An asymmetric spherical-shape structure strain sensor based on few mode fiber

An asymmetric spherical-shape structure strain sensor based on few mode fiber is proposed and demonstrated. It is fabricated by waist enlarge two splicing spots between a section of few mode fiber and two single-mode fibers. Fiber core mode interfere with cladding mode due to the excite and couple function of spherical-shape structure, respectively. Based on the double beam interference principle, the environmental strain will change the optical path difference and then change the output light intensity. Experimental results show that transmission spectrum will become close when FMF length increasing, and the optical power at certain wavelength is increasing with the strain increasing. When the length of the FMF is 5.9cm, the diameter of two asymmetric spherical-shapes are 171.36μm and 194.60μm, the strain sensitivity can be up to 0.00748dB/με. Therefore, this sensor has the advantages of simple structure, easy fabrication, high sensitivity and so on, it has potential applications in structure detecting field.