Marcelo M. Werneck

Tapered plastic optical fiber-based biosensor – Tests and application

Cells detection is crucial in microbiological analysis of clinical, food, water or environmental samples. However, currently employed methods are time consuming. Plastic optical fiber (POF) biosensors consist in a viable alternative for rapid and inexpensive scheme for detection. In order to study the sensitivity of tapers for microbiological detection, geometric parameters are studied, such as the taper waist diameter since the formation of taper regions are the key sensing element in this particular type of sensors. In this study, a series of POF taper sensors were prepared using a specially developed tapering machine, and the dispersion of geometric dimensions is evaluated, aiming to achieve the best tapering characteristics which will provide a better sensitivity on the sensor response. The fiber tapers that presented the finest results were those constructed in U-shaped (bended) configurations, with taper waist diameters ranging from 0.40 mm up to 0.50 mm. These fiber tapers were used as the main section of the monitoring device, and when chemically treated as immunosensors for the detection of bacteria, yeast and erythrocytes.

Plastic optical fiber-based biosensor platform for rapid cell detection

This work presents a novel, fast response time, plastic optic fiber (POF) biosensor to detect Escherichia coli. It discloses the technique for the development, calibration and measurement of this robust and simple-to-construct POF biosensor. The probes in U-shaped format were manufactured with a specially developed device. The calibration process led to the evaluation of the sensitivity, accuracy and repeatability by using solutions of sucrose for obtaining refractive indices (RI) in the range 1.33-1.39 IR equivalent of water and bacteria, respectively. The POF probes were functionalized with antibody anti-E. coli serotype O55 and tested firstly with saline and then with bacterial concentrations of 10(4), 10(6), and 10(8) colony forming units/ml (CFU/ml). The optoelectronic setup consists of an 880 nm LED connected to the U-shaped probe driven by a sine waveform generated by the Simulink (from Matlab(®)). On the other side of the probe a photodetector generates a photocurrent which is amplified by a transconductance amplifier. The output voltage signal is read by the analog-to-digital (A/D) input of the microcontroller. In all tested concentrations, the results presented a tendency of a decrease in the output signal with time, due to the attachment of the bacteria to the POF probe and consequent increase in the RI close to the sensitive area of the fiber surface. It has been shown that the system is capable of providing positive response to the bacterial concentration in less than 10 min, demonstrating good possibilities to be commercially developed as a portable field sensor.

Optical High-Voltage Sensor Based on Fiber Bragg Grating and PZT Piezoelectric Ceramics

Electric power facilities, such as substations, rely on voltage transformers (VTs) for measurement and protection. These pieces of equipment are bulky and heavy and tend to explode, destroying nearby equipment and posing a threat to substation personnel. Optical voltage transducers offer many improvements on traditional inductive and capacitive VTs, such as linear performance, wider dynamic range, lighter weight, smaller size, and improved safety. This paper relates to the development of a high-voltage sensor system using a PZT piezoelectric crystal as a transducer and a fiber Bragg grating as a sensor for an optical VT for a 13.8-kV class. The results show that the developed sensor is capable of attaining the International Electrotechnical Commission 0.2%-accuracy class for the revenue metering system.

Hybrid Optoelectronic Sensor for Current and Temperature Monitoring in Overhead Transmission Lines

This letter describes the development of a hybrid optoelectronic current and temperature sensor for evaluating the sag of conductors in high voltage transmission lines. This 4 kg portable current transformer was developed using alternative materials to the heavy items that constitute a conventional transformer: iron core, copper coil and insulating ceramics. The system uses reliably proven electronic technology to measure temperature and current, while using fiber-optic technology to energize the electronic circuitry and transmit the signals back via optical fibers. The data collected, together with the sag information, will provide support for the development of an algorithm for the estimation of conductor-sag values.

Novel Optimization Algorithm to Demodulate a PZT-FBG Sensor in AC High Voltage Measurements

The application of optical fiber sensors in high-voltage environments has long been recognized as being useful, due to many properties of silica, such as insulation and electromagnetic induction immunity. Thus, optical voltage transducers offer many improvements on traditional inductive and capacitive voltage transformers, such as linear performance, wider dynamic range, lighter weight, smaller size, and improved safety. In this paper, we aim toward a power-line voltage transformer application by using a piezoelectric ceramic crystal stack together with a fiber Bragg grating (FBG) sensor to construct the core of a potential transformer for 13.8 kV class. For the AC demodulation process, we develop a mathematical model to identify the optimization parameters through a novel algorithm to improve sensitivity on FBG demodulation. This new scheme is simple, reduces the cost of the setup implementation and shows a solution to circumvent the temperature drift of the system.

A Guide to Fiber Bragg Grating Sensors

Optical fiber sensors (OFS) appeared just after the invention of the practical optical fiber by Corning Glass Works in 1970, now Corning Incorporated, that produced the first fiber with losses below 20 dB/km. At the beginning of this era, optical devices such as laser, photodetectors and the optical fibers were very expensive, afforded only by telecom companies to circumvent the old saturated copper telephone network. With the great diffusion of the optical fiber technology during the 1980’s and on, optoelectronic devices became less expensive, what favored their use in OFS.

Detection and Monitoring of Leakage Currents in Power Transmission Insulators

An optoelectronic sensor for real-time leakage current monitoring on high-voltage (500 kV) and medium-voltage (13.8 kV) power line insulators was developed. The leakage current drives an ultrabright light-emitting diode producing an amplitude modulated light signal. The optically intensity-encoded signal is coupled to a plastic optical fiber cable and transmitted from the high potential measurement point to the remote unit in ground potential. After the demodulation, the leakage current root mean square values are concentrated in a data logger and sent to a remote station 150-km away by general packet radio service technology. Field tests at real operational conditions on coastal regions have been performed; all data collected are stored in a structured database, which can be consulted from the Internet, while a serially produced head was developed and the sensor is ready for commercialization. Since leakage current on high-voltage insulators depends on local air pollution and microclimate changes, several sensors have to be used to cover the region monitored. For this reason, research has been conducted to determine the sensor representativeness, i.e., the actual area, which can be covered by only one sensor.

Temperature and current monitoring system for transmission lines using power-over-fiber technology

The design of transmission lines (TL) is usually based on conservative aspects, in order to attend safety standards and avoid the deterioration of line construction materials. With the increasing demand of energy, the idea to improve the capacity transmission of already existing lines, designed in a high safety manner, is attractive; instead of duplicate or construct new ones. An equipment for monitoring current and temperature in 138kV transmission lines using photonic power and data communication is presented; which will provode information for a sag-current relation, and consequently a safer ampacity sizing, while a fully operation of the line is being carried out. The power supply for the sensors and data processing circuits in high voltage area is provided by photonic energy, transmitted through an optical fiber. Likewise, the measured results are sent to the low voltage area using another optical fiber, achieving good electrical insulation.

Wavelength demodulation of ultrabright green light-emitting diodes for electrical current sensing

We report on a novel electrical current-sensing principle based on wavelength-encoded modulation of the ultrabright green (at 525 nm) light-emitting diode (LED) transducers. It complies with the optical subsystem of a hybrid current transformer . Real-time wavelength demodulation is performed with the passive spectral edge filter OG 530. Linear calibration plots were achieved with -0.33 nm/mA for dc and +0.99 mA/sup -1/ for ac current sensitivity, respectively. A measurement accuracy of 1.3% for 28.4-mA ac peak current range is achieved. A simple theoretical model is outlined. Issues such as electronic and thermal effects on stability performance are also addressed.

Cross-Correlation-Based Optical Flowmeter

In this paper, an optical flowmeter based on the cross-correlation technique is proposed. Two parallel laser beams are made to cross a transparent pipe wherein a turbulent air flows. The laser beams are detected by two position-sensitive detectors (PSDs) whose output signals are processed by software. The cross-correlation function between the signals is calculated, which yields the time delay between them. The flow velocity is then obtained by the ratio of the distance between the laser beams to the time delay. The flowmeter is applicable for measuring human respiratory flow in a noninvasive way. An experimental prototype is built, and results are provided. A detailed description of the experimental setup and of measurement procedures are presented and discussed. Results have been very promising and have shown the potential of the system developed here in performing human respiratory flow measurements, particularly those suitable for neonates.