SINBAD, the first beamline in Italy designed to work in the far-and-mid-infrared region, is being installed on DAFNE storage ring, the new F-factory at Laboratori Nazionali di Frascati. DAFNE, first injected in September 1997, will work at 0.51 GeV with a beam current in the range 2-5 A. The infrared synchrotron radiation extracted from a bending magnet is expected to be more brilliant than a black body at 2000K up to three orders of magnitude in the wavelength range 10-1000 mm. The optical layout of SINBAD, fully designed by ray tracing simulation, includes six mirrors placed in a 18m long beamline. The infrared radiation is first focused on a wedged diamond window and then re-focused on the entrance of a Michelson interferometer. Diffraction effects and mirror roughness, as well as optical aberrations, have been evaluated.