  Link failures in wide area networks are common and cause significant data
losses. Mesh-based protection schemes offer high capacity efficiency but they
are slow and require complex signaling. Additionally, real-time reconfiguration
of a cross-connect threatens their transmission integrity. On the other hand,
coding-based protection schemes are proactive. Therefore, they have higher
restoration speed, lower signaling complexity, and higher transmission
integrity. This paper introduces a coding-based protection scheme, named Coded
Path Protection (CPP). In CPP, a backup copy of the primary data is encoded
with other data streams, resulting in capacity savings. This paper presents an
optimal and simple capacity placement and coding group formation algorithm. The
algorithm converts the sharing structure of any solution of a Shared Path
Protection (SPP) technique into a coding structure with minimum extra capacity.
We conducted quantitative and qualitative comparisons of our technique with the
SPP and, another technique, known as p-cycle protection. Simulation results
confirm that the CPP is significantly faster than the SPP and p-cycle
techniques. CPP incurs marginal extra capacity on top of SPP. Its capacity
efficiency is lower than the p-cycle technique for dense networks but can be
higher for sparse networks. In addition, unlike p-cycle protection, CPP is
inherently suitable for the wavelength continuity constraint in optical
networks.
