A polarization-based optical fibre vibrometer

A fibre optic heterodyne vibrometer configuration based on the use of birefringent optical fibre components is demonstrated. The heterodyne processing is moved to the receiving section of the interferometer, reducing the optomechanical stability requirements of the system and enabling optimization of the reference to signal beam ratio intensity. The instrument can be configured to have minimum down lead sensitivity. The technique was demonstrated with a laser diode at 833 nm with a minimum detectable phase change of 12 mu rad Hz(-1/2) obtained at 5 kHz.