The invention describes a pyrometer (1) of two-color optical fiber for measuring the temperature of the one piece radiant surface (100) comprising: a single multimode fiber optic section (2) having a front end oriented towards the piece (100); a demultiplexer (3) connected to the rear end of the fiber optic segment (2) to divide the received thermal radiation into two channels corresponding to two narrow bands of near wavelengths; a pair of similar photodetectors (4a, 4b) respectively connected to said channels to transform the thermal radiation of said bands into respective analog electrical signals; a pair of amplifiers (5a, 5b) that amplify the previous analog electrical signals; and a digital analog converter (6) that receives said analog electrical signals and converts them into digital signals for analysis by a processor (7). (Machine-translation by Google Translate, not legally binding)