Escherichia coli (E. coli) is a large and diverse bacteria group that inhabits the intestinal tract of many mammals. Most E. coli strains are harmless, however some of them are pathogenic, meaning they can make one sick if ingested. By being in the feces of animals and humans, its presence in water and food is used as indicator of fecal contamination. The main method for this microorganism detection is the bacterial culture medium that is time-consuming and requires a laboratory with specialized personnel. Other sophisticated methods are still not fast enough because they require sending samples to a laboratory and with a high cost of analysis. In this paper, a gold-coated U-shaped plastic optical fiber (POF) biosensor for E. coli bacteria detection is presented. The biosensor works by intensity modulation principle excited by monochromatic light where the power absorption is imposed by predominant effect of either bending loss or surface plasmon resonance (SPR), depending on the gold thickness. Bacterial selectivity is obtained by antibody immobilization on the fiber surface. The biosensor showed a detection limit of 1.5 × 10³ colony-forming units (CFU)/mL, demonstrating that the technology can be a portable, fast response and low-cost alternative to conventional methodologies for quality analysis of water and food.

This paper presents the design, fabrication, and characterization of two compact fiber-optic current sensors (FOCS) based on fiber Bragg gratings (FBG) and the magnetostrictive alloy Terfenol-D. Finite-element-method (FEM) simulations assisted key optimizations in the geometry of similar FOCS proposed previously, allowing the implementation of magnetic flux density concentration techniques that resulted in sensors using very small amounts of Terfenol-D. Two prototypes of FOCS with the same geometry and size were manufactured for performance comparison purposes, one using a 2.21-g solid, bulk bar of Terfenol-D onto which a sensing FBG was bonded, and the other using magnetostrictive polymer composite (MPC) with oriented magnetic domains using only 0.42 g of Terfenol-D powder and epoxy resin with a sensing FBG embedded within the composite block. Both FOCS were characterized with currents of up to 800 Arms, and presented linearity errors smaller than 1% of full-scale range (FSR). The prototypes presented greater sensitivities taking into account that only less than 6% of Terfenol-D was employed in comparison to previous FBG-based FOCS. Transient-responses of the FOCS prototypes were also measured showing that the proposed sensors might be applied not only to current metering, but also to fault detection in high-voltage lines. Temperature compensation methods were also proposed and discussed for the developed FOCS.

Most of the dam’s disasters that occurred in the world could be avoided if proper and preventive measures were taken, such as long-term surface or underground monitoring to detect small soil displacements. However, due to the complex operation necessary to monitor underground layer displacements, inclinometers are not used with suitable regularity. To circumvent the logistics of field campaigns necessary in conventional inclinometers, a real-time, remote monitoring system was developed. In this paper, a fiberoptic inclinometer system was designed, consisting of FBGs arrays fixed along a flexible tube to be inserted into conventional boreholes to monitor underground layers displacements. Tests on the bench consisted of applying lateral displacements to curve the tube with the Bragg wavelengths acquired by an FBG interrogator. Then, a specially developed algorithm, applying the Frenet-Serret equations, and the cubic spline interpolation method were used to reconstruct the tube profile. For the first validation of the proposed method, the algorithm was applied to real data obtained in-field by a conventional inclinometer. The results of these tests showed a good agreement between the curve reconstruction and the plotted data of field measurements. The final validation was performed by applying lateral displacements to the instrumented tube and comparing the real tube profile measured by a laser ruler with the calculated profile by the algorithm. The errors found in all tests were less than 1% attesting that the proposed system can be an alternative methodology to the conventional techniques of geotechnical instrumentation, through continuous monitoring with fast response and in real-time, with possible application to quantify the mass movement of soils; movements from earth dams, landfills, and slopes.

A flare system in oil platform is a combustion stack used to burn off excess gases that cannot be processed and gases that have to be eliminated in emergency shutdown to avoid the risk of explosion. Gas flow measurement in flares is still considered challenging because the measurement has to attend many specific demands, quite different from any other flow measurement application. For these types of measurements many sensor technologies are available, however they are all very expensive, and only a few ones can attend all demands. The objective of this paper is to present a flow rate sensor based on Fiber Bragg Grating (FBG), cross-correlation and heatwave travel time techniques. The system was developed with inexpensive components and is little-intrusive, capable of attaining the rangeability of the flare demand and independent of gas composition, pressure and temperature.

In this letter, we performed finite element method (FEM) simulations, fabrication, and experimental characterization of two prototypes of fiber-optic current sensors (FOCS) based on fiber Bragg grating (FBG) and Terfenol-D for monitoring current in high-voltage transmission lines. The proposed prototypes were designed in geometrical configurations that allowed a massive reduction of more than 98% in the amount of Terfenol-D employed compared to FBG-based FOCS proposed previously. Using only 5.6 and 2.0 g of Terfenol-D in each prototype, we show that not only the cost of the sensor can be reduced but also greater sensitivity, linearity, and fast response-time to transient events were achieved.