Evanescent absorption based refractive index measurement at 1.3 µm

In this article the different works of optical fiber based refractive index measurements is reviewed. An experimental study and analysis of fiber optic cable based refractive index sensor has been carried out to measure the change in signal for different solutions of known refractive indices. The model is based on evanescent field absorption in medium of different refractive indices.

A multi-mode step index fiber of diameter 62.5/125±5 μm is used to operate at near infrared (@1310 nm) laser source. The cladding of the fiber was removed to a maximum of 40% of its thickness and the fiber was dipped in water, ethanol and chloroform. The output was measured using a digital power meter. Maximum deviation of 0.003 is obtained in the linear fit of the normalized signal with known refractive index values.

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