HFC cable system with shadow fiber and coax fiber terminals

Patent metadata

Field	Value
Publication number	US-9692513-B2
Application number	US-201615089504-A
Country	US
Kind code	B2
Filing date	Apr 2, 2016
Priority date	Jan 22, 2010
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

System and method to extend the upstream data capacity of an HFC CATV system by extending a “shadow” optical fiber network deeper into the various CATV cable neighborhoods, with coax fiber terminals (CFT) spaced roughly according to the distribution of CATV active devices such as RF amplifiers. The CFT can intercept local upstream data from various neighborhood sub-regions and transform this upstream data into upstream optical data, thus relieving upstream data congestion in the 5-42 MHz CATV frequency region. The system can produce an order of magnitude improvement in upstream capability, while maintaining high compatibility with legacy HFC equipment. The CFT may exist in multiple embodiments ranging from low-cost “dumb” CFT to sophisticated CFT that can additionally provide GigE to the home (GTTH) service. Methods to maintain good compatibility with legacy CMTS devices, and methods to utilize DOCSIS MAP data for more efficient data transmission are also discussed.

First claim

The invention claimed is:

1. A method for enhancing upstream data carrying capacity of a hybrid fiber cable (HFC) network, the method comprising:
at a Coax Fiber Terminal (CFT), receiving downstream CATV RF signals from a trunk CATV cable that is connected to a optical fiber node and relaying said downstream CATV RF signal to a branch CATV cable that is connected with a set of cable modems;
intercepting upstream CATV RF signals from said branch CATV cable;
converting said intercepted upstream CATV RF signal into upstream optical signals and transmitting said upstream optical signal to the optical fiber node through a shadow optical fiber in order for said optical fiber node to transmit digital data in said upstream optical signal to said headend.

2. The method of claim 1 , wherein said upstream CATV RF signals comprise DOCSIS signals, and wherein at least some of said DOCSIS signals are removed by said CFT and backhauled using said shadow optical fiber.

3. The method of claim 1 , wherein all of said upstream CATV RF signals are removed by said CFT and transmitted to said optical fiber node using said shadow optical fibers.

4. The method of claim 1 , wherein said at least one shadow optical fiber comprises a passive optical network.

5. The method of claim 1 , wherein said CFT
digitizes at least some of said upstream CATV RF signals and
transduces at least some of the digitized upstream CATV RF signals to optical signals, producing upstream optical signals.

6. The method of claim 5 , wherein the CFT digitizes said upstream CATV RF signals by:
obtaining Mini-slot Allocation Packet (MAP) data for at least some of said upstream CATV RF signals;
using said Mini-slot Allocation Packet (MAP) data to demodulate and extract at least some of the upstream digital information carried by at least some of said upstream CATV RF signals;
repackaging said upstream digital information in an alternative format for optical transmission; and
transmitting said upstream digital information in said alternative format along said shadow optical fiber.

7. The method of claim 6 , wherein said alternative format is an optical Ethernet format.

8. The method of claim 6 , wherein the CFT further digitizes said upstream CATV RF signals by:
using said Mini-slot Allocation Packet (MAP) data to subsequently remodulate said upstream digital information into reconstituted upstream CATV RF signals, producing reconstituted upstream CATV RF signals; and
supplying said reconstituted upstream CATV RF signals to a Cable Modem Termination System (CMTS).

9. The method of claim 5 , wherein the CFT digitizes said upstream CATV RF signals by:
sampling the CATV RF signals at a sample rate that is at least twice the frequency of the highest upstream CATV RF signal frequency;
performing an analog to digital conversion on said sampled CATV RF signals producing digitized upstream CATV signals.

10. The method of claim 9 , wherein the CFT remodulates said digitized upstream CATV RF signals into reconstituted upstream CATV RF signals to produce reconstituted upstream CATV RF signals and supplies said reconstituted upstream CATV RF signals to a Cable Modem Termination System.

11. The method of claim 1 , wherein said branch CATV cable and said trunk CATV cable are part of a CATV Tree and Branch network, wherein at least some remaining upstream CATV RF signals continue to be transmitted along said CATV Tree and Branch Network after at least some CATV RF signals have been intercepted and removed by said Coax Fiber Terminals.

12. The method of claim 11 , wherein said CFT actively regenerates said at least some remaining upstream CATV RF signals and passes said remaining upstream CATV RF signals back onto the CATV trunk cable after first removing and digitizing all of said upstream CATV RF signals.

13. The method of claim 1 , wherein Mini-slot Allocation Packet (MAP) data is used to mask upstream RF signals according to time windows designated for upstream transmission, thereby reducing the amount of noise in the upstream data that is carried by said shadow optical fiber.

14. The method of claim 1 further comprising:
using said shadow optical fiber and said CFT to transmit downstream Gigabit Ethernet data; and
modulating said downstream Gigabit Ethernet data into downstream CATV RF signals at said CFT.

15. The method of claim 1 further comprising using said shadow optical fiber and said CFT to transmit upstream and downstream data according to a Time Division Duplex scheme.

16. The method of claim 1 , wherein said CFT backhaul said information by performing a direct electrical to optical conversion of said intercepted upstream CATV RF signals.

17. A method for enhancing upstream data carrying capacity of a hybrid fiber cable (HFC) network, the method comprising:
at an optical fiber node, receiving downstream optical signals from a headend of the HFC network via an optical fiber and transmits digital data in the received downstream optical signals as CATV RF signals to trunk CATV cables of a trunk and branch CATV network for a set of CATV active devices;
receiving upstream CATV RF signals from the trunk CATV cables;
receiving upstream optical signals from the set of CATV active devices through a set of shadow optical fibers that are connected to a set of Coax Fiber Terminals (CFTs) that are connected to the trunk and branch CATV network, wherein each CFT intercepts local upstream CATV RF signals being transmitted by said set of CATV active devices and remove at least some of said intercepted upstream CATV RF signals from said trunk or branch CATV cables connected to said CATV active devices.

18. The method of claim 17 , wherein a first set of CATV active devices attached to a first CATV trunk cable and a first set of CATV branch cables is served by a first CFT is addressed as a first domain, wherein a second set of CATV active devices attached to a second CATV trunk cable and a second set of CATV branch cables is served by a second CFT is addressed as a second domain.

19. The method of claim 17 , wherein at least one shadow optical fiber transmit downstream Gigabit Ethernet data to a CFT that modulates said downstream Gigabit Ethernet data into downstream CATV RF signals for CATV branch cables.

Assignees

• Gainspeed Inc
• Alcatel Lucent Usa Inc

Inventors

• Rakib Shlomo Selim

Classifications

• H04H20/78

  CATV [Community Antenna Television] systems · CPC title

• H04B10/25751 Primary

  Optical arrangements for CATV or video distribution (adaptations of television systems for optical transmission H04N7/22) · CPC title

• H04N21/6168

  involving cable transmission, e.g. using a cable modem · CPC title

• H04N21/6118

  involving cable transmission, e.g. using a cable modem · CPC title

• H04N7/10 Primary

  Adaptations for transmission by electrical cable (H04N7/12 takes precedence) · CPC title