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This paper proposes a novel network planning
strategy to jointly allocate physical layer resources together with
the routing and spectrum assignment in transparent nonlinear
flexible-grid optical networks with static traffic demands. The
physical layer resources, such as power spectral density, modulation format, and carrier frequency, are optimized for each
connection. By linearizing the Gaussian noise model, both an
optimal formulation and a low complexity decomposition heuristic are proposed. Our methods minimize the spectrum usage
of networks, while satisfying requirements on the throughput
and quality of transmission. Compared with existing schemes
that allocate a uniform power spectral density to all connections,
our proposed methods relax this constraint and, thus, utilize
network resources more efficiently. Numerical results show that
by optimizing the power spectral density per connection, the
spectrum usage can be reduced by around 20% over uniform
power spectral density schemes.
