Abstract: A reconfigurable optical add drop module has a coarse demultiplexer, for outputting sub bands of wavelengths, a fine mux/demux, for adding and/or dropping wavelengths, a coarse multiplexer, for remultiplexing the sub bands, an optical switch in between the coarse demultiplexer and the fine mux/demux, to switch the sub bands for pass through, or for add/drop. Reconfiguration can be remote, automatic, with less interruption to traffic. By switching sub bands rather than individual wavelengths, the number of switches can be reduced, and consequently losses, and space requirements can be reduced. Also, upgrading from pass through to add drop, of one or more sub bands is easier. Hence initial capital cost of nodes and the cost of upgrading can be reduced, since there is less need to provide redundant add drop capacity initially. Mid stage access enables external components to be added to the optical path for the sub bands.

Abstract: The invention is directed to an optical grating device which is capable of processing at least two optical signals concurrently, comprising a plurality of input waveguides, a plurality of output waveguides, a first free propagating region and a second free propagating region, and a composite light pathway. These are arranged such that a first input waveguide and a first output waveguide are connected to said first region; a second input waveguide and a second output waveguide are connected to said second region; and said first region and said second region are connected by the composite light pathway. Light input along the first input waveguide is able to pass through the composite light pathway to be output through the second output waveguide and light input along the second input waveguide is able to pass through the composite light pathway to be output through the first output waveguide.

Abstract: An optical waveguide device for guiding an optical signal comprising a substrate, a waveguide extending at least partially across the substrate, and at least two slots extending transversely across the waveguide. The separation between the slots, the direction of propagation of the optical signal in the waveguide, is substantially ( n ⁢   ⁢ Δ ⁢   ⁢ λ 2 ) , where n is an odd integer and &Dgr;&lgr; the difference in wavelength of the radiation and guided modes of the optical signal resolved in the direction of propagation.

Abstract: An optical demultiplexer has a coarse filter 41,43,45 and a plurality of arrayed waveguide gratings (AWGs) 49 connected to respective outputs of the coarse filter 41,43,45. The AWGs are of like design with a plurality of configurations and are arranged to have a configuration corresponding to be frequency range output on the respective output. The device can be used in WDM systems.

Abstract: An arrayed waveguide grating device 1 has a substrate 1 with an array 41 of waveguides extending across the substrate between an input coupler 37 and an output coupler 39. At least one input waveguide 31 extends between an input end for coupling to an input signal and the input coupler 37 and at least one output waveguide extends between an output end for coupling to an output signal and the output coupler 39. The input end or ends of the at least one input waveguide and the output end or ends of the at least one output waveguide are brought to the same edge 35 of the substrate.