Are fiber Bragg gratings used in pairs

The first in-fiber Bragg grating was demonstrated by Ken Hill in 1978. Initially, the gratings were fabricated using a visible laser propagating along the fiber core. In 1989, Gerald Meltz and colleagues demonstrate. [pdf]

Fabrication of Planar Array Waveguide Gratings

1 × 8 and 1 × 16 traditional/saddle arrayed waveguide grating (AWG) devices with different core layer materials applied in fiber Bragg grating (FBG) system were designed, fabricated and compared. We ap. [pdf]