Calculating The Fiber-Optic Cable Power Margin For A Qfx Series Device; Table 55: Estimated Values For Factors Causing Link Loss - Juniper QFX5100 Hardware Manual

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Calculating the Fiber-Optic Cable Power Margin for a QFX Series Device

Table 55: Estimated Values for Factors Causing Link Loss

Link-Loss Factor
Higher-order mode losses
Modal and chromatic
dispersion
Connector
152
Understanding QFX Series Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion
on page 150
Calculating the Fiber-Optic Cable Power Margin for a QFX Series Device on page 152
Calculate the link's power margin when planning fiber-optic cable layout and distances
to ensure that fiber-optic connections have sufficient signal power to overcome system
losses and still satisfy the minimum input requirements of the receiver for the required
performance level. The power margin (P
attenuation or link loss (LL) has been subtracted from the power budget (P
When you calculate the power margin, you use a worst-case analysis to provide a margin
of error, even though all the parts of an actual system do not operate at worst-case
levels. A power margin (P
M
to operate the receiver and that it does not exceed the maximum receiver input power.
This means the link will work. A (P
to operate the receiver. See the specification for your receiver to find the maximum
receiver input power.
Before you begin to calculate the power margin:
Calculate the power budget. See
a QFX Series Device" on page
To calculate the worst-case estimate for the power margin (P
Determine the maximum value for link loss (LL) by adding estimated values for
1.
applicable link-loss factors; for example, use the sample values for various factors
as provided in Table 55 on page 152
the (P ) is 13 dBm).
B
Estimated Link Loss Value
Multimode—0.5 dBm
Single-mode—None
Multimode—None, if product of
bandwidth and distance is less
than 500 MHz/km
Single-mode—None
0.5 dBm
) is the amount of power available after
M
) greater than zero indicates that the power budget is sufficient
) that is zero or negative indicates insufficient power
M
"Calculating the Fiber-Optic Cable Power Budget for
151.
(here, the link is 2 km long and multimode, and
Sample Link Loss (LL) Calculation Values
0.5 dBm
0 dBm
0 dBm
0 dBm
This example assumes five connectors. Loss for five
connectors: 5 (0.5 dBm) = 2.5 dBm.
).
B
) for the link:
M
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