Design and fabrication of SMS fiber refractometer for liquid

Single-mode/multi-mode/single-mode (SMS) fibers are optimally designed and fabricated as high sensitivity (∼4.6 × 10−6) refractometer sensors for liquid. It is shown that the width of multimode fiber is a key factor in the performance of as-fabricated refractometer sensor, which can be effectively controlled in the fabrication process by monitoring the output power of SMS fiber during wet acid etching process. The experimental results match quite well with the numerical simulation results. As-fabricated refractometer sensor shows promising potential applications in precisely monitoring the refractive index of liquid in chemical and biomedical fields.