Signal processing algorithm of newly developed transmission-type extrinsic Fabry-Perot interferometric optical fiber sensor

The newly developed TEFPI (transmission-type extrinsic Fabry- Perot interferometric) optical fiber sensor can distinguish the direction of measurement more simply and effectively than the conventional reflection-type EFPI optical fiber sensors. The output signal of the TEFPI optical fiber sensor has the characteristics that the signal level of fringes shows a negative slope for a tensile direction and a positive slope for a compressive direction. Based on these characteristics, the direction of measurement of the TEFPI optical fiber sensor can be distinguished with ease. In this paper, the signal processing algorithm adequate to the TEFPI optical fiber sensor was developed. This algorithm can process signal with recognition of the positions of peaks, valleys and signal levels of fringes. Thus this can determine a measurement direction and the positions of direction changes by using the change trend of signal levels. The developed algorithm makes the post-process and real-time process of the signal of the TEFPI optical fiber sensor possible.