Commercial applications for fiber sensing and low-coherence interferometry are rapidly growing in medical, industrial and aerospace markets. These new instruments must be smaller, more robust and less expensive. An all-fiber optical delay line or “fiber stretcher”, using piezoelectric (PZT) actuation, offers a simple solid-state solution that eliminates free space optics. The challenges for PZT fiber stretchers include: reducing non-linearity and hysteresis, achieving sufficient scan range with minimum fiber length, maximizing scan frequency and reducing losses in the drive electronics. PZT actuators are essentially large ceramic capacitors that must be rapidly charged and discharged to achieve fast scanning. The mechanical response of the PZT ceramic is greater than 10 kHz which makes it practical to scan at four kilohertz. A thin-walled piezoelectric disk or cylinder achieves 4.5 millimeters of fiber stretch using 20 meters of coiled fiber. Digitally controlled series resonant electronics produce a 1200 volt sinusoidal drive signal at a fixed frequency of four kilohertz while dissipating only 16 Watts. An all-fiber optical delay line module, using piezoelectric actuators and a series resonant drive, is a miniature, robust and efficient alternative to free-space optics with dithering mirrors or spinning polygons.