Multi-channel, multi-mode redundant optical local loop having a bus topology

• US 20020076143A1
• Filed: 12/15/2000
• Published: 06/20/2002
• Est. Priority Date: 12/15/2000
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Alcatel USA Sourcing L.P. (Nokia Corporation)
• Inventors: Foltzer, Lawrence E.
• Granted Patent: US 6,567,579 B2
• Time in Patent Office: Days
• US Class Current: 385/24
• CPC Class Codes: H04B 10/032 using working and protection systems H04J14/0287 takes precedence
• CPC Class Codes: H04B 10/0793 Network aspects, e.g. central monitoring of transmission parameters
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/028 WDM bus architectures
• CPC Class Codes: H04J 14/0294 Dedicated protection at the optical channel (1+1)
• CPC Class Codes: H04J 14/0295 Shared protection at the optical channel (1:1, n:m)

Abstract

An optical local loop having a bus topology with a pair of optical fibers disposed among a plurality of Optical Network Units (ONUs). A Host Digital Terminal (HDT) is disposed at the head end of the optical local loop for concentrating optical signals for a network. Redundant transceiver banks are provided within the HDT for operating with the optical signals effectuated at a plurality of wavelengths which are multiplexed and de-multiplexed via a pair of Wavelength Division Multiplex (WDM) couplers disposed on corresponding optical fibers. During transmission, the ONUs excite both optical fibers and the received optical signals are monitored in the HDT for quality and integrity of the optical paths. A selectively actuatable mechanism is provided in the HDT to switch downstream transmission to the ONU nodes from one optical path to the other optical path of the local loop based on the path quality and integrity.

Claims

1. An optical local loop, comprising:

a host digital terminal (HDT) operable to transmit in a downstream direction on a pair of optical fibers coupled thereto;

at least one node coupled to said pair of optical fibers, wherein said at least one node is operable to receive and transmit optical signals in at least one wavelength;

a first receiver block disposed in said HDT for receiving optical signals on a first fiber of said pair of optical fibers;

a second receiver block disposed in said HDT for receiving optical signals on a second fiber of said pair of optical fibers; and

a monitor coupled to said first and second receiver blocks for monitoring said first and second fibers.

2. The optical local loop as set forth in claim 1, wherein said HDT comprises a first wavelength-division multiplex (WDM) coupler coupled to said first fiber and a second WDM coupler coupled to said second fiber, each of said first and second WDM couplers operating to multiplex and de-multiplex a plurality of wavelengths for transmitting and receiving said optical signals on said first and second optical fibers.

3. The optical local loop as set forth in claim 2, further comprising means for selectively activating one of said first and second optical fibers for downstream transmission from said HDT.

4. The optical local loop as set forth in claim 3, wherein said at lease one node comprises:

a first optical circulator coupled to said first optical fiber, said first optical circulator operating with a filter for selecting optical signals at said at least one wavelength;

a second optical circulator coupled to said second optical fiber, said second circulator operating with a filter for selecting optical signals at said at least one wavelength; and

a coupler for coupling optical signals at said at least one wavelength to and from a local receiver and transmitter, respectively, disposed at said at least one node.

5. The optical local loop as set forth in claim 4, wherein each of said filters comprises a fiber Bragg grating filter.

6. The optical local loop as set forth in claim 4, wherein said first fiber of said pair of optical fibers is optimized for around 1310 nm.

7. The optical local loop as set forth in claim 4, wherein said second fiber of said pair of optical fibers is optimized for around 1310 nm.

8. The optical local loop as set forth in claim 4, wherein said first fiber of said pair of optical fibers is optimized for around 1550 nm.

9. The optical local loop as set forth in claim 4, wherein said second fiber of said pair of optical fibers is optimized for around 1550 nm.

10. The optical local loop as set forth in claim 4, further comprising means for detecting a fault associated with said pair of optical fibers, said means operating in association with said monitor.

11. The optical local loop as set forth in claim 4, further comprising means for isolating a fault associated with said pair of optical fibers, said means operating in association with said monitor.

12. The optical local loop as set forth in claim 4, further comprising means for localizing a fault associated with said pair of optical fibers, said means operating in association with said monitor.

14. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 13, wherein said first set of optical signals are processed through a first wavelength division multiplex (WDM) coupler connected to said first optical path in said HDT.

15. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 14, wherein said second set of optical signals are processed through a second WDM coupler connected to said second optical path in said HDT.

16. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 15, wherein each of said plurality of nodes is operable at a select wavelength.

17. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 15, wherein said first WDM coupler is operable at around 1550 nm.

18. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 15, wherein said second WDM coupler is operable at around 1550 nm.

19. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 15, wherein said first WDM coupler is operable at around 1310 nm.

20. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 15, wherein said second WDM coupler is operable at around 1310 nm.

21. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 15, wherein at least one of said plurality of nodes is operable at multiple wavelengths.

22. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 15, further including the step of isolating said at least a potential problem with respect to at least one of said first and second optical paths.

23. The method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers as set forth in claim 15, further including the step of localizing said at least a potential problem with respect to at least one of said first and second optical paths.

25. The optical bus operable as a local loop as set forth in claim 24, wherein said HDT further comprises:

a wavelength division multiplex (WDM) coupler connected to each of said first and second fibers;

a receiver bank and a transmitter bank associated with each of said WDM couplers; and

means for selectively actuating one of said transmitter banks for downstream transmission from said HDT towards said plurality of ONUs.

26. The optical bus operable as a local loop as set forth in claim 25, wherein said first fiber and said WDM coupler associated therewith are optimized for operation around 1550 nm.

27. The optical bus operable as a local loop as set forth in claim 25, wherein said first fiber and said WDM coupler associated therewith are optimized for operation around 1310 nm.

28. The optical bus operable as a local loop as set forth in claim 25, wherein said second fiber and said WDM coupler associated therewith are optimized for operation around 1550 nm.

29. The optical bus operable as a local loop as set forth in claim 25, wherein said second fiber and said WDM coupler associated therewith are optimized for operation around 1310 nm.

30. The optical bus operable as a local loop as set forth in claim 25, wherein each of said ONUs comprises:

a first optical circulator coupled to said first fiber, said first optical circulator operating with a filter for selecting optical signals at said at least one wavelength;

a second optical circulator coupled to said second fiber, said second circulator operating with a filter for selecting optical signals at said at least one wavelength; and

a coupler for coupling optical signals at said at least one wavelength to and from a local receiver and transmitter, respectively, disposed at said ONU.

31. The optical bus operable as a local loop as set forth in claim 30, wherein each of said filters is selected from the group consisting of a fiber Bragg grating filter, an interference filter, and a Fabry-Perot filter.

32. The optical bus operable as a local loop as set forth in claim 25, wherein said monitoring means is operable to detect a fault associated with at least one of said first and second fibers.

33. The optical bus operable as a local loop as set forth in claim 25, wherein said monitoring means is operable to isolate a fault associated with at least one of said first and second fibers.

34. The optical bus operable as a local loop as set forth in claim 25, wherein said monitoring means is operable to localize a fault associated with at least one of said first and second fibers.

13. A method of evaluating integrity in an optical local loop arranged as bus having a pair of optical fibers, comprising the steps of:

receiving in a host digital terminal (HDT) a first set of optical signals on a first optical path of said pair of optical fibers, wherein said first set of optical signals are generated by a plurality of nodes disposed on said first optical path;

receiving in said HDT a second set of optical signals on a second optical path of said pair of optical fibers, wherein said second set of optical signals are generated by said plurality of nodes disposed on said second optical path; and

monitoring said first and second set of optical signals to identify at least a potential problem with respect to at least one of said first and second optical paths.

24. An optical bus operable as a local loop, comprising:

a first fiber disposed among a plurality of optical network units (ONUs), each ONU operating at least at a select wavelength;

a second fiber disposed among said plurality of ONUs; and

a host digital terminal (HDT) disposed at a head end of said first and second fibers, said HDT including monitoring means for evaluating integrity of said first and second fibers.