Measurement of sugar concentration by multimodal fiber optics sensor

The primary function of sugar is to provide the energy that our body needs, in addition to contributing to the performance of different organs such as the brain and muscles. However, its excessive consumption can lead to serious health problems including body weight gain as well as metabolic and cardiovascular disorders. Therefore, monitoring sugar content both in physiological conditions and in the food industry is of critical importance. In this work, we report the fabrication and testing of a fiber optics sensor based on multimodal interference (MMI) that is capable of measuring sugar concentration in aqueous solutions. The sensor has a simple singlemode-multimode-singlemode (SMS) architecture, consisting of a segment of multimode fiber spliced between two single-mode fibers. The sensor's operating mechanism is based on the spectral shift due to changes in the effective refractive index (RI) of the solution under test. Thus, when the sensor is immersed in binary sugar-water solutions with different concentrations, the spectral response of the sensor shifts according to the RI of the mixture. The optical sensor was tested with fructose and sucrose, diluted in distilled water. The range of concentrations in which the sensor was tested was from 0% to 18.5%. Preliminary results indicate that the sensor exhibit a linear response with a sensitivity around 0.17524nm/% and 0.16321nm/% for sucrose and fructose, respectively. The optical sensor presented has the advantage of simple construction, low cost, linear response, it does not require additional processes or coatings on the optical fiber, and it has the capability for performing real-time measurements, which makes it suitable for quality control applications.