An optical waveguide crosspoint comprising first and second single multimode interference sections (21, 22), each single multimode interference section (21, 22) comprising an input face, an output face and sidewalls extending therebetween, the distance between the input face and output face for each single multimode interference section (21, 22) being the length of the multimode interference section (21, 22), the lengths of the first and second multimode interference sections (21, 22) being L1 and L2 respectively; at least one primary input optical waveguide connected to the input face of the first single multimode interference section; at least one primary output optical waveguide connected to the output face of the first single multimode interference section; the first single multimode interference section comprising a symmetry axis extending from the center of the input face to the center of the output face; at least one secondary input optical waveguide connected to the input face of the second single multimode interference section; at least one secondary output optical waveguide connected to the output face of the second single multimode interference section; the second single multimode interference section comprising a symmetry axis extending from the center of the input face to the center of the output face; characterised in that the first and second single multimode interference sections (21, 22) intersect to form an L shaped compound multimode interference structure; and, for each single multimode interference section (21, 22) its width in a direction normal to its symmetry axis is less than 15% of the length of the other single multimode interference section (21, 22). first and second single multimode interference sections (21, 22), each single multimode interference section (21, 22) comprising an input face, an output face and sidewalls extending therebetween, the distance between the input face and output face for each single multimode interference section (21, 22) being the length of the multimode interference section (21, 22), the lengths of the first and second multimode interference sections (21, 22) being L1 and L2 respectively; at least one primary input optical waveguide connected to the input face of the first single multimode interference section; at least one primary output optical waveguide connected to the output face of the first single multimode interference section; the first single multimode interference section comprising a symmetry axis extending from the center of the input face to the center of the output face; at least one secondary input optical waveguide connected to the input face of the second single multimode interference section; at least one secondary output optical waveguide connected to the output face of the second single multimode interference section; the second single multimode interference section comprising a symmetry axis extending from the center of the input face to the center of the output face; characterised in that the first and second single multimode interference sections (21, 22) intersect to form an L shaped compound multimode interference structure; and, for each single multimode interference section (21, 22) its width in a direction normal to its symmetry axis is less than 15% of the length of the other single multimode interference section (21, 22).