The invention relates to a sensor system comprising a waveguide, which waveguide comprises a grating in at least a part of the waveguide, which waveguide further comprises a coating, the coating comprising a polymer, which polymer comprises a chain, in which chain are present an aromatic group and a chemical group selected from the group of sulfonyl groups, carbonyl groups, carbonate groups, fluorocarbon groups, siloxane groups, pyridine groups and amide groups.