Fiber-optic sensing technology is best adapted to health monitoring and evaluation of power grids because of its immunity of electromagnetic interference, capabilities of multiplexing and distributed sensing, and tolerance to harsh environments. We review key fiber-optic sensing technologies, including fiber Bragg gratings, fiber-optic interferometers, optical time domain reflectometries, and their applications in three main parts of power grids, transformers, power towers, and overhead transmission lines, during the past 20 years. In particular, optical fiber composite overhead ground wire and optical phase conductor applied in power grids are the areas of great potential to go further. The perspectives of an intelligent fault diagnosis subsystem for power grids based on a fiber-optic sensing network are discussed, and related on-going work is described. The review shall be of benefit to both engineers and researchers in power grids and fiber-optic sensing.
We report unique thermo-optical characteristics of DNA-Cetyl tri-methyl ammonium (DNA-CTMA) thin solid film with a large negative thermo-optical coefficient of -3.4×10-4/°C in the temperature range from 20°C to 70°C without any observable thermal hysteresis. By combining this thermo-optic DNA film and fiber optic multimode interference (MMI) device, we experimentally demonstrated a highly sensitive compact temperature sensor with a large spectral shift of 0.15 nm/°C. The fiber optic MMI device was a concatenated structure with single-mode fiber (SMF)-coreless silica fiber (CSF)-single mode fiber (SMF) and the DNA-CTMA film was deposited on the CSF. The spectral shifts of the device in experiments were compared with the beam propagation method, which showed a good agreement.
An ultrabroadband near-infrared (NIR) emission of Ni 2+ is demonstrated in a highly transparent nano-glass ceramic (nano-GC) containing Ga 2 O 3 nanocrystals with 808 nm excitation of Nd 3+. It is also shown that by adding Yb 3+ as an energy transfer (ET) bridge, the Ni 2+ emission could be substantially enhanced. The dopant distribution was studied using advanced analytical transmission electron microscopy. This, together with optical transmission measurements, steady-state and time-resolved emission spectra, is utilized to understand the underlying ET mechanisms between Nd 3+ , Yb 3+ , and Ni 2+. The feasibility of this device as a viable source is demonstrated using dual-laser pumping at 808 and 980 nm for the greatest Ni 2+ emission enhancement reported to date. The Nd 3+ /Yb 3+ /Ni 2+ triply doped nano-GC offers a promising gain medium for broadband and tunable NIR fiber amplifiers.
We propose a compact multi-parameter fibre sensing module based on a fibre Bragg grating (FBG) in single–multi–single mode fibre structure (FBG-in-SMS). We experimentally demonstrated that the FBG-in-SMS can measure temperature and strain simultaneously. In addition, we found that the process of writing FBG in SMS could be an effective technique for tuning and optimizing SMS spectrum for sensing.
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