Jose D. Guevara
Dept. of Mech. Eng., The Cooper Union, 51 Astor Pl., New York, NY 10003
Daniel R. Raichel
The Cooper Union and the Graduate Ctr. of the City Univ. of New York
An acoustic fiber optic sensor was designed for the miniature version of an acoustic viscometer under development at The Cooper Union Acoustic Research Center. The sensor consists of a single mode fiber optic cable embedded in the center of a 50-mmx50-mmx5 mm compliant polymer layer. It was noted that the geometrical versatility of the sensor could be minimized further, allowing for shorter lengths of sensitized fiber without sacrificing acoustical sensitivity. A Mach--Zender interferometric system is employed to detect the phase shift of the modulated optical signal in the sensitized fiber. A flat frequency response in the 200 Hz to 20 kHz was predicted. The length of the fiber determines the minimum value of detectable pressure. In addition to immersion in water the sensor has the potential to also withstand immersion in mildly acidic and alkaline solutions.