The present invention relates to oligosaccharides of formula: . In particular, the layers are arranged according to an overlapped configuration and then constrained at fastening points, for example, seams made by a stitching head equipped with one or more needles acting along a direction substantially orthogonal to the layers. Optical fiber connectors are employed at a peripheral edge of each plug-in module, and optical fibers interconnecting the transceivers and corresponding edge mounted connectors are bundled into two dimensional arrays at the point where they are optically coupled to two dimensional transceiver arrays.