Femtosecond laser direct writing tilted fiber Bragg gratings in multicore fiber.

In this Letter, we propose a new method utilizing femtosecond laser direct writing technology to rapidly inscribe high-quality tilted fiber Bragg gratings (TFBGs) in multicore fibers (MCFs). A series of TFBGs with varying tilt angles were directly inscribed in MCFs using the Plane-by-Plane (Pl-by-Pl) method, and the writing time for a 4 mm long TFBG was only 3.60 s. The TFBGs couple the transmitted light from the cores of the MCF into the cladding, thereby increasing the cross talk between adjacent cores. By monitoring the wavelength and intensity changes of the core modes coupled back to the central core from the TFBGs inscribed in the edge cores, two-dimensional (2D) vector bending measurements were achieved.