Countermeasures for idle pattern SRS interference in ethernet optical network systems

• US 20060039699A1
• Filed: 08/10/2005
• Published: 02/23/2006
• Est. Priority Date: 08/10/2004
• Status: Active Grant

• Current Assignee: ARRIS Enterprises LLC (CommScope Holding Company, Inc.)
• Original Assignee: Wave7 Optics, Inc. (Enablence Technologies Incorporated)
• Inventors: Brown, Alan, Thomas, Stephen, Kenny, John, Farmer, James
• Granted Patent: US 7,340,180 B2
• Time in Patent Office: Days
• US Class Current: 398/66
• CPC Class Codes: H04B 10/2537 due to scattering processes, e.g. Raman or Brillouin scattering
• CPC Class Codes: H04J 14/0226 Fixed carrier allocation, e.g. according to service
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0232 for downstream transmission
• CPC Class Codes: H04J 14/0247 Sharing one wavelength for at least a group of ONUs
• CPC Class Codes: H04J 14/0252 Sharing one wavelength for at least a group of ONUs, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
• CPC Class Codes: H04J 14/0282 WDM tree architectures
• CPC Class Codes: H04L 2007/045 Fill bit or bits, idle words

Abstract

Optical networks as defined by the IEEE 802.3ah standard suffer from Stimulated Raman Scattering (SRS) that causes data transmission at a first optical wavelength to interfere with broadcast video transmission at a second optical wavelength in single mode optical fibers. The problem is exacerbated when data is not being transmitted across the network; and instead, an idle pattern transmission is being transmitted in order to keep the network synchronized. The repetitive nature of the idle pattern transmission leads to the SRS optical interference effect. This optical interference effect is mitigated when countermeasures are implemented to modify the idle pattern transmissions or to transmit random data in place of the idle pattern transmissions.

Claims

1. A method for mitigating the effects of interference from data signals comprising the steps of:

receiving input from a routing device;

determining whether the input comprises one of an absence of data and an idle pattern; and

in response to detecting one of an absence of data and an idle pattern, generating substitute data in an electrical domain that reduces power at one or more harmonics.

2. The method of claim 1, further comprising the step of converting the substitute data from the electrical domain to the optical domain.

3. The method of claim 2, further comprising the step of propagating the substitute data in the optical domain along with video information in the optical domain through a single optical waveguide, the substitute data reducing any optical interference between data and the video information.

4. The method of claim 1, wherein the step of generating substitute data further comprises generating non-repetitive random data and assigning the random data to a non-existent MAC address.

5. The method of claim 1, wherein the step of generating substitute data further comprises alternating between different idle code pairs based upon a random variable function.

6. The method of claim 1, further comprising determining whether the input comprises data, and if the input comprises data, then converting the data from an electrical domain to an optical domain.

7. The method of claim 6, further comprising propagating the input data in the optical domain along with video information in the optical domain along a single optical waveguide.

8. A method for reducing optical interference between data and video information propagated over a single optical waveguide comprising:

receiving video information in an electrical domain;

converting the video information into an optical domain by modulating the video information on a first optical carrier with a first optical wavelength;

monitoring input in an electrical domain;

determining if the input comprises one of an absence of data and an idle pattern;

if the data comprises an idle pattern code, then generating substitute data;

converting the substitute data into an optical domain by modulating the substitute data on a second optical carrier with a second optical wavelength;

combining the first and second optical carriers; and

propagating the first and second optical carriers along the single optical waveguide wherein the substitute data substantially reduces any optical interference between the first and second optical carriers.

9. The method of claim 8, wherein the step of generating substitute data further comprises generating non-repetitive random data and assigning the random data to a non-existent MAC address.

10. The method of claim 8, wherein the step of generating substitute data further comprises using one of two idle code pairs based upon a random variable function.

11. The method of claim 8, further comprising determining if the input comprises data, and if the input comprises data, then converting the data from an electrical domain to an optical domain.

12. The method of claim 11, further comprising propagating the input data in the optical domain along with video information in the optical domain along a single optical waveguide.

13. A method for reducing optical interference between data and video information propagated over a single optical waveguide comprising:

receiving video information in an electrical domain;

converting the video information into an optical domain by modulating the video information on a first optical carrier with a first optical wavelength;

generating random data assigned with a low priority;

determining if any higher priority data is present for optical transmission;

if higher priority data is not present, then inserting the random data with the low priority for optical transmission;

converting the random data into an optical domain by modulating the random data on a second optical carrier with a second optical wavelength;

combining the first and second optical carriers; and

propagating the first and second optical carriers along the single optical waveguide wherein the substitute data substantially reduces any optical interference between the first and second optical carriers.

14. The method of claim 13, further comprising if higher priority data is present, then using the higher priority data for optical transmission.

15. The method of claim 13, further comprising converting the data from an electrical domain to an optical domain when the data has a priority higher than the random data.

16. The method of claim 13, further comprising propagating the input data in the optical domain along with video information in the optical domain along a single optical waveguide.

17. An optical network comprising:

a routing device for assigning data to optical taps that are coupled to one or more subscribers;

an idle pattern replacement device coupled to the routing device for determining whether data received from the routing device comprises one of an idle pattern and an absence of data, for generating a substitute idle pattern in an electrical domain that reduces power at one or more harmonics;

an optical transmitter for converting the substitute idle pattern from the electrical domain to the optical domain; and

an optical waveguide coupled to the optical transmitter for propagating the substitute idle pattern in the optical domain along with video information in the optical domain along a single optical waveguide, the substitute idle pattern reducing any optical interference between the input data and the video information.

18. The optical network of claim 17, wherein the idle pattern replacement device comprises a downstream data shift register, a replacement data shift register, and a data initializer.

19. The optical network of claim 17, wherein the idle pattern replacement device comprises a detector for sensing the presence of real data, no data, and idle pattern.

20. The optical network of claim 19, wherein the detector is coupled to the data initializer.