Hybrid fiber-coax system having at least one digital fiber node and increased upstream bandwidth

• US 5,963,844 A
• Filed: 09/18/1996
• Issued: 10/05/1999
• Est. Priority Date: 09/18/1996
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Dail, James E.
• Primary Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US08/718,104
• Time in Patent Office: 1,112 Days
• Field of Search: 348/6, 348/7, 348/10, 348/11, 348/12, 348/13, 348/14, 348/15, 348/16, 348/17, 348/18, 455/3.1, 455/4.1, 455/4.2, 455/5.1, 455/6.1, 455/6.2, 455/6.3, 455/14
• US Class Current: 725/125
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

Increased upstream bandwidth and reduced ingress noise in a shared hybrid fiber-coax transmission system (100) are obtained by modulating at least a portion of upstream signals received from subscribers to a high frequency band (e.g., 750-1000 MHz), thereby increasing the upstream bandwidth. The high frequency upstream signals are then digitally regenerated in the coaxial cable (200) plant prior to receipt at a fiber node (180). At the fiber node, the high-frequency upstream signals are again digitally regenerated and are then transmitted optically in a baseband digital format between the fiber node (180) and a head end (120). The digital regeneration of the high frequency upstream signals, and the optical transmission of such signals in a baseband digital format reduces the incidence of ingress noise.

Claims

1. A method for reducing aggregated ingress noise and for increasing upstream bandwidth in a hybrid fiber-coax transmission system that carries information from a head end to a plurality of subscribers via at least one main coax trunk and for carrying information originated by said plurality of subscribers to said head at least in part on said main coax trunk, comprising the steps of:

aggregating onto the main coax trunk information generated by said plurality of subscribers modulating at least a portion of the aggregated upstream signals onto a high frequency band;

digitally regenerating the aggregated upstream signals modulated onto the high frequency band for transmission on the main coax trunk to a fiber node; and

optically formatting, at said fiber node, the digitally-regenerated aggregated upstream signals modulated onto the high frequency band in baseband digital format for transmission to a head end.

2. The method according to claim 1 wherein the high frequency band comprises the band of 750-1000 MHz.

3. The method according to claim 2 wherein the portion of the upstream signals not modulated to the high frequency band are modulated to a frequency band of 5-40 MHz.

4. The method according to claim 1 wherein the hybrid fiber-coax system transmits downstream signals in the 50-750 MHz. frequency band.

5. A method of operating a shared hybrid fiber-coax transmission system in which a downstream signal is destined for transmission from a head end to individual subscribers and in which upstream signals are generated by subscribers for transmission to the head end, the method comprising the steps of:

transmitting the downstream signal in an optical format from the head end to a fiber node for conversion to a downstream electrical signal;

transmitting the downstream electrical signal, via a coaxial cable plant, to the individual subscribers;

aggregating, in the coaxial cable plant, upstream signals generated by the subscribers;

modulating, within the coaxial cable plant, at least a portion of the aggregated upstream signals to a high frequency band;

digitally regenerating, within the coaxial cable plant, the portion of the aggregated upstream signals modulated to the high frequency band;

transmitting the digitally regenerated high frequency upstream signals via the coax plant to the fiber node; and

optically formatting, at the fiber node, the portion of the aggregated upstream signals that were modulated to a high frequency and digitally regenerated into a baseband digital format for transmission from the fiber node to the head end.

6. The method according to claim 5 further including the steps of:

separating, at the fiber node, the portion of the upstream signals that were modulated to a high frequency and digitally regenerated from downstream and upstream signals that are of a lower frequency received on a common cable from the coaxial cable plant; and

further digitally regenerating the portion of the upstream signals that were modulated to a high frequency and digitally regenerated prior to optical formatting.

7. The method according to claim 6 further including the steps of:

separating, at the fiber node, the downstream signals from the upstream signals that are of a lower frequency than portion of the upstream signals modulated to a high frequency;

amplifying the lower frequency upstream signals; and

transmitting the lower frequency upstream signals in a linear optical format to the head end.

8. The method according to claim 5 wherein the high frequency band comprises the band of 750-1000 MHz.

9. The method according to claim 7 wherein the lower frequency comprises the frequency band of 5-40 MHz.

10. The method according to claim 5 wherein the hybrid fiber-coax system transmits downstream signals in the 50-750 MHz. frequency band.