In this chapter, we report on recent numerical and experimental results obtained with Fiber Bragg Grating (FBG) hydrophones for underwater acoustic detection. The optical hydrophones under investigation consist of FBGs coated with ring-shaped polymers of different size. Via fullwave numerical simulations, we study the complex opto-acoustomechanical interaction among an incident acoustic wave traveling in water, the optical fiber surrounded by the ring shaped coating, and the FBG inscribed inside the …