This article provides an overview of strain-induced solid mesophases in polymer fibers, melt-spun from amorphous (polycarbonate, cyclo-olefin polymer, copolyamide, polyethylene terephthalate glycol) and semi-crystalline materials (polyethylene terephthalate, poly-3-hydroxybutyrate). The discussed mesophases are made of stretched, conformationally disordered macromolecules that are highly oriented along the fiber axis, and that reveal variations in their lateral spacing. Fitting algorithms for respective wide-angle x-ray diffraction (WAXD) patterns are put forward, and are directly tested on fibers melt-drawn from amorphous as well as semi-crystalline polymers. Equatorial, meridional, off-axis and azimuthal profiles are extracted from WAXD patterns and are simultaneously fitted. Best fit parameters contain detailed structural information, and lead to simulated 2D WAXD patterns, which in turn can be used to quantify the phases that are present in the fibers. We postulate that mesophases, which lead to broad equatorial reflections in WAXD patterns, can be found in all types of drawn melt-spun polymer fibers.