<p>Nanomaterial-based optical biomedicine and devices have garnered significant attention for their potential in tumor diagnosis and treatment. However, their application in tumor ablation is often hindered by limited functional integration and concerns over excessive radiation exposure. In this study, we address these challenges by developing a multifunctional fiber probe based on lanthanide-doped nanoparticles, featuring decoupled modules for localized heating and optical thermometry. This design enables synergistic therapy under near-infrared (NIR) laser irradiation. Beyond achieving precise photothermal ablation and real-time temperature monitoring, we uncovered a unique phenomenon: the generation of reactive oxygen species (ROS) by these na-noparticles under NIR laser excitation, even in the absence of traditional photosensitizers. Through a combination of experimental and computational approaches, we elucidated the physical mechanisms underlying ROS generation in wide-bandgap lanthanide nanoparticles. Leveraging these insights, we constructed an all-optical fiber system capable of simultaneous precise thermal control and photodynamic therapy. Our findings offer valuable guidance for the development of advanced optical nanomaterials and devices for effective tumor treatment, both <i>in vivo</i> and <i>in vitro</i>.</p>