An optical backplane is formed by defining channels (grooves) in the plane of a polyimide layer (55), laying optical fibres (56,57) in each channels, retaining the fibres (56,57) using an adhesive and bonding an epoxy resin layer (58) to the polyimide layer (55) to form a flexible structure (54). The flexible structure (54) is made rigid by bonding epoxy glass FR4 layers (60,61) to either side of the flexible structure (54). A flexible ribbon (53) with an optical fibre (57) contained therein is formed as an integral portion of the flexible structure (54) using spacers (59,62) to define a ribbon region and to aid removal of the rigid layers (60,61) in the ribbon region.