Path selection in optical network for optical nodes with flexible baud rate and modulation format

An apparatus comprising:

• a network interface unit to communicate with a network of optical nodes configured to communicate with each other at multiple line rates using different tuples of [bits/symbol, symbol rate] for each line rate;
• and
• a processor coupled to the network interface unit and configured to perform operations including:
• determining multiple paths between two optical nodes;
• selecting a desired line rate for the two optical nodes;
• accessing a path database that indicates available optical bandwidth and available optical signal-to-noise ratio (SNR) referenced to a reference symbol rate along each of the multiple paths;
• determining one or more feasible paths among the multiple by, for each of the multiple paths, searching the different tuples of the desired line rate for a tuple for which a desired optical bandwidth and a desired optical SNR are accommodated by the available optical bandwidth and the available optical SNR of the path, respectively, wherein the searching includes:
• scaling the available optical SNR from the reference symbol rate to the symbol rate of the tuple being searched to produce a scaled optical SNR;
• and
• comparing the scaled optical SNR to the desired optical SNR for the tuple being searched;
• and
• programming optical nodes of one of the feasible paths with a tuple found by the searching.

A method comprising:

• at a network controller of a network of optical nodes configured to communicate at multiple line rates using different tuples of [bits/symbol, symbol rate] for each line rate, wherein the bits/symbol of the different tuples increase across the different tuples, while the symbol rates of the different tuples correspondingly decrease across the different tuples:
• determining multiple paths between two optical nodes;
• selecting a desired line rate for the two optical nodes;
• accessing a path database that indicates an available optical bandwidth and an available optical signal-to-noise ratio (SNR) along each path;
• determining one or more feasible paths among the multiple paths by, for each path, searching the different tuples of the desired line rate for a tuple for which a desired optical bandwidth and a desired optical SNR are accommodated by the available optical bandwidth and the available optical SNR of the path, respectively;
• when the determining one or more feasible paths determines multiple feasible paths, selecting a feasible path from the multiple feasible paths based on a predetermined criterion;
• and
• programming optical nodes of a selected feasible path with a tuple found by the searching.