Page 72 - newDATAmagazine | 14>06>2022
P. 72
In Table 2, it is also presented the total In Table 3, the values of the OSNR with in-
crosstalk level at the network output, defined band crosstalk, calculated using
by
are shown for WSS isolations of -30 dB and -35
where P is the power of the interfering term, dB and where p =X x p . These OSNR values
Rx
Xc,i
c
Xc
p is the power of the input primary signal, N are calculated for networks with 10 km spans
Rx
Xc
is the total number of interfering terms, and X and with 60 km spans, with signal insertion at
c,i
is the crosstalk level of the i-th interfering term. node N1 and extraction at node N2 and with
signal insertion at node N2 and extraction at
node N1. At the top of Table 3, the common
parameters between both cases, such as the
OSNR R,min , the power of interfering terms for
isolations of -30 and -35 dB, and the parameter
η NLI are presented. Then, the parameters
associated with each case are shown, such as
Table 2: Total number of interfering terms of in-band the ASE noise power, the optimum channel
crosstalk and crosstalk level for the worst-case
crosstalk in a horseshoe network. power, and the power of NLI.
At last, the OSNR is determined for all
Regarding the crosstalk level and taking combinations of node architectures, span
into account that in the FD&W ChD lengths, WSS isolations, and signal insertion at
architecture, there is no in-band crosstalk node N1 or at node N2. Note that all OSNRs
introduced in the N1 nodes, only the N1 CD values presented in Table 3 are calculated for
ROAD, B&S nodes generate interfering terms. the optimal power per channel. The crosstalk
The nodes N2 also contribute with four power does not modify the OSNRs for
second-order interfering terms. The crosstalk networks with N1 FD&W ChD nodes because
level in Table 2 is calculated using the its value is more than 3 orders of magnitude
expression above, considering that each WSS lower than the ASE noise power for both
inside the node has typical isolation of -30 dB WSSisolations. For this node architecture, the
and -35 dB, which leads to a crosstalk level of - associated OSNRs are at least 6 dB and 2.7 dB
30 or -35 dB per FIRST order interferer, higher, respectively, with signal insertion at
respectively, and -60 or -70 dB per second-order node N1 and with signal insertion at node N2,
interferer. As such, in Tab .2, the architectures than all architectures with CD ROADM B&S
with CD ROADM B&S nodes lead to a higher nodes. This happens because the ASE noise
crosstalk level at the output of the horseshoe and NLI powers that reach the optical receiver
topology, which is 38.5 dB and 35.5 dB above input are lower than in the case of ROADM
the crosstalk level obtained with the FD&W nodes. In the case of networks with N1 CD
ChD architecture for, respectively, A=-35 dB ROADM B&S nodes, due to in-band crosstalk,
and A=-30 dB. The difference of 5 dB in the the OSNR decreases less than 0.14 dB for
\acrshort{wss} isolation produces a 5 dB WSSs with A=-35 dB for all cases studied. For
higher total crosstalk level when first-order WSSs with A=-30 dB, due to in-band crosstalk,
interference is dominant and 10 dB, when there the OSNR decreases less than about 0.4 dB for
exists only second-order interference. all cases studied.
72 newDATAmagazine.com
