Low-Cost Ethanol Concentration Sensor Based on a Balloon-like Curved Optical Fiber in a Mach-Zehnder Interferometric Configuration.

We report an optical configuration to measure the concentration of ethanol (EtOH) using a light-guiding mechanism based on optical fibers in a Mach-Zehnder-type interferometric configuration. The proposed configuration takes advantage of the high sensitivity of fiber optic interferometers, allowing variations in EtOH concentration to be detected from shifts in the interference patterns. The interferometric configuration was implemented using a single-mode optical fiber curved into a balloon shape. During the experiment, some spectral stability and hysteresis tests were performed on the device, obtaining good results. During the characterization stage for measuring EtOH concentration in the 40-71% v/v range, performance parameters were evaluated, achieving EtOH concentration measurements in the 1500-1600 nm wavelength range. The sensitivity of the devices was evaluated in terms of the geometric parameters of the interferometric curved optical fibers, obtaining a maximum sensitivity of 0.1174 nm/% v/v. In this case, the transmitted optical signal analyzed at the end of the optical fiber allowed the identification of spectral shifts toward longer wavelengths with increasing EtOH concentration. In the study, the behavior of the spectral parameters of the interferometric curved optical fibers was analyzed as a function of the geometric parameters, highlighting their low cost, easy tuning control of minimum intensity peaks and good sensitivity.