Page 34 - Optical Switching And Networking Handbook

Introduction to Optical Communications 19

this special copper wire, questions still remain as to whether the
system can transmit 100 Mbps over typical distances.
3. Only high-speed systems need fiber. Fiber can be used effectively
for any system. When demands dictate, new electronics can be
installed as upgrades to higher speeds. Error-free transmission
capability is a critical aspect of any modern communications
system. Many present-day and virtually all future communications
networks will require the extensive bandwidth and flexibility of
optical fiber.
4. Fiber is highly technical and very difficult to handle. Installing
fiberoptic networks is predictable and standardized. Because fiber
cable is smaller, lighter, and more flexible than other types of cable,
some installers feel that it is actually easier to install fiber.

5. Fiber is extremely fragile. Glass fiber is actually stronger than
steel. With an average tensile breaking strength of 600,000 pounds
per square inch, fiber exceeds the strength requirements of all of
today’s communications applications.

Types of Fibers

The differences among fibers are their core sizes (the light-carrying
region of the fiber). Multimode cable is made of multiple strands of
glass fibers and has a much larger core than single-mode fiber.
Multimode cables have a combined diameter in the 50- to 100-
micron range. Each fiber in a multimode cable is capable of carrying
a different signal independent from those on the other fibers in the
cable bundle. These larger core sizes generally have greater band-
width and are easier to couple and interconnect. They enable hun-
dreds of rays of light propagate through the fiber simultaneously.
Multimode fiber today is used primarily in premise applications,
where transmission distances are less than 2 kilometers.
Single-mode fiber is a single strand of glass that has a much
smaller core, enabling only one mode of light to propagate through
the core. Single-mode fiber has a higher bandwidth than multimode
and for this reason, is the ideal transmission medium for many