Partially coated long period fiber Bragg gratings in multicore optical fibers

Multicore optical fibers (MCFs) have attracted considerable interest in the last years due to their potential in many applications including broadband communications, microwave photonics, and optical sensing [1,2]. In optical sensing, MCFs has been used in the past for implementing curvature and shape sensors [3]. However, the potential of MCFs for optical sensing is not limited to mechanical sensors and they can be used for implementing other types of sensors. In this paper, we investigate the use of MCFs for external refractive index (RI) sensing. We use LPGs inscribed in the cores of the fiber to detect changes in the external refractive index. Partially coating the surface of the optical fiber we can modify the sensitivity of the cores.