Highly distributed multi-point, temperature and pressure compensated, fiber optic oxygen sensors (FOxSense) for aircraft fuel tank environment and safety monitoring

Abstract

This paper describes recent progress towards the development and qualification of a highly distributed, multi-point, all optical pressure and temperature compensated, fiber optic oxygen sensor (FOxSense™) system for closed-loop monitoring and safety of the oxygen ullage environment inside fuel tanks of military and commercial aircraft. The alloptical FOxSense™ system uses a passive, multi-parameter (O2/T&P) fiber optic sensor probe with no electrical connections leading to the sensors install within the fuel tanks of an aircraft. The all optical sensor consists of an integrated multi-parameter fiber optic sensor probe that integrates a fuel insensitive fluorescence based optical oxygen optrode with built-in temperature and pressure optical optrodes for compensation of temperature and pressure variants induced in the fluorescence response of the oxygen optrode. The distributed (O2/T&P) fiber optic sensors installed in the fuel tanks of the aircraft are connected to the FOxSense optoelectronic system via a fiber optic cable conduit reaching to each fuel tank in the aircraft. A multichannel frequency-domain fiber optic sensor read-out (FOxSense™) system is used to interrogate the optical signal of all three sensors in real-time and to display the fuel tank oxygen environment suitable for aircraft status and alarm applications. Preliminary testing of the all optical fiber optic oxygen sensor have demonstrated the ability to monitor the oxygen environment inside a simulated fuel tank in the range of 0% O2 to 40% O2 concentrations, temperatures from (-) 40°C to (+) 60°C, and altitudes from 0-ft to 40,000-ft.