Scheduling in a fast optical switch

A pipelined scheduling system comprising:

• at least two scheduler modules arranged in a predetermined order between a first scheduler module and a last scheduler module;
• and
• a pool of resources exclusively associated with each of said scheduler modules;
• said system operable to:
• receive scheduling requests of a first type, each specifying a first amount of resources;
• attempt, at said scheduler modules selected in said predetermined order, to allocate resources, from said associated pool of resources, to satisfy said scheduling requests of said first type;
• receive scheduling requests of a second type, each specifying a second amount of resources;
• and
• attempt, at said scheduler modules selected in a reverse order of said predetermined order, to allocate resources, from said associated pool of resources, to satisfy said scheduling requests of said second type.

A method of scheduling connections in an optical switching node, said optical switching node including a plurality of star couplers, said method comprising:

• receiving a connection request, said connection request specifying connection parameters;
• selecting, based on said connection parameters, an output link of said optical switching node;
• selecting a candidate star coupler from said plurality of star couplers;
• attempting to find an available path through said candidate star coupler to an output wavelength channel in said selected output link.

A method of scheduling connections in an optical switching node, said optical switching node including a plurality of star couplers, said method comprising:

• receiving a connection request;
• determining, from said connection request, an input link from among a plurality of input links, an output link from among a plurality of output links, a required number of continuous channels to be switched and a required number of time slots to be switched;
• where said required number of continuous channels is greater than zero:
• selecting a star coupler, from said plurality of star couplers, to be a channel-switching candidate star coupler;
• attempting to find a number of allocable channels, not exceeding said required number of continuous channels, to said output link through said channel-switching candidate star coupler;
• and
• repeating said selecting said channel-switching candidate star coupler and said attempting to find a number of allocable channels, where said selecting said channel-switching candidate star coupler is performed according to a first predetermined order;
• where a number of found allocable channels equals said required number of continuous channels, and said required number of time slots exceeds zero:
• selecting a star coupler, from said plurality of star couplers, to be a time-slot-switching candidate star coupler;
• attempting to find a number of allocable time slots, not exceeding said required number of time slots, to said output link through said time-slot-switching candidate star coupler;
• and
• repeating said selecting said time-slot-switching candidate star coupler and said attempting to find a number of allocable time slots, where said selecting said time-slot-switching candidate star coupler is performed according to a second predetermined order.

A method of bimodal pipelined scheduling in a scheduling system, said scheduling system including at least two scheduler modules arranged in a predetermined order between a first scheduler module and a last scheduler module, said method comprising:

• receiving a first scheduling request specifying a first amount of resources;
• at said first scheduler module:
• determining a first part of a first subset of allocable resources for satisfying said first scheduling request;
• and
• passing a first internal scheduling request, specifying an amount of resources equivalent to said first amount of resources reduced by the amount of resources in said first subset of allocable resources, to a subsequent scheduler module, said subsequent scheduler module selected according to said predetermined order;
• receiving a second scheduling request specifying a second amount of resources;
• at said last scheduler module:
• determining a first part of a second subset of allocable resources for satisfying said second scheduling request;
• and
• passing a second internal scheduling request, specifying an amount of resources equivalent to said second amount of resources reduced by the amount of resources in said second subset of allocable resources, to a preceding scheduler module, said preceding scheduler module selected according to said predetermined order.

A pipelined scheduling system comprising at least two scheduler modules arranged in a predetermined order between a first scheduler module and a last scheduler module,

• said first scheduler module operable to:
• receive a first scheduling request specifying a first amount of resources;
• determine a first part of a first subset of allocable resources for satisfying said first scheduling request;
• and
• pass a first internal scheduling request, specifying an amount of resources equivalent to said first amount of resources reduced by the amount of resources in said first subset of allocable resources, to a subsequent scheduler module, said subsequent scheduler module selected according to said predetermined order;
• said last scheduler module operable to:
• receive a second scheduling request specifying a second amount of resources;
• determine a first part of a second subset of allocable resources for satisfying said second scheduling request;
• and
• pass a second internal scheduling request, specifying an amount of resources equivalent to said second amount of resources reduced by the amount of resources in said second subset of allocable resources, to a preceding scheduler module, said preceding scheduler module selected according to said predetermined order.