  We present ellipsometric measurements of the far-infrared dielectric response
of polycrystalline samples of the new pnictide superconductor RO0.82F0.18FeAs
(R=Nd and Sm). We find evidence that the electronic properties are strongly
anisotropic such that the optical spectra are dominated by the weakly
conducting c-axis response similar as in the cuprate high-temperature
superconductors (HTSC). Accordingly, we obtain an upper limit of the c-axis
superconducting plasma frequency of $\omega_{{\rm pl},c}^{\rm SC}\leq 260\cm$
which corresponds to a lower limit of the c-axis magnetic penetration depth of
$\lambda_c\geq6\mum$ and an anisotropy of $\lambda_c/\lambda_{ab}\geq 30$ as
compared to $\lambda_{ab}=185$ nm from muon spin rotation [A. Drew {\it et
al.}, arXiv:0805.1042]. Also in analogy to the cuprate HTSC, our spectra
exhibit the signatures of a gap-like suppression of the conductivity in the
superconducting state with a large gap magnitude of $2\Delta\approx300\cm$ (37
meV) and a ratio of $2\Delta/k_{\rm B}\tc\approx8$ that is suggestive of strong
coupling.
