We present a previously unknown equivalence relationship between the spectr
al transfer functions of arrayed-waveguide gratings and fiber Bragg grating
s (FBGs). We find that both devices can be characterized using a functional
ly identical Fourier transform (FT) integral; the single difference being t
hat the FT lies within a simple hyperbolic function for the FBG case. Thus,
the mode of operation of one device informs and yields insights into the o
peration of the other device.