Side Hole Packaged Shell-Encapsulated Etched FBG Hydrophone

An underwater acoustic sensor based on side hole packaged (SHP) shell-encapsulated etched fiber Bragg grating (eFBG) has been developed and demonstrated. The packaged shell cavity provides enhancement of acoustic sensitivity as well as better mechanical protection to eFBG. First, the acoustically driven mechanical behavior of SHP-FBG hydrophone configurations has been characterized using the finite element method (FEM) simulation model. The FEM parametric analysis enables the proper selection of hydrophone’s resonant frequency by a suitable choice of the SHP length. Based on the simulations, the SHP shell-encapsulated eFBG hydrophone is fabricated and experimentally characterized over the frequency range of 0.7–2.4 kHz; a very good responsivity of
$\sim $
210 nm/MPa has been obtained.