Digital signal processing optical transmitter

• US 6,449,071 B1
• Filed: 01/27/2000
• Issued: 09/10/2002
• Est. Priority Date: 06/22/1998
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Scientific-Atlanta Incorporated (Cisco Systems, Inc.)
• Inventors: Sipes, Donald, Mobley, Graham, Farhan, Forrest M.
• Primary Examiner(s): Chan, Jason
• Assistant Examiner(s): SEDIGHIAN, REZA
• Application Number:
  US09/493,045
• Time in Patent Office: 957 Days
• Field of Search: 359/180, 359/187, 359/188, 359/118, 359/125, 359/137, 725/119, 725/120, 725/121, 725/116, 725/118, 725/127, 725/128, 725/149
• US Class Current: 398/79
• CPC Class Codes: H04B 10/504 using direct modulation
• CPC Class Codes: H04J 14/0298 with sub-carrier multiplexing [SCM]
• CPC Class Codes: H04N 7/10 Adaptations for transmission by electrical cable H04N7/12 takes precedence
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications
• CPC Class Codes: H04N 7/22 Adaptations for optical transmission

Abstract

A node (200) for receiving analog signals transmitted within a broadband communication system (100) includes a summer (205) for summing the analog signals to generate a summed analog signal and an analog-to-digital (A/D) converter (210) coupled to the summer (205) for converting the summed analog signal into a digital electrical signal. The node (200) also includes a digital signal processor (DSP) (220) coupled to the A/D converter (210) for filtering the digital electrical signal in accordance with a filter algorithm to generate a filtered digital signal. The DSP (220) including a control port for receiving a control signal (215) indicative of the filter algorithm that is to be used. The filtered signal is then transmitted upstream within the system (100) by a transmitter (240) coupled to the DSP (220).

Claims

1. A node for receiving analog signals transmitted within a broadband communication system, the node comprising:

a summer for summing the analog signals to generate a summed analog signal;

an analog-to-digital (A/D) converter coupled to the summer for converting the summed analog signal into a digital electrical signal;

a digital signal processor (DSP) coupled to the A/D converter for filtering the digital electrical signal in accordance with a filter algorithm to generate a filtered digital signal, the DSP including a control port for receiving a control signal indicative of the filter algorithm that is to be used,

wherein the control signal programs various processing parameters of the DSP, and wherein the filter algorithm specifies center frequency and bandwidth of a filter used by the DSP to process the digital electrical signal; and

a transmitter coupled to the DSP for transmitting the filtered digital signal within the broadband communication system.

2. The node of claim 1, wherein the control signal is provided to the node over a supervisory channel.

3. The node of claim 1, further comprising:

a serializing and frame unit for serializing and framing the filtered digital signal; and

an optical transmitter for transmitting the filtered digital signal as a digital optical signal.

4. The node of claim 1, wherein the analog signals are transmitted to the node at multiple frequencies, and wherein the DSP modulates the digital electrical signal using a plurality of digital modulation formats, each corresponding to a different frequency range.

5. The node of claim 4, wherein the use of different digital modulation formats is specified by information contained in the control signal.

6. The node of claim 1, wherein the node is located within a reverse path of the broadband communication system.

7. A broadband communication system having a forward, downstream path and a reverse, upstream path, the broadband communication system comprising:

subscriber equipment for generating reverse analog signals that are transmitted upstream within the broadband communication system;

a node for receiving the reverse analog signals, the node comprising;

a summer for summing the reverse analog signals to generate a summed analog signal;

an analog-to-digital (A/D) converter coupled to the summer for converting the summed analog signal into a digital electrical signal;

a digital signal processor (DSP) coupled to the AID converter for filtering the digital electrical signal in accordance with a filter algorithm to generate a filtered digital signal, the DSP including a control port for receiving a control signal indicative of the filter algorithm that is to be used; and

a transmitter for transmitting the filtered digital signal upstream, wherein the filtered digital signal is representative of the reverse analog signals; and

a control device located upstream from the subscriber equipment and the node for receiving and processing the filtered digital signal, wherein the control device generates the control signal.

8. The broadband communication system of claim 7, wherein the control device comprises a cable television system headend.

9. The broadband communication system of claim 7, further comprising:

an electrical communication medium coupling the subscriber equipment and the node; and

an optical communication medium coupling the node and the control device.

10. The broadband communication system of claim 7, wherein the control signal programs various processing parameters of the DSP within the node.

11. The broadband communication system of claim 10, wherein the control signal is provided to the node over a supervisory channel that couples the node to the control device.

12. The broadband communication system of claim 10, wherein the node further comprises:

a serializing and frame unit for serializing and framing the filtered digital signal; and

an optical transmitter for transmitting the filtered digital signal as a digital optical signal that is received by the control device.

13. The broadband communication system of claim 10, wherein the filter algorithm specifies center frequency and bandwidth of a filter used by the DSP to process the digital electrical signal.

14. The broadband communication system of claim 10, wherein the reverse analog signals are transmitted to the node at multiple frequencies, and wherein the DSP modulates the digital electrical signal using a plurality of digital modulation formats, each corresponding to a different frequency range.

15. The broadband communication system of claim 14, wherein the use of different digital modulation formats is specified by information contained in the control signal.