Pressure sensor with an interferometric sensor and an in-fiber bragg grating reference sensor

Abstract

A pressure sensor (for medical applications comprises a silica optical fiber extrinsic Fabry-Perot interferometric (EFPI) pressure sensor () and an in-fiber Bragg grating (FBG,). The cavity of the EFPI pressure sensor () is formed by the end face of the FBG (), a glass capillary () and a glass diaphragm (). The glass diaphragm () is secured in place by a fusion splice () and the glass capillary () by a fusion splice (). As illustrated, incident light is directed into the FBGand there are reflections in the EFPI pressure sensor (). Applied pressure causes a deflection of the glass diaphragm () and hence modulation of the EFPI sensor () cavity. The FBG () is used as a reference sensor to eliminate temperature cross-sensitivity of the EFPI pressure sensor (). The EFPI cavity was fabricated using a 200 μm silica glass fiber, a 133/220 μm (inner/outer diameter) silica glass capillary and a standard telecommunication FBG. Initially, the end faces of the 200 μm silica glass fiber and the silica glass capillary were polished and both planar surfaces were spliced together using a fusion splicer. Then the silica glass capillary was cleaved 5 mm away form the capillary/200 μm fiber splice. After that, the FBG () was inserted into the silica glass capillary () and both elements were bonded together using the fusion splicer again.