Gas sensor employing polarization, gas detection system and method employing the same

A hydrogen sensing system (1) for detecting hydrogen in a medium (2) to be monitored, the system comprising a light emitting unit (24) emitting light with two polarization components having a first intensity ratio between the polarization components, an optical element (12, 22), a sensor layer (11) which is attached, with a first face, to a sensing face (12b, 22b) of the optical element, wherein the sensor layer (11) is configured to be in contact, at a second face opposite to the optical element, with the medium (2), and to have a refractive index which is dependent on a hydrogen partial pressure in the medium at the sensor layer (11), a light detection unit (19) configured to detect the intensity of each of the two polarization components of the detected light, and wherein a control unit (20) is configured to determine a gas partial pressure at the sensor layer (11) on the basis of a ratio of the intensities of the polarization components of the reflected light as detected by the light detection unit (19).