Simultaneous measurement of strain and temperature using Bragg gratings written in germanosilicate and boron-codoped germanosilicate fibers

Cavaleiro, P.M.; Araújo, F. M.; Ferreira, L. A.; Santos, J. L.; Farahi, Faramarz

doi:10.1109/68.806871

Cited by 132 publications

(65 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This is higher than values reported for other germanosilicate fiber where dλ Β /dε =7 × 10 -4 nm/µε at lower temperatures [17], though it is consistent with other work in similar B doped (softened) germanosilicate fiber [20]. For two types of regenerated gratings, the response of λ Β are commensurate: dλ Β reg /dε = (9.61 ± 0.16) × 10 -4 nm/µε and dλ Β anneal /dε = (9.62 ± 0.23) × 10 -4 nm/µε.…”

contrasting

confidence: 53%

Temperature and strain characterization of regenerated gratings

et al. 2013

View full text Add to dashboard Cite

Received Month X, XXXX; revised Month X, XXXX; accepted Month X, XXXX; posted Month X, XXXX (Doc. ID XXXXX); published Month X, XXXX Both temperature and strain characterization of seed and regenerated gratings with and without post-annealing is reported. The high temperature regeneration has significant impact to thermal characterization and mechanical strength of gratings whilst the post annealing has little effect. The observed difference is evidence of viscoelastic changes in glass structure.OCIS Codes: 060.3735, 060.2310Codes: 060.3735, 060. , 060.2370 , and used to measure exhaust temperatures from diesel train turbines [7]. In this letter, the temperature and strain properties of regenerated gratings are characterized. Regeneration involves a greater physical contribution through structural relaxation at areas where stresses are altered in the presence of hydrogen, which simply by being present acts to reduce tensile stresses across the core and cladding and between processed regions -a recent review reveals new insight in this regard [8]. The local relaxation differs between areas of high and low laser exposure during fabrication of the seed grating. Hydride and hydroxyl formation helps to accentuate this difference, which leads to stronger grating writing as well as altering stresses [9], and therefore local pressures, periodically.Bragg gratings were inscribed in B-codoped germanosilicate fiber ([GeO2] ~ 33 mol%; [B2O3] ~ 12 mol %) by direct writing through a 10mm optical phase mask using an ArF laser (λ = 193 nm; pulse fluence: fpulse = 95 mJ/cm 2 ; cumulative fluence fcum = 113 J/cm 2 ; RR = 30 Hz; pulse duration τw = 15 ns).Before grating writing, the fiber was hydrogen (H2) loaded (T = 80 °C , P = 180 bar, t = 4 days), avoiding type In formation [10]. For regeneration, two groups of seed gratings were fabricated -Group (1): regenerated gratings, and Group (2): regenerated gratings subjected to post-annealing at 1100 °C. The typical initial spectra with both reflection, R, and transmission, Tr, of the seed gratings are shown in Fig. 1. A high-temperature heater was used for annealing the gratings and temperature monitored with a type K thermocouple. The thermal processing recipe is shown in Fig. 2 along with the grating reflection strengths (normalized to the initial seed grating). The temperature rose to T = 850 °C over t = 60 min before dwelling for t = 40 min. Over this period, the grating decays completely before regenerating and saturating at a peak reflection. At the beginning of the thermal process, a growth in the reflectivity is observed indicating an annealing out of a negative contribution, possibly arising from stress, early on has occurred, reminiscent of behavior observed with type In (type IIA) formation and annealing. For Group (2) gratings, additional annealing (T = 1100 °C, t = 20 min) was undertaken to stabilise the regeneration process for even higher temperature operation, shown in Fig. 2. The strength of the grating decays further before stabilizing. Fig.1 shows the final spec...

show abstract

contrasting

confidence: 53%

Temperature and strain characterization of regenerated gratings

et al. 2013

View full text Add to dashboard Cite

show abstract

“…This paper Single TFBG [3] 2 Co-located FBGs [4] 2 FBGs in fibres of different dopants [5] 2 In summary, a new approach to discriminating between the temperature and strain responses of FBG sensors has been demonstrated. The technique requires the use of a single FBG, tracking features that lie within the same spectral range, and does not require special processing or packaging of the fibre.…”

Section: Reference Number Sensor Systemmentioning

confidence: 99%

“…Appropriate packaging can ensure that one of the sensors is shielded from one of the measurands [2]. FBGs with inherently different sensitivities may be used, for example, FBGs with different centre wavelengths [3], FBGs written in fibres of different composition [4] or with different diameters [5], or FBGs fabricated under different conditions [6,7]. Alternatively, the measurement from an FBG may be combined with that of a different sensing technique, for example, measuring the fluorescence lifetime of ions in doped optical fibre [8] or stimulated Brillouin scattering [9].…”

mentioning

confidence: 99%

Temperature and strain discrimination using a single tilted fibre Bragg grating

Chehura

James

Tatam

2007

Optics Communications

120

View full text Add to dashboard Cite

A fibre optic sensor capable of discriminating between temperature and strain, using a single fibre Bragg grating, is presented. The technique exploits the core-cladding mode coupling of a tilted fibre Bragg grating (TFBG). The core and cladding modes exhibit different thermal sensivities, while the strain sensivities are approximately equal. Monitoring the core-core mode coupling resonance and the core-cladding mode coupling resonance of the TFBG spectrum allows the separation of the temperature and strain induced wavelength shifts.

show abstract

“…The difficulty lies on that most FBGs present similar optical properties from device to device. Measures have to be taken to bring the diversity and there have been reports of using FBGs with different characteristics, by employing the different ratios of the strain response to the temperature response of each FBG [1][2][3], however, the ratio differences have been generally low. Long period gratings (LPGs) are another suitable solution for such a purpose since they are very sensitive to temperature but not to strain.…”

Section: Introductionmentioning

confidence: 99%