Abstract: A cladding material for plastic optical fibers is disclosed. The cladding material comprises mainly a copolymer comprising a fluoroalkyl methacrylate and an N-aliphatic maleimide as monomer units. The cladding material has low refractive index and high thermal stability, so that an optical fiber with a large acceptance angle can be obtained.

Abstract: An optical fiber of a sheath-core structure is disclosed. The fiber has for its core a copolymer which includes an aliphatic N-substituted maleimide as a monomer unit, and preferably methyl methacrylate as an additional monomer unit. These optical fibers have high light transmittance, good mechanical characteristics and an excellent heat-resisting durability.

Abstract: Highly refractive urethane polymers for use in optical lenses and the lenses produced therefrom are obtained by polymerizing at least one unsaturated urethane compound which is the reaction product of at least one xylylene diisocyanate and at least one compound selected from the group comprising: ##STR1## where: R.sub.1 is either H or CH.sub.3R.sub.2 is a remnant radical of a substituent or non-substituent hydrocarbon having 2-4 carbon atoms; ##STR2## where: R.sub.3 is either H or CH.sub.3m=2-5;CH.sub.2 =CH--CH.sub.2 --OH; and 3(CH.sub.2 =CH--CH.sub.2 --O--CH.sub.2).sub.2 CHOH.