Refractometer based on SMS interferometer with two waist-enlarged tapers

A compact refractometer by using interferometer in SMS structure with two waist-enlarged tapers is proposed and experimentally demonstrated. It is fabricated by splicing a short section of multimode fiber (MMF) between two single-mode fibers with two bitapers. A refractive index sensitivity of 152.2nm/RIU with a measurement range of 1.3725–1.462 is achieved. The temperature effect of the proposed refractometer is also discussed.