Dispersion - Juniper MX480 Hardware Manual

MX480 Universal Routing Platform Hardware Guide
Table 88: Estimated Values for Factors Causing Link Loss (continued)
Link-Loss Factor
Fiber attenuation
Understanding Fiber-Optic Cable Signal Loss, Attenuation, and Dispersion
164
Estimated Link-Loss Value
Single-mode—0.5 dB/km
Multimode—1 dB/km
The following sample calculation for a 2-km-long multimode link with a power budget
(P ) of 13 dB uses the estimated values from
B
(LL) as the sum of fiber attenuation (2 km @ 1 dB/km, or 2 dB) and loss for five connectors
(0.5 dB per connector, or 2.5 dB) and two splices (0.5 dB per splice, or 1 dB) as well as
higher-order mode losses (0.5 dB). The power margin (P
P = P – LL
M B
P = 13 dB – 2 km (1 dB/km) – 5 (0.5 dB) – 2 (0.5 dB) – 0.5 dB
M
P = 13 dB – 2 dB – 2.5 dB – 1 dB – 0.5 dB
M
P = 7 dB
M
The following sample calculation for an 8-km-long single-mode link with a power budget
(P ) of 13 dB uses the estimated values from
B
(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
follows:
P = P – LL
M B
P = 13 dB – 8 km (0.5 dB/km) – 7(0.5 dB)
M
P = 13 dB – 4 dB – 3.5 dB
M
P = 5.5 dB
M
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.
To determine the power budget and power margin needed for fiber-optic connections,
you need to understand how signal loss, attenuation, and dispersion affect transmission.
The MX10008 router uses various types of network cables, including multimode and
single-mode fiber-optic cables.
Signal Loss in Multimode and Single-Mode Fiber-Optic Cables on page 165
Attenuation and Dispersion in Fiber-Optic Cable on page 165
Table 88 on page 163 to calculate link loss
) is calculated as follows:
M
Table 88 on page 163 to calculate link loss
) is calculated as
M
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