A highly sensitive liquid-level sensor based on etched fiber Bragg grating is proposed and demonstrated. The fiber Bragg grating is etched to enhance the sensitivity to the refractive index of liquid, when a portion of etched fiber Bragg grating is immersed in the liquid, the original single transmission dip splits into two transmission dips because of the fiber Bragg grating spectrum is affected by the fraction of the length of the etched fiber Bragg grating that is surrounded by the liquid. By measuring the transmission dips variations, the liquid level can be measured. The experiments show that for a liquid level variation of 24mm, the transmission dip difference changes about 32dB. Also in the linear region, a high liquid level sensitivity of 2.56dB/mm is achieved.
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