Method and device for monitoring the mechanical behaviour of a subsea pipe for transporting pressurized fluids

A method of monitoring the mechanical behavior of an undersea pipe for transporting fluid under pressure, the undersea pipe being made by assembling together a plurality of unit pipe elements arranged end to end, the method comprising:

• a mechanical calibration step comprising using at least one measurement cable having at least one optical fiber sensor using at least Brillouin backscattering and positioned along the entire length of the unit pipe elements to measure deformations experienced by each unit pipe element while it is being subjected on land to various different mechanical stresses in predetermined directions and of predetermined magnitudes, and, on the basis of the deformation measurements, in establishing a mechanical signature of each unit pipe element;
• and
• a monitoring step comprising consisting in using a measurement cable having at least one optical fiber sensor that makes use of Brillouin backscattering and that is helically positioned at a constant pitch (p) on each unit pipe element, with the handedness of the helical pitch alternating for two adjacent unit pipe elements, to recover variations in an optical signal injected into said optical fiber sensors while the pipe is in service, and, on the basis of such variations in the optical signal and of the mechanical signature of each unit pipe element, to determine stresses experienced by each unit pipe element.