a temperature sensor comprising : a wave guide with a cylindrical wall ; a material of low emissivity included at the cylindrical wall for generating black body radiation into the wave guide , wherein at least a portion of the generated black body radiation is carried through the wave guide ; a first sensor receiving the generated black body radiation and providing a first output signal indicative of a first magnitude of a first bandwidth of the generated black body radiation ; and a second sensor receiving the generated black body radiation and providing a second output signal indicative of a second magnitude of a second bandwidth of the generated black body radiation , wherein a difference between the first and second output signals is a linearized indication of temperature of at least a portion of the wave guide .