A disturbance detection interferometric fibre optic sensor system

This study proposed a Mach-Zehnder interferometer (M-Z)-based disturbance detection interferometric fibre optic sensor system. In this system, two single-mode optical fibres passing through the central tube of cable were used as the signal arm and reference arm of the M-Z interferometer. In the coherent length range of laser light source, as long as encountering suitable optical path difference, can the photosynthesis generate a series of alternately dark and bright interference fringes. Reference arm is dependent from the external signals, while the signal arm is subject to the disturbance of external signals. Affected by the disturbance, signal interference fringes significantly generated fluctuations with the variation of the optical distance between the two arms. The interference signals were then collected and stored through digital storage oscilloscope. By detecting the variations of the interference fringes from stability to instability, and from regularity to irregularity, it had access to judging whether or not there was external disturbance invasion. Experimental results suggested that the sensor system was very sensitive. In case of slight touch on the cable, the waveform will generate variations.