WYDave - 4/21/2021 22:08

OK, everyone here knows what copper phone cables are like. Lots of smaller-diameter copper pairs twisted around each other. You can do lots of neat things with copper - transmit data, you can send DC or AC voltage down the copper wires, even both at the same time (which is done on the telephone line all the time).

The downside of copper wiring in datacomm is that you're limited in how much bandwidth you can get on copper wires in cables. With capacitive losses on longer runs, you start needing loading coils to balance the impedance issues, and the loading coils then start to put limits on the bandwidth you can shove down the copper lines.

Traditionally, you have -48V DC between the red and green wires on a phone line from the central office when the handset is "on hook," and 3 to 9 VDC when the phone is "off hook." During ringing, a 90V @ 20 Hz AC voltage would be sent down the line from the central office to your phone.


Then, I'm pretty sure everyone knows fiber optic cable. With lasers lighting up the fiber, you can send vast amounts of data at high bandwidths down the glass fiber. But there's downside to glass fiber: you can't send electrical power down the fiber, only data. In many applications in telecom, you want to send a bit of power from the central cabinet to a remote device. So you have lots of cases where the remote devices hooked to fiber runs need to supply their own power locally.

Fiber-copper is a hybrid cable that puts a copper pair (or two) along with a few strands of fiber into one cable - so you can send power and high-speed data down the same cable.  It's a recent product of Belden Cable. I think it can carry enough power to run a 200W device at the far end of the cable.