Twin Multicore Fiber Interferometers for Precision Sensing

Abstract

Multicore fiber (MCF) sensors is an emerging research field. MCFs provide new alternatives for the development of innovative sensing devices whose performance cannot be achieved with conventional optical fibers. In general, MCFs have diameters similar to that of a standard single mode fiber (SMF) and have multiple individual cores sharing a common cladding. So far, a number of sensors based on MCF have been reported. Our group, for example, has reported different sensors based on single MCF interferometers that consist of a piece of MCF spliced to SMF [1,2]. One key issue of such sensors is the difficulty of discriminating the target parameter (measurand) from unwanted external perturbations that may be present during the use of the sensor. To address this issue, here, we introduce an innovative architecture that consists of two identical (twin) MCF interferometers in series that are interrogated in reflection mode, see Fig. 1. Our architecture has important advantages. As there are two MCF interferometers, one can be used as a reference or filter and the other as a sensor [3]. The signal of our twin MCF interferometers is the multiplication of individual reflection spectra. Consequently, their reflection exhibits a single narrow peak whose position in wavelength is easy to track. We have observed that periodic bending (vibrations) in one them resulted in prominent shifts in the reflection spectrum.