Can copper pair wiring really substitute for fiber optic transport at bandwidths above 1.5 Mbps or telephone trunks of more than 24 lines? It can indeed and is available to do so right now. Even corporate LANs based on fiber optic wiring may find that copper WAN connections make perfect sense.
So how is it possible that twisted copper pair can equal fiber optic performance? It seems so counter intuitive. The answer is bonding techniques and new modulation technology. There are also a couple of caveats. At this point, copper bandwidths are most practical up to about 12 Mbps for bonded pairs and 45 Mbps for EoC or Ethernet over Copper. EoC also has distance limitations. But even so, a majority of business needs can be currently served by copper technology that is readily available.
T1 bonded pairs offer a way to multiple T1 line bandwidth from 1.5 Mbps to 3 Mbps, 4.5 Mbps, 6 Mbps and up to 12 Mbps. The bandwidth goes up in 1.5 Mbps increments. Line cost is also incremental steps of T1 line pricing. For ISDN PRI telephone trunking each T1 phone line is independent and supports 23 outside lines plus data and switching. You simply add another T1 line to get an additional 23 phone lines. For data transmission, T1 lines bandwidth is bonded together to create a single larger conduit. With pair bonding, the multiple T1 lines act as a single higher capacity line.
Pair bonding is also part of the technology used to implement Ethernet over Copper. In this case the modulation technique is different from that specified for T1 lines, but the results are similar. MIMO or Multiple Input Multiple Output interference canceling techniques improve performance for multiple pair in the same binder.
Ethernet over Copper provides Metro Ethernet transmission up to several miles from the carrier's POP or Point of Presence. The improved modulation technology supports bandwidths up to 45 Mbps, a level comparable to DS3 delivered on fiber optic cable. Many medium and larger businesses, plus smaller businesses focused on high bandwidth services such as video production, are migrating to DS3 levels to get the performance they need. EoC now makes that possible without the construction costs required for new fiber optic installation.
Can copper replace fiber? In the long run, probably not. Eventually fiber will be installed routinely in all new construction and increasing bandwidth demands will justify retrofits in buildings not currently served. But for the near term, multiple ISDN PRI, bonded T1 data lines, and Ethernet over Copper make copper pair transmission a very cost effective solution to higher bandwidth requirements.