Detector diode circuit noise measurement and power supply method selection for the fiber optic seismograph

This paper investigates the noise levels present at various points in the FOSREM type fiber optic seismograph. The main aim of this research was to discover magnitudes of noise, introduced by various components of the analog and optical circuits of the device. First, the noise present in the electronic circuit without any optics connected is measured. Further experiments show noise levels including the detector diode not illuminated and illuminated. Additional tests were carried out to prove the necessity of analog circuitry shielding. All measurements were repeated using three powering scenarios which investigated the influence of power supply selection on noise. The results show that the electronic components provide a sufficient margin for the use of an even more precise detector diode. The total noise density of the whole device is lower than 4⋅10⁻⁷ rad/(s√Hz). The use of a dedicated Insulating Power Converter as a power supply shows possible advantages, but further experiments should be conducted to provide explicit thermic confirmation of these gains.