Scheduled Light Path Switching in Optical Networks and Automatic Assessment of Traffic Impairments that Would Result from Adding or Deleting a Channel in a Wavelength-Division Multiplexed Optical Communication Network

Patent metadata

Field	Value
Publication number	US-2018123724-A1
Application number	US-201615572936-A
Country	US
Kind code	A1
Filing date	Jun 2, 2016
Priority date	Jun 2, 2015
Publication date	May 3, 2018
Grant date	—

Abstract

A single-wavelength light path is selected between a source access node and a destination access node of a wavelength-division multiplexed optical network, including selecting an illuminated wavelength of the light path and selecting a start time and duration for a data transfer that would not interfere with other data transfers. If no start time/wavelength combination is available with duration sufficient to transport the data, an additional wavelength is automatically selected, based on modeling, that would not impair traffic being carried by other wavelengths in the network, and without a time-consuming manual process of the prior art. The scheduling process may include selecting a set of optical fibers, a wavelength, a start time and an end time to transport proposed traffic. A novel scheduler avoids checking every possible start time, thereby saving significant processing time. The scheduler schedules single-wavelength light paths, rather than relying on complex wavelength shifting schemes.

First claim

What is claimed is:

1 . A method for scheduling a data transmission via a wavelength-division multiplexed optical communication network that includes a plurality of nodes and a plurality of links interconnecting the nodes, wherein each link includes at least one link-length optical fiber and at least some of the nodes are access nodes, the method comprising:
storing, in an electronic memory: (a) information about topology of the optical communication network and (b) information indicating: (i) which wavelengths are illuminated in ones of the link-length optical fibers, (ii) which wavelengths in ones of the link-length optical fibers are assigned to carry traffic and (iii) for each wavelength/link-length optical fiber combination that is assigned to carry traffic, a start time of an assignment and an end time of the assignment; receiving a first electronic signal indicating: (a) a request to transport proposed traffic over the optical communication network between a source access node and a destination access node and (b) an amount of the proposed traffic; using the amount of the proposed traffic to calculate an assignment duration sufficient to carry the proposed traffic; automatically searching the information in the electronic memory for a set of the link-length optical fibers, such that: (a) the set of link-length optical fibers extends contiguously between the source access node and the destination access node, (b) at least one wavelength in common among all the link-length optical fibers of the set is illuminated and (c) each combination of the at least one wavelength and a link-length optical fiber of the set is available to carry traffic at some common start time and thereafter for at least the calculated assignment duration; and if the set of link-length optical fibers is found, automatically:
selecting a wavelength of the at least one wavelength in common;
altering the information stored in the electronic memory so as to indicate, for each link-length optical fiber of the set, the selected wavelength is assigned to carry traffic beginning at the common start time and thereafter for the calculated assignment duration; and
sending a second electronic signal indicating the set of link-length optical fibers, the selected wavelength and the common start time.

2 . A method according to claim 1 , wherein using the amount of the proposed traffic to calculate the assignment duration sufficient to carry the proposed traffic comprises calculating the assignment duration as other than an integral multiple of a fixed time slot duration.

3 . A method according to claim 1 , wherein automatically searching the information in the electronic memory for the set of the link-length optical fibers occurs upon receipt of the first electronic signal, without waiting for a next fixed time slot occurrence.

4 . A method according to claim 1 , wherein the common start time is independent of timing of a next fixed time slot occurrence.

5 . A method according to claim 1 , further comprising, if the set of optical fibers is not found, automatically sending a third electronic signal indicating a failure to schedule transport of the proposed traffic.

6 . A method according to claim 1 , wherein automatically searching the information in the electronic memory for the set of the link-length optical fibers comprises automatically:
(a) determining a path comprising a subset of the plurality of links, such that links of the subset extend contiguously between the source access node and the destination access node; (b) setting a lower limit equal to an initial time; (c) for each link of the path, automatically determining an earliest start time, no earlier than the lower limit, at which at least one link-length optical fiber of the link is available to carry traffic, thereby in aggregate identifying at least one first possible start time; (d) selecting a latest one of the at least one first possible start time, thereby selecting a first candidate start time; (e) for each link of the path, automatically determining an earliest start time, no earlier than the first candidate start time, at which a link-length optical fiber of the link is available to carry traffic, thereby in aggregate identifying at least one second possible start time; (f) selecting a latest one of the at least one second possible start time, thereby selecting a second candidate start time; (g) comparing the first candidate start time to the second candidate start time; (h) if, as a result of the comparing, the first candidate start time is found to be equal to the second candidate start time:
(i) selecting the first candidate start time as the common start time; and
(ii) for each link of the path, selecting the link-length optical fiber of the link that is available to carry traffic, thereby in aggregate selecting the set of the link-length optical fibers;
otherwise, if a predetermined stopping criterion is not met:
(i) setting the lower limit equal to the second candidate start time; and
(ii) repeating (b) to (h).

7 . A method according to claim 6 , wherein:
determining an earliest start time, no earlier than the lower limit, comprises automatically determining the earliest start time without regard to timing of a next fixed time slot occurrence; and determining an earliest start time, no earlier than the first candidate start time, comprises automatically determining the earliest start time without regard to timing of a next fixed time slot occurrence.

8 . A method according to claim 6 , wherein:
identifying the at least one first possible start time comprises, for each link of the path, automatically determining the earliest start time, no earlier than the lower limit, at which the at least one link-length optical fiber of the link is available to carry traffic, including thereafter for at least the calculated assignment duration; and identifying the at least one second possible start time comprises, for each link of the path, automatically determining the earliest start time, no earlier than the first candidate start time, at which the at least one link-length optical fiber of the link is available to carry traffic, including thereafter for at least the calculated assignment duration.

9 . A method according to claim 6 , wherein the initial time represents a current time.

10 . A method according to claim 6 , wherein the initial time represents a future time.

11 . A method according to claim 6 , wherein determining the path comprises automatically finding a lowest cost path between the source access node and the destination access node.

12 . A method according to claim 11 , wherein the lowest cost path comprises a path having a fewest number of links between the source access node and the destination access node.

13 . A method according to claim 6 , wherein:
each link of the plurality of links is associated with a respective link cost; and determining the path comprises automatically determining a least cost path that has a lowest total link cost.

14 . A method according to claim 13 , wherein each link cost is based at least in part on a number of optical amplifiers disposed along the associated link.

15 . A method according to claim 6 , wherein determining the path comprises receiving an electronic signal from another system, wherein the electronic signal indicates the links of the path.

16 . A method according to claim 6 , further comprising:
for each illuminated wavelength of the path, repeating (b) to (h); wherein: automatically determining the earliest start time comprises automatically

Assignees

• Massachusetts Inst Technology

Inventors

• Zhang Lei
• Chan Vincent W S

Classifications

• H04J14/0271 Primary

  Impairment aware routing · CPC title

• H04J14/0257 Primary

  Wavelength assignment algorithms · CPC title

• H04J14/0212

  using optical switches or wavelength selective switches [WSS] · CPC title