Refractive index sensor based on helical long period grating based on dual-hole elliptical core fiber

In this paper, the fabrication of a novel refractive index sensor based on helical long period grating (HLPG) written in a dual-hole elliptical core fiber (DHECF) was demonstrated and the sensing characteristic was experimentally investigated. Due to the structure of the DHECF, The proposed HLPG sensor could work with ultra-small dose testing samples. In addition, since the sample is isolated from the external environment, the testing is immunity to the external interference. The experimental results showed that the testing sensitivity of the sensor was 194nm/RIU with the refractive index range of 1.333 to 1.385. The proposed structure will have a good practicability in the microfluidic sensing system.