Proposed fiber-optic acoustical probe

An optical fiber whose end face is polished to an angle theta close to the critical angle thetac is proposed as an acoustical detector probe. Since thetac can be tuned by optical material dispersion of the glass fiber to bring thetac close to theta, probe sensitivity can be controlled. Also, tuning would allow the probe to be either phase or amplitude modulated by the acoustical wave, depending on whether thetac were tuned to greater than or less than the incident angle theta.