Page 50 - Fiber Bragg Gratings
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2A. Photosensitization techniques 31
Figure 2.8: The refractive index profile of a 2.8% hydrogen-soaked standard
fiber, before and after UV exposure with pulsed radiation at 248 nm (Courtesy
P. Lemaire from: Lemaire P. J., Vengsarkar A. M., Reed W. A., and Mizarhi V.,
"Refractive index changes in optical fibers sensitized with molecular hydrogen,"
in Technical Digest ofConf. on Opt. Fiber Commun., OFC'94, pp. 47-48, 1994.)
as does the 400-nm luminescence [69]. Martin et al. [69] have found a
direct correlation between refractive index change increase and lumines-
cence. Figure 2.9 shows the transmission spectra of two gratings in hydro-
genated standard fiber at different stages of growth, with the UV radiation
at 244 nm CW switched on and off. With the UV switched on, the Bragg
Figure 2.9: Shift in the Bragg wavelength as the UV radiation is switched
on and off for two different strength gratings (after Ref. [70]).
