Hydrogen sensing system with dielectric waveguide

A hydrogen sensor for detecting hydrogen in a medium to be monitored is provided. The sensor comprises a hybrid photonic-plasmonic waveguide (HPWG), comprising a dielectric waveguide, having a substantially rectangular cross-section; a buffer layer, stacked on top of the dielectric waveguide; a sensing layer stacked on the buffer layer, being metallic or semi-metallic and having a refractive index and/or absorption coefficient which is dependent on a hydrogen partial pressure at the sensing layer; and optionally a catalytic layer stacked on the sensing layer. The hydrogen sensor is configured such that a medium to be monitored is in physical contact to the sensor, and configured such that hydrogen in the medium may permeate into the sensing layer, and wherein at least one mode of a propagating wave in the HPWG is affected by a change in the refractive index and/or absorption coefficient of the sensing layer due to a change in the hydrogen concentration in the medium to be monitored. Further, a detection/sensing system employing such sensors, and respective methods are provided.