Mode multiplexing optical interconnection methods and systems

The proposed solution exploits the propagation modes of optical signal in an optical guiding medium (e.g., an optical fiber or an optical waveguide) as an additional domain to carry and switch information. These modes supported by a waveguide have the interesting property of being orthogonal, meaning that the information carried by a mode is not affected by another one even if the data is carried at the same wavelength.

In one embodiment, each card is assigned a unique wavelength distinct from the other cards. In each card, each output port is assigned a unique mode, distinct from the other ports of the same card. Switching of packets from any input port on any card to any output port on any card occurs by optically transmitting the packet data with the wavelength and the mode assigned to the packet’ destination card and port. Thanks to the uniqueness of the combination of wavelengths and modes, it is possible to multiplex the different packets’ transmission (wavelength and mode multiplexing) on the same transmission medium.

The device here described has the following advantages:

•    High transmission speed, as reached by the transmitters

•    Lower power consumption and/or higher throughput than interconnection networks based on space switching, since passive optical components can be used for multiplexing and demultiplexing the different propagation modes

•    Less lasers are required and a broader WDM can be used relaxing  the constraints on optical components and also reducing further the power consumption

•    High bandwidth density thanks to the possibility of multiplexing optical signals one 2 or 3 different domains

•    Smaller footprint