Abstract: A subsea riser integrity diagnosis system comprising: one or more fibres deployed along a riser, preferably along the whole length subject to any potential failure, or alternatively deployed over the interval most subject to failure, a fibre optic sensor interrogation apparatus optically coupled to the fibre(s) and operable to detect changes in temperature (DTS), vibration (CRN), or strain (FBG) sensed by the fibre optic strain sensor, and a central processor means adapted to receive multiple measurement data from the interrogation apparatus and operable to determine from the received data the current status of temperature, pressure, vibration, strain or other parameters along the riser and to determine if the status is within safe limits or whether any number of potentially damaging events has occurred and to inform the operator(s) for possible action to be taken to safeguard the integrity of the riser.