Employing the multiple spatially independent channels offered by multicore fiber (MCF), spatial-division multiplexed (SDM) hybrid Raman and Brillouin distributed sensor has been demonstrated. The interrogation of Raman and Brillouin scattering are performed in distinct cores of the MCF, allowing for flexible management of the input powers between each of them, which is actually incompatible in hybrid Raman/Brillouin distributed system using single mode fibers (SMFs) due to the limitation of nonlinear effects. The proposed SDM system employs shared devices to generate pump pulse, but separate interrogation fiber channels. The combination of Raman and Brillouin sensing provides the capability of discriminative measurement between temperature and strain.
In this paper we demonstrate distributed shape sensing based on stimulated Brillouin scattering in a multi-core fiber (MCF). Brillouin optical time-domain analysis with differential pulse-width pairs is implemented to measure the local tangential strain-induced variation of the Brillouin frequency shift along different cores of the fiber. Employing the differential strain measured in multiple off-center cores in the MCF, distributed profiles of both bending angle and fiber curvature are parametrically retrieved. The paper presents the first demonstration of distributed bending sensing, providing the cornerstone to further develop the system into a fully distributed 3D shape sensor.
KEYWORDS: Digital signal processing, Channel projecting optics, Polarization, Signal processing, Optical amplifiers, Optical fibers, Signal detection, Orthogonal frequency division multiplexing, Spatial resolution, Single mode fibers
A novel Brillouin optical time-domain analysis (BOTDA) system is demonstrated using intensity-modulated optical orthogonal frequency division multiplexing probe signal and direct detection (IM-DD-OOFDM) for stimulated Brillouin spectrum (SBS) measurement without frequency sweep operation. The SBS is reconstructed by channel estimation algorithm and Brillouin frequency shift (BFS) is located by curve fitting. The IM-DD-OOFDM BOTDA is demonstrated experimentally with 25m spatial resolution over 2 km standard single mode fiber.
Nowadays, 3D measurement and re-construction technologies are widely used not only in industry area, but also in the appreciation and research of ancient architecture and historical relics. Many methods are used for the architecture measurement in large scale, but as for the details of architecture or precision historical relics, these methods meet difficulties. Thus, historical relic objects with specular surface or complex sculptural surface could not be measured by traditional method. Focusing on these problems, this paper proposed 3D measurement technique which contains two levels of measurement. Firstly, when measuring ancient architecture in large scale, laser scanning and photometry methods are used. Then, when measuring details of architecture, a fast and adaptive 3D measurement system is used. Multi-view registration is also used for the measurement of hollowed-out structure of sculptural relics. The experiments indicate that the system can achieve 3D measurement and re-construction of different types of ancient architecture and historical relics.
A fiber-optic methane gas sensor system is proposed and demonstrated with accurate gas concentration measurement
with a sensitivity of ~410ppm. We employ the polarization-maintaining photonic crystal fiber (PM-PCF) based Sagnac
loop filter to slice the spectrum of broadband light source so as to precisely match multiple absorption lines of the
methane gas. Meanwhile, a compact gas cell with multiple reflections is designed to enhance the interaction between
methane gas and the light beam. The proposed gas sensor is verified as low cost, temperature-insensitive, and high
sensitivity.
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