  In this paper, we analytically study Surface Plasmon Polaritons (SPPs) in
graphene-based cylindrical structures with gyroelectric layers. In the general
waveguide, each graphene layer is surrounded by two various gyro-electric
materials. New closed-form relations are derived for the field contributions of
SPP waves. As a special case, a gyro-electric cylindrical waveguide with
double-layer graphene is considered in this article. For the designed
structure, the figure of merit (FOM) of 51 is reported for B= 2 T and
{\mu}c=0.7 eV, at the frequency of 33 THz. It is demonstrated that the FOM of
the studied waveguide is varied by tuning the chemical potential and the
magnetic bias. Harnessing the gyro-electric media together with graphene layers
will open a new promising platform for the design and fabrication of novel
plasmonic devices in the mid-infrared region.
