An optical fibre sensor system arranged to detect a temperature change in a zone (2, 3, 4) in an aircraft having at least one zone (2, 3, 4), the optical fibre sensor system comprising: at least one optical fibre (11, 21, 31, 41) comprising a plurality of Fibre Bragg Gratings (20, 30, 40) for detecting a temperature change, wherein each of the Fibre Bragg Gratings (20, 30, 40) is reflecting radiation within a predetermined wavelength range; a radiation source unit arranged to emit radiation into the at least one optical fibre (11, 21, 31, 41); a radiation detector unit arranged to receive radiation from the at least one optical fibre (11, 21, 31, 41); a processing unit configured to identify a spectral response (22, 32, 42) of the received radiation and to determine a temperature change from the spectral response (22, 32, 42) of the received radiation in a predetermined wavelength range; wherein each of the at least one zone (2, 3, 4) solely has Fibre Bragg Gratings (20, 30, 40) which are reflecting radiation within the same predetermined wavelength range, wherein Fibre Bragg Gratings (20, 30, 40) of each of the other zones (2, 3, 4) are reflecting radiation within a different predetermined wavelength; wherein the processing unit is further configured to determine at least one Bragg wavelength of the spectral response (22, 32, 42) and to match the at least one Bragg wavelength to the zone (2, 3, 4) which solely has Fibre Bragg Gratings (20, 30, 40) which are reflecting radiation within the corresponding predetermined wavelength range; characterized in that the processing unit is further configured to determine each of at least one Bragg wavelength of the spectral response (22, 32, 42) by identifying a rising or falling edge of the spectral response (22, 32, 42). at least one optical fibre (11, 21, 31, 41) comprising a plurality of Fibre Bragg Gratings (20, 30, 40) for detecting a temperature change, wherein each of the Fibre Bragg Gratings (20, 30, 40) is reflecting radiation within a predetermined wavelength range; a radiation source unit arranged to emit radiation into the at least one optical fibre (11, 21, 31, 41); a radiation detector unit arranged to receive radiation from the at least one optical fibre (11, 21, 31, 41); a processing unit configured to identify a spectral response (22, 32, 42) of the received radiation and to determine a temperature change from the spectral response (22, 32, 42) of the received radiation in a predetermined wavelength range; wherein each of the at least one zone (2, 3, 4) solely has Fibre Bragg Gratings (20, 30, 40) which are reflecting radiation within the same predetermined wavelength range, wherein Fibre Bragg Gratings (20, 30, 40) of each of the other zones (2, 3, 4) are reflecting radiation within a different predetermined wavelength; wherein the processing unit is further configured to determine at least one Bragg wavelength of the spectral response (22, 32, 42) and to match the at least one Bragg wavelength to the zone (2, 3, 4) which solely has Fibre Bragg Gratings (20, 30, 40) which are reflecting radiation within the corresponding predetermined wavelength range; characterized in that the processing unit is further configured to determine each of at least one Bragg wavelength of the spectral response (22, 32, 42) by identifying a rising or falling edge of the spectral response (22, 32, 42).