Page 24 - Optical Switching And Networking Handbook

Introduction to Optical Communications 9

tions. This new development relied on “total internal reflection” that
confines light in a material surrounded by other materials with a
lower refractive index, such as glass in air. Chronologically, the
events leading up to the use of glass began with several steps, as
shown in Table 1-1.
Today, more than 90 percent of long-distance data traffic in the
United States is transmitted through fiberoptics. More than 15 1/2
million miles of fiberoptic cable has been installed already, all of it
using the original design of Maurer, Keck, and Schultz.
Fiberoptics work by using light pulses traveling along glass fibers
that are less than the thickness of a human hair to transmit data.
These cables are much smaller than conventional copper wires and
are able to transmit data at very high speeds, making them ideal for
video and audio.

The Demand for Bandwidth

Meanwhile, telecommunications engineers were seeking ways of
delivering more transmission bandwidth. Radio and microwave fre-
quencies were already in heavy use. Therefore, the engineers looked
to higher frequencies to carry traffic loads, which they expected to
continue increasing with the growth of television and telephone traf-
fic. Telephone companies thought video telephones lurked just
around the corner and would escalate bandwidth demands even fur-
ther. In 1964, during the World’s Fair in New York,AT&T introduced
an experimental model of the PicturePhone that required a T3 line 1
to transmit motion video across a telephone link (Figure 1-7). The
other end of the connection was at Disneyland (in California). The
commercial version was introduced in 1970 in Pittsburgh. Despite
all the hopes and predictions, the cost and bandwidth demands of
this device made it impractical. Moreover, the device was bulky and
not user-friendly. However, the seed was planted for the future use of
a video conferencing system that would transmit real-time pictures.

1 A T3 is a multiplexed transmission that delivers 44.736 Mbps of information.