To upgrade the capacity of existing optical fiber networks, technologies like dense wavelength-division-multiplexing (DWDM) are advancing rapidly. The management and control of optical frequencies in telecommunication are becoming more and more important. We have measured the absolute frequency of an acetylene-stabilized laser at 1.5 µm using a femtosecond optical frequency comb. The measured result was adopted by the International Committee for Weights and Measures (CIPM) for determining the absolute frequency of the optical frequency standard.