This Tutorial Text delivers essential information concerning fiber Bragg gratings to professionals and researchers with an approach based on rules of thumb and practical aspects, enabling quick access to the main principles and techniques, and allowing readers to set up their own laboratory or application. It provides detailed information about how to operate and use these novel sensors, particularly with respect to the required infrastructure, daily operation, and possible applications. After a discussion of the primary concepts, practical aspects regarding the development of a FBG laboratory and how these components are manufactured and used in practical applications are presented. The following chapters outline the operation of Bragg gratings and, for instance, discuss how measurement information can be retrieved (interrogation techniques), calibration methods, and how to prepare and deploy the devices in real monitoring conditions. The final chapters present several successful, real-world applications of the technology.
This work presents an innovative automated Fiber Bragg Grating (FBG) based tunable optical filter (TOF) controlled by temperature to be used in temperature compensating schemes in FBG sensing set-ups. Mechanical and electronic aspects are discussed, and the implemented FBG-TOF viability and reliability in sensing systems are showed. The system was employed to demodulate a high voltage AC signal applied to a FBG-PZT sensor, showing good linearity and sensitivity.
When using a Fiber Bragg Grating (FBG) for strain measurements it is always necessary to compensate the FBG against temperature fluctuations. In this paper it is shown an innovative method for mechanically compensating an FBG in a high voltage measurement application using an FBG-PZT sensor. The system takes advantage of a mechanical assembly that, as the PZT displaces, the screw where the FBG is bonded on displace in the opposite direction, keeping the FBG length constant. A theoretical analysis is done and experimental results are shown.
This paper presents an immunobiosensor of fast response time to detection of bacteria, made by Plastic Optical Fiber. Probes were tested in U-shaped and Meander-shaped to investigate the best sensitivity, accuracy and repeatability. During calibration was used for sucrose solutions refractive index (RI) from 1.33 to 1.39. This is equivalent to IR range of the water and the highest concentration of bacteria, respectively. Immunobiosensor was able to detecting the presence of enteropathogenic Escherichia coli in water from suspensions of different concentrations of 106 and 104 colonies forming units per millilitre (CFU/mL) in twenty minutes.
Deposition of thin diamond-like carbon films in etched fiber Bragg gratings as substrate was used to increase the sensitivity of a fiber Bragg grating refractometer. The nanometric film was also used for tuning the sensitivity to a maximum for a desired application of liquid refractive index measurement. Simulation and experiments were performed in order to understand the light propagation inside the modified optical fiber and its effects in the refractometry measurements.
The distribution of light intensity of three light-curing units (LCUs) to cure the resin-based composite for dental fillings was analyzed, and a homogeneity index [flat-top factor (FTF)] was calculated. The index is based on the M2 index, which is used for laser beams. An optical spectrum analyzer was used with an optical fiber to produce an x-y power profile of each LCU light guide. The FTF-calculated values were 0.51 for LCU1 and 0.55 for LCU2, which was the best FTF, although it still differed greatly from the perfect FTF=1, and 0.27 for LCU3, which was the poorest value and even lower than the Gaussian FTF=0.5. All LCUs presented notably heterogeneous light distribution, which can lead professionals and researchers to produce samples with irregular polymerization and poor mechanical properties.
This work presents a novel, fast response time, plastic optic fiber (POF) biosensor to detect Escherichia coli. Different forms of probes in U-shaped format were tested: U-shaped with different radii, coil-shaped and meander-shaped. In the calibration process we used solutions of sucrose for obtaining refractive indexes (RI) in the range 1.33 – 1.39 RIUequivalent of water and bacteria, respectively. The POF probes were functionalized with antibody anti-Escherichia coli serotype O55 and tested with bacteria concentrations of 104, 106 and 108 colonies forming unities/mL (CFU/mL). The optoelectronic setup consists of an 880 nm LED connected to the U-shaped probe driven by a current source controlled by an Arduino Microcontroller. At the opposite fiber end, the light received by a photodetector is amplified and read by the A/D port of the microcontroller. The output voltage decreases as the external RI increases, accordingly to the bacteria that is captured by the antibody fixed in the biosensor. The paper presents results obtained with the different shapes of probes tested with the same setup and biochemical protocol. In conclusion the system shows good capabilities of having concentration measurements results in less than 10 minutes with uncertainty of 10-4 RIU enabling a future capacity to read concentration of 103 CFU/mL.
The authors present the development of a opto-magnetostrictive current monitoring device intended to be used in situations where high voltages are involved. The system offers not only measurement reliability, but to be also practical and light weighted. Fiber Bragg gratings (FBG) are employed in the measurement procedure: the current is acquired using a hybrid sensor head set-up, that is, an FBG together with a magnetostrictive rod.
This work has the objective to research and develop a plastic optical fiber biosensor based taper and mPOF LPG techniques to detect Escherichia coli by measurements of index of refraction. Generally, cell detection is crucial in microbiological analysis of clinical, food, water or environmental samples. However, methods current employed are time consuming, taking at least 72 hours in order to produce reliable responses as they depend on sample collection and cell culture in controlled conditions. The delay in obtaining the results of the analysis can result in contamination of a great number of consumers. Plastic Optical Fiber (POF) biosensors consist in a viable alternative for rapid and inexpensive scheme for cells detection. A study the sensitivity of these sensors for microbiological detection, fiber Tapers and Long Period Grating (LPG) both in poly-methyl-methacrylate (PMMA) were realized as possible candidates to take part of a biosensor system to detect Escherichia coli in water samples. In this work we adopted the immunocapture technique, which consists of quantifying bacteria in a liquid sample, attract-ing and fixing the bacteria on the surface of the polymer optical fiber, by the antigen-antibody reaction. The results were obtained by optical setup that consists in a side of the fiber a LED coupled to a photodetector through a POF with the taper in the middle of it. On the other side of the POF a photodetector receives this light producting a photocurrent. The output voltage is fed into the microcontroller A/D input port and its output data is sent via USB to a LabView software running in a microcomputer. The results showed the possibility of the POF in biosensor application capable to detect E. coli for environmental and food industry and for detecting and identifying biological-warfare agents using a very rapid response sensor, applicable to field detection prototypes.
The efforts on the development of Polymeric Optical Fiber (POF) technology are increasing allover the world, covering many areas of application. Following this trend, different research groups in Brazil started to work with this promising technology in partnership. Many works on passive devices, sensors, Bragg gratings, and also on telecom areas are under development. This paper describes some of these works, trying to give an overview of the development of POF technology in Brazil. The efforts to create a POF Discussion Group in the Latin America community are also presented.
This paper describes a real time optical biosensor that utilizes the evanescent field technique for monitoring microorganisms in hospital environment. The biosensor monitors interactions between the analytic (bacteria) and the evanescent field of an optical fiber passing through the culture media where the bacteria grows. The objective is to monitor atmospheres in hospital areas for the Staphylococcus aureus and Streptococcus pneumonia. The results lead us the conclusion that this kind of sensor presents quick response, good performance, easy of construction and low cost. We expect that the sensor will be of great help in controlling the hospital environment.
As widely known, fiberoptics (FO) are being used in a large variety of sensor an systems particularly for their small dimensions and low cost, large bandwidth and favorable dielectric properties. These properties have allowed us to develop sensor and systems for general applications and, particularly, for biomedical engineering. The intravasculator pressure sensor was designed for small dimensions and high bandwidth. The system is based on light- intensity modulation technique and use a 2 mm-diameter elastomer membrane as the sensor element and a pigtailed laser as a light source. The optical power out put curve was linear for pressures within the range of 0 to 300 mmHg. The real time optical biosensor uses the evanescent field technique for monitoring Escherichia coli growth in culture media. The optical biosensor monitors interactions between the analytic and the evanescent field of an optical fiber passing through it. The FO based high voltage and current sensor is a measuring system designed for monitoring voltage and current in high voltage transmission lines. The linearity of the system is better than 2 percent in both ranges of 0 to 25 kV and 0 to 1000 A. The optical flowmeter uses a cross-correlation technique that analyzes two light beams crossing the flow separated by a fixed distance. The x-ray image sensor uses a scintillating FO array, one FO for each image pixel to form an image of the x-ray field. The systems described in this paper use general-purpose components including optical fibers and optoelectronic devices, which are readily available, and of low cost.
As widely known, fiberoptics (FO) are being used in a large variety of sensors and systems particularly for their small dimensions and low cost, large bandwidth and favorable dielectric properties. These properties have allowed us to develop sensors and systems for general applications and, particularly, for biomedical engineering. The intravascular pressure sensor was designed for small dimensions and high bandwidth. The system is based on light-intensity modulation technique and uses a 2 mm-diameter elastomer membrane as the sensor element and a pigtailed laser as a light source. The optical power output curve was linear for pressures within the range of 0 to 300 mmHg. The real time optical biosensor uses the evanescent field technique for monitoring Escherichia coli growth in culture media. The optical biosensor monitors interactions between the analytic (bacteria) and the evanescent field of an optical fiber passing through it. The FO based high voltage and current sensor is a measuring system designed for monitoring voltage and current in high voltage transmission lines. The linearity of the system is better than 2% in both ranges of 0 to 25 kV and 0 to 1000 A. The optical flowmeter uses a cross-correlation technique that analyses two light beams crossing the flow separated by a fixed distance. The x-ray image sensor uses a scintillating FO array, one FO for each image pixel to form an image of the x-ray field. The systems described in these paper use general-purpose components including optical fibers and optoelectronic devices, which are readily available, and of low cost.
In the present work real time interferograms operations are proposed as solution in flowmeters applications. Cross correlation interference patterns are discussed and proposed as possible physical tools to solve this problem. This experimental proposal is particularly important when micro turbulence produce extremely localized phase mismatch in coherent light beams due to little index refraction variations in the flow channel.
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