  We consider a spin-1/2 fermionic ladder with spin-orbit coupling and a
perpendicular magnetic field, which shares important similarities with
topological superconducting wires. We fully characterize the symmetry-protected
topological phase of this ladder through the identification of fractionalized
edge modes and non-trivial spin winding numbers. We propose an experimental
scheme to engineer such a ladder system with cold atoms in optical lattices,
and we present two protocols that can be used to extract the topological
signatures from density and momentum-distribution measurements. We then
consider the presence of interactions and discuss the effects of a contact
on-site repulsion on the topological phase. We find that such interactions
could enhance the extension of the topological phase in certain parameters
regimes.
