Proc. SPIE. 11567, AOPC 2020: Optical Sensing and Imaging Technology
KEYWORDS: Optical fibers, Sensors, Magnetism, Interferometry, Data acquisition, Temperature sensors, Thermal effects, Sensing systems, Magnetic sensors, Bragg cells, Fiber in the loop, Temperature metrology
A fiber loop ring-down (FLRD) magnetic field sensing system combined with frequency-shifted interferometry (FSI) was proposed and the effect of temperature on its performance was experimentally demonstrated. The FSI-FLRD technique measures the light intensity decay rate (called the ring-down distance) in the space domain instead of in the time domain. Compared with conventional time domain FLRD scheme, FSI-FLRD technique greatly reduces the cost due to only need of inexpensive continuous-wave laser and slow detection. The tapered single mode fiber surrounded by magnetic fluid (MF) was utilized to construct the sensor head for temperature measurement. Different temperature was generated due to the thermal effect of MF and the temperature was obtained by measuring the ring-down distance. The experimental results indicated that a sensitivity of 0.31 /(mm·°C) was achieved.
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.