Method of transforming HFC CATV analog fiber transmission to digital fiber transmission

摘要

A method of converting legacy HFC CATV cable systems, which transmit data over the optical fiber portion of the system using the optical counterpart of analog RF waveforms, such as RF QAM waveforms transduced to corresponding optical QAM waveforms, to improved HFC CATV systems that transmit data over the optical fiber using optical fiber optimized protocols, such as Ethernet frames and other optical fiber optimized digital transport protocols. According to the method, most aspects of the legacy HFC CATV system may be retained, however at the CATV head end, the optical fiber transmitter system is replaced by an improved system that extracts the underlying symbols from legacy waveforms, packages these symbols into optical fiber optimized packets, and transmits downstream. The legacy optical fiber nodes are replaced with improved nodes capable of receiving the packets and remodulating the symbols into RF waveforms suitable for injection into the system's CATV cable.

主权项

1. A method of upgrading a legacy Hybrid Fiber Cable (legacy HFC) system previously configured to transmit data downstream over an optical fiber using analog optical QAM waveforms, to a digital HFC system configured to transmit downstream data over said optical fiber using digital optical transmission methods;
wherein said legacy HFC system comprises: a head end configured to produce downstream RF QAM waveforms; a legacy fiber optic transmitter system configured to transduce said RF QAM waveforms into downstream analog optical QAM waveforms; wherein said optical fiber is configured to transmit said analog optical QAM waveforms downstream to at least one legacy optical fiber node; wherein said at least one legacy optical fiber node is configured to receive said downstream analog optical QAM waveforms, transduce said analog optical QAM waveforms into RF QAM waveforms, and transmit said RF QAM waveforms downstream over said at least one set of neighborhood CATV cables; said method comprising: providing a demodulator to demodulate downstream RF QAM waveforms into a plurality of QAM constellation symbols: replacing said legacy fiber optic transmitter system with a digital fiber optic transmitter system configured to transmit at least one downstream QAM channel over said optical fiber as a plurality of QAM constellation symbols by encapsulating said QAM constellation symbols into a plurality of Ethernet frames or other digital transmission format frames, and digitally transmitting said plurality of Ethernet frames or other digital transmission format frames over said optical fiber; and replacing said at least one legacy fiber optic node with a digital optical fiber node (DOFN) configured to receive said plurality of Ethernet frames or other digital transmission format claims, extract said downstream QAM constellation symbols, and use said downstream QAM constellation symbols to modulate at least one DOFN QAM modulator, thus producing downstream QAM RF signals.