Demonstration of uniform multicore fiber Bragg gratings

Fiber Bragg gratings in multicore fibers have significant potential as compact and robust filters for research and commercial applications. With the aid of an innovative, flat-fielded Mach-Zehnder interferometer, we demonstrate deep (>30 dB) narrow (100pm at 3 dB; 90pm at 10 dB) notches in the outer 6 cores of a 7-core fiber at a constant wavelength ( ± 15pm). This is a crucial step in the development of FBGs operating within multimode fibers that carry an arbitrary number of spatial modes.