Data set from "A free-space interferometer design for optical frequency dissemination and out-of-loop characterization below the 10^{-21}-level"

The data set contains the data underlying the improved out-of-loop interferometer layout performance evaluation published in Photonics Research (https://doi.org/10.1364/PRJ.485899). The experimental setup and the methodology used is explained in that publication. The data is stored in the Matlab(R)-native file format. This proprietary file format is also readable by other numerical computing environments. The files 'data_i_*_S*.mat' contain the timeseries of the analysed continuous measurement runs in configuration S*. Each of these files includes the following variables: year, month, day, hour, minute, second: date at which the measurment point was acquired rem_float, rem: observed 1s Lambda-averaged out-of-loop frequency deviation in Hz as float and string, respectively p: measured air pressure in hPa T: measured laboratory temperature inside the cover close to the interferometer in °C pressure_phase_OOL: phase variations of the out-of-loop signal estimated from the measured pressure variations temp_phase_OOL: phase variations of the out-of-loop signal estimated from the measured temperature variations Different barometers have been used for the pressure mesaurements. In the measurement runs for the S1 and S2PM configurations, a barometer placed in a neighboring laboratory in the same building at PTB was used to characterize pressure fluctuations. For the measurement in the S2 configuration, we used air pressure data from the climate station of the department of Hydrology and River Basin Management of the Technical University Braunschweig, which is ≈6km apart. At times of overlapping operation, we have observed matching pressure instabilities of both barometers for averaging times 𝜏>1000s, which shows that on these averaging times the exact placement of the barometer is of lesser importance.