Photonic switching matrix

A photonic switching matrix having n inputs and n outputs for switching data in the form of fixed length cells asynchronously time-division multiplexed onto optical fibers, said photonic switching matrix comprising:

• a plurality of wavelength converters at respective inputs of the photonic switching matrix to assign a wavelength to each cell applied to an input of the photonic switching matrix;
• an optical buffer, connected to outputs of said plurality of wavelength converters, common to all the outputs of the photonic switching matrix for storing each cell for a duration selectable between 0 and k.multidot.T.sub.c where K is an integer and T.sub.c is the duration of a cell;
• a space routing stage, connected to said optical buffer, comprising a filter for each output of the photonic switching matrix passing to a given output only cells having a given wavelength;
• and
• control means for controlling the wavelength converters and the optical buffer according to routing information indicating for each cell the output of the photonic switching matrix to which said cell is addressed and for selecting the duration for which each cell is stored in the optical buffer so as to construct a queue for each output to avoid conflicts between two cells to be switched to the same output;
• wherein said optical buffer comprises:
• k+1 delay lines respectively introducing time-delays 0, . . . , K.multidot.T.sub.c and having outputs connected to inputs of the space routing stage;
• k+1 combiners each having n inputs and an output connected to an input of a delay line;
• n splitters each having an input constituting an input of the optical buffer and k+2 outputs;
• and
• (k+2).multidot.n optical gates each connecting an output of one of the n splitters to an input of a respective one of the k+1 combiners to said control means, said optical gates being controlled by the control means so that each splitter is connected to a single combiner at a time.