Cabletron Systems 100BASE-FX, Руководство по кабельной продукции

Страница: 122 / 192

FDDI Media
11-8 Cabling Types
Type 2
IBM Type 2 cable is constructed in much the same fashion as Type 1 cable. The
two central shielded pairs and the overall braided shield that surround them are
constructed of the same materials, and then two additional pairs of AWG 22
insulated solid copper wires are laid outside the braided shield before the whole
cable is surrounded by the tight outer covering. These outer wires may be used to
carry telephone traffic, as the shields surrounding the inner, network wires is
intended to eliminate the interference that might otherwise occur between the
inner and outer pairs.
The added pairs of wire in a Type 2 cable make it even less flexible than Type 1
cable. For this reason, it is typically used as facility cable.
Fiber Optics
Fiber optic cable is a high performance media constructed of glass or plastic
which uses pulses of light as a transmission method. Because fiber optics do not
utilize electrical charges to pass data, they are free from the possibility of
interference due to proximity to electrical fields. This, combined with the
extremely low rate of signal degradation and dB loss makes fiber optics able to
traverse extremely long distances. The actual maximums are dependent upon the
architecture being used, but distances of up to 50 km (164,000 ft) are not unknown
when using the FDDI technology.
Glass optical fiber is made up of a glass strand, the core, which allows for the easy
transmission of light, the cladding, a less transmissive glass layer around the core
which helps keep the light within the core, and a plastic buffer which protects the
cable.
Figure 11-6. Fiber Optic Cable Construction
NOTE
Cabletron Systems does not recommend combining active
voice and data wiring in the same cable. Degradation of
network performance may result from any non-standard uses
of cable.
Transmissive Core
Cladding
PVC Buffer (Jacketing)
1845n07