Macrobending SMS fiber-optic anemometer and flow sensor

We report a simple, high sensitivity, good resolution and low-cost fiber-optic anemometer and flow sensor based on reflective single mode-multimode-single mode structure bent by air flow. The dragging force on the multi-mode section causes it to bend resulting in multimodal interference (MMI) effects which are related to the fluid velocity and flow rate. Bending effects on the output power profile are investigated and numerical simulation combined with experimental data demonstrate that the output power intensity may increase or decrease with the rise of curvature, depending on MMI conditions and field deformation. The sensor behavior with air flow velocity is evaluated by spectral analysis using a variety of methods as wavelength shifting of a selected peak and output power intensity of selected wavelength and output power intensity of selected points. Experimental tests using air stream inside a wind tunnel provided a reliable dynamic range from 4 to 10 m/s. Peak sensitivities of 435.13 pm/(m/s) with resolution of 17.4x10(-3) m/s for wavelength shifting and 2.62 dB/(m/s) for output power intensity are obtained. These results assure that the sensor can be effectively used in a wide variety of applications, such as anemometer and flow rate meter.