Fiber optic ultrasonic sensor using Raman-Nath light diffraction

摘要

A novel fiber optic ultrasonic sensor using the principle ofnRaman-Nath light diffraction has been developed. The sensor does notnperturb the acoustic field and exhibits a wideband frequency response.nIn addition to the remote sensing of the field, it is suitable fornmeasurements of both continuous and pulsed ultrasonic waves. Thenexperimental results obtained with the sensor were compared to thosenmeasured using a calibrated PVDF needle hydrophone, showing excellentnagreement. The sensor's frequency response in the range from 3 to 15nMHz, typical of that used in medical ultrasound imaging, was determinednusing the time delay spectrometry (TDS) technique. It appears that thenfiber optic sensor provides a useful alternative to the widely used PVDFnultrasonic probes in specific applications where any perturbationnbetween acoustic field and sensor is undesirable. Also, since the activenelement diameter of the sensor can be made comparable to the corendiameter of an optical fiber, the fiber optic sensor minimizes thenspatial averaging effects and offers significant improvement inncomparison with the present state-of-the-art hydrophones which have anminimum diameter on the order of 300 Μm