STABILITY OF THE PROTON-TO-ELECTRON MASS RATIO TESTED WITH MOLECULES USING AN OPTICAL LINK TO PRIMARY CLOCK

of a rovibrational transition in SF6 with the fundamental hyperfine transition in Cs. This result is direct and model-free. As far as we know, it is the most precise absolute frequency measurement of a molecular transition. It was performed using an optical link to transfer the primary standard frequency controlled with a Cs fountain from LNESYRTE to LPL. Last developments on that optical link show a resolution of a few 10 at 1 s integration time and around 10 at 1 day. This resolution is preserved when a nondedicated fiber is used. In that case, the metrological signal is transferred together with the digital data signal from the Internet traffic using two different frequency channels in a dense wavelength division multiplexing scheme.