D-Shaped POF Sensors for Refractive Index Sensing—The Importance of Surface Roughness

Abstract

In this study the influence of the surface roughness on the transmission capacities of D-shaped plastic optical fibers (POFs) and sensors performance was investigated. Five D-shaped POF sensors were produced and characterized for refractive index sensing between 1.33 and 1.41. The sensors were characterized using a low-cost optical sensing system based on the variation of the transmitted light though the POF with refractive index changes (RI). Higher surface roughness increases the scattering losses through the POF and influences the sensors’ performance; therefore, a balance must be attained. Generally, the best performance was achieved when the sensing region was polished with P600 sandpaper as a final polishing step. Polishing with sandpapers of lower grit size resulted in lower scattering, higher linearity of the sensor response and generally lower performance for RI sensing. A sensor resolution of 10−3–10−4 RIU, dependent on the value of the external refractive index, was obtained through simple and low-cost manufacturing procedures. The obtained results show the importance of surface roughness in the development of POF sensors which can be used in several applications, such as for water quality assessment.

Pressure Sensitive Adhesive Tape: A Versatile Material Platform for Optical Sensors

“…These sensors are compact and can be designed for distributed [ 58 , 59 ] or tip-based [ 60 , 61 ] sensing. In order to increase the interaction of the optical field with the liquid analyte, that is, the refractive index sensitivity, optical fiber sensors can adopt different configurations, such as stripped [ 61 ] tapered [ 62 ], D-shaped [ 63 , 64 , 65 , 66 ], microstructured [ 67 , 68 ], and U-shaped [ 69 , 70 ] fibers. As compared to glass fibers, plastic optical fibers (POFs) are easy to handle and cost-effective.…”

Low-Cost Sensing with Plastic Optical Fibers—From Turbidity and Refractive Index to Chemical Sensing

“…The low-cost sensing system allows real time monitoring through Bluetooth technology and the data is saved through a LabVIEW application, which can be further analyzed, allowing for remote sensing and in-site monitoring. D-shaped POF sensors were developed in collaboration with researchers from the University of Aveiro, University of Pavia and University of Campania Luigi Vanvitelli, allowing the measurement of RI variations with resolution of 10 −3 RIU [13][14][15][16]. These sensors are produced by side-polishing the POF with sandpapers of known grit size after embedding the POF in a planar platform.…”

Treatment of Mode Coupling in Step-Index Multimode Microstructured Polymer Optical Fibers by the Langevin Equation

“…POFs are good candidates for short-range transmission systems such as automotive and home network connections [ 2 , 3 ]. Moreover, due to their advantages such as a large negative thermo-optic coefficient, high bending flexibility, and large elastic strain limits, POFs are promising for sensing applications [ 4 , 5 , 6 , 7 , 8 , 9 ]. A microstructured optical fiber or photonic crystal fiber (PCF) was first demonstrated in 1996 with silica material [ 10 ], which can realize a wide variety of properties by different microstructures with a solid core and a hollow core [ 11 , 12 ].…”