  Polycrystalline silicon core fibers (SCFs) fabricated via the molten core
drawing (MCD) method are emerging as a flexible optoelectronic platform. Here,
the optical transmission properties of MCD SCFs that have been tapered down to
a few micrometer-sized core dimensions are characterized from the Telecom band
to the mid-infrared spectal regime. The SCFs exhibit low linear losses on the
order of a few dB/cm over the entire wavelength range. Characterization of the
two-photon absorption coefficient \b{eta}_TPA and nonlinear refractive index
n_2 of the SCFs reveals values consistent with previous measurements of single
crystal silicon materials, indicating the high optical quality of the
polysilicon core material. The high nonlinear figure of merit obtained for
wavelengths above 2{\mu}m highlight the potential for these fibers to find
application in infrared nonlinear photonics.
