Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
Search results
97 records were found.
This paper describes the first demonstration of increasing the dynamic range of Brillouin-based distributed temperature sensor at 1533 nm using Raman amplification provided by a 1450 nm pump source.
We demonstrate a high spatial resolution single-ended spontaneous Brillouin-based distributed temperature sensor for a 500m length of single-mode silica fibre. Using a short pulsewidth laser source at 1.5μm, measurements down to a spatial resolution of 20cm and temperature resolution of 4.4°C were achieved.
We report for the first time a diode pumped electro-optically Q-switched and mode-locked Erbium doped fibre laser. Simultaneous Q-switching and mode-locking produces 4 ns pulses of 540 Watts peak power in a 20 ns Q-switched envelope.
The Landau Placzek ratio method for distributed fibre optic temperature sensing is based on the ratio of the Rayleigh and Brillouin backscattered light. However, because of the coherent nature of Rayleigh scattering. use of the same narrow bandwidth source as required for the Brillouin signal results in significant coherent noise in the Rayleigh signal. A novel technique is demonstrated whereby the amplified spontaneous emission noise and amplifying properties of an erbium doped fibre amplifier may be exploited to reduce the coherent noise on the Rayleigh backscatter signal. This results in a significant improvement in both temperature and spatial resolution over previously reported results.
It is shown experimentally that the ratio of the intensities of Rayleigh and Brillouin backscattered light (Landau Placzek ratio) in an optical fibre has a temperature dependence which may be used for the basis of a distributed temperature sensor. This result, combined with the known frequency dependence of be Brillouin backscattering on temperature and strain, indicates that spontaneous Brillouin backscatter may be used for the unique determination of either temperature or strain in a distributed optical fibre sensing system.
Measurements of Brillouin scattering coherence length using a fibre Mach-Zehnder interferometer are presented. It is shown experimentally that the SBS lineshape narrows as the Brillouin pump power is increased from below to above threshold and that the coherence length approaches a limiting value.
We demonstrate a scheme which allows for temperature-corrected distributed strain measurements with improved spatial and strain resolutions and reduced data collection time. The technique utilizes the combination of frequency-based Brillouin optical correlation domain analysis with Brillouin intensity measurements for a fully temperature-compensated strain sensor with a strain resolution of 56 µe and spatial and temperature resolutions of 10 cms and 0.95 °C
We experimentally examine the validity of previous assumptions that the Brillouin coefficients describing the variation of the power of the spontaneous Brillouin and its frequency shift with respect to either strain or temperature are independent of the other parameter
We propose and demonstrate a scheme which utilizes the temperature dependence of spontaneous Raman scattering to provide temperature compensation for a sub-metre spatial resolution Brillouin frequency based strain sensor. Temperature compensated strain sensor measurements have been demonstrated with a strain resolution of 94uå and a spatial resolution of 10cms. This paper describes the combination of Brillouin frequency based BOCDA technique [1] with an independent measurement of temperature, based on the determination of the intensity of the anti-Stokes Raman scattering (R-OTDR) with very much higher spatial resolution than previously reported [2], in order to produce a fully temperature compensated strain sensor with high spatial resolution.
We demonstrate a scheme which allows for temperature corrected distributed strain measurements under environments involving simultaneous application of strain and temperature, with enhanced spatial (5 cms), strain (66με) and temperature resolutions (1.9°C). The technique utilizes the combination of frequency based BOCDA with Brillouin intensity measurements.
