1.1 Reasons for Fiber Optic Communications
3
1.1 Reasons for Fiber Optic Communications
1.1.1 The Road to Optical Networks
Figure 1.1 shows the schematic of a generic optical fiber structure. Most other fiber
constructions are based on material, size, and layering variations of this fundamental
configuration. A standard fiber consists of a solid glass cylinder called a core. The
core is the region in which light propagates along the fiber. This is surrounded by a
dielectric cladding, which has a different material property from that of the core in
order to achieve light guiding in the fiber. A standard cladding diameter is 125 μm
for most types of fibers. A polymer buffer coating with a nominal 250 μm diameter
surrounds these two layers to protect the fiber from mechanical stresses and environmental effects. Finally an outer protective polymer jacket with a nominal 900 μm
diameter encapsulates the fiber. Chaps. 2 and 3 give details on the structural and
performance characteristics of common optical fibers.
The first generation optical fiber had a 50 μm core diameter and a 125 μm cladding
diameter. Six such buffered fibers were enclosed in a single optical cable, which was
used in the first installed optical fiber links in the late 1970s. These commercial links
were used for transmitting telephony signals at about 6 Mb/s over distances of around
10 km. As research and development progressed, the sophistication and capabilities
of these systems increased rapidly during the 1980s to create links carrying aggregate data rates beyond terabits per second over distances of hundreds of kilometers.
These achievements were based on new technology developments using single-mode
optical fiber with nominally 9 μm core diameters.
Starting in the 1990s there was a burgeoning demand on communication network
assets for bandwidth-hungry services such as database queries, home shopping,
high-definition interactive video, remote education, telemedicine and e-health, highresolution editing of home videos, blogging, and large-scale high-capacity e-science
and Grid computing. This demand was fueled by the rapid proliferation of personal
computers (PCs) and sophisticated smart phones coupled with a phenomenal increase
in their storage capacity and processing capabilities. Furthermore, the widespread
Core
Cladding
Buffer coating
n 1
n 2 < n 1
2a
Outer jacket
125 μm
250 μm
900 μm
Fig. 1.1 Schematic of a generic optical fiber structure; nominal core diameters are 2a = 9 μm for
single-mode and 50 μm for multimode fibers
3
1.1 Reasons for Fiber Optic Communications
1.1.1 The Road to Optical Networks
Figure 1.1 shows the schematic of a generic optical fiber structure. Most other fiber
constructions are based on material, size, and layering variations of this fundamental
configuration. A standard fiber consists of a solid glass cylinder called a core. The
core is the region in which light propagates along the fiber. This is surrounded by a
dielectric cladding, which has a different material property from that of the core in
order to achieve light guiding in the fiber. A standard cladding diameter is 125 μm
for most types of fibers. A polymer buffer coating with a nominal 250 μm diameter
surrounds these two layers to protect the fiber from mechanical stresses and environmental effects. Finally an outer protective polymer jacket with a nominal 900 μm
diameter encapsulates the fiber. Chaps. 2 and 3 give details on the structural and
performance characteristics of common optical fibers.
The first generation optical fiber had a 50 μm core diameter and a 125 μm cladding
diameter. Six such buffered fibers were enclosed in a single optical cable, which was
used in the first installed optical fiber links in the late 1970s. These commercial links
were used for transmitting telephony signals at about 6 Mb/s over distances of around
10 km. As research and development progressed, the sophistication and capabilities
of these systems increased rapidly during the 1980s to create links carrying aggregate data rates beyond terabits per second over distances of hundreds of kilometers.
These achievements were based on new technology developments using single-mode
optical fiber with nominally 9 μm core diameters.
Starting in the 1990s there was a burgeoning demand on communication network
assets for bandwidth-hungry services such as database queries, home shopping,
high-definition interactive video, remote education, telemedicine and e-health, highresolution editing of home videos, blogging, and large-scale high-capacity e-science
and Grid computing. This demand was fueled by the rapid proliferation of personal
computers (PCs) and sophisticated smart phones coupled with a phenomenal increase
in their storage capacity and processing capabilities. Furthermore, the widespread
Core
Cladding
Buffer coating
n 1
n 2 < n 1
2a
Outer jacket
125 μm
250 μm
900 μm
Fig. 1.1 Schematic of a generic optical fiber structure; nominal core diameters are 2a = 9 μm for
single-mode and 50 μm for multimode fibers