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So, for CD ROADM B&S-based networks, the CONCLUSION
highest OSNRs are achieved in networks with
60 km spans, with a difference between 0.8 dB
and 1.1 dB above the corresponding cases with
10 km spans, as a consequence of the lower
impact of ASE noise, NLI, and in-band
crosstalk. Although the OSNR that reaches the
optical receiver input decreases in all cases, it
is still higher than the minimum OSNR of 8.5 dB
required to reach the target line BER.
Analyzing the final OSNRs considering the
accumulation of the ASE noise, NLI and
crosstalk effects, the ASE noise power is the
one that most impacts. The NLI power
contributes to the OSNR always with half the
ASE noise power at the optimum power per
channel, and the crosstalk is the one that
contributes less to the OSNR degradation,
mainly in the FD&W ChD node architecture,
where it is negligible.
On networks with N1 CD ROADM B&S nodes,
the crosstalk contributes around 10% to the
total noise power used to calculate the OSNR
compared to the total noise power used to
calculate the OSNR without considering
crosstalk. In all cases, the OSNRs in networks
with FD&W ChD nodes are higher than in
networks with CD ROADM B&S nodes, as
expected.
As all networks comply with the minimum
OSNR required, our results indicate that any of
the networks studied can be implemented.
However, if we add a safety margin to the
OSNR, networks with N1 CD ROADM B&S
nodes will hardly accomplish the minimum
OSNR. In these networks, the solution to
increasing the OSNR margin is to increase the
line BER by considering a stronger FEC or
decreasing the network's reach below 10
cascaded nodes.
The NLI contribution, at the optimal channel
power, leads to a minimum 2.6 dB degradation
for FD&W-based networks, while in ROADM-
based networks, the degradation is between 1
and 2 dB. Also, the passband narrowing due to
optical filtering is negligible, and the in-band
crosstalk only influences the performance on
CD ROADM B&S-based node architectures by
decreasing the OSNR by about 1 dB. The
addition of the NLI effect contributes to a
difference of 7.4 dB in the 46 Chapter 2 General
Concepts of Optical Metropolitan Networks
O S N R h i g h e r i n F D & W- b a s e d n o d e
architectures than in networks with CD
ROADM B&S nodes in the worst case.
Among the two architectures, the
architecture using ROADM nodes provides
more capacity to the network (8 Tbps/node
against 4 Tbps/node considering FD&W
nodes), but at the expense of higher cost and
power consumption and requiring higher
system margins to work has considering all
PLIs compared to the FD&W ChD architecture.
Filipa Gomes
NOS Alfa Tech trainee
Fiber centric | Planeamento
e Gestão @NOS SGPS
Perfil | Profile
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coherent transmissions with gaussian-distributed non-
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