HYBRID FIBER-COAXIAL (HFC) CABLE COMMUNICATION SYSTEMS HAVING WELL-ALIGNED OPTICAL AND RADIO-FREQUENCY LINKS TO FACILITATE UPSTREAM CHANNEL PLANS HAVING HIGH AGGREGATE DATA CAPACITY

• US 20140282783A1
• Filed: 03/17/2014
• Published: 09/18/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Certusview Technologies LLC (Dycom Industries Incorporated)
• Original Assignee: Certusview Technologies LLC (Dycom Industries Incorporated)
• Inventors: Totten, Ronald, West, Lamar
• Granted Patent: US 8,949,918 B2
• Time in Patent Office: Days
• US Class Current: 725/111
• CPC Class Codes: H04B 10/2575 Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
• CPC Class Codes: H04B 10/25751 Optical arrangements for CATV or video distribution adaptations of television systems for optical transmission H04N7/22
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• CPC Class Codes: H04L 12/2885 Arrangements interfacing with optical systems optical network equipment H04B10/00; optical multiplexers H04J14/05 and H04J14/07
• CPC Class Codes: H04N 21/61 Network physical structure; Signal processing H04B takes precedence

Abstract

An HFC cable communication system comprising: a CMTS having a first attenuator to attenuate one or more upstream signals applied to the CMTS; an optical link having a dynamic range and comprising an optical receiver having a second attenuator to attenuate the upstream signal(s) and an optical transmitter having a third attenuator to attenuate the upstream signal(s); a coaxial RF link comprising one or more RF amplifiers having a fourth attenuator to attenuate the upstream signal(s); and one or more subscriber modems to generate the upstream signal(s) at respective transmit RF signal levels. The CMTS implements a long loop ALC to set the transmit RF signal level(s) based on received RF signal levels of the upstream signal(s) at the CMTS. Respective values for the first, second, third and fourth attenuators are selected based on the dynamic range of the optical link so as to facilitate implementation of the long loop ALC and effective transmission of upstream information carried by the upstream signal(s).

Claims

1. a hybrid fiber-coaxial (HFC) cable communication system, comprising:

a cable modem termination system (CMTS) having associated therewith at least one first attenuator to attenuate at least one upstream signal applied to the CMTS;

an optical link communicatively coupled to the CMTS, the optical link having a dynamic range and comprising;

an optical receiver having associated therewith at least one second attenuator to attenuate the at least one upstream signal; and

an optical transmitter having associated therewith at least one third attenuator to attenuate the at least one upstream signal;

a coaxial radio frequency (RF) link communicatively coupled to the optical link, the coaxial RF link comprising at least one RF amplifier having associated therewith at least one fourth attenuator to attenuate the at least one upstream signal; and

at least one subscriber modem, communicatively coupled to the coaxial RF link, to generate from an output of the at least one subscriber modem the at least one upstream signal at a transmit RF signal level,

wherein;

the CMTS implements a long loop automatic level control (ALC) to set the transmit RF signal level of the at least one upstream signal generated from the output of the at least one subscriber modem, based at least in part on a received RF signal level of the at least one upstream signal as applied to the CMTS; and

respective values for the at least one first attenuator, the at least one second attenuator, the at least one third attenuator, and the at least one fourth attenuator are selected based at least in part on the dynamic range of the optical link so as to facilitate implementation of the long loop ALC and effective transmission to the CMTS of upstream information carried by the at least one upstream signal.

2. The system of claim 1, wherein the coaxial RF link includes an ingress-mitigated hardline cable plant.

3. The system of claim 2, wherein a value of the at least one fourth attenuator associated with the at least one RF amplifier is selected and/or adjusted such that a signal level of the at least one upstream signal at a junction of the coaxial RF link and the optical link corresponds to a predetermined input RF reference signal level to be applied to the optical link.

4. The system of claim 3, wherein the predetermined input RF reference signal level is 18-19 dBmV.

5. The system of claim 3, wherein:

the at least one RF amplifier includes a plurality of RF amplifiers;

the at least one fourth attenuator includes a plurality of fourth attenuators;

each RF amplifier of the plurality of RF amplifiers includes at least one of the plurality of fourth attenuators; and

the plurality of fourth attenuators are selected and/or adjusted such that the signal level of the at least one upstream signal at the junction of the coaxial RF link and the optical link corresponds to the predetermined input RF reference signal level to be applied to the optical link.

6. The system of claim 2, wherein the at least one RF amplifier of the coaxial RF link further has associated therewith at least one equalizer, and wherein the at least one equalizer and a value of the at least one fourth attenuator associated with the at least one RF amplifier are selected and/or configured such that at least a portion of the coaxial RF link including the at least one RF amplifier provides essentially flat gain for the at least one upstream signal across a substantial portion of an upstream path bandwidth for the at least one upstream signal.

7. The system of claim 6, wherein the at least one equalizer and a value of the at least one fourth attenuator associated with the at least one RF amplifier are selected and/or configured such that at least the portion of the coaxial RF link provides essentially unity gain for the at least one upstream signal across a substantial portion of an upstream path bandwidth for the at least one upstream signal.

8. The system of claim 1, wherein:

the at least one subscriber modem includes a plurality of subscriber modems communicatively coupled to the coaxial RF link, the plurality of subscriber modems generating a corresponding plurality of upstream signals respectively having corresponding transmit RF signal levels according to the long loop ALC;

each upstream signal of the plurality of upstream signals includes at least one encoded carrier wave having a carrier frequency in an upstream path bandwidth of the coaxial RF link and being modulated, using quadrature amplitude modulation (QAM), with voice and/or data information;

at least some of the plurality of upstream signals have different carrier frequencies to respectively define a plurality of upstream physical communication channels in the upstream path bandwidth; and

a first upstream signal defining a first upstream physical communication channel of the plurality of upstream physical communication channels has a first carrier frequency of less than 19.6 MHz.

9. The system of claim 8, wherein a QAM modulation order of the first upstream signal is at least 32.

10. The system of claim 8, wherein a QAM modulation order of the first upstream signal is at least 64.

11. The system of claim 8, wherein a QAM modulation order of the first upstream signal is at least 256.

12. The system of claim 8, wherein the plurality of upstream physical communication channels occupy a substantial portion of the upstream path bandwidth including carrier frequencies in a range of from approximately 5 MHz to at least approximately 42 MHz.

13. The system of claim 12, wherein the plurality of upstream physical communication channels includes at least four physical communication channels respectively defined by upstream signals having a QAM modulation order of at least 64.

14. The system of claim 12, wherein the plurality of upstream physical communication channels includes at least six physical communication channels respectively defined by upstream signals having a QAM modulation order of at least 64.

15. The system of claim 12, wherein the plurality of upstream physical communication channels includes at least four physical communication channels respectively defined by upstream signals having a QAM modulation order of at least 256.

16. The system of claim 12, wherein the plurality of upstream physical communication channels includes at least six physical communication channels respectively defined by upstream signals having a QAM modulation order of at least 256.

17. The system of claim 1, wherein

the at least one subscriber modem includes a plurality of subscriber modems communicatively coupled to the coaxial RF link, the plurality of subscriber modems generating a corresponding plurality of upstream signals respectively having corresponding transmit RF signal levels according to the long loop ALC;

each upstream signal of the plurality of upstream signals includes at least one encoded carrier wave having a carrier frequency in an upstream path bandwidth of the coaxial RF link and being modulated, using quadrature amplitude modulation (QAM), with voice and/or data information;

at least some of the plurality of upstream signals have different carrier frequencies to respectively define a plurality of upstream physical communication channels in the upstream path bandwidth constituting a channel plan; and

the dynamic range of the optical link is based at least in part on the channel plan.

18. The system of claim 17, wherein the dynamic range of the optical link is based at least in part on a highest QAM modulation order of at least one upstream physical communication channel of the channel plan.

19. The system of claim 18, wherein the dynamic range of the optical link is based on the highest QAM modulation order of the at least one upstream physical communication channel of the channel plan and an information transfer characteristic of the optical link.

20. The system of claim 19, wherein the information transfer characteristic of the optical link includes a Noise Power Ratio (NPR) curve for the optical link.

21. The system of claim 20, wherein:

the dynamic range of the optical link is defined by an input RF power window for the at least one upstream signal as applied to the optical transmitter of the optical link;

the input RF power window is determined by at least one intersection of a target carrier-to-noise (C/N) value for the highest modulation order of the at least one upstream physical communication channel of the channel plan and the NPR curve;

a target operating power point for the optical transmitter is selected within the input RF power window; and

an attenuation value of the third attenuator associated with the optical transmitter is selected based at least in part on the target operating power point for the optical transmitter.

22. The system of claim 21, wherein the target operating power point for the optical transmitter is selected at a midpoint of the input RF power window.

23. The system of claim 19, wherein the information transfer characteristic of the optical link includes a Bit Error Ratio (BER) curve for the optical link.

24. The system of claim 23, wherein:

the dynamic range of the optical link is defined by an input RF power window for the at least one upstream signal as applied to the optical transmitter of the optical link;

the input RF power window is determined by at least one intersection of a target BER value for the highest modulation order of the at least one upstream physical communication channel of the channel plan and the BER curve;

a target operating power point for the optical transmitter is selected within the input RF power window; and

an attenuation value of the third attenuator associated with the optical transmitter is selected based at least in part on the target operating power point for the optical transmitter.

25. The system of claim 19, wherein the information transfer characteristic of the optical link includes a Modulation Error Ratio (MER) curve for the optical link.

26. The system of claim 25, wherein:

the dynamic range of the optical link is defined by an input RF power window for the at least one upstream signal as applied to the optical transmitter of the optical link;

the input RF power window is determined by at least one intersection of a target MER value for the highest modulation order of the at least one upstream physical communication channel of the channel plan and the MER curve;

a target operating power point for the optical transmitter is selected within the input RF power window; and

an attenuation value of the third attenuator associated with the optical transmitter is selected based at least in part on the target operating power point for the optical transmitter.

27. A hybrid fiber-coaxial (HFC) cable communication system, comprising:

A) a cable modem termination system (CMTS) having associated therewith at least one first attenuator to attenuate a plurality of upstream signals applied to the CMTS;

B) an optical link communicatively coupled to the CMTS, the optical link having a dynamic range and comprising;

an optical receiver having associated therewith at least one second attenuator to attenuate the plurality of upstream signals; and

an optical transmitter having associated therewith at least one third attenuator to attenuate the plurality of upstream signals;

C) a coaxial radio frequency (RF) link communicatively coupled to the optical link, the coaxial RF link comprising;

an ingress-mitigated hardline cable plant; and

at least one RF amplifier having associated therewith at least one fourth attenuator to attenuate at least some of the plurality of upstream signals; and

D) a plurality of subscriber modems, communicatively coupled to the coaxial RF link, to generate from respective outputs of the plurality of subscriber modems the corresponding plurality of upstream signals at respective transmit RF signal levels,

wherein;

each upstream signal of the plurality of upstream signals includes at least one encoded carrier wave having a carrier frequency in an upstream path bandwidth and being modulated, using quadrature amplitude modulation (QAM), with voice and/or data information from at least some of the plurality of subscriber premises;

at least one first upstream signal of the plurality of upstream signals has a QAM modulation order of 32 and a first carrier frequency of between approximately 5 MHz and 19.6 MHz;

the CMTS implements a long loop automatic level control (ALC) to set the respective transmit RF signal levels of the plurality of upstream signals generated from the respective outputs of the plurality of subscriber modems, based at least in part on respective received RF signal levels of the plurality of upstream signals as applied to the CMTS; and

respective values for the at least one first attenuator, the at least one second attenuator, the at least one third attenuator, and the at least one fourth attenuator are selected based at least in part on the dynamic range of the optical link so as to facilitate implementation of the long loop ALC and effective transmission to the CMTS of upstream information carried by the plurality of upstream signals.

28. A hybrid fiber-coaxial (HFC) cable communication system, comprising:

A) a cable modem termination system (CMTS) having associated therewith at least one first attenuator to attenuate a plurality of upstream signals applied to the CMTS;

B) an optical link communicatively coupled to the CMTS, the optical link having a dynamic range and comprising;

an optical receiver having associated therewith at least one second attenuator to attenuate the plurality of upstream signals; and

an optical transmitter having associated therewith at least one third attenuator to attenuate the plurality of upstream signals;

C) a coaxial radio frequency (RF) link communicatively coupled to the optical link, the coaxial RF link comprising at least one RF amplifier having associated therewith at least one fourth attenuator to attenuate at least some of the plurality of upstream signals; and

D) a plurality of subscriber modems, communicatively coupled to the coaxial RF link, to generate from respective outputs of the plurality of subscriber modems the corresponding plurality of upstream signals at respective transmit RF signal levels,

wherein;

each upstream signal of the plurality of upstream signals includes at least one encoded carrier wave having a carrier frequency in an upstream path bandwidth and being modulated, using quadrature amplitude modulation (QAM), with voice and/or data information from at least some of the plurality of subscriber premises;

at least some of the plurality of upstream signals have different carrier frequencies to respectively define a plurality of upstream physical communication channels in the upstream path bandwidth constituting a channel plan;

a first upstream signal defining a first upstream physical communication channel of the plurality of upstream physical communication channels has a first carrier frequency of less than 19.6 MHz;

the channel plan includes at least four physical communication channels respectively defined by upstream signals having a QAM modulation order of at least 64;

the CMTS implements a long loop automatic level control (ALC) to set the respective transmit RF signal levels of the plurality of upstream signals generated from the respective outputs of the plurality of subscriber modems, based at least in part on respective received RF signal levels of the plurality of upstream signals as applied to the CMTS;

respective values for the at least one first attenuator, the at least one second attenuator, the at least one third attenuator, and the at least one fourth attenuator are selected based at least in part on the dynamic range of the optical link so as to facilitate implementation of the long loop ALC and effective transmission to the CMTS of upstream information carried by the plurality of upstream signals; and

the dynamic range of the optical link is based at least in part on the channel plan including the at least four physical communication channels respectively defined by upstream signals having a QAM modulation order of at least 64.

29. The system of claim 28, wherein:

the dynamic range of the optical link is defined by an input RF power window for the plurality of upstream signals as applied to the optical transmitter of the optical link, the input RF power window determined by at least one intersection of

     1) a target carrier-to-noise (C/N) value for a highest QAM modulation order of at least one upstream physical communication channel of the channel plan and

     2) a Noise Power Ratio (NPR) curve for the optical transmitter of the optical link;

a target operating power point for the optical transmitter is selected within the input RF power window; and

an attenuation value of the third attenuator associated with the optical transmitter is selected based at least in part on the target operating power point for the optical transmitter.

30. A hybrid fiber-coaxial (HFC) cable communication system, comprising:

A) a cable modem termination system (CMTS) having associated therewith at least one first attenuator to attenuate a plurality of upstream signals applied to the CMTS;

B) an optical link communicatively coupled to the CMTS, the optical link having a dynamic range and comprising;

an optical receiver having associated therewith at least one second attenuator to attenuate the plurality of upstream signals; and

an optical transmitter having associated therewith at least one third attenuator to attenuate the plurality of upstream signals;

C) a coaxial radio frequency (RF) link communicatively coupled to the optical link, the coaxial RF link comprising at least one RF amplifier having associated therewith at least one fourth attenuator to attenuate at least some of the plurality of upstream signals; and

D) a plurality of subscriber modems, communicatively coupled to the coaxial RF link, to generate from respective outputs of the plurality of subscriber modems the corresponding plurality of upstream signals at respective transmit RF signal levels,

wherein;

each upstream signal of the plurality of upstream signals includes at least one encoded carrier wave having a carrier frequency in an upstream path bandwidth and being modulated, using quadrature amplitude modulation (QAM), with voice and/or data information from at least some of the plurality of subscriber premises;

at least some of the plurality of upstream signals have different carrier frequencies to respectively define a plurality of upstream physical communication channels in the upstream path bandwidth constituting a channel plan;

the channel plan occupies a substantial portion of the upstream path bandwidth that includes carrier frequencies in a range of from approximately 5 MHz to at least approximately 42 MHz;

the CMTS implements a long loop automatic level control (ALC) to set the respective transmit RF signal levels of the plurality of upstream signals generated from the respective outputs of the plurality of subscriber modems, based at least in part on respective received RF signal levels of the plurality of upstream signals as applied to the CMTS;

the dynamic range of the optical link is defined by an input RF power window for the plurality of upstream signals as applied to the optical transmitter of the optical link, the input RF power window determined by at least one intersection of

     1) a target carrier-to-noise (C/N) value for a highest QAM modulation order of at least one upstream physical communication channel of the channel plan and

     2) a Noise Power Ratio (NPR) curve for the optical transmitter of the optical link;

a target operating power point for the optical transmitter is selected within the input RF power window;

a first attenuation value of the third attenuator associated with the optical transmitter is selected based at least in part on the target operating power point for the optical transmitter;

a second attenuation value of the at least one fourth attenuator associated with the at least one RF amplifier is selected and/or adjusted such that a signal level of the at least one upstream signal at a junction of the coaxial RF link and the optical link corresponds to a predetermined input RF reference signal level to be applied to the optical link; and

respective values for the at least one first attenuator and the at least one second attenuator are selected so as to facilitate implementation of the long loop ALC and effective transmission to the CMTS of upstream information carried by the plurality of upstream signals.