Patent Application

App. No. 13/047,356

Abstract

Claims (32)

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 F 1 .

5 . The optical communications system as claimed in claim 4 , wherein each up-link data stream has a baud-rate of F 1 /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 F 1 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.

Assignments (8)