  In this paper, we report high-precision absolute distance and vibration
measurements performed with frequency scanned interferometry. Absolute distance
was determined by counting the interference fringes produced while scanning the
laser frequency. High-finesse Fabry-Perot interferometers were used to
determine frequency changes during scanning. A dual-laser scanning technique
was used to cancel drift errors to improve the absolute distance measurement
precision. A new dual-channel FSI demonstration system is also presented which
is an interim stage toward practical application of multi-channel distance
measurement. Under realistic conditions, a precision of 0.3 microns was
achieved for an absolute distance of 0.57 meters. A possible optical alignment
system for a silicon tracker is also presented.
