Optical fiber Fabry-Perot cavity applied to an optical microphone

摘要

A new installation structure of optical fiber Fabry-Perot (F-P) cavity is proposed to function in an optical microphone. The F-P cavity consists of an optical fiber end with self-focused lens and a sound-sensitive membrane. Distance between the two parts is the F-P cavity length. The sound membrane is produced by semiconductor sculpture, which guarantees its tiny size, uniform thickness and high sensitivity to sound. The membrane responds to the sound vibration and vibrates in concavo-convex shape, which results in the change of cavity length, so the F-P cavity performs as an optical microphone. A mathematical model for this kind of arc F-P cavity is also proposed to study the optical microphone. The arc end is assimilated to a step-like model, so the arc F-P cavity equals an assembly of annular plane-end F-P cavities. The mathematical model is educed by simple integral of the annular plane-end F-P cavities and multi-beam interference theory. Relevant simulation and experiments are executed, which confirm the accuracy of the mathematical model and feasibility of the installation structure.