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Sunil K. Khijwania

Bio: Sunil K. Khijwania is an academic researcher from Indian Institute of Technology Guwahati. The author has contributed to research in topics: Fiber optic sensor & Optical fiber. The author has an hindex of 16, co-authored 49 publications receiving 1208 citations. Previous affiliations of Sunil K. Khijwania include Indian Institutes of Technology & University of Tokyo.


Papers
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Journal ArticleDOI
TL;DR: A novel intrinsic fiber optic pressure sensor realized with a polarization-maintaining photonic crystal fiber (PM-PCF) based Sagnac interferometer is proposed and demonstrated experimentally.
Abstract: A novel intrinsic fiber optic pressure sensor realized with a polarization-maintaining photonic crystal fiber (PM-PCF) based Sagnac interferometer is proposed and demonstrated experimentally. A large wavelength-pressure coefficient of 3.42 nm/MPa was measured using a 58.4 cm long PM-PCF as the sensing element. Owing to the inherently low bending loss and thermal dependence of the PM-PCF, the proposed pressure sensor is very compact and exhibits low temperature sensitivity.

287 citations

Journal ArticleDOI
TL;DR: A fiber optic relative humidity (RH) sensor based on the evanescent wave absorption spectroscopy using a single U-bend plastic-clad silica fiber with high dynamic range and high sensitivity was reported in this article.
Abstract: We report a fiber optic relative humidity (RH) sensor based on the evanescent wave absorption spectroscopy using a single U-bend plastic-clad silica fiber with high dynamic range and high sensitivity. The sensor is fabricated using a CoCl 2 doped thin polymer film coated on the bare fiber core. A comprehensive study of the sensor was made in terms of performance optimization. Sensor response was investigated in terms of the chemically synthesized cladding thickness over the centrally de-cladded U-bent probe. The effect of fiber core diameter on the sensitivity was also studied and the fiber with smaller core diameter was observed to be more sensitive unlike the previously reported results. In addition, we observed that the sensor was having a very fast response to the relative humidity, and was fully reversible, repeatable with a large dynamic range.

170 citations

Journal ArticleDOI
TL;DR: In this article, a comparative experimental study of the fiber-optic evanescent field absorption sensor based on straight and U-shaped probes is presented, where the effect of core radius on the sensitivity depends on the bending radius of the probe.
Abstract: A comparative experimental study of the fiber-optic evanescent field absorption sensor based on straight and U-shaped probes is presented. The effects of numerical aperture and the core radius of the fiber on the sensitivity of the sensor are experimentally investigated. Increase in the numerical aperture of the fiber increases the sensitivity of the sensor in the case of both the probes. The effect of core radius on the sensitivity depends on the bending radius of the probe. In the case of straight probe (i.e. infinite bending radius) the fiber with smaller core radius has high sensitivity while in the case of U-shaped probe with 0.17 cm bending radius, the fiber with larger core radius has high sensitivity. Thus, which fiber (with small or large core radius) has maximum sensitivity depends on the bending radius of the probe. For a given fiber, decrease in the bending radius increases the sensitivity of the U-shaped probe. An inverse power law relationship between the bending radius and the evanescent absorbance and hence the sensitivity is established.

135 citations

Journal ArticleDOI
TL;DR: In this article, the influence of the bending radius of the probe on the sensitivity of the fiber optic evanescent field absorption sensor based on the U-shaped probe is experimentally investigated.

76 citations

Journal ArticleDOI
TL;DR: In this article, a temperature-insensitive fiber Bragg grating (FBG) based smart tilt sensor is presented, which is free from any inherent mechanical joints/frictions with a capability to measure magnitude and direction of the inclination.
Abstract: We present a novel and simple temperature-insensitive fiber Bragg grating (FBG) based smart tilt sensor. The sensor design is free from any inherent mechanical joints/frictions with a capability to measure magnitude as well as the direction of the inclination. The first design is with a sensitivity of 0.00282 nm/° in a very large dynamic range of ± 35°. The sensor response is optimized against design parameters and observed to be completely reversible. Since there is a strain discrepancy on individual FBGs of the first design, a modified design is then proposed for optimization. An excellent sensitivity of 0.0395 nm/° , resolution of 0.013° and accuracy of 0.051° have been achieved. These features along with the freedom to tune the dynamic range, accuracy of measurement and the sensitivity of the proposed sensor to a desired operation range make the proposed sensor of extreme importance for practical engineering applications.

70 citations


Cited by
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Journal ArticleDOI
TL;DR: Tapered fiber-optic biosensors (TFOBS) as mentioned in this paper are a type of FOBS which rely on special geometries to expose the evanescent field to interact with samples.
Abstract: Fiber-optic biosensors (FOBS) are optical fiber-derived devices which use optical field to measure biological species such as cells, proteins, and DNA. Because of their efficiency, accuracy, low cost, and convenience, FOBS are promising alternatives to traditional immunological methods for biomolecule measurements. Tapered fiber-optic biosensors (TFOBS) are a type of FOBS which rely on special geometries to expose the evanescent field to interact with samples. In order to amplify sensitivity and selectivity, TFOBS are often used with various optical transduction mechanisms such as changes in refractive index, absorption, fluorescence, and Surface Plasmon Resonance. In this review, the basic principles of TFOBS are summarized. Various common geometries for evanescent sensing and the influence of geometric parameters on optical principles are reviewed. Finally, a detailed account of the studies done to date for biomolecules detection using TFOBS will be provided. © 2007 Elsevier B.V. All rights reserved.

623 citations

Journal ArticleDOI
23 Feb 2012-Sensors
TL;DR: Each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields and some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications.
Abstract: Fiber optic interferometers to sense various physical parameters including temperature, strain, pressure, and refractive index have been widely investigated. They can be categorized into four types: Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac. In this paper, each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields. Some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications. Some of the simple to fabricate but exceedingly effective Fabry-Perot interferometers, implemented in both extrinsic and intrinsic structures, are discussed. Also, a wide variety of Mach-Zehnder and Michelson interferometric sensors based on photonic crystal fibers are introduced along with their remarkable sensing performances. Finally, the simultaneous multi-parameter sensing capability of a pair of long period fiber grating (LPG) is presented in two types of structures; one is the Mach-Zehnder interferometer formed in a double cladding fiber and the other is the highly sensitive Sagnac interferometer cascaded with an LPG pair.

524 citations

Journal ArticleDOI
Tingting Yang1, Dan Xie1, Zhihong Li1, Zhihong Li2, Hongwei Zhu1 
TL;DR: Wearable tactile sensors as mentioned in this paper can collect mechanical property data of the human body and local environment, to provide valuable insights into the human health status or artificial intelligence systems, thus, emerging as a promising development direction toward the Internet of Things (IoT) applications.
Abstract: Tactile sensors, most commonly referred as strain and pressure sensors, can collect mechanical property data of the human body and local environment, to provide valuable insights into the human health status or artificial intelligence systems. The introduction of a high level of wearability (bendability and stretchability) to tactile sensors can dramatically enhance their interfaces with the contact objects, providing chronically reliable functions. Therefore, the developed wearable tactile sensors are capable of conformably covering arbitrary curved surface over their stiff counterparts without incurring damage, emerging as a promising development direction toward the Internet of Things (IoT) applications. Fundamental parameters of the wearable tactile sensors such as sensitivity and stretchability have experienced unprecedented advancement, owing to the progress of device fabrication techniques and material structural engineering. Moreover, novel smart materials and mechanically durable sensor design concepts endow these sensors with multi-functionality integration (e.g., simultaneous force, temperature and humidity detection, simultaneous pressure and strain discrimination) and stirring properties (e.g., biocompatibility, biodegradability, self-healing, self-powering and visualization), further broadening the application scope of current wearable tactile sensors. Besides, it is desirable that a tactile sensor is compatible with a printing process that presents a new era of feasible wearable technology due to its large-area and high-throughput production capability. In addition to the development of sensors, packaging, and integration of the rest of the tactile device system (data memory, signal conversion, power supply, wireless transmission, feedback actuator, etc.) to build a wearable platform also emerge as major research frontiers in recent years. This review attempts to summarize the current state-of-the-art wearable tactile sensors concerning basic concepts, functional materials, sensing mechanism, promising applications, performance optimization strategies, multifunctional sensing, and system integration. Finally, the discussion will be presented regarding potential challenges, pathways, and opportunities.

516 citations

Journal ArticleDOI
TL;DR: A review of the use of fiber-optic sensor technologies for humidity sensing is presented in this article, where a brief overview on the basic concept of what is meant by humidity and on conventional detection methods is provided.
Abstract: A review of the use of fibre-optic sensor technologies for humidity sensing is presented. The paper first provides a brief overview on the basic concept of what is meant by humidity and on conventional detection methods. This is followed by an extensive review on the various fibre-optic techniques reported for humidity sensing, covering both intrinsic and extrinsic sensor configurations.

424 citations

Journal Article

380 citations