Although the stability of high-temperature superconductors (HTS) such as ReBCO and BSCCO makes them good candidates as valuable components of superconductor systems, quench protection remains a challenge. The same stability that makes HTS less likely to quench makes it difficult to detect the development of quench using conventional voltage-based approaches, which are also highly susceptible to noise from electromagnetic interference. Such an issue must be addressed to allow the development of fast and reliable quench protection for HTS systems.

We present ultra-long fibre Bragg gratings (ULFBG) as a novel optical fibres-based technology for hot spots detection in HTS tapes. Primarily addressed here are the data processing techniques for the extraction of hot spots information from the ULFBG reflectance spectra and how well they perfrom in short HTS tapes. Unlike conventional FBG sensors, which act as point temperature sensors who have reflectance spectra with sharply narrow peaks that reliably track temperature changes, ULFBGs have broad reflectance spectra that may not contain clearly defined peaks. We present the algorithms as applied to experimental data on short HTS samples on which hot spots were simulated using resistance heaters.

Keywords: ULFBG, optical fibre, fbg, cFBG, HTS,  quench protection