We propose a new method for introducing a chirp on a fiber Bragg grating. Uniformly written fiber Bragg gratings are linearly chirped through the use of a controllable temperature gradient device. This device allows the linear chirp conditions to be totally adjustable in a nondestructive repeatable manner. These conditions can be selected with great precision and are very stable, once defined. To characterize the resulting chirped gratings, we have measured their dispersion. Dispersion of the order of 200 ps/nm have been obtained for 1-cm-long fiber Bragg gratings with temperature gradients near 20 degrees C.

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Recycling of hydrogen at a neutralizer plate in a tokamak divertor is considered, with particular emphasis on the effects of multistep atomic processes and photoexcitation by the resonant Lyman α line. These effects are shown to be significant for parameters relevant to International Thermonuclear ExperimentaL Reactor (ITER) [S. A. Cohen et al., J. Nucl. Mater. 176&177, 909 (1990)].

We propose a theoretical investigation of the length and coupling profile of a linearly chirped fiber Bragg grating for maximum dispersion compensation in a repeaterless optical communication system. The system consists of 100 km of standard optical fiber in which a 1550-nm signal, directly modulated at 2.5 Gbits/s, is launched. We discuss the results obtained with 6-, 4.33-, and 1-cm-long linearly chirped fiber Bragg gratings having Gaussian and uniform coupling profiles. We numerically show that a 4.33-cm-long chirped fiber Bragg grating having a uniform coupling profile is capable of compensating efficiently for the dispersion of our optical communication system.