Optical energy delivery apparatus 10 for ablation or embolization includes an optical fibre 12 having a distal end 14 provided with a light directing element, such as a lens. The light directing element is configured to direct optical energy beyond the distal end 14 of the optical fibre 12. The optical fibre 12 includes at least one Bragg grating 25 proximate the distal end 14 for sensing a change in the optical fibre 12 during its operation. The apparatus includes a control unit 40 configured to drive an optical source 20 and to obtain signals from a sensor unit 30. The controller 40 may drive the source 20 at one or more different wavelengths between 600 nm and 1400 nm, especially 970 nm. The controller 40 may also drive the energy source 20 at a sensing wavelength such as 1550 nm or 800 nm. The optical fibre 12 may have a tapering diameter towards its distal tip for increased flexibility at its distal end. The optical fibre 12 may have a stiffening structure towards the proximal end.
