Summary form only given. All-fiber phase modulators have recently received considerable attention because of their advantages for applications in the field of lightwave technology. In this paper, new results are presented on the characterization of all-fiber phase modulators with a radially symmetrical piezoelectric ZnO jacket tested over a wide frequency range of up to 1 GHz. 2 mm long modulators were fabricated by thermal evaporation and reactive dc magnetron sputtering techniques. The modulators consist of a 125-μm-diameter single-mode standard telecommunications fiber coated with a 6-μm-thick piezoelectric ZnO jacket that was sandwiched between coaxial Cr-Au electrodes