SINGLE WAVELENGTH SOURCE-FREE OFDMA-PON COMMUNICATION SYSTEMS AND METHODS

• US 20100215368A1
• Filed: 08/21/2009
• Published: 08/26/2010
• Est. Priority Date: 02/24/2009
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Laboratories America Inc (NEC Corporation)
• Inventors: Cvijetic, Neda, Hu, Junqiang, Qian, Dayou, Wang, Ting
• Granted Patent: US 8,233,797 B2
• Time in Patent Office: Days
• US Class Current: 398/67
• 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: H04J 14/0298 with sub-carrier multiplexing [SCM]
• CPC Class Codes: H04L 25/0216 with estimation of channel length

Abstract

Methods and systems for processing communication signals in an Orthogonal Frequency Division Multiple Access (OFDMA)-Passive Optical Network (PON) are disclosed. An optical carrier at a wavelength generated at an optical line terminal (OLT) may be reused by optical network units (ONUs) in the network for upstream transmission of data signals to the OLT. In addition, each ONU may perform carrier suppression to avoid broadband beating noise resulting from the simultaneous transmission of upstream data signals on the same wavelength. Further, the optical source at the OLT used to generate the optical carrier may be reused as a local oscillator for coherent detection of received upstream signals to minimize any frequency offsets.

Claims

1. A system for processing communication signals in an Orthogonal Frequency Division Multiple Access (OFDMA)-Passive Optical Network (PON) comprising:

an optical line terminal (OLT) configured to transmit first signals on a wavelength generated by an optical source in the OLT;

a plurality of optical network units (ONUs), wherein each optical network unit (ONU) is configured to receive the first signals on the wavelength, perform carrier suppression on an optical carrier on the wavelength received from the OLT and modulate the suppressed optical carrier to generate upstream optical OFDM data signals for transmission to the OLT on the wavelength.

2. The system of claim 1, wherein the OLT is further configured to perform coherent detection on the upstream OFDM optical data signals received from the ONUs on the wavelength by reusing the optical source in the OLT as a local oscillator to minimize frequency offset of the upstream signals.

3. The system of claim 2, wherein the upstream optical data signals are received simultaneously.

4. The system of claim 2, wherein the OLT is further configured to couple the upstream optical data signals with a continuous wave signal, generated by the optical source in the OLT, such that the continuous wave signal has a higher intensity than the intensities of the upstream optical data signals.

5. The system of claim 4, wherein the OLT is further configured to photodetect the upstream optical data signals after coupling the upstream optical data signals with the continuous wave signal.

6. The system of claim 1, wherein each of the ONUs is further configured to perform the carrier suppression by adjusting a direct current bias such that the intensity of the upstream OFDM optical data signals is higher than the intensity of the optical carrier on the wavelength so as to minimize beating noise at the OLT stemming from receiving the upstream signals from the plurality of ONUs operating on the same wavelength.

7. The system of claim 1, wherein the first signals are continuous wave signals, wherein said wavelength is a first wavelength and wherein said OLT is further configured to combine the continuous wave signals with downstream optical Orthogonal Frequency Division Multiplexed (OFDM) data signals on a second wavelength that is generated by a different optical source in the OLT.

8. The system of claim 7, wherein each ONU is further configured to receive the combined signals and separate the continuous wave signals on the first wavelength from the downstream optical data signals on the second wavelength and wherein each ONU is configured to modulate the continuous wave signals to generate said upstream optical OFDM data signals for transmission on the first wavelength.

9. The system of claim 1, wherein the first signals are downstream optical Orthogonal Frequency Division Multiplexed (OFDM) data signals.

10. A method for processing communication signals in an optical line terminal (OLT) of an Orthogonal Frequency Division Multiple Access (OFDMA)-Passive Optical Network (PON) comprising:

generating first signals that are on a wavelength generated by an optical source in the OLT;

distributing the first signals to a plurality of optical network units (ONUs); and

performing coherent detection on upstream optical OFDM data signals received from the ONUs on the wavelength by reusing the optical source in the OLT as a local oscillator to minimize frequency offset of the upstream signals.

11. The method of claim 10, wherein the performing further comprises coupling the upstream optical signals with a continuous wave signal generated by the optical source such that the continuous wave signal has a higher intensity than the intensities of the upstream optical data signals.

12. The method of claim 11, wherein the performing further comprises photodetecting the upstream optical data signals subsequent to the coupling.

13. The method of claim 10, wherein said first signals are continuous wave signals, wherein said wavelength is a first wavelength and wherein the method further comprises:

combining the continuous wave signals with downstream optical Orthogonal Frequency Division Multiplexed (OFDM) data signals that are on a second wavelength that is generated by a different optical source, wherein said distributing comprises distributing the combined downstream optical signals to the plurality of optical network units.

14. The method of claim 10, wherein said first signals are downstream optical Orthogonal Frequency Division Multiplexed (OFDM) data signals.

15. The method of claim 10, wherein the upstream optical signals are received simultaneously.

16. A method for processing communication signals in an optical network unit (ONU) of an Orthogonal Frequency Division Multiple Access (OFDMA)-Passive Optical Network (PON) comprising:

receiving first signals on a wavelength from an optical line terminal (OLT);

performing carrier suppression, at the ONU, on an optical carrier on the wavelength received from the OLT; and

modulating the suppressed optical carrier to generate upstream optical OFDM data signals for transmission on the suppressed optical carrier on the wavelength.

17. The method of claim 16, wherein the performing further comprises adjusting a direct current bias such that the intensities of the upstream optical OFDM data signals are higher than the intensity of the optical carrier to minimize beating noise at the OLT stemming from receiving the upstream signals from a plurality of ONUs operating on the same wavelength.

18. The method of claim 16, wherein said first signals are continuous wave signals, wherein said wavelength is a first wavelength, wherein said first signals are combined with downstream optical Orthogonal Frequency Division Multiplexed (OFDM) data signals on a second wavelength when received by the GNU, and wherein the method further comprises:

separating the continuous wave signals on the first wavelength from the downstream optical data signals on the second wavelength, wherein the performing comprises performing carrier suppression on the continuous wave signals and wherein the modulating comprises modulating the suppressed continuous wave signals to generate the upstream optical OFDM data signals for transmission on the first wavelength.

19. The method of claim 18 further comprising:

photodetecting the downstream optical data signals.

20. The method of claim 16, wherein said first signals are downstream optical Orthogonal Frequency Division Multiplexed (OFDM) data signals.