Vibration Sensing Using Liquid-Filled Photonic Crystal Fiber With a Central Air-Bore

A highly sensitive vibration frequency and acceleration sensor is demonstrated, using a liquid-filled photonic crystal fiber. The designed fiber has a unique structure that a central air-bore of microscale was introduced during fiber fabrication, for the purpose of enhanced sensitivity to mechanical perturbations. The transmission properties of this novel fiber waveguide can, therefore, be significantly altered when the fiber is filled with liquids, making it a sensitive carrier to vibrations. This sensor performs stably and reliably in measuring vibration frequencies of extended range from 10 Hz to 20 kHz, as well as the detection of dual-frequency signals, damped vibrations, and acceleration measurements. Extremely weak vibrations, such as finger movement and human breathing, can be monitored in real time as a crucial feature of this sensor. The vibration mechanism is further discussed in terms of enhanced sensitivity, when the fiber is filled with liquids. This sensor possesses advantageous properties such as compact structure and enhanced sensitivity, which show promising potentials in versatile vibration signal monitoring.