Table 27: Estimated Values For Factors Causing Link Loss - Juniper QFX5200 Hardware Manual

Table 27: Estimated Values for Factors Causing Link Loss

Link-Loss Factor
Higher-order mode losses
Modal and chromatic
dispersion
Connector
Splice
Fiber attenuation
Clock Recovery Module
(CRM)
Copyright © 2017, Juniper Networks, Inc.
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 27 on page 49
(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
0.5 dBm
Multimode—1 dBm/km
Single-mode—0.5 dBm/km
1 dBm
Chapter 7: Transceiver and Cable Specifications
) 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
48.
(here, the link is 2 km long and multimode, and the
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.
This example assumes two splices. Loss for two splices:
2 (0.5 dBm) = 1 dBm.
This example assumes the link is 2 km long. Fiber
attenuation for 2 km: 2 km (1 dBm/km) = 2 dBm.
This example assumes the link is 2 km long. Fiber
attenuation for 2 km: 2 km (0.5 dBm/km) = 1 dBm.
1 dBm
).
B
) for the link:
M
49