Novel light-leaking optical fiber liquid-level sensor for aircraft fuel gauging

Abstract

We present a novel light leaking optical fiber liquid level sensor for aircraft fuel measuring systems that is based on the side-emitting optical fiber. In operation, the fiber is bent as a spiral and inserted into the liquid, then the conducting light in the fiber will be scattered and transformed to be cladding mode and radiation mode. The radiation mode power in the scattering light is determined by the ambient refractive index. Since more power is lost in liquids than in the air, the output power of the sensor will monotonically decrease while the liquid level increases. The fiber is bent as a spiral to increase the sensor’s sensitivity. A laboratory prototype with a range of 1 m, a radius of 14 mm, and a screw pitch of 15 mm has been built and successfully demonstrated in water level measurement. The sensor’s response to liquid level is presented and shown to be consistent with the theory.