Underwater acoustic sensing by using cascaded-chirped long period fiber gratings

Cascaded chirped long period fiber gratings (C-CLPG) are provided as sensing elements for use in intensity-based underwater acoustic fiber-optic sensors, in which C-CLPGs are inscribed in photosensitive fiber by means of point-by-point technique with UV radiation. For a demonstration, C-CLPGs are immersed in a water vessel and exerted by underwater acoustic waves. In the demonstration, higher sensitive underwater acoustic detection is obtained by employing a C-CLPG with the steeper channeled spectrum.