  In optical-processing-enabled network, transitional lightpaths crossing the
same node could be optically encoded to each other to achieve greater spectral
efficiency. In this context, we present a new research problem, entitled,
routing, wavelength, network coding assignment and protection configuration
(RWNCA-PC) arisen in exploiting photonic network coding (NC) for dedicated path
protection in wavelength division multiplexing (WDM) networks with an extra
degree of freedom in the selection of protection triggering mechanism, that is,
network-side and client-side, tailoring to each connection. In order to
maximize the NC benefits, we thus provide a weighted multi-objective
optimization model for solving RWNCA-PC problem so as to minimize the
wavelength count as the strictly prioritized goal and the redundant resources
measured by the number of client-side connections as the secondary objective.
Numerical results on the realistic COST239 network reveal that a saving of up
to $25\%$ wavelength resources could be achieved thanks to the optimal use of
NC compared to the non-coding designs and among coding-aware designs, the use
of mixed protection configurations would be spectrally more efficient than the
design with only network-side protection scheme. Our proposal yields the
highest spectrum efficiency compared to all reference designs and moreover,
features an average saving of more than $40\%$ transponder count compared with
its single objective counterpart.
