We demonstrate common spectroscopic trends occurring during discharge of of Li-S batteries based on S/DIB copolymer cathodes involving both short and long sulfur chains. Moreover, we predict spectroscopic fingerprints during the discharge specific to the copolymers having either short of long sulfur chains only. Our theoretical predictions are validated against Raman spectroscopy measurements on coin cells at different discharge states. These findings will contribute to the advancement of material analysis using operando measurements and thereby can lead to enhanced performance of Li-S batteries.