FBG hydrophone: Theory and experiment

A fiber Bragg grating (FBG) hydrophone with enhanced sensitivity is demonstrated. A novel piston-like diaphragm with a hard core fixed at the center is used as the sensing element. Theoretical analysis shows that the Young´s modulus of the diaphragm and the radius of the hard core have significant effect on the pressure sensitivity. Experiments are carried out to test this effect and the performance of the hydrophone. The static measurement result is in good agreement with the theoretical result and an acoustic sensitivity of 7 nm/MPa has been achieved.