This paper proposes and investigates a partial discharge (PD) detector based on fiber Bragg grating (FBG) sensor and a mandrel to detect and localize PD in power transformers. An identification of PD in the early stages is important, so using high-resolution sensor is considerable. A Teflon hollow mandrel with attached FBG is chosen as the inner transformer PD detector. The design of the sensor in terms of materials, dimensions, and the shape is chosen; it receives signal strength according to the obtained distance and angle. Standard deviation of angle data is <0.4 mV and as the distance increases, the received signal strength decreases exponentially and oscillatory. Simulation results verify the performance of the proposed sensor in the detection of the transformer PD signals. The proposed sensor is experimentally tested. It succeeded in detecting PD, and can simultaneously detect four frequencies of acoustic signal in the range of 14 to 350 kHz, which is superior to similar sensors.
A magnetic field fiber optic sensor based on Nano-magnetic fluid and Hi-Bi non-adiabatic tapered optical fiber in fiber loop mirror (HB-TFLM) is proposed and theoretically explained. As compared to the reported magnetic fluid (MF) based sensors, the achieved sensitivity of the proposed sensor is 255 pm/mT, which is enhanced by 3.6 times of magnitude relative to in line non-adiabatic tapered optical fiber sensor, used only 0.1% of the volume concentration of MF nanoparticles. Detection limit of the HB-TFLM to external magnetic field in range from 0 to 21 mT and 22 to 50 mT was 7.8 μT and 39.2 μT, respectively.
A magnetic field sensor using a non-adiabatic tapered optical fiber (NATOF) interacting with magnetic fluid (MF) nanoparticles is proposed and experimentally demonstrated. The NATOF is surrounded by a MF whose RI changes with external magnetic field which MF is as a cladding of tapered fiber. The Output interference spectrum is shifted by the change of the applied magnetic field intensity in the range up to 44 mT with a sensitivity of -7.17×10-2 nm/mT.
A high-birefringent fiber (HBF) was tapered as adiabatic in sequence steps by utilizing a CO<sub>2</sub> laser and its birefringence
was measured in fiber loop mirror (FLM) setup. The birefringence of tapered section and total sensor was obtained to be
-8.02×10<sup>-2</sup>, and 2.46×10<sup>-4</sup>, respectively. Then, refractive index (RI) sensitivity increased and temperature sensitivity of
the tapered Hi-Bi fiber (THBF) decreased. The sensitivity of the proposed FLM interferometer for RI changes in the
range from 1.3380 to 1.3470 was measured to be 389.85 nm/RIU. The temperature sensitivity in the range from 50°C to
90 °C was measured to be -1.19nm/°C.
A theoretical and experimental study of a new fiber loop mirror based on a "figure-of-eight"configuration, is reported.
For the theoretical model, the Jones matrix analysis is analyzed. The configuration is tested as an interrogation system
where the spectral response arises from the combination of the reference signal modulated by the sensor signal. The
configuration is characterized in mechanical strain and presents a phase sensitivity of 8.2 mrad/με.