| 摘要 |
53 byte ATM compliant cells transmitted over a digital optical fiber path interconnected with a coaxial feeder cable TV system supporting two-way digital services at sites connected to the TV cable system. At the point of interconnection between the fiber optic path and the cable TV feeder subsystem, digital signals are converted to a UHF rf carrier frequency above the cutoff pass-band of the analog signal feeder amplifier carrying TV broadcast signals. RF carrier conveys a high data rate digitally modulated signal limited to sections of feeder cable between the cable TV broadcast channel amplifiers. In-house access to UHF carrier signal is via the normal TV cable tap and drop cable to a SIU, located near the subscriber's TV set. Feeder cable and the passive taps used in cable TV practice have a higher cutoff frequency than the feeder amplifiers themselves. This allows passage of an UHF signal over the feeder cable. Low pass filters at the feeder amplifiers prevent UHF signal from being shorted out by in-cable amplifiers. Each SIU sends and receives UHF carrier signal, which conveys the ATM type cells. Each cell's payload contains local address of source and destination of that cell. Each SIU decodes each cell's address and accepts only those cells that are for itself. The common channel conveying the ATM cells alternatively sends and receives cells in a ping-pong fashion.
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