請参考 "Downstream data rates depend on a number of factors, including the length of the copper line, its wire gauge, presence of bridged taps, and cross-coupled interference. Line attenuation increases with line length and frequency, and decreases as wire diameter increases. Ignoring bridged taps, ADSL will perform as follows:
Data Rate Wire Gauge Distance Wire Size Distance
1.5 or 2 Mbps
24 AWG
18,000 ft
0.5 mm 5.5 km
1.5 or 2 Mbps
26 AWG
15,000 ft
0.4 mm
4.6 km
6.1 Mbps
24 AWG
12,000 ft
0.5 mm
3.7 km
6.1 Mbps
26 AWG
9,000 ft
0.4 mm
2.7 km
While the measure varies from provider to provider, these capabilities can cover up to 95% of a loop plant depending on the desired data rate. Customers beyond these distances can be reached with fiber-based digital loop carrier systems. As these DLC systems become commercially available, telephone companies will offer virtually ubiquitous access in a relatively short time. "
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