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PPENDIX
D: C
ABLING
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EQUIREMENTS
Multi-mode Fiber
Standards
The MMF-PMD standards define the requirements for an ATM cable plant
to support an interstation distance of up to 2 kilometers (1.25 miles) of
multi-mode fiber. The cable plant includes all fiber optic components
between any two communicating ATM devices and their associated
“station-to-network” connectors at each end.
To determine whether the cable plant complies with the MMF-PMD
standard, do the following:
1
Compare the specifications of the fiber you are using to standard
specifications, as described in Table 25 and Table 26.
2
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 in Table 27 and Table 28.
3
Verify that the fiber's modal bandwidth is within an acceptable range for
the length of the link, as described on page 115.
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 25, which
describes the standard set forth in MMF-PMD. Table 26 describes
62.5/125 cable, commonly sold as “ATM Spec,” which meets all the
requirements of the MMF-PMD standard.
Table 25
Standard Multi-mode Fiber Specification
Specification Description
Core 62.5 µm diameter
Cladding 125 µm diameter nominal
122 µm minimum
128 µm maximum
Numerical aperture 0.275
Maximum attenuation 11 dB* (1dB allowed for reflection and
dispersion penalties.)
Modal bandwidth 500 MHz. km