High capacity optical node

An optical core node in a wavelength division multiplexed network wherein links between nodes carry wavelength channels, said optical core node comprising:

• a plurality of demultiplexers, each of said plurality of demultiplexers receiving at least two wavelength channels on a corresponding input link;
• a plurality of multiplexers, each of said plurality of multiplexers transmitting at least two wavelength channels on a corresponding output link;
• a plurality of optical switching planes including:
• at least one full-coverage optical switching plane receiving at least one wavelength channel from each of said plurality of demultiplexers and transmitting at least one wavelength channel to each of said plurality of multiplexers;
• and
• at least one partial-coverage optical switching plane receiving at least one wavelength channel from fewer than all of said plurality of demultiplexers and transmitting at least one wavelength channel to fewer than all of said plurality of multiplexers.

A method of connecting a plurality of channels to a plurality of ports of a switching node, the quantity of said plurality of channels not exceeding the quantity of said plurality of ports, where said plurality of channels are arranged into M groups, M>1, each of said M groups having a specified number of channels, where said plurality of ports are arranged in N rows, N>1, each of said N rows having a specified number of ports and where each of said plurality of ports connects to at most one of said plurality of channels, said method comprising:

• sorting said M groups in a descending order according to said specified number of channels, to give a plurality of sorted groups indexed from 0 to (M−1);
• sorting said N rows in a descending order according to said specified number of ports, to give a plurality of sorted rows indexed from 0 to (N−1);
• considering each of said plurality of sorted groups in order from most channels to least channels, where considering a given group includes assigning a channel from said given group to a selected port, where said selected port is an unassigned port in the row having the lowest row index of said plurality of sorted rows;
• repeating said considering until the row of index (N−1) has been reached;
• examining said sorted groups sequentially starting with the sorted group of index 0;
• scanning each of said plurality of sorted rows in a cyclic discipline starting with the sorted row of index (N−1) and progressing towards the sorted row of index 0;
• and
• assigning one unassigned channel from each group having at least one unassigned channel to an unassigned port until all channels of said groups are assigned.

A data structure for determining port vacancy in an optical core node that includes a plurality of optical switching planes, said data structure comprising:

• a plurality of fields, where each field of said plurality of fields corresponds to a port in one optical switching plane among said plurality of optical switching planes;
• where said fields are logically arranged into rows according to corresponding optical switching plane and logically arranged into columns according to an edge node from which said port receives optical signals;
• and
• where said rows are logically arranged by monotonically increasing coverage of corresponding optical switching plane, where said coverage of a given optical switching plane is a measure of a number of input links on which said given optical switching plane receives optical signals and a number of output links on which said given optical switching plane transmits optical signals.

An optical core node comprising:

• a plurality of optical switching planes;
• a plurality of demultiplexers, each of said plurality of demultiplexers adapted to receive a signal on an input link from a source edge node, demultiplex said signal into a plurality of wavelength channels and send at least one of said plurality of wavelength channels to at least one of said plurality of optical switching planes;
• and
• a core node controller adapted to receive a connection request, where said connection request specifies a source edge node, a sink edge node and a requested capacity, said core node controller operable to:
• identify a subset of optical switching planes, in said plurality of optical switching planes, where each of said optical switching planes in said subset has an unassigned path from an input link originating from said source edge node to an output link terminating on said sink edge node;
• select a candidate optical switching plane, where said candidate optical switching plane has the least coverage index in said subset of optical switching planes, where a coverage index of a given optical switching plane is a measure of a number of input links and output links with which said optical switching plane communicates;
• and
• indicate, to said source edge node, an identity of a wavelength channel corresponding to said candidate optical switching plane.

A method of selecting an optical switching plane to satisfy a connection request within an optical core node having a plurality of optical switching planes connecting to a plurality of input links and a plurality of output links, where said connection request includes a specified input link, a specified output link and a requested capacity, said method comprising:

• determining a coverage index for each of said plurality of optical switching planes, where a coverage index for a given optical switching plane is a metric based on a number of input links having at least one wavelength channel connected to said given optical switching plane and a number of output links having at least one wavelength channel connected to said given optical switching plane;
• identifying a subset of optical switching planes, in said plurality of optical switching planes, where each optical switching plane in said subset is connected to said specified input link and said specified output link;
• selecting a candidate optical switching plane, where said candidate optical switching plane has the least coverage index in said subset of optical switching planes;
• and
• indicating to a source edge node connected to said specified input link a wavelength channel corresponding to said candidate optical switching plane.

A method of selecting a candidate optical switching plane through which to route a connection within an optical core node having a plurality of optical switching planes, a plurality of input links, and a plurality of output links, where said selecting is responsive to receiving, at said optical core node, a connection request specifying a specified source node, a specified sink node and a required number of wavelength channels, said method comprising:

• identifying a source input link, from said plurality of input links, originating from said specified source node;
• identifying a sink output link, from said plurality of output links, terminating on said specified sink node;
• identifying a subset of optical switching planes, in said plurality of optical switching planes, where said subset includes those optical switching planes that are connected to said source input link and said sink output link;
• selecting said candidate optical switching plane from said subset of optical switching planes, such that said candidate optical switching plane has a least coverage index among said subset of optical switching planes, a coverage index of a given optical switching plane being a metric based on a number of input links and a number of output links to which said optical switching plane connects;
• determining a number of available input ports, of said candidate optical switching plane, connected to said source input link;
• determining a number of available output ports, of said candidate optical switching plane, connected to said sink output link;
• determining a number of allocable paths through said candidate optical switching plane as the least of said number of available input ports, said number of available output ports and said required number of wavelength channels;
• and
• where said number of allocable paths is equal to said required number of wavelength channels, sending an acceptance indication to said specified source node indicating an acceptance of said connection request, where said acceptance indication includes an identification of wavelength channels corresponding to said candidate optical switching plane.

An optical core node receiving optical signals on a plurality of input links and transmitting optical signals on a plurality of output links, said optical core node comprising:

• a plurality of optical switching planes, wherein at least two of said plurality of optical switching planes have a different coverage index, where a coverage index of a given optical switching plane is a metric based on a number of links, including input links from said plurality of input links and output links from said plurality of output links, in communication with said given optical switching plane;
• a plurality of demultiplexers, each of said plurality of demultiplexers adapted to receive an optical signal from a source edge node on one of said plurality of input links, demultiplex said optical signal into a plurality of wavelength channels and transmit at least one of said plurality of wavelength channels to at least one of said plurality of optical switching planes;
• a plurality of multiplexers, each of said plurality of multiplexers adapted to receive a plurality of wavelength channels from at least one of said plurality of optical switching planes, multiplex said plurality of wavelength channels into an outgoing optical signal and transmit said outgoing optical signal on one of said plurality of output links to a sink edge node;
• and
• a core node controller adapted to:
• receive a connection request, where said connection request specifies a specified source edge node, a specified sink edge node and a requested number of wavelength channels;
• form a subset of optical switching planes, where said subset includes all optical switching planes, of said plurality of optical switching planes, that receive at least one wavelength channel originating at said specified source edge node and transmit at least one wavelength channel to terminate at said specified sink edge node;
• select a candidate optical switching plane in said subset of optical switching planes, where said candidate optical switching plane has a least coverage index among said optical switching planes in said subset;
• determine a number of available input ports, of said candidate optical switching plane, connected to said specified source edge node, determine a number of available output ports, of said candidate optical switching plane, connected to said specified sink edge node;
• determine an allocable number of paths as the least of said number of available input ports, said number of available output ports and said required number of wavelength channels;
• and
• where said allocable number of paths is equal to said number of required paths, transmit an acceptance indication to said specified source edge node indicating an acceptance of said connection request, where said acceptance indication includes an identity of wavelength channels corresponding to said candidate optical switching plane.

A method of generating a schedule for a connection within an optical core node having a plurality of optical switching planes, where said generating is responsive to receiving, at said optical core node, a connection request specifying a specified source edge node, a specified sink edge node and a required number of time slots in a time division multiplexed frame, said method comprising:

• identifying a subset of said plurality of optical switching planes, where said subset includes all optical switching planes, of said plurality of optical switching planes, that receive at least one wavelength channel from said specified source edge node and transmit at least one wavelength channel to said specified sink edge node;
• selecting a first candidate optical switching plane in said subset of optical switching planes, such that said first candidate optical switching plane has a minimum coverage index among said optical switching planes in said subset, where a coverage index of a given optical switching plane is a metric based on a number of links, including input links and output links, with which said given optical switching plane communicates;
• for a first time slot in said time division multiplexed frame and for said first candidate optical switching plane:
• determining a number of available input ports in communication with said specified source edge node;
• determining a number of available output ports in communication with said specified sink edge node;
• determining an allocable number of paths as the least of said number of available input ports, said number of available output ports and said required number of time slots;
• and
• where said allocable number of paths is equal to said required number of time slots, sending an acceptance indication to said specified source edge node indicating an acceptance of said connection request, where said acceptance indication includes a schedule including an identity of said first time slot and an identity for each wavelength channel corresponding to said available input ports at said first candidate optical switching plane.

An optical core node comprising:

• a plurality of optical switching planes, wherein at least two of said plurality of optical switching planes have a different coverage index, where a coverage index of a given optical switching plane is a metric based on a number of links, including input links from said plurality of input links and output links from said plurality of output links, in communication with said given optical switching plane;
• a plurality of demultiplexers, each of said plurality of demultiplexers adapted to receive an optical signal from a source edge node on one of said plurality of input links, demultiplex said optical signal into a plurality of wavelength channels and transmit at least one of said plurality of wavelength channels to at least one of said plurality of optical switching planes;
• a plurality of multiplexers, each of said plurality of multiplexers adapted to receive a plurality of wavelength channels from at least one of said plurality of optical switching planes, multiplex said plurality of wavelength channels into an outgoing optical signal and transmit said outgoing optical signal on one of said plurality of output links to a sink edge node;
• and
• a core node controller adapted to:
• receive a connection request, where said connection request specifies a specified source edge node, a specified sink edge node and a requested capacity;
• form a subset of optical switching planes, where said subset includes all optical switching planes, of said plurality of optical switching planes, that receive at least one wavelength channel originating at said specified source edge node and transmit at least one wavelength channel to terminate at said specified sink edge node;
• select a candidate optical switching plane in said subset of optical switching planes, where said candidate optical switching plane has a selected coverage index among said optical switching planes in said subset;
• determine whether an input port, of said candidate optical switching plane, in communication with said specified source edge node is available for a particular time slot in a time division multiplexed frame;
• and
• determine whether an output port, of said candidate optical switching plane, in communication with said specified sink edge node is available for said particular time slot.