Initial results on the fabrication of long-period fiber Bragg gratings with a CO₂ laser

Abstract

Long-period fiber Bragg gratings (LPG) where the grating period is much longer than the wavelength of light have many unique characteristics and find uses in gain-flattening filters and mode converters. This paper describes the characteristics of the initial LPGs fabricated at the University of Adelaide using an infrared CO2 laser. The optical system implemented promotes uniform irradiation of the full circumference of the fiber, avoiding many of the non-uniformities, associated with a single sided system. Some initial gratings have been made using this method, which typically show an attenuation of 10dB within a wavelength range (FWHM) of 8 nm. Work is now focused on improving these devices through an understanding of the writing process and its effect on the transmitted spectrum.