Growth of long-period gratings in H₂-loaded fiber after 193-nm UV inscription

Abstract

This letter reports and provides an explanation for the growth behavior of long-period gratings in H 2 -loaded fiber immediately after 193-nm UV inscription. Growth of grating resonance peak by as much as 14 dB was measured. Impact of temperature and grating strength, immediately after UV inscription, on the growth behavior are also discussed.

Representations of multivalued groups on graphs

“…To perform the experiments an LPG was inscribed through the direct written methodology, using an amplitude mask and a 193 nm UV laser [22]. The length of the grating is l g = 40.0 mm, with a period = 427 μm, leading to an attenuation peak wavelength at λ m = 1556 nm.…”

“…The minimum transmission at this particular wavelength is given by the expression T m = 1 − sin 2 (κ m l g ), (2) where l g is the length of the LPG and κ m is the coupling coefficient for the mth cladding mode, which is determined by the overlap integral of the core and cladding modes and by the amplitude of the periodic modulation of the mode propagation constants [3]. The most used inscription techniques of LPGs are based on induced changes in the refractive index of the fiber core through electric discharge [5], exposure to 193 nm UV light [6] and 10.6 μm (CO 2 ) laser radiation [7]. Another technique uses the formation of microbends in the fiber through transversal pressure of the fiber axis [8].…”

Review of Fiber Optic Sensors for Structural Fire Engineering

“…Electric arc fabrication of an LPFG relies upon a combination of several different mechanisms to generate the periodic property modulation of the fiber. The mechanisms include the induction of microbend into the fiber [48], the periodic tapering of the fiber [49], the diffusion of dopants [50], ion implantation [51], and the relaxation of internal stresses [52]. The operating temperature range of such LPFGs has been demonstrated to be up to 800 °C without permanent modification of their properties [53], and, if annealed they may operate at temperatures up to 1190 °C [46].…”

Fabrication of long-period fiber gratings using low-pressure mercury lamp: Shortening of exposure time

“…7,8) To fabricate an LPG, an optical fiber is exposed to an ultraviolet laser beam through an amplitude mask with a periodic stripe pattern. A KrF excimer laser (248 nm), 1,[9][10][11] an ArF excimer laser (193 nm), 12) a frequency-doubled Ar + laser (244 nm), 13) and a frequency-quadrupled Nd 3+ :YAG laser (266 nm) 14) were used in the fabrication. Ion implantation 15) was also studied.…”