Thermal decay of fiber Bragg gratings written in boron and germanium codoped silica fiber

Regenerated Fibre Bragg Gratings

“…An approximation of the expected lifetime of a material is often extrapolated from an Arrhenius fit of the rate constant k = 1/τ where k = Aexp(-E a /RT). Using similar parameters to those applied in previous work (Inglis 1997;Baker et al 1997), an estimate of the 3dB lifetime at each temperature for a grating stabilised at 745°C can be obtained, as shown in Figure 4. Although the lifetime falls of rapidly with temperature, these are extremely remarkable results -a grating operating continuously at 400°C can be expected to last for ~10 years, whilst at 350°C >500 years and at 300°C >300,000 years.…”

“…It also implies that the thermal processing history and the quenching rate can play a critical role in determining the final index change of the glass. Stretched exponential fits have been successfully used, for example, to determine the aging process of UV-induced periodic changes in glass that make up a fibre Bragg grating [Baker et al 1997;Inglis 1997]. However, the success of this approach belies the fact that a comprehensive understanding of glass and glassy materials, as a result of the huge distribution of processes in materials that are not governed by an overwhelming and simple periodicity, remains one of the greatest challenges in condensed matter physics.…”

Continuous anneal method for characterizing the thermal stability of ultraviolet Bragg gratings

“…However, problems arise in obtaining satisfying fits for gratings written in hydrogen loaded fibers. 4,5,[10][11][12] We present here a novel continuous isochronal anneal method to obtain the aging curve. The procedure was inspired by Redhead.…”

“…Both step isochronal 1-3 and isothermal anneals [4][5][6][7] have been applied. Accelerated aging has been used to predict the long-term behavior at the designated operating temperature from the short-term behavior at elevated temperatures.…”

Distributed High Temperature Sensing Using Fiber Bragg Gratings

“…From the figure, we can see that the coefficient of temperature-induced spectral shift is about 13.5 pm= C. Fiber Bragg gratings may be used as distributed temperature sensors by cascading several gratings with different Bragg wavelengths. However, when the fiber is exposed to high temperatures, the reflectivity of the grating decreases as some of the defects contributing to the UV-induced index changes are transformed to their original state (Baker et al 1997). We have experimentally verified that the gratings inscribed in B-Ge doped fibers will erase completely at 900…”