An optical fibre assembly (10) disposed within a catheter (12) for ablating mammalian, such as heart tissue. The optical fibre assembly has a plurality of optical cores (16A-16C), each core defining a leading end and a trailing end and being adapted to carry an optical imaging beam. An optical lens arrangement (25) is operatively connected to the leading end of the plurality of optical cores for causing divergence of the light beams emitted therefrom. The optical fibre assembly (10) creates a field of view by directing a plurality of said optical imaging beams onto a tissue portion and capturing a reflected portion of said beams. The divergence of the beams provides a greater field of view than may otherwise be provided.
