Abstract: A backplane assembly for a line replaceable module enclosure or rack includes an electrical backplane and a fiber optic backplane separately attachable to a single frame. The frame serves as a common datum for the electrical and fiber optic backplanes, and includes integral mating interface features for enabling line replaceable module connectors having a common shell to mate with the separate electrical and fiber optic connector structures on the backplane. The optical backplane is a one-piece structure to which pairs of individual fiber optic connectors, including input/output connectors, may be directly secured via a simple retention plate arrangement, the fiber optic connectors all having the same orientation to enable direct routing of fiber ribbons between rows of connectors serving different line replaceable modules.