An optical fibre comprising: an optical waveguide comprising a core surrounded by a cladding; a primary coating surrounding the optical waveguide; and a coating, surrounding the primary coating, comprising a polymer material obtained by radiation curing a polymerizable composition, the polymer material having a degree of crystallinity of at most 12. The coating of the optical fiber according to the present invention exhibits enhanced resistance upon exposure to high temperature, preferably a temperature over 250° C., while endowed with required features such as protective capability, elasticity, adhesion to underlying layer and simple manufacturing.