<title>Advances in the extrinsic Fabry-Perot interferometric optical fiber sensors</title>

Abstract

In this paper, recent advances in the extrinsic Fabry-Perot interferometric (EFPI) optical fiber sensors are reported. We present a theoretical analysis of the output from an optical fiber extrinsic Fabry-Perot interferometer (EFPI) based on Kirchhoff diffraction theory. The resulting equation is solved using numerical integration. The results of the theoretical analysis predict the fringe period and contrast typically seen for the EFPI. Experimental verification of the theoretical analysis is presented. An extrinsic Fabry-Perot interferometric (EFPI) fiber sensor with a micro-lens is demonstrated. The micro-lens is formed at the output endface of the lead-in fiber by fusing this fiber endface into a spherical surface. Experiments for the lensed EFPI and standard EFPI fiber sensors indicate that the decay rate of the fringe contrast versus the air gap in the lensed EFPI sensor is much smaller than that in a standard EFPI sensor.