Systems and methods for performing optical line terminal (OLT) failover switches in optical networks

• US 10,608,735 B2
• Filed: 05/04/2017
• Issued: 03/31/2020
• Est. Priority Date: 05/04/2016
• Status: Active Grant

• Current Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Original Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Inventors: Cress, Jared D., Polk, Jr., Charles E., Padur, Nagaraj
• Primary Examiner(s): Sanchez, Dibson J
• Application Number:
  US15/587,146
• Publication Number:
  US 20170324471A1
• Time in Patent Office: 1,062 Days
• Field of Search: 398 1- 8, 398 43-103
• CPC Class Codes: H04B 10/03 Arrangements for fault recovery
• CPC Class Codes: H04B 10/032 using working and protection systems H04J14/0287 takes precedence
• CPC Class Codes: H04J 14/0257 Wavelength assignment algorithms
• CPC Class Codes: H04J 14/0282 WDM tree architectures
• CPC Class Codes: H04J 14/0297 Optical equipment protection
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• CPC Class Codes: H04Q 11/00 Selecting arrangements for multiplex systems multiplex systems H04J
• CPC Class Codes: H04Q 11/0005 Switch and router aspects
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 11/0067 Provisions for optical access or distribution networks, e.g. Gigabit Ethernet Passive Optical Network (GE-PON), ATM-based Passive Optical Network (A-PON), PON-Ring
• CPC Class Codes: H04Q 2011/0018 using tunable transmitters or receivers
• CPC Class Codes: H04Q 2011/0033 using time division switching
• CPC Class Codes: H04Q 2011/0043 Fault tolerance
• CPC Class Codes: H04Q 2011/0081 Fault tolerance; Redundancy; Recovery; Reconfigurability
• CPC Class Codes: H04Q 2011/0086 Network resource allocation, dimensioning or optimisation

Abstract

A system for performing failover switches in an optical network, such as a time and wavelength division passive optical networks (TWDM PON) like NG-PON2, includes a backup optical line terminal (OLT) for backing up communications of a primary OLT. The backup OLT is configured to allocate small upstream time slots, referred to herein as “de minimis” time slots, to at least one optical network terminal (ONT) communicating with the primary OLT during normal operation. When a failure occurs that prevents communication between the ONT and the primary OLT, the ONT autonomously tunes to the upstream and downstream wavelength pairs of the backup OLT and begins to transmit data to the backup OLT in the de minimis time slot allocated to it. The presence of data in the de minimis time slot indicates the occurrence of a failover switch to the backup OLT, and the backup OLT then begins to allocate time slots to this ONT, which is normally serviced by the primary OLT according to its normal TDM algorithm.

Claims

1. An optical network, comprising:

an optical fiber;

a first optical line terminal (OLT) coupled to the optical fiber;

a first optical network terminal (ONT) having a tunable optical transmitter coupled to the optical fiber and a tunable optical receiver coupled to the optical fiber, the first ONT configured to tune the tunable optical transmitter and the tunable optical receiver to a first wavelength pair of the first OLT for communication with the first OLT through the optical fiber;

a second OLT coupled to the optical fiber and configured to communicate with the first ONT through the optical fiber on a second wavelength pair, the second OLT configured to allocate a first plurality of time slots to the first ONT, at least a first time slot of the first plurality of time slots allocated to the first ONT by the second OLT prior to a communication failure between the first ONT and the first OLT while the tunable optical transmitter and the tunable optical receiver are tuned to the first wavelength pair for communication with the first OLT,

wherein the second OLT is configured to allocate the first plurality of time slots to the first ONT by transmitting control data through the optical fiber at a wavelength of the second wavelength pair,

wherein a first portion of the control data indicates that at least the first time slot of the first plurality of time slots is allocated to the first ONT,

wherein a second portion of the control data indicates that at least a second time slot of the first plurality of time slots is allocated to the first ONT,

wherein the tunable optical transmitter and the tunable optical receiver are tuned to the first wavelength pair during transmission of the first portion of the control data by the second OLT such that the first ONT does not respond to the first portion of the control data,

wherein the first ONT is configured to detect the communication failure between the first ONT and the first OLT and to tune the tunable optical transmitter and the tunable optical receiver to the second wavelength pair in response to detection of the communication failure,

wherein the second portion of the control data is received by the first ONT after detection of the communication failure,

wherein the first ONT is configured to transmit data to the second OLT in at least the second time slot based on the second portion of the control data, and

wherein the second OLT is configured to detect a failover switch associated with the first ONT based on a presence of the data in the second time slot of the first plurality of time slots and to allocate a second plurality of time slots to the first ONT according to a time division multiplexing (TDM) algorithm in response to detection of the failover switch.

2. The optical network of claim 1, wherein according to the TDM algorithm the second OLT is configured to determine sizes of the second plurality of time slots based on dynamic load conditions at the first ONT and a plurality of ONTs in communication with the second OLT.

3. The optical network of claim 1, wherein the first OLT is configured to range with the first ONT and to command the first ONT to range with the second OLT.

4. The optical network of claim 1, further comprising a plurality of ONTs coupled to the optical fiber and configured to communicate with the second OLT through the optical fiber on the second wavelength pair, wherein the second OLT is configured to transmit the control data through the optical fiber at the wavelength of the second wavelength pair to the plurality of ONTs.

5. A system for use in an optical network, comprising:

a first optical line terminal (OLT) for communicating with an optical network terminal (ONT) through an optical fiber via a first wavelength pair, the ONT having a tunable optical transmitter and a tunable optical receiver tuned to the first wavelength pair; and

a second OLT for communicating with the ONT through the optical fiber via a second wavelength pair, the second OLT configured to allocate a first plurality of time slots to the ONT by transmitting control data indicating that the first plurality of time slots are allocated to the ONT, at least a first time slot of the first plurality of time slots allocated to the ONT by the second OLT while the tunable optical transmitter and the tunable optical receiver are tuned to the first wavelength pair for communication with the first OLT,

wherein the tunable optical transmitter and the tunable optical receiver are tuned to the first wavelength pair during transmission of a portion of the control data indicating that the first time slot of the first plurality of time slots is allocated to the ONT such that the ONT does not respond to the control data for transmitting to the second OLT via the second wavelength pair during the first time slot of the first plurality of time slots,

wherein the second OLT is configured to detect a failover switch associated with the ONT based on a presence of data in at least a second time slot of the first plurality of time slots and to allocate a second plurality of time slots to the ONT according to a time-division multiplexing (TDM) algorithm in response to detection of the failover switch.

6. The system of claim 5, wherein according to the TDM algorithm the second OLT is configured to determine sizes of the second plurality of time slots based on dynamic load conditions at the ONT and a plurality of ONTs in communication with the second OLT.

7. The system of claim 5, wherein the first OLT is configured to range with the ONT and to command the ONT to range with the second OLT.

8. The system of claim 5, wherein the second OLT is further configured to allocate by transmitting, through the optical fiber, control data indicating that the first plurality of time slots are allocated to the ONT by the second OLT on the second wavelength pair, and wherein the ONT is configured for communication with the first OLT via the first wavelength pair when a portion of the control data is transmitted through the optical fiber on the second wavelength pair.

9. A method for use in an optical network, comprising:

ranging between a first optical line terminal (OLT) and a first optical network terminal (ONT) through an optical fiber;

ranging between a second OLT and the first ONT through the optical fiber;

communicating between the first OLT and the first ONT via a first wavelength pair through the optical fiber subsequent to each of the ranging;

allocating a first plurality of time slots to the first ONT by the second OLT, at least a first time slot of the first plurality of time slots allocated to the first ONT while a tunable optical transmitter and a tunable optical receiver of the first ONT are tuned to the first wavelength pair, the allocating comprising transmitting control data from the second OLT through the optical fiber via a second wavelength pair, the control data indicating that the first plurality of times slots are allocated to the first ONT, wherein the tunable optical transmitter and the tunable optical receiver are tuned to the first wavelength pair during transmission of a portion of the control data such that the first ONT does not respond to the portion of the control data for transmitting via the second wavelength pair to the second OLT during the first time slot of the first plurality of time slots, and wherein the portion of the control data indicates that the first time slot of the first plurality of time slots is allocated to the first ONT;

detecting, at the first ONT, a communication failure between the first OLT and the first ONT;

initiating a failover switch at the first ONT in response to the detecting, the failover switch for switching communication with the first ONT from the first OLT to the second OLT, wherein the initiating comprises;

(1) tuning the tunable optical transmitter of the first ONT to an upstream wavelength of the second wavelength pair;

(2) tuning a tunable optical receiver of the first ONT to a downstream wavelength of the second wavelength pair; and

(3) transmitting data to the second OLT in at least one of the first plurality of time slots,

receiving the data at the second OLT; and

allocating a second plurality of time slots to the first ONT by the second OLT according to a time-division multiplexing algorithm in response to the receiving.

10. The method of claim 9, wherein the allocating the second plurality of time slots comprises determining sizes of the second plurality of time slots based on dynamic load conditions at the first ONT and a plurality of ONTs in communication with the second OLT.

11. The method of claim 9, further comprising instructing the first ONT by the first OLT to range with the second OLT.

12. A method for use in an optical network, comprising:

ranging between a first optical line terminal (OLT) and a first optical network terminal (ONT) through an optical fiber;

ranging between a second OLT and the first ONT through the optical fiber;

communicating between the first OLT and the first ONT via a first wavelength pair through the optical fiber subsequent to each of the ranging;

allocating a first plurality of time slots to the first ONT by the second OLT, at least one of the first plurality of time slots allocated to the first ONT during the communicating between the first OLT and the first ONT, the allocating comprising transmitting control data from the second OLT to the first ONT via a second wavelength pair, the control data indicating that the first plurality of time slots are allocated to the first ONT, wherein a portion of the control data is transmitted to the first ONT while the first ONT is tuned for communication with the first OLT via the first wavelength pair such that the portion of the control data is not received by the first ONT, and wherein the portion of the control data indicates that at least a first time slot of the first plurality of time slots is allocated to the first ONT;

detecting a communication failure between the first ONT and the first OLT by the first ONT;

transmitting data in at least a second time slot of the first plurality of time slots from the first ONT to the second OLT through the optical fiber via the second wavelength pair;

detecting, at the second OLT, a failover switch associated with the first ONT based on a presence of the data in the second time slot of the first plurality of time slots; and

allocating a second plurality of time slots to the first ONT by the second OLT based on the detecting the failover switch.

13. The method of claim 12, wherein the allocating the second plurality of time slots comprises determining sizes of the second plurality of time slots based on dynamic load conditions at the first ONT and a plurality of ONTs in communication with the second OLT.

14. The method of claim 12, further comprising instructing the first ONT by the first OLT to range with the second OLT.

15. The method of claim 12, wherein the allocating comprises transmitting control data from the second OLT through the optical fiber, the control data indicating that at least one of the first plurality of time slots are allocated to the first ONT, wherein the transmitting the control data is performed while the first ONT is configured for communication with the first OLT.

16. An optical network, comprising:

an optical fiber;

a first optical line terminal (OLT) coupled to the optical fiber;

an optical network terminal (ONT) having a tunable optical transmitter coupled to the optical fiber and a tunable optical receiver coupled to the optical fiber, the ONT configured to tune the tunable optical transmitter and the tunable optical receiver to a first wavelength pair of the first OLT for communication with the first OLT through the optical fiber; and

a second OLT coupled to the optical fiber and configured to communicate with the ONT through the optical fiber on a second wavelength pair, the second OLT configured to allocate a first plurality of time slots to the ONT, at least a first time slot of the first plurality of time slots allocated to the ONT by the second OLT prior to a communication failure between the ONT and the first OLT while the tunable optical transmitter and the tunable optical receiver are tuned to the first wavelength pair for communication with the first OLT,

wherein the tunable optical transmitter and the tunable optical receiver are tuned to the first wavelength pair during transmission via the second wavelength pair of control data indicating the first time slot of the first plurality of time slots such that the ONT does not respond to the control data for transmitting to the second OLT via the second wavelength pair during the first time slot of the first plurality of time slots,

wherein the ONT is configured to detect the communication failure between the ONT and the first OLT and to tune the tunable optical transmitter and the tunable optical receiver to the second wavelength pair in response to detection of the communication failure,

wherein the ONT is configured to transmit data to the second OLT in at least a second time slot of the first plurality of time slots, and

wherein the second OLT is configured to detect a failover switch associated with the ONT based on a presence of the data in the second time slot of the first plurality of time slots and to allocate a second plurality of time slots to the ONT according to a time division multiplexing (TDM) algorithm in response to detection of the failover switch.

17. A system for use in an optical network, comprising:

an optical network terminal (ONT) coupled to an optical fiber, the ONT having a tunable optical transmitter and a tunable optical receiver tuned to a first wavelength pair;

a first optical line terminal (OLT) coupled to the optical fiber and configured to communicate with the ONT through the optical fiber via the first wavelength pair; and

a second OLT coupled to the optical fiber and configured to communicate with the ONT through the optical fiber via a second wavelength pair, the second OLT configured to allocate a first plurality of time slots to the ONT by transmitting to the ONT first control data while the tunable optical transmitter and the tunable optical receiver are tuned to the first wavelength pair such that the ONT does not respond to the first control data, wherein the first control data indicates that the first plurality of time slots are allocated to the ONT,

wherein the ONT is configured to detect a communication failure between the ONT and the first OLT and to tune the tunable optical transmitter and the tunable optical receiver to the second wavelength pair in response to detection of the communication failure,

wherein the second OLT is configured to allocate a second plurality of time slots to the ONT by transmitting to the ONT second control data indicating that the second plurality of time slots are allocated to the ONT, wherein the second control data is transmitted by the second OLT after the communication failure, and

wherein the second OLT is configured to detect a failover switch associated with the ONT based on a presence of data in the second plurality of time slots and to allocate a third plurality of time slots to the ONT according to a time-division multiplexing (TDM) algorithm based on detection of the failover switch.