What are the disadvantages of optical fiber versus copper cables?

Answer 1

The major disadvantage of fiber optic versus metal cable is that it is difficult to make connections to fiber optic cable. Single-mode optical cable (the type used for communications) has a core as fine as a human hair (although the entire fiber is thicker). When making splices, the fiber cores must be perfectly aligned. Also, the ends of the optical fiber must be highly polished to allow light to pass with little loss. There is also the problem of converting back and forth from a light signal to an electrical signal. However, the advantages of fiber-optics far outweigh the problems. One single mode fiber can replace a metal cable that is thousands of times larger and heavier. Multi-mode optical cable has a larger diameter and can be used to carry signal over short distances.

Answer 2

Principles

o Copper cables carry information as an electrical signal, which may be digital, as in phone lines, or analogue, as in audio speaker cable. In optical fibers, however, data is carried digitally by light from a laser or LED. This travels along the cable by means of Total Internal Reflection, bouncing from one side of the glass's inner surface to another and therefore following the cable's path.

Bandwidth

o Although new techniques may allow copper cables to carry much more data than in the past, in most cases optical fibers provide much greater bandwidth. The first generation of submarine fiber optic cables carried 280 megabits per second, compared with only 2.5 megabits per second through copper cables. Modern optical fibers can carry terabits, or millions of megabits, per second.

Electromagnetism

o Copper cables are inherently vulnerable to electromagnetic interference. Although fiber optic lines do have metallic components, these do not carry the signal, so interference is not a problem. Copper cables can also be "tapped" electromagnetically, allowing the signal to be covertly monitored. Optical fibers, on the other hand, cannot be tapped without disrupting the signal.

2. Traditional copper wires transmit electrical currents, while fibre optic technology sends pulses of light generated by a light emitting diode or laser along optical fibres.

3. "In both cases you're detecting changes in energy, and that's how you encode data.

4. "With copper wires you're looking at changes in the electromagnetic field, the intensity of that field and perhaps the phase of the wave being sent down a wire.

5. "With fibre optics, a transmitter converts electronic information into pulses of light - a pulse equates to a one, while no pulse is zero. When the signal reaches the other end, an optical receiver converts the light signal back into electronic information," explains Malaney.

6. The throughput of the data is determined by the frequency range that a cable will carry - the higher the frequency range, the greater the bandwidth and the more data that can be put through per unit time.

7. And this is the key difference - fibre optic cables have much higher bandwidths than copper cables.

8. "Optical fibre can carry much higher frequency ranges - note that light is a very high frequency signal - while copper wire attenuates or loses signal strength at higher frequencies," says Malaney.

9. Also, fibre optic technology is far less susceptible to noise and electromagnetic interference than electricity along a copper wire.

10. "You can send the signal for over 200 kilometres without any real loss of quality while a copper cable signal suffers a lot of degradation over that distance," says Malaney.

Answer 3

The signal runs at similar speeds, with copper cable a bit slower, around 60~80% of the speed of light, fibre optic around 90%.

Which one carries the higher data rate?

In theory, fibre optic.

The issue is being able to switch the light beam fast enough to get higher signal rates than copper cable, which can run up to tens of gigahertz.

Answer 4

Twisted pair cabling is based on copper wire; fiber optic cable is not twisted and uses a glass or plastic wire with light pulses rather than electrical voltage.