Comparisons of coaxial cable, fiber optic cable and twisted pair cable

This tip is in response to a question posed to Carrie Higbie, our Emerging Technology expert. The question was, "Could you provide me with details on coaxial cable, fiber optic cable and twisted pair cable? I'm looking for information on transmission rates, price, usable length, ease of installation, security and resistance to interference and fading."

Here's what Carrie had to say:
Coaxial cable is used predominantly for video and not used much at all anymore for networks, so I would not worry about that one unless you are looking for legacy information. As for fiber and twisted pair, I will address your questions one at a time and compare the two.

Transmission rates:
This will vary with the electronics, category of fiber or copper and distances spanned. Category 5e is supposed to be capable of providing gigabit performance. However it is estimated that 50% of all Category 5e UTP is not really 5e and can't perform to 5e as it was installed prior to the standards. The standards recommend recertification of all 5e channels prior to moving to gigabit. Cat 6 is generally what is being installed today. Work is ongoing at the IEEE for 10GBASE-T (10 Gigabits per second) over Category 6 or an augmented 6 that is characterized out to 625MHz. Today's category 6 is 250 MHz, 5e is 100MHz. You will also notice that many vendors have cabling and connectivity that are in excess of these numbers. This is because they have "margin and headroom" which basically

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is a forgiveness factor for what can happen over a cable channel, such as interference, etc.

Fiber transmission rates depend on distance, diameter of the fiber and the light source used to move the light over the fiber. This can be done via laser, VCSEL, etc. Here's a chart –

Application Wavelength 62.5
160/500		 62.5
200/500		 50
500/500		 50
2000/500		 SMF
100BASE-SX 850nm 300m 300m 300m 300m N/A
1000BASE-SX 850nm 220m 275m 550m 550m N/A
100BASE-LX 1300nm 550m 550m 550m 550m 5km
10GBASE-SX 850nm 28m 28m 86m 300m N/A
10GBASE-LX 1310nm N/A N/A N/A N/A 10km
10GBASE-EX 1550nm N/A N/A N/A N/A 40km
10GBASE-LX4 1310nm 300m 300m 300m 300m 10km

Price:
Fiber is more expensive than copper due to the light emitting equipment and cost. Copper comes in two varieties, shielded and non-shielded. In the US most companies use non-shielded. PC's come with copper ports in them already, so that is also a benefit. Fiber to the desktop can be very expensive when you have to add fiber NICs and Fiber switches. For instance – 10G fiber is supposed to settle at around 10x the cost of gigabit, while the copper alternative should settle at around 3.

Ease of Installation:
If properly trained, none of them are hard to install. However, proper training should include the entire channel, not just the termination.

It does take a bit longer to terminate fiber than copper.

Lengths are in the table above for fiber and copper is 100m as a standard although most are not that long.

Security Interference, etc.
One problem with UTP is that it can be "snooped" or eavesdropped. You can not do this with shielded systems or with fiber. Interference is also not an issue with shielded systems or fiber. They key to controlling interference with UTP (unshielded) is to have it properly installed by someone that understands all of the channel specifications including proper distances from any source of interference.

This was first published in April 2004

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