Fig. 3. Network blocking probability for 50 GHz grid (top left), 25 GHz
grid (top right), 12.5 GHz grid (bottom left) and 6.25 GHz grid (bottom
right). In all cases the congestion aware algorithms (CA1 and CA2 detailed
in section VI) offer improved performance compared with shortest path (SP).
In all cases for network blocking probabilities greater than 1%, the extreme
value distribution is indistinguishable from the observed points (denoted
as dots).
Of particular relevance for the SNR based RMSA is that the
shortest and longest shortest path between nodes are 300 km
and 7800 km respectively such that we expect the SNR to
vary between 5.6 dB and 19.7 dB. We consider four possible
grid options, namely 50, 25, 12.5 and 6.25 GHz grids, in order
to assess the impact of this on the performance. In all cases
it is assumed the signal may occupy multiple slots should
the available SNR dictate this. We also consider the three
routing algorithms, shortest path (SP), a simple congestion
aware routing algorithm (CA1) and a weighted congestion
aware routing algorithm (CA2) detailed in section VI.
Fig. 3 indicates excellent agreement between the observed
network blocking probabilities and the fitted generalized
extreme value distribution (7) validating our hypothesis that
we are concerned with the distribution of a minimum.
As can be seen in Table I, the two congestion aware routing
algorithms significantly increase the capacity for a 1% network
blocking probability for all of the frequency grids considered,
with the maximum benefit afforded by combining a flexgrid
with congestion aware routing. For the 6.25 GHz flexgrid with
a weighted congestion aware routing algorithm (CA2), the
network capacity is 1744 demands each of 100 GbE, compared
to just 328 demands with standard shortest path routing with
a 50 GHz grid. These results indicate the benefit that might be
obtained in a sequentially loaded optical network, mirroring
the current operation of installed optical networks [16]. While
dynamic optical networks have not been studied, the results
for the sequentially loaded network indicate that this would
warranty further investigation.
For the results obtained, one of the striking features
contained within Table I, is the significant increase in the