Formation of thermally stable chemical composition gratings in optical fibers

Thermal Evaluation of Fiber Bragg Gratings at Extreme Temperatures

“…Throughout this work many similarities to the work of Fokine were observed including the formation O-CCGs [8], similar ratios of decay rate to heat rate in formation of O-CCGs [4], and similar gratings decay behavior [4,5]. However we saw a trend of shifting to longer wavelengths at high temperatures whereas he indicated a shift to shorter wavelength [2].…”

“…They are described by Fokine as a modulation of the chemical composition in the core of an optical fiber [8]. The thermal stability of the original photoinduced gratings is likely limited by the thermal stability of the induced birefringence whereas the thermal stability of the O-CCG is "limited by the fringe-to-fringe diffusion of the modulated concentration of … dopants [5]. "…”

“…The survivability of FBGs up to and above 1000°C has generated interest [4,5], but their per-formance and long term survivability at these temperatures is not well published. This paper looks at, in great detail, the performance and long term survivability of FBGs up to 1000°C through more than 700 hours of thermal cycling and over 400 hours of continuous operation.…”

Regenerated Fibre Bragg Gratings

“…For a general review on photosensitivity and grating types, see [Canning 2008a]. Another variant with superior high temperature stability is the so-called "chemical composition grating (CCG)" [Fokine 2002] where a periodic index modulation can be regenerated after erasure of the UV induced type-I grating written in H-loaded germanosilicate fibre, which happens to contain fluorine, if annealed ~1000°C. The prediction was a local reduction, or increase, of fluorine in the UV-exposed zones at that high temperature through diffusion of hydrogen fluoride.…”

Improvement of transparency and durability to deep ultraviolet light in fluorine-doped silica glass fiber by optimizing the preform fabrication process

“…7),8) However, the fiber still had absorption band derived from some defects such as ODC, which are absent for the pre-processed core material. It is also known that fluorine in silica glass is easy to diffuse by thermal processes especially in wet atmosphere, 9) such as fiberpreform-fabrication and fiber-or tube-making processes. In this work, we report that we have developed a preform-fabrication technique to maintain maximum advantage of characteristics of the fluorine-doped silica glass.…”