Fiber optical liquid level sensor under cryogenic environment

This paper reports a preliminary experimental investigation and characterization of an optical fiber based liquid level detection system for applications in aerospace industry. The sensor system is composed of a multiplexed array of point liquid probes. Two different designs of the probe were fabricated and tested. Probe tests were conducted in water/air and liquidlgas nitrogen environments. Response speed of the liquid probe was measured and compared experimentally with a Linear Variable Differential Transducer (LVDT). In addition, the multiplexing of multiple liquid probes using an OTDR device was successfully demonstrated. Finally, a novel liquid probe made by direct polishing the fiber tip is proposed, which may provide further miniaturization and performance improvements.