Hydrophone all optical insensitive to temperature and static pressure

The invention consists in an optical hydrophone, a fiber optic element forming a laser cavity, housed in a mechanical structure comprising a rigid open cylindrical body, defining the cavity containing a fluid in which is housed the optical fiber element, and closed at its ends by two caps which continuously maintain the optical fiber element in tension in longitudinal rectilinear position within the cavity. The caps are configured so that when the external pressure varies, they undergo a deformation causing a variation in the length of the optical fiber element and that when the temperature varies, they undergo a deformation causing a variation in the length of the optical fiber element which compensates for the induced over this element by the temperature change. The mechanical structure also has one or more holes for balancing static pressure.