Liquid level detection in cryogenic environment

This paper reports a preliminary experimental investigation and characterization of an optical fiber based liquid level detection system for: applications in cryogenic environment. The sensor system comprises a multiplexed array of point liquid probes. Two different designs of the probe were fabricated and tested. Probe tests were conducted in different liquid/vapor interfaces including water/air, liquid/gas nitrogen and liquid/gas hydrogen. Key performances of the liquid probe, such as vapor-liquid signal ratio, response speed were measured and compared experimentally. 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.