Judging the Speed of Fiber Optics

We’re always talking about how fast fiber optic networks are, but “fast” has several meanings. How well do you understand fast in fiber optics?

1. When we talk about how fast fiber optics is, we really mean fiber optics _______.

Correct Answer: Transmits signals at higher bit rates than other media

2. The original fiber optic telecom networks operated at 145 Mbps, about _______ times faster than the typical digital copper or wireless networks of the era.

Correct Answer: 100

3. Multimode optical fiber was originally optimized for a bandwidth at _______ nm wavelength, where attenuation was lower to allow longer telecom links.

Correct Answer: 1,300

4. The first 100 Mbps fiber optic LAN FDDI (fiber distributed data interface), was designed around fiber optics.

Correct Answer: True

5. Single-mode fiber was introduced in the mid-1980s and immediately dominated telecom because it offered _______ and _______. (Choose two)

Correct Answer: Virtually infinite bandwidth
Correct Answer: Much lower attenuation

6. The next big step up in single-mode fiber bandwidth came from the introduction of _______ division multiplexing in the late 1990s.

Correct Answer: Wavelength

7. Long-distance single-mode networks above 100 Gbps are now moving to a new type of system called _______ that greatly increases transmission links’ capability.

Correct Answer: Coherent transmission

8. Many LANs still use _______ fiber because it was adequate for the speed and distances in these networks.

Correct Answer: Multimode

9. When LANs reached 1 Gbps, the LED sources could not provide adequate speed, so the _______, a new type of inexpensive laser, was needed.

Correct Answer: VCSEL (vertical-cavity surface-emitting laser)

10. The speed of a pulse transmitted down an optical fiber is actually only two-thirds the speed of light in a vacuum because light slows down in glass compared to its speed in air or the vacuum of space.

Correct Answer: True