Comparing Fiber To Specifications - 3Com CoreBuilder 2500 Getting Started Manual

D-2 A D: FDDI S
PPENDIX
If unlike fibers are mated in the cable plant,
calculate insertion losses to see whether they
exceed the maximum attenuation value allowed
for a link, as described on page D-3.
Verify that the fiber's modal bandwidth is within
an acceptable range for the length of the link,
as described on page D-4.
The following sections describe each of these steps
and give examples.
Comparing Fiber to Specifications
Compare the specifications of the fiber you are
using to those in the following tables. If the fiber
does not meet the specifications, use a different
fiber or contact 3Com's Technical Support.
The fiber you use must meet the specifications listed
in Table D-1, which describes 62.5/125 cable,
commonly sold as "FDDI Spec." It meets all the
requirements of the MMF-PMD standard.
TANDARDS
Table D-1 Standard Multimode Fiber Specifications
Specification
Core
Cladding
Numerical aperture
Maximum attenuation
Modal bandwidth
Maximum distance between
nodes
Output power (from transmitter)
Receive power
*Maximum attenuation includes cable attenuation and the
loss induced by other components such as connectors,
splices, and the mating of unlike fiber types. Although
some 2 km cable plants have a total attenuation of less than
11.0 dB, the 2 km interstation distance must be maintained
to comply with modal bandwidth requirements.
The maximum attenuation value is based on a cable
diameter of 62.5, 80, or 100 mm. If you are using fiber
with a diameter of 50 mm, the maximum attenuation is 8 dB
for links connecting two CoreBuilder
dB for links connecting a CoreBuilder
equipment from another vendor.
Description
62.5 mm diameter
125 mm diameter
nominal
122 mm minimum
128 mm maximum
0.275
11 dB* (1 dB allowed
for reflection and
dispersion penalties)
500 MHz km
•
2 km
–20 dB minimum
–14 dB maximum
–32 dB minimum
sensitivity
–14 dB maximum
sensitivity
™
2500 systems and 6
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2500 system with