In this paper physical quantities were measured using by the fiber optic sensor when a pendulum ball collides to the fixed ball on the wall. Both steel ball dimensions are 1 inch in diameter. The fiber optic Sagnac interferometer was used to detect the impact time. It is made a 1mm penetrated hole and optical fiber in the Sagnac loop passed through the hole. A ball was welded on the steel plate wall as a fixed ball. When the another ball collides to the fixed ball the fiber optic sensor detects the impact force in between them. Based on the experimental result impact time was measured about 0.14ms at the angle of 30 degree. This fiber optic sensor technique can be expanded to the moving bodies.
In this paper it is shown that a fundamental technology of hybrid system combining Sagnac interferometer and FBG.
Fiber optic sensor array, i.e. two sensors in the Sagnac loop was suggested. Fiber optic sensor array was fabricated in the
transformer oil and external sound applied to the sensor directly using by piezoelectric. Tunable laser source was used as
a light source. Applied sound frequency range is from 5kHz to 90kHz. From this experiment it is confirmed that fiber
optic sensor using Sagnac interferometer in the transformer oil can detect applied sound frequency. In real electric
transformer system suggested fiber optic sensor array can be applied to monitoring physical quantities such as internal
temperature, sound pressure and vibration due to partial discharge.
For condition monitoring of large scale electrical power transformers, a fiber-optic multi-stress sensor system was
constructed by combining fiber-optic acoustic sensors and fiber Bragg grating temperature sensors in a fiber-optic
Sagnac interferometer. To separate the grating signals from the interferometer output, an attenuator was placed at an
asymmetrical position in the Sagnac loop. By balancing the counter propagating light intensities with the attenuator, the
background noises could be suppressed to obtain grating signals with enough signal-to-noise ratio. With the preliminary
experiments, the temperature and the vibration information at multiple locations could be measured simultaneously with
single optical circuit and signal processing unit.
Fiber Bragg grating (FBG) sensors are employed in a fiber-optic Sagnac interferometer sensor to measure multi-stress
information of electric power systems. By using the hybrid sensor configuration, it was possible to measure the
temperature and the vibration signal in an insulating transformer oil bath at the same time. A novel fiber-optic Sagnac
interferometer design and a signal processing technique were used to separate the FBG sensor signals from the
interference signal. The preliminary experimental results are presented to show the feasibility of the sensor system.
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