A radiation curable, optical glass fiber coating composition containing:
- a) a urethane-containing polymer, with a vinyl addition polymer backbone, having at least one functional group capable of polymerization in the presence of actinic radiation and an average functionality of at least about 1.2;
- b) a urethane compound, with a hydrocarbon, a polyether, a polyester, a polycarbonate, a silicone or a fluorocarbon backbone, having at least one functional group capable of polymerization in the presence of actinic radiation and an average functionality of at least about 1;
- and
- c) a reactive diluent
- wherein said urethane-containing polymer is derived from a solvent-free urethane-forming reaction.