On the application of coupled mode theory for modeling fiber Bragg gratings

We remove some ambiguities associated with the coupled mode description of light propagation in fiber Bragg gratings (FBC´s). We show, in particular, that different methods employed in the literature lead to physically distinct results. The significant distinctions are discussed both for interferometric systems and intensity-only spectral measurements. Analysis of the reflection spectrum of a suitably designed double-grating structure is shown to result in a novel form of spectral hole, similar to the well-known effect derived from discontinuous phase gratings.