Juniper NFX150, Hardware Manual

Page: 52 / 152

P
R
= –28 dBm
NOTE: See the specifications for your transmitter and receiver to find the
minimum transmitter power and minimum receiver sensitivity.
2.
Calculate the power budget (PB) by subtracting (P
R
) from (PT):
–15 dBm – (–28 dBm) = 13 dBm
See Also Understanding NFX150 Devices Fiber-Optic Cable Signal Loss, Attenuation, and
Dispersion on page 50
•
•
Calculating the Fiber-Optic Cable Power Margin for an NFX150 Device on page 52
Calculating the Fiber-Optic Cable Power Margin for an NFX150 Device
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
M
) is the amount of power available after
attenuation or link loss (LL) has been subtracted from the power budget (P
B
).
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
) greater than zero indicates that the power budget is sufficient
to operate the receiver and that it does not exceed the maximum receiver input power.
This means the link will work. A (P
M
) that is zero or negative indicates insufficient power
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 “Calculating the Fiber-Optic Cable Power Budget for
an NFX150 Device” on page 51 .
To calculate the worst-case estimate for the power margin (P
M
) for the link:
1.
Determine the maximum value for link loss (LL) by adding estimated values for
applicable link-loss factors—for example, use the sample values for various factors
as provided in
Table 25 on page 52 (here, the link is 2 km long and multimode, and
the (P
B
) is 13 dBm):
Table 25: Estimated Values for Factors Causing Link Loss
Sample Link Loss (LL) Calculation Values Estimated Link-Loss Value Link-Loss Factor
0.5 dBm Multimode—0.5 dBm Higher-order mode losses
0 dBm Single-mode—None
Copyright © 2018, Juniper Networks, Inc. 52
NFX150 Network Services Platform Hardware Guide