Inter-Cross De-Modulated Refractive Index And Temperature Sensor By An Etched Multi-Core Fiber Of A MZI Structure

We present a relative sensitivity of in-fiber inter-cross demodulation of a Mach-Zehnder interferometer (MZI) based on an etched multi-core fiber (eMCF). The sensor can measure the external refractive index (RI) and temperature with a large fringe visibility of 15 dB. It is tuned using a simple technique of slow chemical etching. When the outer cores of MCF will be exposed to the surrounding, a large difference of relative effective RI is observed, which enhances the sensitivity of the sensor. The sensor\u27s wavelength and intensity responses have displayed that it can function with three different inter-cross-demodulation phenomena. A superior RI sensitivity of 178.20 dB/RIU in the range of 1.334 to 1.370, and temperature sensitivity of 66.73 pm/°C in the range of 30 to 80 °C are obtained, with an adequate linear response. Besides, it can readily resolve the issues of cross-sensitivity. Moreover, it has many advantages including easy fabrication, compact size, multiplex, repeatable, stable, and can easily differentiate RI and temperature, which lack others

Numerical Solution Of Strongly Guided Modes Propagating In Sapphire Crystal Fibers (α-Al2O3) For UV, VIS/IR Wave-guiding

A numerical solution, using the general formulation of the transcendental equation and eigenmode values, is proposed to demonstrate number of strongly guided modes propagating in sapphire crystal fibers (SCF). The SCF is considered to have hexagonal geometry of a single crystal and multimode step-index profile. Several distinguished characteristics are naturally embedded in SCF compared to other ordinary optical fibers. The eigenmodes of the SCF are numerically determined and are a combination of transverse electric, transverse magnetic, and hybrid modes. The numerical solution for wave-guiding in ultra-violet (UV), visible infrared (VIS/IR) spectrum, is investigated by the number of modal propagations under strongly guided approximation. The cross-sectional energy distribution of fundamental mode (FM) and higher order modes (HoM) describe the variation of the effective mode index with respect to the change in the core radius. The proposed waveguide is of ~35micron radius, exhibit −0.077 dB/m confinement loss at 200 nm. The simulations in this study are performed by the COMSOL multi-physics® software

Highly Sensitive Strain Sensor by Utilizing a Tunable Air Reflector and the Vernier Effect

A highly sensitive strain sensor based on tunable cascaded Fabry–Perot interferometers (FPIs) is proposed and experimentally demonstrated. Cascaded FPIs consist of a sensing FPI and a reference FPI, which effectively generate the Vernier effect (VE). The sensing FPI comprises a hollow core fiber (HCF) segment sandwiched between single-mode fibers (SMFs), and the reference FPI consists of a tunable air reflector, which is constituted by a computer-programable fiber holding block to adjust the desired cavity length. The simulation results predict the dispersion characteristics of modes carried by HCF. The sensor\u27s parameters are designed to correspond to a narrow bandwidth range, i.e., 1530 nm to 1610 nm. The experimental results demonstrate that the proposed sensor exhibits optimum strain sensitivity of 23.9 pm/με, 17.54 pm/με, and 14.11 pm/με cascaded with the reference FPI of 375 μm, 365 μm, and 355 μm in cavity length, which is 13.73, 10.08, and 8.10 times higher than the single sensing FPI with a strain sensitivity of 1.74 pm/με, respectively. The strain sensitivity of the sensor can be further enhanced by extending the source bandwidth. The proposed sensor exhibits ultra-low temperature sensitivity of 0.49 pm/°C for a temperature range of 25 °C to 135 °C, providing good isolation for eliminating temperature–strain cross-talk. The sensor is robust, cost-effective, easy to manufacture, repeatable, and shows a highly linear and stable response for strain sensing. Based on the sensor\u27s performance, it may be a good candidate for high-resolution strain sensing

Thermo-coupled Temperature Sensors By Seven-core MCF Structures

In this paper, we present an enhanced sensitivity of temperature sensors based on thermo-coupled Multicore Fiber (MCF) structures. The sensors are all fabricated using a controlled arc power of a splicing device. Two different principles of a Mach-Zehnder interferometer (MZI) and Michelson interferometer (MI) have been observed experimentally. The MZI and MI structures exhibit temperature sensitivity as 136.67 pm/°C and 70.61 pm/°C, respectively, and found insensitive to the refractive index (RI). Also, its RI response can readily resolve the issues of cross-sensitivity

A Simple Optical Fiber Spr Sensor with Ultra-High Sensitivity for Dual-Parameter Measurement

This work reports a simple optical fiber Surface Plasmon Resonance (SPR) sensor with ultra-high sensitivity for simultaneous measurement of the dual-parameter. The sensor is based on a D-shaped fiber with a nanolayer coating of Silver (Ag) and Hematite (α-Fe2O3). The Ag/α-Fe2O3 layer is deposited on the longitudinal surface of residual cladding, and a Fiber Bragg Grating (FBG) is inscribed on the single-mode fiber (SMF) for temperature compensation. The α-Fe2O3 layer protects the Ag layer from oxidation and effectively enhances the surface plasmon wave while interacting with free electrons. Finite Element Method (FEM) modeling is employed to investigate the refractive index (RI) and temperature response of the SPR sensor. The SPR sensor exhibits an ultra-high RI sensitivity of 8,518 nm/RIU (refractive index unit) in the RI range of 1.33 to 1.40, and a temperature sensitivity of-52 pm/°C in the temperature range of 20 °C to 60 °C. The SPR performance suggests that it is a potential candidate for various applications of dual-parameter sensing

Scattering from a PEC Slightly Rough Surface in Chiral Media

The scattering of left circularly polarized wave from a perfectly electric conducting (PEC) rough surface in isotropic chiral media is investigated. Since a slightly rough interface is assumed, the solution is obtained using perturbation method. Zeroth-order term corresponds to solution for a flat interface which helps in making a comparison with the results reported in the literature. First-order term gives the contribution from the surface perturbations, and it is used to define incoherent bistatic scattering coefficients for a Gaussian rough surface. Higher order solution is obtained in a recursive manner. Numerical results are reported for different values of chirality, correlation length, and rms height of the surface. Diffraction efficiency is defined for a sinusoidal grating

Numerical Approach To Approximate The Electromagnetic Scattering From Random PEC Cylinder Placed Below In Dielectric Half-space

A numerical solution is presented for electromagnetic scattering from a random cross-section of a cylinder placed inside a dielectric half-space. Assumed that a plane wave of known parameters is incident from the half space. The incident electric field of an electromagnetic plane wave is parallel to the z-axis of the random cylinder. The method of moment is employed to obtain surface currents and Electric field integral solution is used to obtain the scattered field. The problem consists of two regions, the observer located in the free space region above from interface and the second region is an underground region where the random cylinder is placed. In the whole scenario, the medium is considered as homogeneous and lossless. The average scattered field is observed by varying different parameters for realization. To diversify the solution, COMSOL Multiphysics® and Matlab is used for simulations to investigate backscattered field involving transverse electric (TE) and transverse magnetic (TM) polarizations

Design and analysis of Gold-nanowires based multi-channel SPR sensor

This research reports the simultaneous multi-analyte sensing capabilities of a d-shaped multi-channel surface plasmon resonance (SPR) sensor. Three channels are truncated in a U-shaped pattern at the side-polished surface of the d-shaped three-core fiber. Three Gold-nanowires (AuNWs) are positioned at the bottom of each sensing channel. To examine the SPR sensor's multi-channel characteristics, a finite element method (FEM) is applied. In order to detect a variety of analytes, y-polarized modes-multiplexing is used, which offers a sufficient wavelength range. At an infiltrated refractive index (RI) of 1.35, 1.38, and 1.41, respectively, the maximal RI sensitivities of c-1 (channel-one), c-2 (channel-two), and c-3 (channel-three) are found as 7,611 nm/RIU, 5,128 nm/RIU, and 12,974 nm/RIU, respectively. Moreover, the sensing structure with three external sensing channels is being demonstrated first time, to the best of our knowledge, using multicore fiber for the detection and discrimination of three different analytes simultaneously. According to expectations, the proposed sensor may be helpful for the detection of a wide range of chemicals and bio-analytes

An Efficacious Hybrid Interferometer Based On A Vernier-like Effect For Dual Parameter Sensing

Objective: An efficacious hybrid optical device based on a Vernier-like effect for dual parameter sensing is proposed. The device may find potential applications for simultaneous strain and temperature monitoring for many industries such as, environmental, biotechnology, and chemical engineering. Method: The device configuration is composed of a Michelson interferometer (MI) cascaded with a Fabry-Perot interferometer (FPI). In the manufacturing, cascaded formation of single-mode fiber (SMF), a small segment of multi-mode fiber (MMF), double side hole fiber-1 (DSHF-1), hollow Core fiber (HCF), and an infinitely extended double side hole fiber-2 (DSHF-2) are spliced together. A series of experiment demonstrates that the proposed interferometer generates an efficacious Vernier-like effect with a slight differential factor of MI and FPI spectral interferences, and this hybrid device is fully capable of measuring strain and temperature simultaneously. Results: The device is easy to fabricate and is made entirely by using ordinary laboratory equipment. The device is composed of unmodified optical fibers, which guarantees the robustness of the device. The experimental demonstration shows that the maximal strain sensitivity of the device is obtained as ~8.77 pm/µε with high resolution tracing steps, whereas temperature sensitivity is achieved as ~213 pm/°C