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A fiber optic accelerometer-magnetometer (FLAM), which can measure acceleration and magnetic field simultaneously, based on fiber laser sensing is proposed. The principle of the FLAM and the theory of the decoupling the signals of acceleration and magnetic field are presented. The FLAM was interrogated using phase-generated-carrier (PGC) method. A test of simultaneously measuring acceleration and...
We demonstrate three microfluidic chip based microfiber/nanofiber sensors for ultra-sensitive absorption, fluorescence, and femtoliter-scale sensing, respectively. The sensors shown here may open up new opportunities for ultra-sensitive biosensing and single molecule analysis.
We report the efficient coupling of optical whispering gallery modes (WGMs) in liquid crystal microdroplets suspended in immiscible aqueous environment. Individual nematic liquid crystal (NLC) microdroplet is confined at the tip of a microcapillary used to generate the microdroplets and coupled through a tapered optical fiber waveguide positioned in the vicinity of the microdroplets. Efficient coupling...
We investigate the sensitivity improvement of fiber Bragg grating (FBG) sensors based on the optical attenuation-based weak value amplification (WVA). We successfully enhance the strain sensitivity of the FBG sensor based on the proposed WVA. The amplification factor (A) controlled by the optical attention is optimized to improve the sensitivity of the FBG sensing probe. The strain sensitivity of...
A fiber sensor capable of discriminating the strain and temperature variations is presented and fully investigated. Its simple configuration is a Sagnac interferometer containing only one piece of high birefringence few-mode fiber and a polarization controller in the loop arm. The Sagnac and intermodal interferences are generated simultaneously. Based on the combined interferences, it is possible...
Guided acoustic waves Brillouin scattering (GAWBS) was recently shown to facilitate chemical sensing outside the cladding of an unmodified fiber, even though the guided light wave never reaches the substance under test. In this work, the study of GAWBS is extended to commercially-available, multi-core fibers. We show that GAWBS leads to inter-core cross-phase modulation, between cores that are otherwise...
We present results of recent research where we have utilized a femtosecond laser to micro-structure silica and polymer optical fibres in order to realize versatile optical components such as diffractive optical elements on the fibre end face, the inscription of integrated waveguide circuits in the fibre cladding and novel optical fibre sensors designs based on Bragg gratings in the core. A major hurdle...
We report on a thermal stability study of the resonant wavelength of fiber Bragg gratings fabricated by femtosecond laser. We propose a new method to analyze the decay of the central wavelength shift of Bragg gratings based on isothermal and isochronal processes up-to a maximum temperature of 800 °C. The obtained thermal decay follows a typical power-law function, which allowed us to fit theoretical...
A high-speed fiber Bragg grating(FBG) interrogation system is realized by using the high-speed sweep characteristic of Distributed feedback(DFB) laser to constitute a high-speed wavelength-swept laser. To solve the problem of narrow scanning width of the DFB laser and low reuse capacity of the system, the method of building a time division multiplexing(TDM) sensor network with identical weak fiber...
In this paper, we propose a novel approach to measurements of low relative humidity (RH) levels based on the whispering gallery modes (WGMs) phenomenon in a silica microsphere resonator coated with Agarose. The spectral dips of the WGM resonances excited in the proposed sensor depend strongly on the changes in the refractive index (RI) of the coating material as well as the surrounding RI. A study...
We demonstrate a distributed temperature sensor based on quasi-single mode (QSM) Raman scattering in few mode fibers (FMFs). The FMF allows much larger input pump power before the initiate of stimulated Raman scattering compared with the standard single mode fiber (SSMF) and mitigates the detrimental differential mode group delay (DMGD) existing in the conventional multimode fiber (MMF) based Raman...
The use of an optical fibre long period grating (LPG) as a soil moisture sensor is reported. Characterization of the device in both clay and sandy soils revealed a sensitivity to moisture levels in the range 10–50%, and the results were compared with the output from a Theta probe, the standard soil moisture sensor, which measures the impedance of the soil.
Distributed sensing by means of polarimetric analysis of the Rayleigh scattering has been among the first distributed optical fiber sensors ever proposed. Despite offering some unique features, like distributed sensing of magnetic fields and torsion, the method has not yet achieved full commercial maturity. The talk will review the present state of art, highlighting limits and potentialities.
We present novel optical fiber designs to improve performance of distributed optical fiber sensors based on Rayleigh and Brillouin scatterings, including hybrid core fiber for increasing Rayleigh backscattered signal, dual core fiber for simultaneous measurement of temperature and stain, few mode fiber for enhancing sensitivity and spatial resolution and Brillouin frequency managed fiber for increasing...
We review our recent work on chirped-pulse phase-sensitive optical time-domain reflectometry along optical fibers and its application in the measurement of true nanostrain variations in the kHz frequency range over km-long fibers. We also show how this technique can be used to perform distributed photothermal measurements of gas presence in suitable microstructured fibers.
In recent years, whispering gallery mode devices have extended their functionality across a number of research fields from photonics to sensing applications. Here, we will discuss environmental sensing applications, such as pressure, flow, and temperature using ultrahigh Q-factor microspheres fabricated from ultrathin optical fiber and microbubbles fabricated from pretapered glass capillary. We will...
Distributed fibre optic acoustic sensing (DAS) can serve as an excellent tool for real-time condition monitoring of a variety of industrial and civil infrastructures. In this paper, we portray a subset of our current research activities investigating the usability of DAS based on coherent optical time-domain reflectometry (C-OTDR) for innovative and demanding condition monitoring applications. Specifically,...
A polarization-preserving optical system that includes a dual photoelastic modulator (PEM) has been designed and fabricated for the motional Stark effect (MSE) diagnostic system which measures internal magnetic field structures inside the tokamak for the Korea Superconducting Tokamak Advanced Research. The collection optics located outside the vacuum window is composed of four lenses, a dielectric...
We propose the noncontact measurement of elasticity by using an optical fiber heterodyne interferometer and laser ultrasonics. The surface acoustic wave (SAW), that is generated by the laser pulse irradiation on the sample surface and propagating along the surface, is optically monitored by the heterodyne interferometer without taking any contact with the sample. By taking several measurements with...
In this paper, a light intensity monitoring method based on FBG is proposed. The method establishes a light intensity monitoring model with cantilever beam structure and BP neural network algorithm, which is based on fiber grating sensing technology. The accuracy of the model can meet the requirements of engineering project and it can monitor light intensity in real time. The experimental results...
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