In this paper, we report on the metrological capabilities of CO2/OsO4 optic
al frequency standards operating around 29 THz. Those frequency standards a
re currently involved in various fields, such as frequency metrology, high
resolution spectroscopy, and Rydberg constant measurements. The most impres
sive features of the standards lies in the 10(-15) level frequency stabilit
y allied to a long-term reproducibility (1 yr) of 1.3 x 10(-13).