AN ECONOMICAL PIEZOELECTRIC PHASE MODULATOR FOR FIBER OPTIC SENSORS

A homemade piezoelectric phase modulator for interferometric fiber opt ic sensors was fabricated using piezoelectric butters as strain elemen ts. Six piezoelectric elements were embedded between the two halves of a bakelite cylinder split along its axis and secured tightly together again to form a cylinder. Single-mode optical fiber was then wound ar ound the cylinder to complete the unit. Up to a frequency of 500 Hz, t he phase shift produced by the modulator is linearly proportional to t he amplitude of the applied voltage. The sensitivity of the phase modu lator is about 3.6 rad/V and has a dynamic range of 1,000 rad, which i s sufficient for most phase modulation purposes.