title: Long-range vibration detection system using heterodyne interferometry.
abstract: We present the design and performance of an extremely sensitive coherent remote vibration detection system using optical heterodyne vibration of phase shifts produced by laser light scattered off a remote target. The resulting phase-modulated intermediate RF of 200 MHz, which carries the vibrational motion of the target, is demodulated down to baseband using an RF in-phase and quadrature demodulator. Acquisition and calculation of the target phase angle is carried out on a custom-made control board which utilizes high-resolution A/D converters, variable gain amplifiers, and a Spartan-6 field programmable gate array.
authors.forename: John R
authors.initials: JR
authors.lastname: Rzasa
authors.forename: Kyuman
authors.initials: K
authors.lastname: Cho
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Davis