Controllable Light Scattering on Fiber Bragg Gratings in Multimode Fibers: Tailoring Angular Emission for Advanced Fiber-Based Light Sources

We study lateral light scattering on fiber Bragg gratings(FBG)with the goal of creating an optical fiber-based linear light sourcewith controllable emission angles. The scattering from two FBGs wasmeasured for polar angles (measured from the fiber axis) in the range & theta; = 27.1-152.9 & DEG; and for all azimuth angles aroundthe fiber. The observed light emission is strongly concentrated inone or more scattering cones around the fiber axis, showing four intensitypeaks on opposite sides. These scattering phenomena are describedand explained using the volume current method. This method shows anovel and simple way to understand the side scattering on FBGs asa combined effect of the grating's longitudinal period, thegrating harmonics, and its transversal shape. Further, this work contributesto a better understanding of the azimuth FBG-scattering caused byan interplay of the transversal grating shape and the fiber modes.The presented method can generate tailored side emissions for fiberlight source applications, create light power sensors, or suppressunwanted scattering on FBGs for low optical loss applications.