This work explores the use of fiber optical evanescent wave (FOEW) sensors for monitoring chemical and electrochemical reactions in lithium- and sodium-ion batteries under working conditions. FINESSE is a collaborative research and training network, gathering 26 European universities, research centers and industrial partners with complementary expertise in distributed optical fibre sensor systems for a safer society. It is possible to measure strain, temperature and vibrations. (b) A map of Sunet's Swedish fiber network with the 524-kmroute round-trip from Gothenburg to Karlstad and back highlighted in blue. (c) Zoom-in of the route consisting of aerial fiber,including five ROADM nodes, which were connected with the aerial cables using shorter segments of buried fiber. We connect companies, academic institutions, research organizations, and public.