In this work, we present the design, laboratory tests, and the field trial results of a power-over-fiber (PoF) low power instrument transformer (LPIT) for voltage and current measurements in the medium voltage distribution networks. The new proposed design of this power-over-fiber LPIT aims to overcome the drawbacks presented by the previous technologies, such as the continuous operation (measuring and data transmission) for a wide current range conducted in the medium voltage transmission lines, damage due to lightning strikes, accuracy dependency on vibration, position and temperatures. The LPIT attends the accuracy criteria of IEC 61869-10 and IEC 61869-11 in terms of current and voltage accuracy and it attends the practical criteria adopted by Utilities companies including voltage measurements without removing the coating of the covered conductors. The PoF based LPIT was developed to be applied at 11.9 kV, 13.8 kV, and 23.0 kV phase-to-phase nominal voltages, and in two current ranges 1.25–30 A and 37.5–900 A. The digital data transmission of current, voltage, and temperature from the sensing unit to the processing unit uses a special synchronism technique and it is performed by two 62.5 µm multimode fibers in 850 nm. The optical powering in 976 nm is also performed by one 62.5 µm multimode fiber from the processing unit to the sensor unit. We presented all details of the sensor design and its laboratory characterization in terms of accuracy and temperature correction. We also presented the results of field tests of the sensor made in two different conditions: in a standard distribution network and an experimental hybrid fiber/power distribution network. We believe that these studies aim to incorporate optical fiber and devices, digital technologies, communications systems in electrical systems driving their evolution.

In this work we proposed a sealing method of fiber Bragg grating (FBG) in pressure sensors using electroless nickel-plating. The sensor is designed to be used in harsh environments of thermoelectric power plant engines. In order to be applied in the engine injector nozzle the FBG has just a single attached point in the pressure sensor and the combustion chamber pressure will freely compress the FBG. The fixation material used to seal the FBG in the pressure sensor is the key for the sensor performance considering the engine environment used in thermoelectric power plant. Typical level of pressure in the engine monitoring point is around 200 bar and the temperature exceed 300 °C. We detailed the method of fabrication and the characteristics of this method. Next the FBG pressure sensors using electroless nickel-plating sealing were studied and submitted to laboratorial and field trial evaluation. In addition, we evaluated the signal characteristics of the FBG pressure sensor and we compared it with a standard pressure sensor used in this application.

The distributed gain of single- and dual-wavelength-pumped thulium-doped fiber amplifiers is modeled. The excellent agreement between the model and coherent optical frequency domain reflectometry measurements enables us to estimate intrinsic loss, branching ratios of fluorescence originating from the ${{}^{3}H}_4$ level, and cross sections of upconversion pumping at 1050 and 1410 nm for the ${\mathrm{Tm}}^{3+}$ ions in the fiber. With the branching ratios obtained it is possible to describe induced signal absorption when pumping at 800 nm.

In this work, we described a study of the influence of dynamical temperatures on pressure measurements in two different packaging types used in FBG pressure sensors. We developed these sensors to measure internal combustion pressure in closed-loop control of thermoelectric engines. The packaging techniques development considered the available monitoring points in the thermoelectric engine and the harsh environment of the monitoring points. In a monitoring point, the temperature can exceed 300 °C and the pressure can reach 250 bar. We detailed the use of single-ended and double-ended FBG fixation methods as packaging techniques. The FBG pressure sensors using these techniques were tested in the laboratory and a thermoelectric engine. The results demonstrated that the dynamical behavior of the high-temperature gas originated from the combustion chamber affects the dynamical pressure measurements performed by the single-ended FBG pressure sensors when they were exposed to the hot gas. This effect can be suppressed by using a double-ended FBG pressure sensor mainly due to its packaging method. Its signal shape is comparable to a reference sensor used in the same condition became this FBG packaging solution the most suitable to use in the closed-loop control of thermoelectric engines.