  We study analytically the plasmonic modes in the graphene-coated dielectric
nanowire, based on the explicit form of nonlinear surface conductivity of
graphene. The propagation constants of different plasmonic modes can be tuned
by the input power at the order of a few tenths of mW. The lower and upper mode
bifurcation branches are connected at the limitation value of the input power.
Moreover, due to the nonlinearity of graphene, the dispersion curves of
plasmonic modes at different input powers form an energy band, which is in
sharp contrast with the single dispersion curve in the limit of zero input
power.
