We propose and demonstrate a thinned fiber based Mach-Zehnder interferometer for multi-purpose sensing applications. The sensor head is formed by all-fiber in-line singlemode-multimode-thinned-singlemode (SMTS) fiber structure, only using the splicing method. The principle of operation relies on the effect that the thinned fiber cladding modes interference with the core mode by employing a multimode fiber as a mode coupler. Experimental results showed that the liquid refractive index information can be simultaneously provided from measuring the sensitivity of the liquid level. A 9.00 mm long thinned fiber sensor at a wavelength of 1538.7228 nm exhibits a water level sensitivity of -175.8 pm/mm, and refractive index sensitivity as high as -1868.42 (pm/mm)/RIU, respectively. The measuring method is novel, for the first time to our knowledge. In addition, it also demonstrates that by monitoring the wavelength shift, the sensor at a wavelength of 1566.4785 nm exhibits a refractive index sensitivity of -25.2935 nm/RIU, temperature sensitivity of 0.0615 nm/°C, and axial strain sensitivity of -2.99 pm/μe, respectively. Moreover, the sensor fabrication process is very simple and cost effective.

All-fiber Mach-Zehnder interferometers for sensing applications

Ferrofluids are suspensions of magnetic nanoparticles that have the attractive feature of being controlled by applied magnetic fields. Ferrofluids have been studied for decades in an ever growing number of applications that take advantage of their response to applied magnetic fields. Here, we provide a summary of recent advances in established and emerging applications of ferrofluids, including applications in optics, sensors, actuators, seals, lubrication, and static/dynamic magnetically driven assembly of structures.

Recent progress in ferrofluids research: novel applications of magnetically controllable and tunable fluids

Photonic crystal fibers are a kind of fiber optics that present a diversity of new and improved features beyond what conventional optical fibers can offer. Due to their unique geometric structure, photonic crystal fibers present special properties and capabilities that lead to an outstanding potential for sensing applications. A review of photonic crystal fiber sensors is presented. Two different groups of sensors are detailed separately: physical and biochemical sensors, based on the sensor measured parameter. Several sensors have been reported until the date, and more are expected to be developed due to the remarkable characteristics such fibers can offer.

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Photonic crystal fibers for sensing applications

An optical fiber magnetic field sensor based on the single-mode-multimode-single-mode (SMS) structure and magnetic fluid (MF) is proposed and demonstrated. By using a piece of no-core fiber as the multimode waveguide in the SMS structure and MF sealed in a capillary tube as the magnetic sensitive media, which totally immersing the no-core fiber, an all-fiber magnetic sensor was fabricated. Interrogation of the magnetic field strength can be achieved either by measuring the dip wavelength shift of the transmission spectrum or by detecting the transmission loss at a specific wavelength. A demonstration sensor with sensitivities up to 905 pm/mT and 0.748 dB/mT was fabricated and investigated. A theoretical model for the design of the proposed device was developed and numerical simulations were performed.

Optical fiber magnetic field sensor based on single-mode-multimode-single-mode structure and magnetic fluid

Optical fibers provide much more than a means to transport light between different locations. This article reviews how integration of functional fluid, solid, and gaseous materials in photonic crystal fibers enables control of their linear and nonlinear properties with applications in optoelectronics, sensing, and laser science.

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Hybrid photonic-crystal fiber

We report a magnetic field sensor having advantages of both photonic crystal fiber and optofluidics, combining them on a single platform by infiltrating small amount of Fe3O4 magnetic optofluid/nanofluid in cladding holes of polarization-maintaining photonic crystal fiber We demonstrated that magnetic field of few mT can be easily and very well detected with higher sensitivity of 242 pm/mT The change in the birefringence values has been correlated to the response of nanofluid to applied field

Photonic crystal fiber injected with Fe3O4 nanofluid for magnetic field detection

In the present work, Structural Health Monitoring (SHM) of a composite beam using embedded Polarization Maintaining Photonic Crystal Fiber (PM-PCF) has been investigated with emphasis on better monitoring of composite materials and the wide range of potential applications this class of materials currently have. This new concept of using PM-PCF for SHM is attractive because it enables the design of a vibration sensor that is highly sensitive to vibration and at the same time is insensitive to temperature. Vibration measurements up to 50 Hz have been demonstrated in this work.

All-fiber embedded PM-PCF vibration sensor for Structural Health Monitoring of composite

In this letter, the nonlinear photonic crystal fiber (NLPCF) has been exploited for the first time, as a high-temperature sensor based on the modal interferometric technique with a sensitivity that is remarkably higher along with low strain sensitivity We have obtained a very high temperature sensitivity of 73 pm/°C and a very low strain sensitivity of 093 pm/μe The temperature to strain cross sensitivity is found to be significantly low in the very high range of temperature and strain The proposed sensor may find application in strain-effective areas requiring accurate temperature measurement even at a high temperature range

Photonic Crystal Fiber Strain-Independent Temperature Sensing Based on Modal Interferometer

An all-fiber modal interferometric torsion sensor based on simple splicing configuration is presented wherein a photonic crystal fiber is spliced in between multimode fiber and single mode fiber. Appreciable torsion sensitivity of ~79.83 pm/° is obtained in the long dynamic range of 180°. It is also found that there is no effect of strain and temperature on torsion sensitivity in the range of 0-4500 μe and 30-200°C, respectively, leading to zero cross-sensitivity of torsion with strain and temperature.

Harneet V. Thakur

Papers

Photonic crystal fiber injected with Fe3O4 nanofluid for magnetic field detection

All-fiber embedded PM-PCF vibration sensor for Structural Health Monitoring of composite

Photonic Crystal Fiber Strain-Independent Temperature Sensing Based on Modal Interferometer

Temperature and Strain Independent Modal Interferometric Torsion Sensor Using Photonic Crystal Fiber

Polarization Maintaining Photonic Crystal Fiber sensor embedded in carbon composite for structural health monitoring