In this thesis, the level sensor of water by detecting the phase difference of 2 optical signals was implemented. The laser diode was modulated by the 20 MHz sinusoidal wave. This optical signal was splitted to 2 signals. One signal was launched directly to a fiber, and the other signal after reflection from the surface of water was launched to another fiber. These 2 signals have phase difference due to path difference experienced by 2 signals. The level of water can be calculated by detecting the phase difference of the 2 signals.
This optical level sensor cannot be interfered by electromagnetic noise and can be safe in dangerous circumstances.
