber bragg grating(FBG)

We have proposed and demonstrated a flow sensor using fiber bragg grating(FBG). The flow sensor has no electronics and no mechanical parts in its sensing part and the structure is thus simple and immune to electromagnetic interference(EMI). The sensor was consisted of the sensing element(FBG) and metal heater. The metal wire was used to supply the current to the sensor. While some currents supply to a coil, the refractive index of the FBG under the coil is changed. Due to the thermo-optic effect of a fiber, the resonance wavelength split into two peaks. In this work, the wavelength shirt according to flow-rate was experimentally studied and was used to evaluate the air flow-rate in a air tube. As a result, it was possible to measure the flow-rate in a linear range from 5 to 15 ℓ/min with a resolution of approximately 1 ℓ/min at the applied current of 120mA.