OPTICAL NETWORK FAULT IDENTIFICATION

• US 20170279523A1
• Filed: 08/25/2015
• Published: 09/28/2017
• Est. Priority Date: 09/03/2014
• Status: Active Grant

• Current Assignee: British Telecommunications PLC (BT Group PLC)
• Original Assignee: British Telecommunications PLC (BT Group PLC)
• Inventors: PARKIN, Neil, MOHSIN, Anas
• Granted Patent: US 10,693,555 B2
• Time in Patent Office: Days
• CPC Class Codes: H04B 10/07 Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
• CPC Class Codes: H04B 10/071 using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
• CPC Class Codes: H04B 10/0773 Network aspects, e.g. central monitoring of transmission parameters
• CPC Class Codes: H04B 10/25 Arrangements specific to fibre transmission
• 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 2011/0083 Testing; Monitoring

Abstract

An optical network node capable of being powered, comprising—a reflector arranged to reflect an optical signal, and—a switch arranged to direct the optical signal to the reflector in dependence on whether the optical network node is powered.

Claims

1. An optical network node capable of being powered, comprising

a transceiver,

a retro-reflective reflector arranged to reflect an optical signal back to its source, and

a switch arranged to direct the optical signal to the transceiver or the reflector in dependence on whether the optical network node is powered.

2. An optical network node according to claim 1 wherein the switch is arranged to direct the optical signal to the retro-reflective reflector when the optical network node is unpowered.

3. An optical network node according to claim 1 wherein the switch comprises a micro-electromechanical systems switch.

4. An optical network node according to claim 3 wherein the retro-reflective reflector comprises at least one of:

a Fibre Bragg Grating reflector;

a thin film filter;

an optical fibre having a cleaved end with a predetermined reflective value;

an optical fibre having a cleaved end with a predetermined reflective pattern; and

an optical fibre having a cleaved end of a predetermined length having a cleaved end.

5. An optical network node according to claim 1 further comprising a socket for receiving an optical connector plug, the socket including a retro-reflective reflector configured to reflect back to its source an optical signal received via the connector plug.

6. A telecommunications network including an optical network node according to claim 1 operationally linked by an optical fibre to an optical transmitter, the switch being arranged to direct an optical signal output by the optical transmitter to the retro-reflective reflector in dependence on whether the optical network node is powered.

7. A telecommunications network according to claim 6 wherein the optical transmitter comprises an optical time domain reflectometer.

8. A telecommunications network according to claim 6 including a head end comprising a network management system and an optical line terminal, wherein the network management system comprises a persistent management agent arranged in use to receive messages concerning a loss of connection between the optical network node and the optical line terminal.

9. A telecommunications network according to claim 6 wherein the optical transmitter is co-located with the optical line terminal.

10. A telecommunications network according to claim 6 wherein the optical link comprises an optical connector for plugging into the optical network node, wherein the optical connector comprises at least one retro-reflective reflector.

11. A method of remotely detecting the power status of an optical network node, comprising:

in a first operational state in which the optical network node is powered, using a transceiver to send or receive an optical signal at the optical network node, and

in a second operational state, in which the optical network node is not powered, using a switch to direct an optical signal to a retro-reflective reflector arranged to reflect the optical signal back to its source.

12. A method according to claim 11 wherein the optical signal is received at a wavelength different from the wavelength of optical data communications transmitted between the optical network node and an optical line terminal.

13. A method according to claim 12 wherein the optical signal is received continuously when the optical network node is powered.

14. A method according to claim 11 wherein the optical signal is output by an optical time domain reflectometer over an optical fibre operationally connected to the optical network node, and wherein a retro-reflected optical signal received at the optical time domain reflectometer is compared against a reference value based on the length of the optical link.

15. A method according to claim 14 further comprising using the optical time domain reflectometer to establish the reference value at set up.