摘要： The photonic guitar pickup: a high-sensitivity, high-bandwidth fiber strain sensor. Fiber-strain sensors have found numerous applications from structural health monitoring for vibrations, to pressure and temperature sensing. Many of these sensors exploit the strain-sensitivity of the reflection wavelength of fiber-bragg gratings, (cid:83)-shifted gratings or other waveguide devices. The strain is typically inferred from a change of reflected or transmitted light intensity. Light intensity measurements are not very robust and have an inherently limited accuracy. We propose that a frequency-based strain measurements using fiber Fabry-Perot (FFP) cavities provide not only superior sensitivity but also retain a very high measurement bandwidth. Here, we present a fiber optic vibration sensor based on an FFP cavity, which consists of a matched pair of 23 dB fiber Bragg gratings coupled to a custom-built signal processing circuit. The wavelength of a laser diode is locked to one of the many cavity resonances using the Pound–Drever–Hall scheme. We demonstrate that such a strain sensor has an ultrawide dynamic sensing range, from less than 1 Hz to clinical ultrasound frequencies near 6 MHz. Its linear sensitivity range extends from below 1 n(cid:72) to 2 (cid:80)(cid:72), and its dynamic response limit is as high as 12 m(cid:72)/s. To demonstrate the high fidelity of the strain measurements we attached the FFP cavity sensor to the top plate of an acoustic guitar and recorded several melodies. As expected the sensor system was largely immune to noise arising from optical intensity fluctuations. We made distortion-free audio recordings of musical pieces from infrasound (~8 Hz) to 30 kHz with a 50 dB dynamic range in acoustic power. The remaining noise in our measurements arises from electronic sources and not optical sources, giving hope that future developments may be able to further increase the dynamic range of the measurements, if needed. In separate experiments the same sensor was affixed to the rim of a wineglass and to the side of a steel cantilever to monitor the (photo-)acoustic response of these mechanical resonators to periodic photo-excitation. We found, for example, that the limit of detection for orthophosphate through the photoacoustic excitation of the respective molybdenum-blue complex was below 2 ppm. Finally, the sensor was embedded in tissue phantoms to validate that it accurately responds to low frequencies (heart beat) and high frequencies (ultrasound pulse). In its most recent version the laser driver and the PDH circuit are addressed through a Raspberry-Pi microcontroller, making the sensor system very compact and relatively inexpensive. We propose that sensor systems based on PDH-interrogated FFP-sensor heads are robust and versatile for a large variety of monitoring applications.