High-precision Absolute Distance Measurement using Dual-Laser Frequency   Scanned Interferometry Under Realistic Conditions
  In this paper, we report on new high-precision absolute distance measurements performed with frequency scanned interferometry using a pair of single-mode optical fibers. Absolute distances were determined by counting the interference fringes produced while scanning the frequencies of the two chopped lasers. High-finesse Fabry-Perot interferometers were used to determine frequency changes during scanning. Dual lasers with oppositely scanning directions, combined with a multi-distance-measurement technique previously reported, were used to cancel drift errors and to suppress vibration effects and interference fringe uncertainties. Under realistic conditions, a precision about 0.2 microns was achieved for a distance of 0.41 meters. 
Hai-Jun Yang and Keith Riles