Juniper EX4100 User Manual

occurs in both mulmode and single-mode transmissions. An ecient opcal data link must transmit
enough light to overcome aenuaon.
Dispersion is the spreading of the signal over me. The following two types of dispersion can aect
signal transmission through an opcal data link:
• Chromac dispersion, which is the spreading of the signal over me caused by the dierent speeds
of light rays
• Modal dispersion, which is the spreading of the signal over me caused by the dierent propagaon
modes in the ber
For mulmode transmission, modal dispersion usually limits the maximum bit rate and link length.
Chromac dispersion or aenuaon is not a factor.
For single-mode transmission, modal dispersion is not a factor. However, at higher bit rates and over
longer distances, chromac dispersion limits the maximum link length.
An ecient opcal data link must have enough light to exceed the minimum power that the receiver
requires to operate within its specicaons. In addion, the total dispersion must be within the limits
specied for the type of link in Telcordia Technologies document GR-253-CORE (Secon 4.3) and
Internaonal Telecommunicaons Union (ITU) document G.957.
When chromac dispersion is at the maximum allowed, you can consider its eect as a power penalty in
the power budget. The opcal power budget must allow for the sum of component aenuaon, power
penales (including those from dispersion), and a safety margin for unexpected power loss.
Calculate the Fiber-Opc Cable Power Budget for EX Series Devices
To ensure that ber-opc connecons have sucient power for correct operaon, calculate the link's
power budget when planning ber-opc cable layout and distances. This planning helps you ensure that
ber-opc connecons have sucient power for correct operaon. The power budget is the maximum
amount of power the link can transmit. When you calculate the power budget, you use a worst-case
analysis to provide a margin of error. You use a worst-case analysis even though not all the parts of an
actual system operate at the worst-case levels.
To calculate the worst-case esmate for a ber-opc cable power budget ( P
B
) for the link:
1. Determine values for the link's minimum transmier power ( P
T
) and minimum receiver sensivity
( P
R
). In the following example, we measure both ( P
T
) and ( P
R
) in decibels relave to one milliwa
(dBm).
P
T
= – 15 dBm
P
R
= – 28 dBm
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Juniper EX4100 Specifications

General

Brand	Juniper
Model	EX4100
Category	Switch
Language	English