We investigated the effects of photodegradation on the emission properties of a poly(9,9-dioctylfluorene) (PF8) active waveguide operating in air. We demonstrate that the PF8 degradation results in an unexpected wavelength dependent intensity variation, with an intensity enhancement of the PF8 0-0 line, an exponential decrease of the amplified spontaneous emission (ASE) intensity stronger than the one expected due to exciton quenching and a weak intensity quenching in the green emission range. We ascribe these results to the PF8 exciton quenching and keto defect formation due to photodegradation, affecting not only the exciton densities but also the waveguide losses, reducing the intrinsic PF8 self-absorption and increasing the keto defect absorption.