The compensation of the noise due to angular oscillations of the laser beam in the Precision Laser Inclinometer

An experimental method for the compensation of the noise originated by the laser ray angular oscillations was proposed and experimentally proved for the Precision Laser Inclinometer (PLI). The PLI noise spectral density was reduced by factor 30× and reached 10^–8 rad/Hz^1/2 level at the frequency of 5 × 10^–5 Hz. The angular noise of a laser ray leaving the one-mode optical fiber in the vacuum and in stabilized temperature conditions has been measured. The amplitude of the oscillations for one-day observation reached 0.46 μrad.