Cisco Cisco ONS 15454 SONET Multiservice Provisioning Platform (MSPP) Guía De Diseño
OL-4556-01
101
panels, etc.) between the transmitter and receiver. The main objective is to assure that the power
of the optical signal at the receiver is greater than the sensitivity of the receiver.
Power gain and loss (in dB) is additive. Start with the power of the optical signal to be launched
into the fiber, expressed a 0 dB. Then, for each loss item, the dB loss is subtracted from it, and
for optical amplifiers, the gain is added to it. The remaining is compared with the receiver
sensitivity. Typically a net power margin of 3 dB or more is desirable. The power budget formula
is as follows:
(Margin) = (Transmitter output power) – (Receiver sensitivity) – (S losses dB)
Table 4-10 specifies the optical power of the composite signal with respect to the number of
individual channels being muxed and demux by typical passive DWDM filters.
of the optical signal at the receiver is greater than the sensitivity of the receiver.
Power gain and loss (in dB) is additive. Start with the power of the optical signal to be launched
into the fiber, expressed a 0 dB. Then, for each loss item, the dB loss is subtracted from it, and
for optical amplifiers, the gain is added to it. The remaining is compared with the receiver
sensitivity. Typically a net power margin of 3 dB or more is desirable. The power budget formula
is as follows:
(Margin) = (Transmitter output power) – (Receiver sensitivity) – (S losses dB)
Table 4-10 specifies the optical power of the composite signal with respect to the number of
individual channels being muxed and demux by typical passive DWDM filters.
Table 4-10: Composite Power
Number of
channels
Composite Power
Number of channels Composite Power
1
0 dB
10
+10 dB
2
+3.0 dB
11
+10.4 dB
3
+4.8 dB
12
+10.8 dB
4
+6.0 dB
13
+11.1 dB
5
+7.0 dB
14
+11.5 dB
6
+7.8 dB
15
+11.8 dB
7
+8.5 dB
16
+12.0 dB
8
+9.0 dB
17
+12.3 dB
9
+9.5 dB
18
+12.6 dB
Table 4-10 adopts the standard practice that each channel has the same optical power. It does
not take into account insertion loss, however, which must be applied to the table’s values. You
can typically add 0.3 dB of insertion loss per connector and 0.1 dB of loss per splice. Cisco
recommends that you allow a 3 dB optical power design margin and equalize the individual
optical signals forming a composite signal.
Metro DWDM Design Example
Network ring designs including amplifiers must include at least one Mux/Demux site.
Network rings containing only Optical Add/Drop Multiplexers (OADMs) are not recommended due
to the risk of receiver saturation caused by auto-amplification of propagated noise, which may
cause the network to collapse.
to the risk of receiver saturation caused by auto-amplification of propagated noise, which may
cause the network to collapse.
Extreme care must be taken when meshed channels are patched through a
Mux/Demux. If the OADMs belonging to the channel that is patched through the mux/demux are
removed, the patch can propagate noise, which is auto-amplified. This may cause the network to
collapse. Same care must be taken when patches through a mux/demux site are inserted so that
they address the correct wavelengths.
removed, the patch can propagate noise, which is auto-amplified. This may cause the network to
collapse. Same care must be taken when patches through a mux/demux site are inserted so that
they address the correct wavelengths.