@INPROCEEDINGS {1669,
author={M. J. N. Lima and A. Teixeira and P.S André and R. F. Rocha and O. Frazão},
doi={},
booktitle={International Microwave and Optics Conf.},
title={Fiber Bragg gratings with variable negative mean index change},
year={2003},
month={September},
volume={-},
pages={---} 
}