Regenerated gratings

Abstract

Strong regenerated gratings with a maximum grating strength exceeding (40-50) dB are fabricated inside an optical fibre by bulk macro thermal processing ∼ 900˚C using a UV-laser seeded Bragg grating. Further annealing between 1000˚C and 1100˚C leads to a stabilised grating ∼ 18 dB in strength. This suffers no further degradation at 1100˚C for the period monitored, over 4 hours. The potential resolution of this process is demonstrated by regenerating two complex profiles. Phase information is retained between seed and regenerated structures. This opens the way for nano-engineering of materials using thermal processing and seed templates.

Effects of doping concentrations on the regeneration of Bragg gratings in hydrogen loaded optical fibers

“…It was reported that RBGs formed in Er 3+ codoped optical fibers can sustain high temperature up to 800°C without reduction of reflection [13]. Canning et al demonstrated that RBGs formed in Boron codoped optical fibers can sustain temperature more than 1000°C without significant grating degradation [14][15][16]. They proposed that glass structural transformation rather than the diffusive interpretation is an efficient alternative approach for the formation of RBGs because of the relaxation of high internal pressures in the hightemperature process.…”

“…It was shown that fluorine is not necessary and the diffusion of hydroxyl group through the reaction and formation of molecular water could produce a grating as periodic modulation of oxygen. Recently RBGs were also demonstrated in Er 3+ -or boron-codoped germanosilicate optical fibers and highly photosensitive germanium doped fibers [13][14][15][16]. It was reported that RBGs formed in Er 3+ codoped optical fibers can sustain high temperature up to 800°C without reduction of reflection [13].…”

“…The proposed highly thermal stable gratings include type-II gratings formed with single excimer pulses [6,7] or femtosecond laser pulses [8,9], and the regenerated Bragg gratings (RBGs) (i.e. gratings regenerated by using an annealing process after the erasure of the seed gratings) [10][11][12][13][14][15][16]. Compared with type-II gratings, RBGs are more attractive because they are essentially formed from the Type-I "seed" gratings by using conventional grating fabrication process and have superior thermal stability sustainable in high temperature more than 1000°C.…”

“…compactness, high sensitivity, multiplexing and self-reference capabilities [1][2][3]. In recent years, thermal stability enhanced FBGs attracted a lot of attention because of their promising applications as high-temperature sensors [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The proposed highly thermal stable gratings include type-II gratings formed with single excimer pulses [6,7] or femtosecond laser pulses [8,9], and the regenerated Bragg gratings (RBGs) (i.e.…”

Combining regenerated gratings and optical fibre Fabry-Pérot cavities for dual sensing of ultra-high temperature and strain

“…In the past few years, the field of regenerated fibre Bragg gratings (FBGs) has been the subject of intense research activity as this member of the FBG family continues to prove itself as a versatile choice when ultrahigh temperature performance is required [1][2][3][4]. The remarkable stability at extreme temperatures means that regenerated gratings are now finding applications in a wide variety of sensing applications such as diesel locomotive engine temperature regulation [5], assessment of fire damage to concrete building structures [6] and dual pressure/temperature sensing of gas turbines [7].…”