Fabrication and Temperature Characteristics of Thermal Regenerated Fiber Bragg Grating

High-Density Fiber Optical Sensor and Instrumentation for Gas Turbine Operation Condition Monitoring

“…From 1200 ∘ F to 1500 ∘ F, accompanying the fiber material structural transition, the FBG's reflected power has experienced a dramatic variation, and the Bragg resonant wavelength eventually stabilized at 1500 ∘ F, which is defined as a new maximum allowed temperature. Obviously, this fiber material morphology transition has resulted in an offset of Δ ∼ 80 ∘ F than real temperature, which is unacceptable for any machinery system control because of this material physical phenomenon if the FBG is operated up to 1500 ∘ F. It should be pointed out that the observed "dips" in the FBG's reflected power are more or less related to socalled grating regeneration process, similar to described in [2,5,13]. However, to guarantee a FBG sensor's accuracy and reliability, the maximum operation temperature is normally 10% less than its maximum allowed temperature.…”

“…Conventional Type-I FBG has been used in various infrastructural healthmonitoring applications [6,7]. However, this type of FBG has poor thermal survivability and accuracy degradation at relative elevated temperature of greater than 300 ∘ C. Research has shown that some Type-IIA, Type-II, regenerated FBGs (fabricated either by ultraviolet lasers or femtosecond lasers), and chiral gratings have also shown survivability even at 1000-1100 ∘ C [8][9][10][11][12][13]. With thermal stable FBGs, they can be used as temperature sensor.…”

“…FBG elements used in this work have used high-power ultraviolet (UV) laser with a phase mask technology for inscribing Bragg grating in a single-mode fiber core [12,13]. This forms a periodic mass density-modulated grating pattern that can be characterized by a Bragg resonant peak at…”

The use of optical coherence tomography envelope statistics to quantify local temperature changes in tissue-mimicking phantoms

“…where, ∆λ b is the shift in wavelength, p e is the strain-optic coefficient, is the strain, α Λ is the thermal expansion coefficient, α Π is the thermo-optic coefficient and ∆T is the change in temperature [30][31][32][33]. For a single mode fiber that contains a silica core doped in GeO2, the thermal [31,35]. When the grating is exposed to any change in temperature and/or strain, the grating spacing and the index of refraction is temporarily altered, until the environment is at room temperature and strain-less.…”

The use of optical coherence tomography envelope statistics to quantify local temperature changes in tissue-mimicking phantoms

“…where, ∆λ b is the shift in wavelength, p e is the strain-optic coefficient, is the strain, α Λ is the thermal expansion coefficient, α Π is the thermo-optic coefficient and ∆T is the change in temperature [30][31][32][33]. For a single mode fiber that contains a silica core doped in GeO2, the thermal [31,35]. When the grating is exposed to any change in temperature and/or strain, the grating spacing and the index of refraction is temporarily altered, until the environment is at room temperature and strain-less.…”