In-fiber Mach-Zehnder interferometer as a promising tool for optical nose and odor prediction during the fermentation process.

In this paper, we present an in-fiber Mach-Zehnder interferometer (MZI) applied to coffee bean fermentation monitoring. Two MZIs, based on a combination of a fiber taper cascaded by a micro-tapered long-period fiber grating, were installed in a fermentation barrel to monitor the liquids and gases released during the fermentation process. During this process, a variety of odors arise due to the yeast activity and their classification is important to decide when to stop the fermentation process.

Identification of external media using a long-period grating and optical time-domain reflectometry.

The application of signal processing and feature extraction to reflectometry traces aiming at sensor interrogation is not sufficiently explored. In this work, traces produced by an optical time-domain reflectometer in experiments using a long-period grating in different external media are analyzed using signal processing techniques inspired by audio processing. The objective is to demonstrate that, using this type of analysis, it is possible to correctly identify the external medium through the characteristics of the reflectometry trace.

Etched fiber Bragg grating probe using a regular CNC machine and a 3D printer.

Etched fiber Bragg gratings (EFBGs) have been widely employed for refractive index (RI) measurements that can be used to monitor sugar consumption during the fermentation of alcoholic beverages. EFBGs are obtained by removing the cladding of a fiber Bragg grating, which is traditionally performed by a chemical attack with hydrogen fluoride, an extremely hazardous corrosive substance that causes severe wounds and even death. To overcome such drawbacks, this technical note presents a simple, practical, and low cost method for the diameter reduction of single mode optical fibers by mechanical polishing, employing a small scale computer numerical control device and an ad hoc 3D-printed rod.

An Optical Fiber Sensor and Its Application in UAVs for Current Measurements.

In this paper, we propose and experimentally investigate an optical sensor based on a novel combination of a long-period fiber grating (LPFG) with a permanent magnet to measure electrical current in unmanned aerial vehicles (UAVs). The proposed device uses a neodymium magnet attached to the grating structure, which suffers from an electromagnetic force produced when the current flows in the wire of the UAV engine. Therefore, it causes deformation on the sensor and thus, different shifts occur in the resonant bands of the transmission spectrum of the LPFG.