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Likarn Wang

Bio: Likarn Wang is an academic researcher from National Tsing Hua University. The author has contributed to research in topics: Optical fiber & Fiber Bragg grating. The author has an hindex of 6, co-authored 20 publications receiving 235 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate the higher temperature sensitivity of a fiber Bragg grating (FBG) sensor when it is clad with a metal of a large thermal expansion coefficient and show that the sensitivity of Bragg wavelength shift can be enhanced by about five (four) times.
Abstract: We demonstrate the higher temperature sensitivity of a fiber Bragg grating (FBG) sensor when it is clad with a metal of a large thermal expansion coefficient. With lead (solder) cladding, the sensitivity of Bragg wavelength shift can be enhanced by about five (four) times. A theoretical model was adopted to show quite consistent results. It was found that thermal annealing was crucial for preparing high-quality fiber Bragg grating sensors with metal claddings.

76 citations

Journal ArticleDOI
TL;DR: In this article, a temperature-insensitive sensing scheme for pressure measurement is presented, where a single optical fiber Bragg grating (FBG) is axially strained by its surrounding pressure, and is thermally compensated by a bimaterial effect.
Abstract: A temperature-insensitive sensing scheme for pressure measurement is presented. In the sensing scheme, a single optical fiber Bragg grating (FBG) is axially strained by its surrounding pressure, and is thermally compensated by a bimaterial effect. The FBG is kept tight (i.e., in a positive strain) initially in the sensing structure. When the surrounding temperature increases, a negative strain (to loosen the FBG) is incurred on the FBG and produces a blue shift of the Bragg wavelength. Temperature compensation is, thus, made by balancing such blue shift and the inherent thermally induced red shift of the FBG. Experimental results show a pressure sensitivity of the fractional change in the Bragg wavelength of 1.8/spl times/10/sup -2/ (MPa)/sup -1/, and demonstrate quite a low response to the temperature varying from 10/spl deg/C to 60/spl deg/C.

67 citations

Journal ArticleDOI
TL;DR: In this article, a double-pass EDF amplifier with a narrow-band Bragg grating at each channel wavelength is used to back-reflect the L-band signal to make it amplified twice by the pair of EDFs.

40 citations

Journal ArticleDOI
TL;DR: In this article, a residual pump power was used for implementation of low-noise and high-gain L-band erbium-doped fiber amplifiers (EDFAs).

15 citations

Journal ArticleDOI
20 Mar 2006
TL;DR: In this paper, a temperature-insensitive multipoint strain sensor based on fiber Bragg gratings is presented, where a divider circuit at the post detection port compensates for optical power variation and thermal instability induced by the nonflatness of the source spectrum.
Abstract: This work presents a new temperature-insensitive multipoint strain sensor based on fiber Bragg gratings. A divider circuit at the post detection port compensates for optical power variation and thermal instability induced by the nonflatness of the source spectrum. Experimental results show a measurement resolution of /spl plusmn/0.35 /spl mu/S and a temperature stability of /spl plusmn/0.005% for no strain (/spl plusmn/0.48% for a strain of <400 /spl mu/S) in an example with two sensing points. A measurement linearity of /spl plusmn/0.17% is estimated in the range 0 to 350 /spl mu/S with no crosstalk.

9 citations


Cited by
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Journal ArticleDOI
TL;DR: A flexible bimodal sensor is demonstrated that can separate a target signal from the signal by mechanical strain through the integration of a multi-stimuli responsive gate dielectric and semiconductor channel into the single field-effect transistor (FET) platform.
Abstract: Diverse signals generated from the sensing elements embedded in flexible electronic skins (e-skins) are typically interfered by strain energy generated through processes such as touching, bending, stretching or twisting. Herein, we demonstrate a flexible bimodal sensor that can separate a target signal from the signal by mechanical strain through the integration of a multi-stimuli responsive gate dielectric and semiconductor channel into the single field-effect transistor (FET) platform.

365 citations

Journal ArticleDOI
TL;DR: Fiber Bragg grating has embraced the area of fiber optics since the early days of its discovery, and most fiber optic sensor systems today make use of fiber Bragg-grating technology as discussed by the authors.
Abstract: Fiber Bragg grating has embraced the area of fiber optics since the early days of its discovery, and most fiber optic sensor systems today make use of fiber Bragg grating technology Researchers have gained enormous attention in the field of fiber Bragg grating (FBG)-based sensing due to its inherent advantages, such as small size, fast response, distributed sensing, and immunity to the electromagnetic field Fiber Bragg grating technology is popularly used in measurements of various physical parameters, such as pressure, temperature, and strain for civil engineering, industrial engineering, military, maritime, and aerospace applications Nowadays, strong emphasis is given to structure health monitoring of various engineering and civil structures, which can be easily achieved with FBG-based sensors Depending on the type of grating, FBG can be uniform, long, chirped, tilted or phase shifted having periodic perturbation of refractive index inside core of the optical fiber Basic fundamentals of FBG and recent progress of fiber Bragg grating-based sensors used in various applications for temperature, pressure, liquid level, strain, and refractive index sensing have been reviewed A major problem of temperature cross sensitivity that occurs in FBG-based sensing requires temperature compensation technique that has also been discussed in this paper

163 citations

Journal ArticleDOI
Jaehoon Jung1, Hui Nam1, Byoungho Lee1, Jae Oh Byun1, Nam Seong Kim1 
TL;DR: A fiber Bragg grating sensor with controllable sensitivity is demonstrated by connecting two metal strips that have different temperature-expansion coefficients by changing the lengths of the metal strips.
Abstract: We demonstrate a fiber Bragg grating (FBG) sensor with controllable sensitivity by connecting two metal strips that have different temperature-expansion coefficients. By changing the lengths of the metal strips we successfully controlled and improved the temperature sensitivity to 3.3 times of that of bare FBG.

154 citations

Journal ArticleDOI
TL;DR: The results show that nanometre-scale control of semiconducting polymer chain orientation and position leads to novel and desirable optical properties.
Abstract: We control the chain conformation of a semiconducting polymer by encapsulating it within the aligned nanopores of a silica host. The confinement leads to polarized, low-threshold amplified spontaneous emission from the polymer chains. The polymer enters the porous silica film from only one face and the filling of the pores is therefore graded. As a result, the profile of the index of refraction in the film is also graded, in the direction normal to the pores, so that the composite film forms a low-loss, graded-index waveguide. The aligned polymer chains plus naturally formed waveguide are ideally configured for optical gain, with a threshold for amplified spontaneous emission that is twenty times lower than in comparable unoriented polymer films. Moreover, the optimal conditions for ASE are met in only one spatial orientation and with one polarization. The results show that nanometre-scale control of semiconducting polymer chain orientation and position leads to novel and desirable optical properties.

106 citations

Journal ArticleDOI
TL;DR: In this article, a new technique is proposed for embedding a fiber optic sensor into metallic structures, such as nickel, with minimized residue stress, and the thermal performance of such an embedded FBG sensor is studied.
Abstract: With embedded sensors it is possible to monitor structural parameters at critical locations which are not accessible to ordinary sensors. Recently, the fiber optic sensor has emerged as a promising technology to be integrated with structures. The embedding of fiber optic sensors into composites and some metals, especially those with low melting points, have been reported. However, all reported embedding techniques so far are either complicated or it is difficult to achieve coherent bonding with low residue stresses. Thus, it is of interest to pursue some economical ways to embed fiber optic sensors into metallic structures with low residue stresses. In this work, a new technique is proposed for embedding a fiber optic sensor into metallic structures, such as nickel, with minimized residue stress. Fiber Bragg grating (FBG) sensors have been embedded into nickel structures. The thermal performance of such an embedded FBG sensor is studied. Higher temperature sensitivity is demonstrated for the embedded FBG sensors. For temperature measurements, the embedded FBG sensor yields an accuracy of about 2 °C. Under rapid temperature changes, it is found that thermal stresses due to the temperature gradient in the metallic structures would be the main cause for errors.

101 citations