We report an empirical pseudopotential study of the optical properties of several InAs/GaSb superlattice structures, some of these additionally containing Ga1-xInxSb and AlSb layers, designed for infrared (IR) applications. The optical absorption and emission spectra of these nanostructures are modelled, with a view to establishing a quantitative link with the microscopic signature of the interface. The emission spectra of the structures having laser applications are investigated for various population inversions. We gauge the role of atomic disorder and determine the degree of alloy layer disorder for which the virtual crystal (VC) approximation provides an adequate description of the overall lineshape. An analogous study was carried out for structures having applications as detectors. We find good agreement between the experimental absorption spectra and our computer model, and investigate the effects of Auger recombination on device performance.