The incredible current density and high magnetic field generation possible with high-temperature superconductors (HTS) have the potential to revolutionize energy generation, e.g. high-power generators, and compact fusion energy devices. However, the challenge of rapidly detecting a localized hot spot in HTS before a quench is even developed, remains unsolved. Our group previously demonstrated the functionality of an ultra-long fibre Bragg grating (ULFBG), an array of FBGs with the same Bragg wavelength, in detecting a hot spot in a HTS tape. In this talk, a 10 m ULFBG is shown to behave like a ‘distributed’ sensor, which can detect 30 mm localized hot spots along its length at 80 K within a 5 K temperature rise. ULFBG can significantly improve the limitations of spatial resolution of discrete FBGs in hot-spot detection of HTS and maximize the sensing length for a given wavelength window of an interrogator.