  We propose a transmission line working at telecom wavelengths with cross
section as small as ${\lambda}^2/39$, which is 1.6 times smaller than that of
optimized silicon waveguide. The proposed line can be implemented as a
subwavelength fiber with plasmonic cladding. This considerable decrease in the
line cross section is achieved by utilizing a plasmonic quasi-antisymmetric
mode. The required plasmonic cladding is rather thin, therefore, losses are
moderate and could be compensated by using amplifying core materials. Such a
transmission line can find applications in densely integrated optical systems.
