Different chemical substances as well as several physical and biological parameters can be detected through measurements of the refractive index (RI). For this reason, RI sensors have gained considerable attention by the sensor community. Fiber-based refractometric devices are attractive, owing to the inherent advantages over their counterparts based on other techniques. For example, they can be multiplexed on a single fiber network and are suitable for in situ and remote RI measurements. Moreover, they are compact and lightweight. In addition, the amount of sample needed to carry out the...