  A novel approach for a delay line interferometer (DLI) based purely on
forward Bragg scattering is proposed. We have numerically and experimentally
demonstrated that a Bragg grating can deliver the functionality of a DLI in its
transmission mode along a single common interfering optical path, instead of
the conventional DLI implementation with two interfering optical paths. As a
proof of concept, a fiber Bragg grating has been designed and fabricated,
showing the desired functionality in the transmission mode of the Bragg
grating. The proposed "Bragg-DLI" approach is applicable to any kind of Bragg
grating technology, such as volume Bragg gratings, dielectric mirrors, silicon
photonics, and other optical waveguide based Bragg structures.
