Juniper Networks EX8208 - Manual (Page 146)

NOTE: We recommend that you maintain N +1 or N+N power supplies in your switch
at all times. Replace failed power supplies immediately to prevent unexpected failures.
Power management raises a minor alarm if the number of online power supplies in your
switch is less than the number required to maintain the configured power redundancy
(N+1 in Junos OS Release 10.1 or earlier; N+1 or N+N in Junos OS Release 10.2 or later).
If the problem is not corrected in 5 minutes, a major alarm is issued.
Power management raises a major alarm if the number of online power supplies in your
switch is less than N power supplies. If your switch is running Junos OS Release 10.1 or
earlier, all line cards are powered off. If your switch is running Junos OS Release 10.2 or
later, power management provides power to line cards in priority order until power is
exhausted. The remaining line cards are powered off.
If a new line card is installed in an operational switch, power management does not
power on the line card if the increased power demand exceeds the total available power,
including redundant power. If redundant power is used to power on the line card, a minor
alarm is raised, which becomes a major alarm in 5 minutes if the condition is not
corrected.
Related Topics AC Power Supply in an EX8200 Switch on page 40 •
• DC Power Supply in an EX8200 Switch on page 48
• Understanding Power Management on EX Series Switches
Calculating the EX8200 Switch Fiber-Optic Cable Power Budget
Calculate the link's power budget when planning fiber-optic cable layout and distances
to ensure that fiber-optic connections have sufficient power for correct operation. 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, even though
all the parts of an actual system do not operate at the worst-case levels.
To calculate the worst-case estimate for fiber-optic cable power budget ( P
B
) for the
link:
1. Determine values for the link's minimum transmitter power ( P
T
) and minimum
receiver sensitivity ( P
R
). For example, here, ( P
T
) and ( P
R
) are measured in decibels,
and decibels are referred to one milliwatt (dBm).
P
T
= –15 dBm
P
R
= –28 dBm
NOTE: See the specifications for your transmitter and receiver to find the minimum
transmitter power and minimum receiver sensitivity.
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Complete Hardware Guide for EX8208 Ethernet Switches