Spatial-Division Multiplexing Approach for Simultaneous Detection of Fiber-Optic Ball Resonator Sensors: Applications for Refractometers and Biosensors.

Fiber-optic ball resonators are an attractive technology for refractive index (RI) sensing and optical biosensing, as they have good sensitivity and allow for a rapid and repeatable manufacturing process. An important feature for modern biosensing devices is the multiplexing capacity, which allows for interrogating multiple sensors (potentially, with different functionalization methods) simultaneously, by a single analyzer. In this work, we report a multiplexing method for ball resonators, which is based on a spatial-division multiplexing approach. The method is validated on four ball resonator devices, experimentally evaluating both the cross-talk and the spectral shape influence of one sensor on another. We show that the multiplexing approach is highly efficient and that a sensing network with an arbitrary number of ball resonators can be designed with reasonable penalties for the sensing capabilities. Furthermore, we validate this concept in a four-sensor multiplexing configuration, for the simultaneous detection of two different cancer biomarkers across a widespread range of concentrations.