Fiber-optic microbending acoustic sensor

Abstract

A new mechanism for fiber-optic acoustic sensing is proposed: displacement induced microbending. The microbending is introduced to the fiber by a set of two corrugated plates, the deformer. When pressure is applied on the diaphragm attached to one of the plates a relative displacement of the plates will be introduced, which will cause light coupling from core modes to clad modes. Thus, pressure applied on the deformer could be detected by monitoring the light intensity in the clad modes. The proposed sensor could be also utilized to detect displacement, temperature, stress, etc. Such a sensor was tested and displacements less than 1 A or pressure 50–60 dB (re 1 μPa) could be detected. The dynamic range of the sensor was found to be 110 dB or better with linearity of ≃ 1%.