Fiber-Optic Liquid Level Sensor

A fiber-optic liquid level sensor based on multimode interference (MMI) effects is proposed and demonstrated. We show that MMI and self-image effects can be effectively applied for multiplexed liquid level sensing, because the natural response as a band-pass filter for each sensor is clearly distinct from each other, in the case for several sensors working at the same time. Using a standard 105/125 step-index multimode fiber (MMF) a simple discrete level sensor was fabricated, that can also discriminate the refractive index (RI) of the liquid during the level measurement. The MMI liquid level sensors are not only inexpensive, but their fabrication is simple. © 2011 IEEE