The integration of fiber Bragg grating (FBG) sensors in lithium-ion cells for in-situ and in-operando temperature monitoring is presented herein. The measuring of internal and external temperature variations was performed through four FBG sensors during galvanostatic cycling at C-rates ranging from 1C to 8C. The FBG sensors were placed both outside and inside the cell, located in the center of the electrochemically active area and at the tab-electrode connection. The internal sensors recorded temperature variations of 4.0 ± 0.1 °C at 5C and 4.7 ± 0.1 °C at 8C at the center of the active area, and 3.9 ± 0.1 °C at 5C and 4.0 ± 0.1 °C at 8C at the tab-electrode connection, respectively. This study is intended to contribute to detection of a temperature gradient in real time inside a cell, which can determine possible damage in the battery performance when it operates under normal and abnormal operating conditions, as well as to demonstrate the technical feasibility of the integration of in-operando microsensors inside Li-ion cells.

We report the inscription of a Bragg grating in an undoped polymethylmethacrylate based microstructured fiber in a time record. The fiber has been irradiated with a 248 nm ultraviolet radiation, through the phase mask technique using low fluence and low repetition rate. The experimental conditions were chosen to modify the core refractive index of the fiber at the incubation regime and avoiding polymer ablation. The peak reflection of the Bragg grating was centered in the infrared region with 20 dB reflection and 0.16 nm bandwidth. These spectral properties are well attractive for sensors and communications applications.

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International audienceThis paper analyzes the performance of two implementations of J-Flow, the flow measurement tool deployed on most Juniper routers. Our work relies on both controlled experiments and analysis of traces collected at Abilene and GEANT, which provide most of the flow traces used in the research community. We uncover two measurement artifacts in J-Flow traces: a periodic pattern and measurement gaps. We investigate routers’ features that trigger these artifacts and show their impact on applications that use flow traces

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We report the development of an optical fiber sensor capable of simultaneously measuring strain, temperature and refractive index. The sensor is based on the combination of two fiber Bragg gratings written in a standard singlemode fiber, one in an untapered region and another in a tapered region, spliced to a nocore fiber. The possibility of simultaneously measuring three parameters relies on the different sensitivity responses of each part of the sensor. The results have shown the possibility of measuring three parameters simultaneously with a resolution of 3.77 με, 1.36 °C and 5 × 10 −4 , respectively for strain, temperature and refractive index. On top of the multiparameter ability, the simple production and combination of all the parts involved on this opticalfiberbased sensor is an attractive feature for several sensing applications.

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