SENSEI aims to develop new photonic devices and technologies to enhance the security, resilience, and efficiency of telecommunication fibre networks through improved supervision capabilities, while exploiting them as large-scale distributed environmental sensors. Funded by the European Commission under the Horizon Europe programme with €5 million over 3 years, the project brings together 15 partners from 6 EU countries with diversified and complementary expertise in photonics, optical metrology, geoscience, optical networking and network provisioning.