Nortel Communication Server 1000 Series Manual page 33

Maximum calculated signal attenuation across the link is 10.2 dB, which
allows 4.8 dB safety margin for a single-mode fiber.
Fiber-optic cable types
If a fiber-optic link already exists, it must be evaluated to determine if it
will support the Fiber Remote Multi-IPE Interface and, if it will, at what
distance from the local system. The distance of the link can be determined
by finding a point of the fiber-optic link where the signal loss is less than 15
dB for a given transmission rate over a single-mode fiber and less than 10
dB for the multi-mode fiber.
To evaluate an existing link, measure the end-to-end attenuation to
determine the link's suitability for the Fiber Remote Multi-IPE Interface
application.
A fiber-optic link may be composed of single-mode or multi-mode fibers,
splices, and fiber-optic connectors. ST-type fiber-optic connectors have
to be installed onto fibers of the fiber-optic link cables so that the link can
be directly connected to the ST-type fiber-optic connectors on the Fiber
Remote Multi-IPE Interface unit faceplate.
Fiber-optic link calculation examples
The following fiber-optic link calculations for both single-mode and
multi-mode fibers illustrate how to evaluate the distance of a link based on
the type of fiber and attenuation of the fiber and splices.
Example 1 - Medium quality multi-mode fiber-optic cable and splices
Medium quality multi-mode fiber-optic cable has a loss of 1.5 dB per km.
Medium quality splices have 0.5 dB loss per splice.
Assumptions:
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Note:
Actual attenuation must be determined by measuring the
end-to-end signal loss. Because of the 45 Mbps data rate, dispersion
loss is not a factor with either single-mode or multi-mode fibers. With
good quality cable and splices, the Remote IPE modules can be located
up to 15 miles from the network module for single-mode fibers and up to
6 miles for the multi-mode fibers. A safety margin for the attenuation
loss is designed into the Fiber Remote Multi-IPE Interface unit over
the specified usable power budget.
dB loss allowed over multi-mode fiber by the Fiber Remote Multi-IPE
Interface: 10 dB
dB loss per km of fiber: 1.5 dB
dB loss per splice: 0.5 dB
Nortel Communication Server 1000
Fiber Remote Multi-IPE Interface Fundamentals
NN43021-556 03.01
11 May 2009
Engineering guidelines 33