Abstract

In 1978, Hill et al.¹ observed that subjecting optical fibers to illumination with green light from an Ar⁺ ion laser for approximately ten minutes could establish a grating along the fiber core. Reflectivities as high as 90% were achieved, with a bandwidth of approximately 200 MHz. In spite of considerable effort,^2,3 no explanation of why these gratings are formed has yet been given. Only recently was it reported⁴ that these gratings could be formed in any fiber other than the one used in the original experiments by Hill. The use of these fibers as narrow-band reflection filters in various applications has been discussed in the literature.⁵ However, the work reported here was prompted by an article proposing that optical-fiber gratings would exhibit large negative group-velocity dispersion (GVD) in the vicinity of the wavelength used to create the grating.⁶ The obvious advantage of this would be the possibility of pulse compression in the visible wavelength region in an optical fiber without having to use an external grating pair. The negative GVD would also make it possible to produce "visible solitons."

© 1988 Optical Society of America