Sensitivity enhancement of LPG vibration sensor using higher-order cladding mode

摘要

Long-period fiber gratings (LPGs) are fabricated and investigated for use in an LPG vibration sensor based on intensity modulation scheme in which a tunable laser with its wavelength tuned to a slope of an attenuation dip of an LPG is used for an optical source and the light partially transmitted through the LPG is modulated in intensity according to the applied vibrations. In the experiment, it is demonstrated that the LPG vibration sensor yields a clear and stable output waveform. In addition, it is confirmed that the sensitivity of the sensor depends on the wavelength-shift of attenuation dip per unit strain and the gradient of a slope of the attenuation dip. Since an LPG shows higher sensitivity to static or dynamic strain when an appropriate higher-order cladding mode is adopted, proper choice of the order of cladding mode enables a highly sensitive operation of the LPG vibration sensor.