The present disclosure relates to thiol-ene based coating compositions and polymeric compositions that are resistant to high temperature, as well as optical fibers coated with such polymeric compositions. In one aspect, the disclosure provides a radiation-curable optical fiber coating composition that includes at least 20 wt % of one or more at least trifunctional ethylenically unsaturated monomers, each having three or more free radical polymerizable ethylenic unsaturations; at least 20 wt % of one or more at least trifunctional thiol monomers, each having three or more free radical polymerizable thiols; and an effective amount of a free radical photoinitiator, wherein the ratio of the number of polymerizable ethylenic unsaturations of the curable composition to the number of polymerizable thiols of the curable compositions is at least about 1.