The present invention provides a switch device for an optical signal which has high extendibility and which can suppress an increase of loss in extension. A switch device in one embodiment of the present invention includes, in a housing, four splitter portions, four switch portions, and extension splitter portions. The splitter portions are connected to path-side ports, the switch portions are connected to client-side ports, and the splitter portions and the switch portions are connected to one another via shuffle fiber arrays. One ends of the extension splitter portions are connected to path-side extension ports, and the other ends thereof are connected to client-side extension ports. The number of wavelengths processable by the switch device can be easily changed by changing a connection state of optical fibers to the path-side ports, the client-side ports, the path-side extension ports, and the client-side extension ports.

A modular routing node includes a single input port and a plurality of output ports. The modular routing node is arranged to produce a plurality of different deflections and uses small adjustments to compensate for wavelength differences and alignment tolerances in an optical system. An optical device is arranged to receive a multiplex of many optical signals at different wavelengths, to separate the optical signals into at least two groups, and to process at least one of the groups adaptively.

Wavelength division multiplexing technology in which a layer of arrayed waveguides is used to extend the number of ports of wavelength selective switches used in multiplexing and/or demultiplexing the optical signals transported over the optical network. In some examples, the wavelength division multiplexing technology is used as part of an optical signal communication system, such as between data centers or as part of a larger network.

Telecommunications switches are presented, including expandable optical switches that allow for a switch of N inputsM outputs to be expanded arbitrarily to a new number of N inputs and/or a new number of M outputs. Switches having internal switch blocks controlling signal bypass lines are also provided, with these switches being useful for the expandable switches.

An optical switch suitable for use in a ROADM of an optical network node having one or more optical fiber per direction, the fibers together carrying optical signals comprising up to N independent wavelength channels, is disclosed. The switch includes an Optical Cross-Connect (OXC) having F.sub.1 input ports and F.sub.2 output ports. At least one optical splitter, at least one optical combiner and at least two wavelength blockers are separately connected to the OXC, the input and output parts thereof defining ports of the OXC. The OXC is controllable to switch optical signals arriving at any of the F.sub.1 switch input ports to any of the F.sub.2 switch output ports via one or more of the optical splitters, wavelength blockers and/or optical combiners. A method for switching optical signals is also disclosed.