Abstract: A system for interconnection of a stack of circuit boards, wherein each of at least a plurality of the circuit boards has an end region carrying one or more light transmitters or light receivers, an optical structure forming an interconnecting backplane for the circuit boards, the optical structure comprising a first surface carrying a multiplicity of hologram elements disposed to receive light beams from said light transmitters and to route said light beams to a second reflective surface where said light beams are reflected back to said hologram elements for routing to said light receivers.

Abstract: Concentricity of a light-transmissive core and its cladding is measured by stimulating U-V fluorescence in the core but not the cladding, independently imaging the core/cladding boundary and the outer surface of the cladding and determining their radial separation for different angular orientations of the core and its axis.