Design of a low-cost D-shape optical fiber sensor based on intensity modulation for low refractive index

In this study, a low-cost D-shape optical fiber sensor was fabricated using a multi-mode optical fiber, which means that light can pass through it in several different paths. A D-shape optical fiber sensor based on intensity modulation was used to show how well it can detect the concentration of a substance by measuring its refractive index. The D-shaped fiber sensor is a particular type of optical fiber polished on one side to remove the outer layer. The sensor has different lengths, and the polishing can be done at different depths. Experimental results confirm that this sensor is expected to be helpful in materials with low refractive index (RI) and tiny amounts of those materials. So, the best D-shape fiber sensor was used to find the smallest part of sodium chloride (NaCl) in a liquid with a low refractive index, and it was found that a minor amount concentration that could be detected was 0.012% with a high sensitivity of 327.32 a.u./ RIU. A fiber sensor, shaped like the letter D, is expected to be useful for materials with a very low concentration and low refractive index (RI).