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Optical Fiber and Component Technology
Paek, Un-Chul 경북대학교 센서기술연구소 1991 센서技術學術大會論文集 Vol.2 No.1
This paper reviews the recent results of optical fiber and component applications including optical fiber sensors. The topic includes the fabrication processes of a variety of optical components and devices. Particularly, with regard to optical amplifiers, the erbium-doped fiber is most attractive for use in optical communications applications as a line booster and pre-amplifier since it has all the desirable characteristics for an amplifier (e.g. high gain, low noise, polarisation independent, low input power and so forth). As one of the system applications we will illustrate the most updated development of the optical amplifier used in a submarine cable repeater system. Also, a detailed description of principles as well as applications of optical fiber sensors will be presented.
Kim, Jinchae,Paek, Un-Chul,Lee, Byeong Ha,Hu, Jonathan,Marks, Brian,Menyuk, Curtis R Optical Society of America 2006 Optics letters Vol.31 No.9
<P>We have investigated the spectral properties of a band rejection filter made with a long-period fiber grating written in photonic crystal fiber that has interstitial air holes. Experiments showed that only one mode was coupled strongly to the fundamental core mode over a 600 nm spectral range. The central wavelength of the filter could be tuned over that range without being appreciably affected by any other mode. By using the multipole method, we found that the interstitial air holes of the photonic crystal fiber played a critical role in limiting the number of modes that could strongly interact with the fundamental mode and in obtaining well-separated resonance peaks. Excellent agreement between theory and experiment was obtained.</P>
Tunable photonic crystal fiber coupler based on a side-polishing technique.
Kim, Hokyung,Kim, Jinchae,Paek, Un-Chul,Lee, Byeong Ha,Kim, Kwang Taek Optical Society of America 2004 Optics letters Vol.29 No.11
<P>A tunable photonic crystal fiber (PCF) coupler, which couples part of the optical power in one PCF with that in another PCF, has been made by side polishing. We fabricated the PCF coupler by mating two side-polished PCFs. We achieved evanescent field coupling between the core modes of the two PCFs by using side polishing to bring the cores close to each other. By adjusting the mating angle between the two side-polished PCFs we obtained as much as 90% tunability in the coupling ratio. The spectrum of the coupling ratio was almost flat, with small ripples, over a 400-nm wavelength range.</P>
The Fabrication of a Photonic Crystal Fiber and Measurement of its Properties
Kim, Jin-Chae,Kim, Ho-Kyung,Paek, Un-Chul,Lee, Byeong-Ha,Eom, Joo-Beom 한국광학회 2003 Current Optics and Photonics Vol.7 No.2
In this paper, we describe the fabrication process of a photonic crystal fiber and present the measured optical properties of the photonic crystal fiber. The fabrication of the photonic crystal fiber involves stacking, jacketing, collapsing, and drawing using a conventional drawing tower The photonic crystal fiber drawing needs higher tension to maintain the uniform air hole structure. Thus, the temperature of the photonic crystal fiber drawing is lowered by a few hundred degrees Celsius than for the case of conventional optical fiber drawing. The optical properties of the fabricated photonic crystal fiber such as mode profile, optical loss, transmission spectrum, bending loss, and polarization dependent loss are measured.
Effect of Soaking Temperature on Erbium Doping of Optical Fiber Core in MVCD Solution Doping Process
Han, Won-Taek,Kim, Yune-Hyoun,Paek, Un-Chul 한국광학회 2003 Current Optics and Photonics Vol.7 No.2
Effect of soaking temperature on erbium doping of the optical fiber core during solution doping procedure, especially in the modified chemical vapor deposition (MCVD) process, was investigated. The concentration of dopants such as $Er^{3+} and Al^{3+}$ in the preforms and the optical fibers measured by the electron probe microanalysis (EPMA) and the optical spectrum analyzer (OSA) was found to increase with decreasing the soaking temperature. The increase in the concentration of the $Er^{3+}$ is attributed to the precipitation of the erbium due to the decrease in the solubility as well as the increase of capillary force and viscosity of the doping solution by decreasing the temperature.
박철훈,하병국,백운상,한시준,Park, Chul-Hoon,Ha, Byoung-Kuk,Paek, Un-Sang,Hahn, See-Joon 대한약리학회 1972 대한약리학잡지 Vol.8 No.2
Zea mays Linne, which belongs to Graminae family, has been ordinarily used as edibles and fodder. Its stigma, Maydis Stigma, has been discarded without any special application with the exception of being used as diuretic in the sphere of Chinese medicine. Moreover, the pharmacological research toward Maydis Stigma as a medicinal herb has not been regretfully undertaken at all. The authors hereby paid attention to this point of view and made experiment to find out whether the water extract of Maydis Stigma might possess some pharmacological effect on the blood pressure of the rats or not. $LD_{50}$ to the mice was determined and the experiment was performed making the use of several agents related to the blood pressure such as atropine, Avil, dichloroisoproterenol and hexamethonium. The blood pressure of the rats and rabbits was recorded with the equipment of polygraph (Grass model 7 DAB) and its accessory, Statham pressure transducer. The results of the experiment are as follows. 1. $LD_{50}$ to the mice weighing 20g is determined 1,125 mg/kg. 2. The blood pressure manifests the gradual decrease by the rate of $-15.50{\pm}3.32,\;-22.14{\pm}8.73$ and $-46.25{\pm}5.17\;mmHg$ in proportion to ZW 25, 50 and 150mg/kg administered to the rats. 3. The blood pressure also manifests the same gradual decrease in proportion to ZW administered to the rabbits. 4. It is of significant difference to manifest the increase of $+5.14{\pm}4.65\;mmHg$ in the rats pretreated with atropine as compared with $-22.14{\pm}8.73\;mmHg$ of control group when administered each ZW 50mg/kg. 5. The administration of ZW 50 mg/kg to the rats pretreated with Avil, dichloroisoproterenol and hexamethonium does not manifest the significant difference in comparison with the control group.
Kim, Myoung Jin,Eom, Tae Joong,Paek, Un-Chul,Lee, Byeong Ha IEEE 2005 Journal of lightwave technology Vol.23 No.2
Optical fiber connectors that had a long working distance and wide alignment tolerance were implemented by utilizing long-period fiber gratings (LPGs) written in double-cladding fiber. The power coupling between two separated pieces of fiber was accomplished through the inner cladding modes of both fibers. Assisted by the LPGs, approximately 450 μm was achieved for a 1-dB working distance, as well as about 3 mm of 3-dB working distance. When the separation between two fiber tips was 1.5 mm, the 3-dB lateral tolerance was measured to be about 30 μm, which was five times better than was the case when not utilizing the LPGs. By using the inner cladding mode of a dispersion-compensating fiber, it was possible to implement a fiber connector that was insensitive to the perturbations at the cladding surface of the fiber. The total insertion loss of the device at the maximum coupling was 2.06 dB, from which the loss purely induced by inserting the fiber gratings was analyzed to be smaller than 0.9 dB. The experimental results show strong feasibility for implementing a simple and cost-effective fiber connector that does not require any bulk optic elements.