COHERENT OPTICAL HUBBING

• US 20110222854A1
• Filed: 03/14/2011
• Published: 09/15/2011
• Est. Priority Date: 03/12/2010
• Status: Abandoned Application

• Current Assignee: Ciena Corporation
• Original Assignee: Ciena Corporation
• Inventors: HARLEY, James, ROBERTS, Kim B.
• Application Number:
  US13/047,356
• Publication Number:
  US 20110222854A1
• Time in Patent Office: Days
• US Class Current: 398/70
• CPC Class Codes: H04B 10/532 Polarisation modulation
• CPC Class Codes: H04B 10/548 Phase or frequency modulation
• CPC Class Codes: H04J 14/002 Coherencemultiplexing
• CPC Class Codes: H04L 27/2633 using partial FFTs
• CPC Class Codes: H04L 27/2636 with FFT or DFT modulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] transmitter or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 27/2697 in combination with other modulation techniques

Abstract

An optical communications system includes a hub modem and a set of two or more remote modems. Each remote modem includes a transmitter stage for transmitting a respective uplink data stream within a selected one of a set of two or more sub-channels. The hub modem optically communicates with the set of remote modems. The hub modem includes a receiver stage having an optical front-end for receiving an uplink optical channel signal within a spectral range that encompasses the set of two or more spectral sub-bands; a photodetector for detecting modulation components of the received uplink optical channel signal and for generating a corresponding high bandwidth analog signal; and a digital signal processor for processing the high bandwidth analog signal to recover the respective uplink data stream transmitted by each remote modem.

Claims

1. An optical communications system comprising:

a set of two or more remote modems, each remote modem including a transmitter stage for transmitting a respective uplink data stream within a selected one of a set of two or more spectral sub-bands; and

a hub modem optically communicating with the set of remote modems, the hub modem including a receiver stage comprising;

an optical front-end for receiving an uplink optical channel signal within a spectral range that encompasses the set of two or more spectral sub-bands;

a photodetector for detecting modulation components of the received uplink optical channel signal and for generating a corresponding high bandwidth analog signal; and

a digital signal processor for processing the high bandwidth analog signal to recover the respective uplink data stream transmitted by each remote modem.

2. The optical communications system as claimed in claim 1, wherein the optical front-end comprises a coherent receiver tuned to receive the uplink optical channel signal.

3. The optical communications system as claimed in claim 1, wherein the optical front-end comprises a DEMUX filter for separating the uplink optical channel signal from a set of two or more Wavelength Division Multiplexed (WDM) optical channel signals.

4. The optical communications system as claimed in claim 1, wherein a sub-band has a spectral width of F₁.

5. The optical communications system as claimed in claim 4, wherein each up-link data stream has a baud-rate of F₁/2

6. The optical communications system as claimed in claim 4, wherein the uplink optical channel signal has a spectral width approximately equal to the sum of the F₁ for each sub-band.

7. The optical communications system as claimed in claim 1, wherein an encoding scheme used by a selected one remote modem is the same as that used by another remote modem.

8. The optical communications system as claimed in claim 1, wherein an encoding scheme or a bandwidth used by a selected one remote modem is different from that used by another remote modem.

9. The optical communications system as claimed in claim 1, wherein the digital signal processor is configured to compensate a respective different dispersion of each sub-band.

10. The optical communications system as claimed in claim 1, wherein the digital signal processor is configured to compensate a respective different polarization impairment of each sub-band.

11. The optical communications system as claimed in claim 1, wherein:

the hub modem further includes a transmitter stage for transmitting a respective downlink data stream to each remote modem, the transmitter stage comprising;

a signal processor for processing the downlink data streams to derive a high bandwidth analog signal;

an optical modulator for modulating a narrow-band optical carrier light in accordance with the high bandwidth analog signal to generate a downlink optical channel signal having a spectral range that encompasses the set of two or more spectral sub-bands;

wherein modulation components of the optical channel signal corresponding to the respective downlink data stream destined to any given remote modem are contained within the spectral sub-band of that remote modem; and

each remote modem comprises a receiver for receiving the modulation components of the optical channel signal within its respective spectral sub-band.

12. The optical communications system as claimed in claim 11, wherein the transmitter stage of each remote modem is frequency locked to the narrow-band optical carrier light of the downlink optical channel signal.

13. The optical communications system as claimed in claim 11, wherein the receiver stage of at least one remote modem is a coherent receiver.

14. The optical communications system as claimed in claim 11, wherein the signal processor is configured to compensate a respective different dispersion of each sub-band.

15. The optical communications system as claimed in claim 14, wherein the receiver stage of at least one remote modem is a direct detection receiver.

16. A modem comprising:

a transmitter section configured to generate a high speed analog signal having a predetermined bandwidth and comprising a plurality of sub-channels, each sub-channel comprising spectral components of a respective data signal; and

a receiver section configured to receive a high speed analog signal having a predetermined bandwidth and comprising a plurality of sub-channels, each sub-channel comprising spectral components of a respective data signal, the receiver stage comprising a receiver digital signal processor for recovering the respective data signal of each sub-channel.

17. The modem as claimed in claim 16, wherein the transmitter section comprises a transmitter digital signal processor for predistorting the high speed analog signal to compensate dispersion.

18. The modem as claimed in claim 17, wherein the transmitter digital signal processor is configured to predistort each sub-channel independently, so as to compensate a respective different amount of dispersion in each sub-channel

19. The modem as claimed in claim 16, wherein the receiver section digital signal processor is configured to compensate dispersion in the received high speed analog.

20. The modem as claimed in claim 19, wherein the receiver section digital signal processor is configured to compensate a respective different amount of dispersion in each sub-channel.