P
M
= 13 dB – 2 dB – 2.5 dB – 1 dB – 0.5 dB
P
M
= 7 dB
The following sample calculation for an 8-km-long single-mode link with a power budget
(P
B
) of 13 dB uses the estimated values from Table 29 on page 74 to calculate link loss
(LL) as the sum of fiber attenuation (8 km @ 0.5 dB/km, or 4 dB) and loss for seven
connectors (0.5 dB per connector, or 3.5 dB). The power margin (P
M
) is calculated as
follows:
P
M
= P
B
– LL
P
M
= 13 dB – 8 km (0.5 dB/km) – 7(0.5 dB)
P
M
= 13 dB – 4 dB – 3.5 dB
P
M
= 5.5 dB
In both examples, the calculated power margin is greater than zero, indicating that the
link has sufficient power for transmission and does not exceed the maximum receiver
input power.
Related
Documentation
QFX5110 Port Panels on page 26•
• QFX5110 Power System on page 45
QFX5110 Management Cable Specifications and Pinouts
•
Cable Specifications for Console and Management Connections for the QFX
Series on page 75
•
RJ-45 Management Port Connector Pinout Information on page 76
•
Console Port Connector Pinouts for the QFX Series on page 76
•
RJ-45 Port, QSFP+ Port, QSFP28 Port, SFP+ Port, and SFP Port Connector Pinout
Information on page 77
•
USB Port Specifications for the QFX Series on page 83
Cable Specifications for Console and Management Connections for the QFX Series
Table 30 on page 76 lists the specifications for the cables that connect the QFX Series
to a management device.
NOTE: The QFX Series can be configured with SFP management ports that
support 1000BASE-SX transceivers. See the Hardware Compatibility Tool for
more on the fiber-optic cables required for use with these transceivers.
75Copyright © 2019, Juniper Networks, Inc.
Chapter 2: Site Planning, Preparation, and Specifications
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