Geometrically modified optical fibers have been widely exploited for realizing refractive index (RI) sensors. In particular, U-bent fiber optic sensors (FOS) have been reported to be efficient for chemical and biosensing applications. Experimental investigations show that the U-bent FOS are highly sensitive, when the bend diameter is less than 5 times the fiber core diameter. However, the phenomenon behind high RI sensitivity is yet to be fully understood. So far, geometric effects alone have been considered to significantly contribute to medium-sensitive refractive losses. In this work, a simple ray optics model is developed to evaluate the light propagation and attenuation in a U-bent FOS. These numerical simulations point to a significant contribution from modified core RI profile as result of bend induced inhomogeneity in the material towards high sensitivity of acutely bent probes. © 2018 IEEE.

Sai V V Raghavendra

Department of Applied Mechanics

Fiber optics

Light

Optical fibers

Refractive index

Refractometers

BENT FIBER

Biosensing applications

Experimental investigations

FIBER CORE DIAMETERS

GEOMETRIC EFFECTS

LIGHT ATTENUATION

RAY OPTICS MODEL

Refractive index sensor

Fiber optic sensors

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Ray Optics Model for Light Attenuation in U-Bent Fiber Optic Sensors

Proceedings of IEEE Sensors

This study demonstrates a simple evanescent wave absorbance based sensing scheme for plasmonic sandwich immunoassay with the help of U-bent fiber probes as transducers. High absorbance sensitivity of the U-bent probes (200 μm core and 1.5 mm bend diameter) is exploited for sensitive detection of a small number of gold nanoparticles (AuNP) labels bound to the probe for the first time. Using 13 nm AuNP labels conjugated with recognition antibodies, picomolar detection limit (2 pM or 0.3 ng/ml) for human immunoglobulin (HIgG) is achieved. The absorbance sensitivity and dynamic range were 0.019 A530nm/log (ng/ml) and 1-105 ng/ml respectively. Nonspecific adsorption (NSA) of labels is minimized to less than 2% by PEGylation. The ease in U-bent probe fabrication and simple optoelectronic instrumentation consisting of an LED and a fiber optic spectrometer could facilitate extensive use of U-bent probes for several biosensing applications. © 2015 Elsevier B.V. All rights reserved.

Sensors and Actuators, B: Chemical

Evanescent wave absorbance based U-bent fiber probe for immunobiosensor with gold nanoparticle labels

This study presents design and development of evanescent wave absorbance based U-bent plastic optical fiber (POF) probe with high sensitivity and its applications to refractive index (RI) sensing. The probes were fabricated by a controlled decladding procedure to remove the fluorinated polymer without damaging the poly methyl methacrylate (PMMA) core and a simple and scalable fabrication technique to obtain POF U-bent probes of desired geometry. U-bent probes of fiber diameter from 250 to 1000 μm were fabricated and optimum bend diameter for each fiber diameter was investigated. The sensitivity was found to be maximum when the bend diameter of the probe varies from 2 to 3 times the fiber diameter. Probes with 500 μm core and 1.25 mm bend diameter showed highest sensitivity (5.57ΔA560 nm/ΔRIU) in the visible region to RI changes from 1.33 to 1.47 with a resolution better than 1 milli RI units. Furthermore, U-bent probes were amine functionalized and coated with gold nanoparticles to obtain a localized surface plasmon resonance (LSPR) based RI sensor that has an 8-fold improvement in RI sensitivity, hence extending their applicability to plasmonic biosensing. © 2016 Elsevier B.V. All rights reserved.

Development of LSPR based U-bent plastic optical fiber sensors

Applied Optics

Investigation of a macrobending micro-plastic optical fiber for refractive index sensing

The aim of this study is to develop an optical absorbance based biosensor suitable for wide scale use in resource-poor locales. A sensor for sensitive measurement of refractive index (RI) with the help of optical absorbance properties of gold nanoparticles (GNP) coupled to an efficient optical transducer in the form of a U-bent fiber optic probe is described. A U-bent probe was fabricated by a simple procedure. The absorbance due to the localized surface plasmon resonance (LSPR) of fiber-bound GNP was found to be linear to refractive index changes between 1.33 and 1.35. A U-bent probe of 200 μm diameter with a bend radius of 0.75 mm gave rise to a sensitivity of 35 ΔA/RIU at 540 nm. The resolution of the sensor probe was 3.8 × 10-5 RIU. Label-free biosensing was demonstrated using these probes with the help of IgG-anti IgG as bioreceptor-analyte pair. © 2009 Elsevier B.V. All rights reserved.

Biosensors and Bioelectronics

Novel U-bent fiber optic probe for localized surface plasmon resonance based biosensor

Journal of Physics D: Applied Physics

Theoretical modelling of a bi-dimensional U-shaped surface plasmon resonance based fibre optic sensor for sensitivity enhancement

Journal	Data powered by TypesetProceedings of IEEE Sensors
Publisher	Data powered by TypesetInstitute of Electrical and Electronics Engineers Inc.
ISSN	19300395
Open Access	No