High-quality fiber fabrication in buffered hydrofluoric acid solution with ultrasonic agitation. 
An etching method for preparing high-quality fiber-optic sensors using a buffered etchant with ultrasonic agitation is proposed.  The effects of etching conditions on the etch rate and surface morphology of the etched fibers are investigated.  The effect of surface roughness is discussed on the fibers' optical properties.  Linear etching behavior and a smooth fiber surface can be repeatedly obtained by adjusting the ultrasonic power and etchant pH. The fibers' spectral quality is improved as the ratio of the pit depth to size decreases, and the fibers with smooth surfaces are more sensitive to a bacterial suspension than those with rough surfaces.