Perimeter Lighting Perimeter lighting in pools creates an outline of the pool shape or water line through the use of SideGlow® fiber optic cable, track and an illuminator. The SideGlow® cable is applied to a track that is placed under the coping of the pool or spa. Perimeter/Step Lighting will enhance the overall design of the pools shape or unique features. In darker pools the cables reflection on the waters surface will create a dramatic %u201Cdouble line%u201D effect.