T. Erdogan, ‘Fiber Grating Spectra,’ J. Lightwave Technol., vol.15, No.8, pp.1277-
The example demonstrates a sampled grating exhibiting periodic superstructure. The
superstructure is a collection of 99 identical gratings and phase shift blocks. The
gratings are uniform and have a uniform average index.
The main result is the multi-peak, periodic superstructure of the reflected power
spectrum. If the phase shift blocks were replaced by the gratings, thus producing a
single uniform grating, the resulting spectrum would have a well-known single-lobe
shape (with ripples due to the grating uniformity). That single-lobe spectrum would be
much narrower than the superstructure spectrum.