Versatile Vibration Sensing Using a Tapered Photonic Crystal Fiber With a Featured Core

On the basis of intensity modulation, a vibration sensor using a tapered photonic crystal fiber (PCF) is demonstrated. The fiber is a solid-core PCF with a central air hole embedded in the core region. The addition of the air-hole initiates the core/cladding intermodal coupling, and consequently, modulates the output light intensity when the fiber is under external disturbance. The sensing unit is configured by firstly tapering the PCF down to a waist of 72.6 μm, and then splicing its two ends to a single-mode fiber (SMF) and a multi-mode fiber (MMF), respectively. The sensor is then used for measuring a variety of vibrational signals, such as single frequency (in the range of 30∼10000 Hz), dual-frequency vibrations, and vibration accelerations (with linear responses from 0.5 to 10 m/s
²
). In addition, the sensitivity, influenced by varying the length of the sensor head, is also investigated.