Distribution network comprising coax and optical fiber paths for transmission of television and additional signals

• US 5,499,047 A
• Filed: 11/28/1994
• Issued: 03/12/1996
• Est. Priority Date: 12/30/1993
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Terry, John B., Warwick, Alastair A., Anderson, Carl W. C.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US08/348,850
• Time in Patent Office: 470 Days
• Field of Search: 348/6, 348/12, 348/8, 348/13, 455/3.1, 455/5.1, 455/4.2
• US Class Current: 725/127
• CPC Class Codes: H04N 7/16 Analogue secrecy systems; Analogue subscription systems
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A cable television network is supplemented with optical fibers and fiber termination units to communicate additional downstream digital signals and upstream signals. A drop unit for each customer premises is provided in the drop cable. The drop unit demodulates downstream signals and selects for delivery to the customer premises only those downstream signals addressed to the customer premises, modulating the selected signals using binary phase shift keying (BPSK) which provides relative immunity to noise for forwarding the signals to the customer premises. Upstream BPSK signals from the customer premises are demodulated and remodulated in the drop unit to isolate the customer premises wiring from the rest of the network.

Claims

1. A cable television signal distribution network in which television signals on a distribution cable are supplied to customer premises via respective customer taps and drop cables, comprising:

an optical fiber path and a fiber termination unit for supplying digital signals to the distribution cable modulated at higher frequencies than the television signals, the digital signals including signals addressed to particular customer premises; and

a drop unit coupled in the drop cable of a particular customer premises, the drop unit comprising;

a receiver for receiving and demodulating the digital signals;

a control unit responsive to the addressed signals for identifying digital signals addressed to the particular customer premises; and

a transmitter for modulating the identified digital signals addressed to the particular customer premises and for forwarding the modulated signals to the customer premises with the television signals.

2. A network as claimed in claim 1 wherein the transmitter is arranged to modulate the digital signals forwarded to the customer premises by binary phase shift keying.

3. A network as claimed in claim 1 wherein the digital signals on the distribution cable are modulated in accordance with a first form of modulation and the digital signals forwarded to the customer premises are modulated in accordance with a second form of modulation, the second form of modulation having a greater bandwidth and noise immunity than the first form of modulation.

4. A network as claimed in claim 3 wherein the second form of modulation comprises binary phase shift keying.

5. A network as claimed in claim 3 wherein the drop unit further comprises an upstream signal receiver for receiving and demodulating upstream digital signals from the respective customer premises, and an upstream signal transmitter controlled by the control unit for modulating the demodulated upstream digital signals and for forwarding the modulated upstream digital signals to the fiber termination unit.

6. A network as claimed in claim 5 wherein the upstream signal receiver comprises a binary phase shift keying demodulator.

7. A network as claimed in claim 6 wherein the upstream signal transmitter comprises a phase shift keying modulator.

8. A network as claimed in claim 5 wherein the drop unit is coupled directly to the customer tap and via the drop cable to the customer premises.

9. A network as claimed in claim 5 wherein the drop unit is coupled directly to the customer premises and via the drop cable to the customer tap.

10. A network as claimed in claim 1 wherein the drop unit further comprises an upstream signal receiver for receiving and demodulating upstream digital signals from the respective customer premises, and an upstream signal transmitter controlled by the control unit for modulating the demodulated upstream digital signals and for forwarding the modulated upstream digital signals to the fiber termination unit.

11. A network as claimed in claim 10 wherein the drop unit is coupled directly to the customer tap and via the drop cable to the customer premises.

12. A network as claimed in claim 10 wherein the drop unit is coupled directly to the customer premises and via the drop cable to the customer tap.

13. A drop unit for connection via a drop cable between a customer tap and a customer premises in a cable television signal distribution network in which television signals and higher frequency modulated digital signals are supplied to the customer tap via a distribution cable, the digital signals including signals addressed for a particular customer premises, the drop unit comprising:

a downstream signal receiver for receiving and demodulating the digital signals;

a control unit for identifying particular addressed digital signals;

a downstream signal transmitter for modulating the identified particular addressed digital signals and for forwarding the modulated signals to the customer premises with the television signals;

an upstream signal receiver for receiving and demodulating upstream digital signals from the respective customer premises; and

an upstream signal transmitter controlled by the control unit for modulating the demodulated upstream digital signals and for forwarding the modulated upstream digital signals to the distribution cable via the customer tap.

14. A drop unit as claimed in claim 13 wherein the downstream signal receiver comprises a demodulator for demodulating digital signals from the distribution cable which are modulated in accordance with a first form of modulation, and the downstream signal transmitter comprises a modulator for modulating identified particular addressed digital signals for forwarding to the customer premises in accordance with a second form of modulation, the second form of modulation having a greater bandwidth and noise immunity than the first form of modulation.

15. A drop unit as claimed in claim 13 wherein the downstream signal transmitter comprises a binary phase shift keying modulator.

16. A drop unit as claimed in claim 15 wherein the upstream signal receiver comprises a binary phase shift keying demodulator.

17. A drop unit as claimed in claim 16 wherein the upstream signal transmitter comprises a phase shift keying modulator.