Multipoint strain sensing system based on fiber loop ringdown and frequency-shifted interferometry

We proposed a novel multipoint sensing method for large strain measurement combined fiber loop ringdown (FLRD) and frequency-shifted interferometry (FSI). Using this method, a biconical tapered multimode fiber was used as a sensor head for large strain measurement and a serial dual-point strain sensing system was experimentally validated. By measuring the ringdown distance of each FSI-FLRD strain sensor, the strain and position of each sensor can be simultaneously obtained. Using such strain sensors, the strain sensitivities of 0.51337 km^-1·mε^-1 and 0.8667 km^-1·mε^-1 within a large measurement range of up to 6 mε were achieved.