Temperature Insensitive Liquid Level Sensor Based on Antiresonant Reflecting Guidance in Silica Tube

We propose and demonstrate an optical fiber sensor based on a section of silica tube fusion spliced between single mode fibers. When light is conducted into the hollow core of the silica tube, anti-resonant reflecting guidance occurs, which leads to the periodic attenuation dips in the transmission spectra of the structure. The transmission intensity of the attenuation dips can be influenced by the surrounding medium, which gives rise to the application for liquid level sensing. A liquid level sensitivity of 0.4 dB/mm is achieved by immersing the sensor head vertically into water. Experimental results also prove that such a sensor is insensitive to temperature, eliminating the requirement for temperature compensation.