Distributed, Advanced Fiber Optic Sensors

India is poised to use nuclear energy in a big way. The safety of these systems depends upon monitoring various parameters in hazardous environment like high radiation, high temperature exceeding 1000°C, and gas/coolant leakages. In this chapter, we shall dwell on basics of distributed sensing, related instrumentation, device fabrication, and actual advanced field applications. Techniques like Raman scattering, resonance response of fiber gratings, and selective absorption are employed for design, development, and fabrication of distributed sensors and devices. Raman distributed sensors with advanced data processing techniques are finding increasing applications for fire detection, coolant leak detection, and safety of large structures. The systematic investigations related to portable systems developed at the author’s lab have been described. Wavelength-encoded fiber gratings are the attractive candidate for high gamma radiation dose measurements in environment such as particle accelerators, fission reactors, food processing facilities, and ITER-like installations. The basics of fiber gratings, their operational designs, and devices based on fiber gratings have been described with advanced applications like high temperature sensing, strain measurements at cryogenic temperatures, and strain in nuclear environment. Finally, novel approaches are described for distributed hazardous gas monitoring for large areas such as airports, train stations, and reactor containment buildings

Aerobic Bacteria Associated with Symptomatic Gallstone Disease and their Antimicrobial Susceptibility in Western Nepal

Introduction: Gallstone disease is one of the most common disease affecting the gastrointestinal tract. Biliary tract infection results from bile stasis due to chronic obstruction, mainly (80%) gallstones. Biliary obstruction increases ductal pressure, resulting in bacterial proliferation and dissemination. Proper guidelines for appropriate use of antibiotics in managing uncomplicated and complicated gallstone disease are lacking; on the other hand, the antibiotic usage for its management cover a broad spectrum of organism which may not be required most of the times. This study aims to determine the microbiology of the bile culture and antimicrobial susceptibility in patients with symptomatic gallstone disease in our setup. Methods: This prospective study included patients admitted in surgery department with a diagnosis of symptomatic gallstone disease and subjected for laparoscopic or open cholecystectomy from 1st of Oct 2015 to 30th Sep 2016. The intraoperative bile of patients subjected for cholecystectomy were cultured aerobically in Blood agar and MacConkey agar. The isolates were identified and tested for their sensitivity pattern. The data were collected, entered and then analyzed using SPSS version 23. The descriptive statistics were calculated. Results: Of the total 259 patients, bile culture was negative in 183 patients (70.7%) and was positive in only 76 patients (29.3%). Pseudomonas was the most common cultured organism in 52 (68.4%) patients. Other isolated organisms included E. coli, Staphylococcus, Klebsiella, Enterococci, and Acinetobacter. Imipenem and amikacin were the most effective prophylactic antibiotics. Conclusion: Bile culture was negative in majority of patients with symptomatic gallstone disease. Few patients are positive in culture with predominantly Pseudomonal growth, mostly sensitive to amikacin or imipenem

Transverse Micro-structuring of Photonic Crystal Fibers for Industrial Sensors and Side Viewing Probes for Optical Coherence Tomography Applications

In this work, we report a simple and easily adaptable technique of lateral micro-machining of Photonic Crystal fibers (PCFs) using modulated CO2-laser in conjunction with electrical arc system. The technique is controlled, convenient and precise over wide dimensions (50-250 mm). Lateral access to the holes of PCF provides additional flexibility for sensitive real time detection of gases such as green-house gases. Long period gratings are made in PCF through inscription of micro-grooves for sensitive detection of longitudinal strain. A unique and versatile PCF based probe for possible endoscopic Optical Coherence Tomography (OCT) applications is reported

Fiber Bragg Granting Sensor for Detection of Nitrate Concentration in Water

The concentrations of chemical species in drinking water are of great interest. We demonstrated etched fiber Bragg grating (FBG) as a concentration sensor for nitrate by analyzing the Bragg wavelength shift with concentration of chemical solution. The FBG is fabricated by phase mask technique on single mode Ge-B co-doped photosensitive fiber. Sensitivity of FBGs to the surrounding solution concentration can be enhanced by reducing diameter of the cladding with 40 % HF solution. The maximum sensitivity achieved is 1.322 10-3 nm/ppm. The overall shift of Bragg wavelength is of the order of 6.611 10-2 nm for 10 to 50 ppm concentration. Copyright © 2011 IFSA

Highly Sensitive Cadmium Concentration Sensor Using Long Period Grating

In this paper we have proposed a simple and effective Long Period Grating chemical sensor for detecting the traces of Cadmium (Cd++) in drinking water at ppm level. Long Period gratings (LPG) were fabricated by point-by-point technique with CO2 laser. We have characterized the LPG concentration sensor sensitivity for different solutions of Cd concentrations varying from 0.01 ppm to 0.04 ppm by injecting white Light source and observed transmitted spectra using Optical Spectrum Analyzer (OSA). Proper reagents have been used in the solutions for detection of the Cd species. The overall shift in wavelength is 10 nm when surrounding medium gradually changed from water to 0.04 ppm of cadmium concentrations. A comparative study has been done using sophisticated spectroscopic atomic absorption spectrometer (AAS) and Inductively Coupled Plasma (ICP) instruments. The spectral sensitivity enhancement was done by modifying grating surface with gold nanoparticles

Fiber Bragg Grating Sensor for Detection of Nitrate Concentration in Water

The concentrations of chemical species in drinking water are of great interest. We demonstrated etched fiber Bragg grating (FBG) as a concentration sensor for nitrate by analyzing the Bragg wavelength shift with concentration of chemical solution. The FBG is fabricated by phase mask technique on single mode Ge-B co-doped photosensitive fiber. Sensitivity of FBGs to the surrounding solution concentration can be enhanced by reducing diameter of the cladding with 40 % HF solution. The maximum sensitivity achieved is 1.322 ´ 10-3 nm/ppm. The overall shift of Bragg wavelength is of the order of 6.611 ´ 10-2 nm for 10 to 50 ppm concentration