  Motivated by biochemical reaction networks, a generalization of the classical
secant condition for the stability analysis of cyclic interconnected
commensurate fractional-order systems is provided. The main result presents a
sufficient condition for stability of networks of cyclic interconnection of
fractional-order systems when the digraph describing the network conforms to a
single circuit. The condition becomes necessary under a special situation where
coupling weights are uniform. We then investigate the robustness of
fractional-order linear networks. Robustness performance of a fractional-order
linear network is quantified using the $\mathcal{H}_2$-norm of the dynamical
system. Finally, the theoretical results are confirmed via some numerical
illustrations.
