Span restoration for flexi-grid optical networks under different spectrum conversion capabilities

Orthogonal Frequency Division Multiplexing (OFDM) has been proposed as a new modulation technique for fiber-optic transmission owing to its high spectral efficiency, flexibility in bandwidth allocation, and tolerance to the impairments such as chromatic dispersion. An optical transport network based on optical OFDM transmission technique is often called flexi-grid elastic optical network. In this paper, we investigate the span restoration (SR) technique for this type of network under three different spectrum conversion capabilities, namely, (1) without spectrum conversion, (2) partial spectrum conversion, and (3) full spectrum conversion. For all the three cases, we develop integer linear programming (ILP) models to minimize required spare capacity and maximal used link frequency slots. Our results indicate that spectrum conversion shows great benefit of improving spare capacity redundancy and spectrum efficiency for the flexi-grid elastic optical network.