Non-Contact Fiber Optic Vibrometer

A novel fiber optic vibrometer has been built and characterized. The vibrometer's optical design is based on the Sagnac interferometer. Due to the nature of the Sagnac's optical configuration, the optical phase shift induced by the surface being probed is differentiated, and therefore results in a measured optical phase shift that is directly proportional to the velocity of surface. The path matched Sagnac design eliminates the need for a coherent light source wed in laser doppler vibrometers and offers great design flexibility for tuning the vibrometer's frequency response and dynamic range. A fiber optic Sagnac vibrometer was built and operated with a modulation frequency of 100 kHz. The vibrometer's dynamic range exceeds 70 dB with a maximum velocity of >10 m/s and a noise floor of <1 micron/s/root Hz. Experimental results demonstrating the vibrometers performance will be presented.