QUIZ BY JIM HAYES
How Many Multimode Fibers?
Multimode fiber has had many variations, almost as many as unshielded twisted-pair copper
cable and for most of the same reasons—the search for bandwidth for higher speed networks.
How well do you know (or remember) all of the varieties of multimode fiber?
ANSWERS ARE ON PAGE 110. TO TAKE THE QUIZ IN AN ELECTRONIC FORMAT, VISIT WWW.ECMAG.COM.
1. Which multimode fiber in this list is “real” (i.e., it was
manufactured and sold commercially)?
A. 50/125 micron
B. 62.5/125 micron
C. 85/125 micron
D. 100/140 micron
E. All of them
2. The first commercial long-distance telephone systems
installed by AT&T around 1980 used __________ fiber.
A. 62.5/125 micron multimode
B. 85/125 micron multimode
C. 50/125 micron multimode
D. 9/125 micron single-mode
3. The large core of 100/140 micron fiber was designed
A. Be easier to splice and terminate
B. Couple more light into the fiber from cheap
C. Make the fiber cheaper to produce
D. Provide more bandwidth for LANs
4. The 100/140 micron fiber was dropped because __________.
A. Companies did not want to make special
connectors with a different hole size
B. Its attenuation was too high
C. It was hard to polish by hand
D. It required a striped color code
5. The 85/125 micron fiber was designed as a large core
fiber for LEDs with a diameter compatible with regular
connectors that had a 125 micron hole, but it was never
accepted anywhere except in France (like comedian
6. The 62.5/125 micron fiber we now call OM1 fiber
became the standard for most premises cabling because
of its use by __________ in its computer products.
7. The 50/125 micron fiber we now call OM2, OM3 and
OM4 fiber returned to prominence with the introduction of
gigabit Ethernet because of its __________.
A. Higher bandwidth than OM1 fiber
B. Lower attenuation than OM1 fiber
C. Lower cost than other multimode fibers
D. Easier termination
8. OM3 and OM4 fibers are called __________ fibers because
of their compatibility with VCSEL sources.
9. The grades of 50/125 micron fiber called OM2, OM3
and OM4 indicate its __________.
A. Attenuation, with OM4 being the lowest
B. Bandwidth, with OM4 being the highest
C. Bending strength, with OM4 being the highest
D. Compatibility with various connector types
10. A new version of OM4 fiber is being developed to allow
wavelength-division multiplexing with 850-nanometer
VCSEL sources for links up to 100 gigabits per second.
HA YES is a VDV writer and educator and the president of The Fiber Optic Association. Find him at www. JimHayes.com.