Inverse scattering algorithm for reconstructing lossy fiber Bragg gratings

source: ยฉ 2004 Optical Society of America

We demonstrate an inverse scattering algorithm for reconstructing the structure of lossy fiber Bragg gratings. The algorithm enables us to extract the profiles of the refractive index and the loss coefficient along the grating from the grating transmission spectrum and from the reflection spectra, measured from both sides of the grating. Such an algorithm can be used to develop novel distributed evanescent-wave fiber Bragg sensors that measure the change in both the refractive index and the attenuation coefficient of the medium surrounding the grating. The algorithm can also be used to analyze and to design fiber Bragg gratings written in fiber amplifiers. A novel method to overcome instability problems in extracting the parameters of the lossy grating is introduced. The new method also makes it possible to reduce the spectral resolution needed to accurately extract the grating parameters. [Read more…]

Fig. 1 Reconstruction of a grating with a chirped Gaussian coupling coefficient, ๐‘ž(๐‘ง)=600 exp[โˆ’105(๐‘งโˆ’๐ฟ/2)2(2.5+20๐‘–)] mโˆ’1 and with a sinusoidal loss profile ๐›ผ=70[1โˆ’cos(10๐œ‹๐‘ง/๐ฟ)] mโˆ’1 written in the region [0, L=1 cm]. The reconstructed parameters (solid curves) are compared with the original parameters (dashed curves). The reflection spectra, obtained from both sides of the grating, and the transmission spectrum were sampled over a bandwidth of 10 nm with a spectral resolution of 0.02 nm.

Amir Rosenthal and Moshe Horowitz, “Inverse scattering algorithm for reconstructing lossy fiber Bragg gratings,” J. Opt. Soc. Am. A 21, 552-560 (2004)