Studies of the stress-strain birefringence behavior of isoprene-acrylonitrile copolymers, 2,3-dimethylbutadiene-acrylonitrile co-polymers, butadiene-acrylonitrile copolymers of three compositions, emulsion polybutadiene, and high cis-1,4-polybutadiene are reported. The stress-optical behavior of the radiation cross-linked samples was determined over the range of 30° to 110°C at small elongations. Rubber photoelasticity theory could be applied, and the optical link anisotropy and its temperature and composition dependence were determined for the copolymers. The temperature dependence of segmental anisotropy indicated in a qualitative manner the effect of substitution along the chain backbone.