Burst-mode digital transmitter

• US 20020157114A1
• Filed: 04/23/2001
• Published: 10/24/2002
• Est. Priority Date: 04/23/2001
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta LLC (Cisco Systems, Inc.)
• Inventors: West, Lamar E. Jr., Mobley, J. Graham
• Granted Patent: US 7,614,074 B2
• Time in Patent Office: Days
• US Class Current: 725/121
• 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: H04B 10/25755 Ring network topology
• CPC Class Codes: H04B 10/504 using direct modulation
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04N 21/6118 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 21/6168 involving cable transmission, e.g. using a cable modem
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A transmitter (305) for transmitting reverse optical signals in a broadband communications system (300) that includes a converter (320) for digitizing the analog RF signals and a carrier-detect circuit (330) coupled to the converter (320) for detecting when digital RF signals are present at the output of the converter (320). When the carrier-detect circuit (330) detects digital RF signals, the carrier-detect circuit (330) allows the digital RF signals to be transmitted upstream through the broadband communications system (300). A digital network (310) then combines the received digital RF signals with other digital RF signals from additional transmitters (305). The combined digital signals are then provided to a receiver (315) that includes a converter (335) for returning the digital RF signals to analog RF signals and then providing the analog signals to a headend for further processing.

Claims

1. A transmitter for transmitting reverse optical signals in a broadband communications system, the transmitter comprising:

an input port for receiving analog RF signals from downstream;

a converter for digitizing the analog RF signals; and

a carrier-detect circuit coupled to the converter for detecting the presence of digital RF signals and for allowing the digital RF signals to be provided to an output of the transmitter and transmitted upstream.

2. The transmitter of claim 1, further comprising:

a delay circuit coupled to the converter for delaying the digital RF signals; and

a switch coupled to the delay circuit and controlled by the carrier-detect circuit,

wherein the carrier-detect circuit closes the switch enabling a path for the transmission of the digital RF signals.

3. The transmitter of claim 1, wherein the broadband communications system includes:

a plurality of transmitters;

a digital network coupled to each of the plurality of transmitters for receiving and combining the digital RF signals;

a receiver coupled to the digital network for receiving the combined digital RF signals, and for converting the combined digital RF signals to analog RF signals; and

a headend coupled to the receiver for receiving and processing the analog RF signals,

whereby, due to a burst-mode transmission from each of the plurality of transmitters, the digital network combines the digital RF signals from the plurality of transmitters using header identifier information.

4. The transmitter of claim 3, wherein the broadband communications system is a cable television system that may include both a digital headend and an analog headend for generating and receiving the digital RF signals and the analog RF signals.

5. The transmitter of claim 4, wherein the broadband communications system further includes:

a descriminator circuit coupled to the digital network for analyzing the header identifier information,

wherein dependent upon the header identifier information, the descriminator circuit provides the digital RF signals to the digital headend and provides the analog RF signals to the analog headend.

6. A communications system for transmitting and receiving signals over a communications medium, the communications system comprising:

subscriber equipment for transmitting reverse signals;

a plurality of transmitters coupled to at least one of the subscriber equipment for digitizing the reverse signals;

a digital network coupled to each of the plurality of transmitters for combining the digital signals;

a receiver coupled to the digital network for converting the digital signals back to the original reverse signals; and

a headend coupled to the receiver for processing the reverse signals,

whereby the communications system combines the reverse signals from each of the plurality of transmitters within the digital network and delivers the reverse signals to the receiver.

7. The communications system of claim 6, the plurality of transmitters further comprising:

a carrier-detect circuit for detecting when reverse signals are present within the transmitter;

a delay circuit for delaying the reverse signals; and

a switch coupled to the delay circuit and controlled by the carrier-detect circuit,

wherein when the carrier-detect circuit detects reverse signals, the carrier-detect circuit allows the reverse signals to be transmitted upstream through the digital network.

8. The communications system of claim 6, wherein digitizing the reverse signals is accomplished with an analog-to-digital converter.

9. The communications system of claim 6, wherein each of the plurality of transmitters blocks the reverse signals and encapsulates the blocks into packets with associated identifier header information for identification within the headend.

10. The communications system of claim 9, wherein the communications system is a cable television system that may include both a digital headend and an analog headend.

11. The communications system of claim 10, wherein the communications system further comprises:

a descriminator circuit coupled to the digital network for analyzing the associated identifier header information,

wherein dependent upon the identifier header information, the descriminator circuit provides the packets to one of the digital headend and the analog headend.

12. The communications system of claim 6, wherein the communications medium is a hybrid fiber coaxial cable.

13. The communications system of claim 10, wherein a control system is used in connection with both the digital and the analog headends for preventing collision of the reverse signals.