CATV video and data transmission system with RF input
View Patent ↗Improved systems and methods for delivering CATV content over a fiber optic network from a transmitter.
1. A method for delivering CATV content between a head end and a node over a fiber optic network, said method comprising:
(a) receiving a radio frequency (RF) spectrum including CATV content;
(b) encoding the signals in the RF spectrum based on a modulation format for a destination node;
(c) frequency converting the encoded signals and generating a digital representation of a RF spectrum comprising a series of digital codewords, each codeword representing an instantaneous power level of the RF spectrum based on a high speed conversion clock,
wherein said digital codewords are generated based on the high speed conversion clock without generating a corresponding RF waveform, the generated codewords represent a relative power level of the composite RF spectrum at intervals of the conversion clock, and the conversion clock is at least twice the maximum frequency contained in the RF spectrum; and
(d) propagating said digital codewords onto said fiber optic network, said digital signal representing said RF spectrum of said CATV content.
2. The method of claim 1 where said digital signal is delivered to said fiber optic network at at least one of: 256 QAM, 1024 QAM, or 4096 QAM.
3. The method of claim 1 where said digital codewords are generated in the head-end without digital to analog or analog to digital conversion of the received signals.
4. The method of claim 1 where said digital signal is delivered over said fiber optic network to a said node over 1 km away from said head end.
5. The method of claim 1 wherein conversion of the digital signal to analog is performed remotely at the node.
6. The method of claim 1 wherein the generated codewords are input to a digital processing subsystem in order to prepare them for serial transmission for conversion by a digital to analog converter located remote to the head-end.
7. A transmitter in a head-end, the transmitter comprising:
(a) an input that receives a radio frequency (RF) spectrum including CATV content;
(b) an encoder for encoding the signals in the RF spectrum based on a modulation format for a destination node;
(c) a digital up-converter for frequency converting the encoded signals and generating a digital representation of a RF spectrum comprising a series of digital codewords, each codeword representing an instantaneous power level of the RF spectrum based on a high speed conversion clock,
wherein said digital codewords are generated based on the high speed conversion clock without generating a corresponding RF waveform, the generated codewords represent a relative power level of the composite RF spectrum at intervals of the conversion clock, and the conversion clock is at least twice the maximum frequency contained in the RF spectrum; and
(d) an emitter that propagates said digital codewords from said head end to a node through a fiber optic network.
8. The transmitter of claim 7 where said emitter is at least one of a directly modulated laser, an externally modulated laser, an externally modulated coherent laser, and an EML transmitter.
9. The transmitter of claim 7 where said emitter is externally modulated and including an Optical Duo-Binary (ODB) encoder.
10. The transmitter of claim 9 including an ODB pre-coder.
11. The transmitter of claim 10 including a Clock Data Recovery (CDR) retimer operatively between said ODB precoder and said ODB encoder.
12. The transmitter of claim 7 including a CDR retimer.
13. The transmitter of claim 7 including inband management insertion.
14. The transmitter of claim 7 where said digital signal is Wavelength Division Multiplexed (WDM).
15. The transmitter of claim 7 wherein said transmitter includes a Direct Digital Synthesis (DDS) module.
16. The transmitter of claim 15 wherein said DDS module includes a digital up-converter (DUC) that prepares said digital signals for DAC conversion, but where said transmitter is free from including a DAC along the signal path between said input and a laser emitter of said transmitter.
17. The transmitter of claim 7 wherein said digital codewords are generated based on the high speed conversion clock without generating a corresponding RF waveform.
18. The transmitter of claim 7 wherein said digital signal is delivered over said fiber optic network to a said node over 1 km away from said head end.
19. The transmitter of claim 7 wherein conversion of the digital signal to analog is performed remotely at the node.
20. The transmitter of claim 7 wherein the generated codewords are input to a digital processing subsystem in order to prepare them for serial transmission for conversion by a digital to analog converter located remote to the head-end.