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J.C. Kim, D.Y. Kim,
S.M. Jung,
M.H. Lee,
K.S. Kim,
C.K. Lee,
J.Y. Nah,
S.H. Lee,
J.H. Kim,
W.J. Choi,
S.K. Yoo
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ABSTRACT: So far we have developed Emergency Telemedicine System (ETS) which is a robust system using heterogeneous networks. In disaster areas, however, ETS cannot be used if the primary network channel is disabled due to damages on the network infrastructures. Thus we designed network management software for disaster communication network by combination of Mobile Ad hoc Network (MANET) and Wireless LAN (WLAN). This software maintains routes to a Backbone Gateway Node in dynamic network topologies. In this paper, we introduce the proposed disaster communication network with management software, and evaluate its performance using ETS between Medical Center and simulated disaster areas. We also present the results of network performance analysis which identifies the possibility of actual Telemedicine Service in disaster areas via MANET and mobile network (e.g. HSDPA, WiBro).
Engineering in Medicine and Biology Society, 2009. EMBC 2009. Annual International Conference of the IEEE; 10/2009
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ABSTRACT: We present a reflectometric measurement scheme of group-velocity dispersion for an optical fiber, whose measurement range covers the entire band of optical communication from 1200 to 1700 nm in wavelength by using a wideband supercontinuum source. In our measurement scheme, wavelength-dependent temporal delays are measured for spectrum-sliced supercontinuum pulses that have passed through a fiber under measurement (FUM). A reflectometric configuration is used to increase the accuracy of the measurement results by eliminating the effect of timing instabilities of the light source and the detection electronics. The time of flight is measured by taking the relative delay between two pulses back reflected by the two ends of an FUM. The delay measurement is performed for two wavelengths simultaneously to minimize the effect of the temperature-sensitive drift. We have successfully demonstrated that our scheme can characterize a relatively short single-mode fiber of 10 m with a good measurement accuracy.
IEEE Photonics Technology Letters 10/2009; · 2.19 Impact Factor
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ABSTRACT: We present a low coherent hybrid detection technique for the differential model delay (DMD) measurement of a conventional optical multimode fiber with a modified Mach-Zehnder interferometer. A low coherent hybrid detection technique enhances mode coupling between guided modes and the reference mode to easily resolve the modal distribution. An optical spectrum analyzer and a broadband source were used to obtain time-resolved optical beat signals. The measured interference signal was Fourier transformed to obtain time-delay information. A scanning offset launching method was used to excite every available mode in a multimode fiber (MMF). Measurements of a conventional 8-m-long MMF demonstrated the validity of our proposed method. The experimental results of our proposed method agree well with results obtained using a conventional time domain measurement method. Our proposed method can be used to measure the DMD in a short length of optical MMF with a temporal resolution better than 0.72 ps when using an 8-m-long single-mode fiber as a reference.
Applied Optics 03/2008; 47(6):725-30. · 1.41 Impact Factor
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ABSTRACT: We propose an angular offset technique for launching optical signals into multimode fibers (MMFs) used in short distance optical fiber links. The signal is launched onto the angled facet of an MMF. The presented method shows better bandwidth enhancement in comparison with the conventional lateral offset launching method with a little power penalty. This method is simple and can be easily adopted in transmitters for high-speed MMF links. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 165–168, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22988
Microwave and Optical Technology Letters 11/2007; 50(1):165 - 168. · 0.62 Impact Factor
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ABSTRACT: We present a novel spectrum-slicing method for measuring the chromatic dispersion of an optical fiber in Fourier-domain low-coherence interferometry. Broadband spectral interference data obtained from a low-coherence interferometer is sliced with Gaussian window functions. Each sliced spectral datum is used to calculate a relative group delay with Fourier transformation at the peak wavelength of a narrow window function. We have demonstrated that our proposed method is very powerful and simple for measuring chromatic dispersion and second-order dispersion in optical fibers and optical devices. Comparison of the proposed method with a conventional measurement method agrees within 0.5%.
Applied Optics 11/2007; 46(29):7289-96. · 1.41 Impact Factor
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ABSTRACT: We present a novel differential mode delay (DMD) measurement method for a multimode optical fiber (MMF) based on Fourier-domain low-coherence interferometry (fLCI) for the first time. An optical spectrum analyzer and a mode scrambler were used to obtain intermodal interference signal in spectral-domain after light pass an MMF. The MMF was used as a common path interferometer by itself without using any reference arm in an interferometer. Our proposed method can measure a short or long optical multimode fiber simply, accurately, and rapidly.
Lasers and Electro-Optics - Pacific Rim, 2007. CLEO/Pacific Rim 2007. Conference on; 10/2007
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ABSTRACT: Direct refractive index profiling for a core-doped photonic crystal fiber with complex and nonsymmetric refractive index structure has been demonstrated for the first time. A new index profiling technique based on a reflectivity measurement technique using a confocal microscope has been employed. This improved, straightforward, and robust method enables us to measure the index structure of a complex structured fiber with high refractive index precision and spatial resolution
IEEE Photonics Technology Letters 07/2007; · 2.19 Impact Factor
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ABSTRACT: A novel differential mode delay (DMD) measurement for a multimode optical fiber using the Fourier-domain low-coherence interferometry (fLCI) for the first time has been proposed. Our experimental results have a good agreement with those results obtained using a conventional method
Optical Fiber Communication Conference, 2006 and the 2006 National Fiber Optic Engineers Conference. OFC 2006; 04/2006
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ABSTRACT: We propose a novel transmission scheme to extend the single-mode operation range of a conventional single-mode fiber (C-SMF) to wavelengths shorter than the cutoff wavelength. It involves the use of a tapered-fiber mode filter (MF) in order to remove the high-order-mode power from the C-SMF and hence, makes the fiber work as a virtually single-mode transmission link. High-order mode suppression of above 10 dB has been achieved at wavelengths of 850 and 980 nm with a fabricated tapered-fiber MF. We have also demonstrated the feasibility of the technique by evaluating the transmission quality with the MF at 850 nm through a 5-km C-SMF having a cutoff wavelength of 1.2 μm.
IEEE Photonics Technology Letters 01/2006; · 2.19 Impact Factor
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ABSTRACT: Near-field patterns of uniplanar compact photonic bandgap (UC-PBG) and non-UCPBG finite-width conductor-backed coplanar waveguides (FW-CBCPWs) are characterized using an electro-optic near-field mapping system. This system is very effective in visually showing the role of the UC-PBG structure in the suppression of microstriplike (MSL) modes in the FW-CBCPWs. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 119–122, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21098
Microwave and Optical Technology Letters 08/2005; 47(2):119 - 122. · 0.62 Impact Factor
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ABSTRACT: The mode analysis and modal delay measurement based on the optical frequency domain reflectometry is suggested. Modal delay of few modes fiber is measured by OFDR and is compared with traditional pulse delay measurement method
Quantum Electronics and Laser Science Conference, 2005. QELS '05; 06/2005
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ABSTRACT: We report detailed axial stress distribution along the splice between dissimilar optical fibers. Variation in magnitude, sign as well as discontinuity in the stress distribution were experimentally analyzed for splicing DCF, DSF and EDF with SMF.
Optical Fiber Communication Conference, 2004. OFC 2004; 03/2004
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ABSTRACT: Bandwidth improvement due to the mode-filtering effect caused by mode-dependent loss mechanism in a hard-polymer cladding fiber was investigated experimentally as well as numerically. We believe this principle can be applied to silica and plastic multimode fibers.
Optical Fiber Communications Conference, 2003. OFC 2003; 04/2003
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ABSTRACT: We report experimental results on the development of residual stress due to OH impurity in optical fibers. The effect of OH impurity on residual stress is demonstrated by direct residual stress measurement. The residual stress at the outer-cladding/jacketing-tube boundary of the fiber drawn at 3.48 N was found to be -61 MPa . The residual compressive stress is attributed to the viscosity decrease induced by a significant OH impurity at the boundary, as measured by a Fourier transform infrared microscope.
Optics Letters 06/2002; 27(10):806-8. · 3.40 Impact Factor
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ABSTRACT: In this letter, we report a new self-starting figure-eight fiber laser based on a dispersion-imbalanced nonlinear optical loop mirror (DI-NOLM) with lumped dispersive elements for the first time. We have shown that the device can operate in several different operation modes such as a noiselike square pulse, a harmonic mode-locked multipulse, and a single-pulse operation modes depending on its pump power and polarization state in the cavity. As no active elements is inside the DI-NOLM and no continuous-wave light can pass through the DI-NOLM, this laser potentially has many advantages over conventional pulsed fiber laser systems.
IEEE Photonics Technology Letters 05/2002; · 2.19 Impact Factor
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04/2002;
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ABSTRACT: The compressive residual stress was found to develop at the outer-cladding/jacketing boundary of the optical fibers during the fiber drawing process. The residual stress of the fiber drawn at 3.48 N was found to be -61 MPa and it was due to the viscosity decrease induced by a significant OH impurity of ∼582 ppm.
Optical Fiber Communication Conference and Exhibit, 2002. OFC 2002; 04/2002
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ABSTRACT: We observed residual stress relaxation by CO(2) laser irradiation in the cores of optical fibers by direct stress measurement. It was demonstrated that the mechanical stress was fully relaxed by CO(2) laser irradiation and that the remaining stress in the core was thermal stress that was due to a mismatch of the thermal expansion coefficients of the fiber core and cladding. The net core stresses after relaxation were 17, 68, and 203 MPa in Ge-B-codoped fibers drawn at 0.53, 1.38, and 3.48 N, respectively. Changes in the refractive indices of the cores as a result of residual stress relaxation were also estimated.
Optics Letters 12/2001; 26(21):1657-9. · 3.40 Impact Factor
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ABSTRACT: Mode locking of a figure-eight fiber laser using a dispersion-imbalanced nonlinear optical loop mirror with lumped dispersive elements is demonstrated for the first time. The modelocked pulses show noise-like properties whose pulse width and average optical power are 3.26 ns and 6.526 mW respectively when 95 mW pump power is provided at 980 nm wavelength.
Optical Fiber Communication Conference and Exhibit, 2001. OFC 2001; 04/2001
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ABSTRACT: For the first time, self-adjustments of positions of quantised
modelocked optical pulses are observed in a passively harmonic
modelocked fibre laser by using a dispersion-imbalanced nonlinear
optical loop mirror with lumped dispersive elements
Electronics Letters 03/2001; · 0.96 Impact Factor
