A fiber Bragg grating(FBG) liquid level sensing head with a accordion pipe substrate was disigned,and the reference grating was used to compensate for FBG pressure measurement.We tested the sensor′s characteristics at the liquid level range of 3～30 cm.The temperature compensated experimental curve of the wavelength shift caused by the liquid level change was acquired.The results show that the sensitivity of this liquid level sensor is -0.055 3 nm/cm.The sensing head uses nickel-based alloy as pa...