Evolution of Optical Fiber Temperature during Fiber Bragg Grating Fabrication Using KrF Excimer Laser

Abstract

The temperature distribution in an optical fiber during the fabrication of fiber Bragg gratings (FBGs) using a KrF excimer laser with a phase mask has been analyzed experimentally for typical fabrication conditions. The fluence of UV laser light at the fiber surface has been varied up to 420 mJ/cm 2. These experiments show that (1) scanning electron microscope (SEM) images of the fiber surface facing the excimer laser beam reveal partial physical damage apparently owing to partial melting, so that the surface temperature has increased beyond the softening point of silica glass, which is approximately 1200 C, (2) the optical spectrum transmitted through the FBG during laser irradiation contains spikes coincident in time with the laser pulses that correspond to a near instantaneous shift of the FBG spectrum to a higher temperature spectrum representing fiber core heating of approximately 8 C, and (3) analysis of the energy absorbed by the fiber indicates a bulk temperature rise of approximately 3 C in the fiber. The resulting large variation in the temperature rise over the fiber cross section from a few C to 1200 C, along with partial physical damage on the surface, will certainly induce large internal stresses in the fiber material and reduce the mechanical strength of the FBG.

Wavelength Evolution of Fiber Bragg Gratings Fabricated From Hydrogen-Loaded Optical Fiber During Annealing

“…The growth of the grating during this stage, i.e., the increase of , of course, raises background value by the averaged amount of the modulation, but its magnitude is much smaller than the decrease of caused by the depletion, probably by the magnitude of the ratio to in Table I which is ; hence, the shift of the wavelength to shorter values is to be expected. Unlike this expectation, however, we observe a shift to longer wavelengths by the amount of 0.08 nm momentarily, coincident in time with laser pulse in SP-FBGs, which is caused, we believe, by the temperature increase of the fiber heated by the UV laser pulse [19]. The LP-FBG also did not show the shift.…”

Growth and Properties of Core‐Shelled SiC–SiO2 Nanowires Using Chemical Vapor Deposition

“…It is noted that the softening point of SiO 2 is 1100-12001C. 28 Also, the addition of oxides often leads to reduced T g . 29 Therefore, it is thought that the presence of Fe and/or FeSi particles inside the SiO 2 would help to reduce the softening point.…”

Effect of Spherical Aberration on Fabrication of Fiber Bragg Gratings

“…1. 2) The excimer laser (Lamda Physik, COMPex-102) delivers up to 240 mJ/pulse at 248 nm with a pulse width of 25 ns at repetition rates of 1-20 Hz. The 8 Â 24 mm 2 rectangular output beam is shaped by a 7 Â 7 mm 2 stop to select a higher quality uniform portion of the beam.…”