Abstract: A system for hybrid electronic/photonic switching of traffic in a node of a communications network includes a plurality of interfaces; an electronic cross-connect (EXC); and a photonic cross-connect (PXC). Each interface is designed to translate a respective traffic stream between corresponding electronic and optical signals. The EXC selectively maps an electronic signal through a selected one of the interfaces, and the PXC selectively couples an optical signal between the selected interface and a selected one of at least two optical channels of the communications network.

Abstract: A system for hybrid electronic/photonic switching of traffic in a node of a communications network includes a plurality of interfaces; an electronic cross-connect (EXC); and a photonic cross-connect (PXC). Each interface is designed to translate a respective traffic stream between corresponding electronic and optical signals. The EXC selectively maps an electronic signal through a selected one of the interfaces, and the PXC selectively couples an optical signal between the selected interface and a selected one of at least two optical channels of the communications network.

Abstract: In a photonic network, signals are degraded by passing through amplifiers. A maximum number of amplifiers may be traversed before regeneration is necessary. Regeneration (typically carried out in an optical cross-connect) involves relatively expensive hardware and is to be avoided if possible. An algorithm is set out which operates in two stages. In a first stage untenable paths are rejected and in a second stage the shortest path analyses are carried out which maximises the number of amplifiers interspersed between regenerative nodes thereby to minimise the use of regenerative nodes but ensures that all paths have regenerative nodes spaced at no more than a maximum interval of non-regenerative nodes.

Abstract: A strain-compensated III-V quantum well device is grown by vapor phase epitaxy using the same relative atomic proportions of indium and gallium in both the quantum well layers (20) and the barrier layers (21). The top and bottom barrier layers of the quantum well stack are half the thickness of the other barrier layers of the stack.