PIEZOELECTRICALLY INDUCED OPTICAL-PHASE MODULATION OF LIGHT IN SINGLE-MODE FIBERS

Optical phase modulation induced in piezoelectric copolymer, vinylidene fluoride (73 mol%)/trifluoroethylene (27 mol%), coated single-mode fibers has been examined and analyzed from both experimental and theoretical aspects. High-sensitive phase modulation, which is more than four times as large as those of vinylidene fluoride/tetrafluoroethylene copolymer, is obtained over a flat response range from 10 KHz to 3 MHz. At frequencies below 7 KHz and higher than 6 MHz the optical responses are dominated by axial and radial resonances, respectively, of the fiber-jacket composite. The theoretical prediction on induced phase shifts at high frequencies is carried out based on radial vibration analysis and followed by the experimental results.