Miniaturised free-space wavelength-division multiplexing photonic circuit for passive double star network systems

A novel free-space wavelength-division multiplexing photonic circuit is reported, consisting of stacked computer generated holograms, for an optical network unit in passive double star subscriber systems. Computer generated holograms are fabricated on a fused silica substrate using conventional photolithography and etching techniques. Therefore, a significant reduction in the cost of the optical network unit, which is crucial for the realisation of all-optical subscriber systems, is expected