The detection of the state of polarization (SOP) of light is essential for many optical applications. However, cost-effective SOP measurement is a challenge due to the complexity of conventional methods and the poor transferability of new methods. We propose a straightforward, low-cost, and portable SOP measurement system based on the multimode fiber speckle. A convolutional neural network is utilized to establish the mapping relationship between speckle and Stokes parameters. The lowest root-mean-square error of the estimated SOP on the Poincaré sphere can be 0.0042. This method is distinguished by its low cost, clear structure, and applicability to different wavelengths with high precision. The proposed method is of great value in polarization-related applications.
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.
KEYWORDS: Signal to noise ratio, Signal processing, Electronic filtering, Optical fibers, Raman scattering, Temperature sensors, Spatial resolution, Fiber optics sensors, Fusion splicing, Temperature metrology, Reflectometry
We demonstrate a distributed temperature sensor based on quasi-single mode (QSM) Raman scattering in few mode fibers (FMFs). The FMF allows much larger input pump power before the initiate of stimulated Raman scattering compared with the standard single mode fiber (SSMF) and mitigates the detrimental differential mode group delay (DMGD) existing in the conventional multimode fiber (MMF) based Raman distributed temperature sensor (RDTS). Distributed temperature sensing is realized using conventional RDTS hardware over 20km FMFs within 90s, with a spatial resolution of 3m. The temperature resolution is 2.3°C @10km and 6.7°C @20km, respectively.
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