• Information and Communications Magazine
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• v.11 no.2
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• pp.77-89
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• 1994

High speed optical fiber transmission technology has been remarkably improved during the past 20 years. This paper presents recent research status and future technological issues for the future information society, that is, the Tb/s transmission by frequency division multiplexing and the ultra long-distance by optical soliton transmission. Erbium-doped fiber amplifier and recent optical technology have brought optical transmission system of up to 10 Gb/s to the point of commercialization. Taking into account the future super information highway, that is, B-ISDN network, ultra wide-band picture-based information can be provided for many subscribers via existing optical fiber cables. However, to achieve the high speed transmission, the technologies must be developed not only for transmission lines but also for transmission nodes. Since the conventional signal transmission/processing technique using electronics has the limit in its speed, novel photonic technology is being developed for this purpose. On the other hand, optical solitons propagate stably through optical fibers, without pulse broadening effect of the fiber dispersion. Since the pulse broadening effect becomes serious as the transmission speed increases, optical solitons is the important technologies to realize the high speed, long distance transmission.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1757-1763
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• 2014

Optical wavelength division multiplexing signals of eight non-return-to-zero 10 Gb/s channels were transmitted on the long-haul link up to 720 km. The link span was composed of 80 km single mode fiber, dispersion compensation fiber for complete compensation, and EDFAs. A circulating loop method was applied to the link experiment and the loop was optimized for the transmission link. Wavelength-dependent gain variation of EDFA was compensated using EDFAs of opposite gain slopes without expensive gain flattening filters. Average OSNR was aggravated to 22 dB and the worst OSNR channel variation was 9.7 dB after the transmission. It was confirmed by analyzing optical spectra that this OSNR variation was mainly caused by the hole burning effect of EDFA.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.558-564
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• 2009

POF(Polymer optical fiber) offers advantages of lighter, inexpensive, and easier to use over GOF(glass optical fiber). Its higher transmission loss and low bandwidth, however, make it suitable only for short distance networking such as LAN. The polymer materials and its synthesis technology of low transmission loss and the broader application for flexible POF are the two of many critical areas to be investigated more. In the current study, low-noise POF modules are developed and optimized with a low noise amplifier and low cost LED of 650 nm. In order to demonstrate the dynamic characteristics of the POF module for optical communication and sensing, we have built an image transfer module, optical transmission speed measurement module, optical transceiver for RS-232, and sound-transfer module, and the signal characteristics of them are evaluated. It is found that the module can be readily used for a quick and simple measurement of optical transfer speed. With help of analog amplifier, LED, and PD, sound and image transfers through a maximum 60 m optical waveguide have been confirmed. Real-time data transfer was also demonstrated in PID control, which is thought to be valuable to industrial plant design and control.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.242-243
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• 2000

Erbium 첨가 광섬유(EDF) 광원은 출력 특성과 온도에 대한 파장 특성이 우수하여 Sagnac 간섭계의 원리를 이용한 광섬유 자이로스코프(이하 줄여 자이로라 함)에 많이 사용되고 있다. 이득매질인 EDF를 광원 겸 광증폭기로 사용하는 광섬유 증폭기형 광원 (Fiber Amplifier/source : FAS) 방식$^{[l-2]}$ 은 기존의 single-pass 방식$^{[3]}$ 에 비해서 구조가 단순하고 검출광 power가 크다는 장점이 있다. 그런데, 검출광 power가 큰 경우에 자이로의 SNR이 광원의 과잉잡음(excess noise)에 의해서 제한되므로 실제로 자이로의 측정감도는 개선되지 않는 문제점이 있다.$^{[4]}$ Single-pass 방식의 광원을 사용하는 경우, 적절한 신호처리를 통해 자이로 출력신호에 포함된 광원의 과잉잡음의 적정주파수 성분을 소거함으로써 자이로 신호의 SNR을 개선시킨 바 있었다.$^{[5]}$ 그러나, 일반적으로 single-pass 방식의 경우에는 검출광 power가 작아서 자이로의 SNR이 광원의 과잉잡음에 의해서 제한되는 경우는 드물다. 반면에 증폭기형 광원 방식은 자이로로부터 되돌아오는 신호광이 다시 광원으로 입사되어 EDF를 반대 방향으로 진행하는 동안 증폭되기 때문에 충분히 큰 검출광 power를 얻을 수 있다. 따라서, 자이로 신호에 포함된 광원의 과잉잡음이 소거된다면 자이로 신호의 SNR은 크게 개선될 것으로 여겨진다. 이 논문에서는 광섬유 증폭기형 광원 방식(FAS)의 자이로에 대해 위와 같은 신호처리를 이용하여 광인의 과잉잡음의 적정주파수 성분을 소거하는 실험을 하였다. (중략)한 흡수를 확인하고, $^4$T$_2$$\longrightarrow$$^4$A$_2$(650-800 nm), $^2$E$\longrightarrow$$^4$A$_2$에 의한 nophonon line R$_1$, R$_2$(680.4, 678.5 nm) 및 $^2$T$_1$$\longrightarrow$$^4$A$_2$(655.7, 649.3, 645.2 nm)의 형광방출 스펙트럼을 얻었으며, 형광수명은 0.264 ms로 조사되었다. 제조된 레이저 발진봉은 직경 6.3 m, 길이 45 nm이었다.\pm$0.06kHz Ge $F_4$; -1.84$\pm$0.04kHz$0.04kHz/TEX>0.04kHz 모국어 및 관련 외국어의 음운규칙만 알면 어느 학습대상 외국어에라도 적용할 수 있는 보편성을 지니는 것으로 사료된다.없다. 그렇다면 겹의문사를 [-wh]의리를 지 닌 의문사의 병렬로 분석할 수 없다. 예를 들어 누구누구를 [주구-이-ν가] [누구누구-이- ν가]로부터 생성되었다고 볼 수 없다. 그러므로 [-wh] 겹의문사는 복수 의미를 지닐 수 없 다. 그러면 단수 의미는 어떻게 생성되는가\ulcorner 본 논문에서는 표면적 형태에도 불구하고 [-wh]의미의 겹의문사는 병렬적 관계의 합성어가 아니라 내부구조를 지니지 않은 단순한 단어(minimal $X

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.21-28
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• 2004

We have demonstrated a low speed weigh-in motion system using FBG sensors and performed field test at a trial road. Technique, called identical chirped grating interrogation, have used for a demodulation relying on the mismatching of two identical broadband chirped gratings. We compensated the fluctuation of LED power and the temperature of sensor and used a lock-in amplifier to reduce effect of noise. We could design a bending plate that the measurement results are independent of position of weight. The FBG sensors weigh-in motion system showed linearity and reproducibility.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.64-67
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• 1999

We have been implemented 10 Gb/s-320 km of dispersion-shifted fiber (DSF) transmission. The optical link consists of a 10 Gb/s optical transceiver, an optical booster amplifier, 3 sets of optical in-line amplifiers, an optical preamplifier and transmission fibers. Firstly, we investigated the Q-factor characteristics in terms of optical signal to noise ratio (OSNR) of 320 km of DSF, measured receiver sensitivity is -27 dBm and power penalty is 2 dB, respectively. We concluded that optical SNR degradation and path penalty gives rise to 1 dB penalty, respectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.2 no.1
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• pp.40-45
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• 2007

The repeaterless system can be designed by applying EDFA technology in receiver, transmitter and optical cable in the case of connecting several hundred km from coast to coast, between continents or islands. Because of no repeater the repeaterless system do not need power system to feed laser diode in repeater for signal amplification and cooper tuber in submarine cable. So we can be configured more reliable and economical compared to repeater system. But lower loss optical fiber must be used to get enough signal amplitude without the amplification of repeater. This report consider long distance optical repeaterless system by reflecting the limitation factor of optical amplification.

• ETRI Journal
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• v.23 no.3
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• pp.97-105
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• 2001

$1.6\;{\mu}m$ emission originated from $Pr^{3+}:\;(^3F_3,\;^3F_4)\;{\longrightarrow}\;^3H_4$ transition in $Pr^{3+}-\;and\;Pr^{3+}/Er^{3+}$-doped selenide glasses was investigated under an optical pump of a conventional 1480 nm laser diode. The measured peak wavelength and fullwidth at half-maximum of the fluorescent emission are ~1650nm and 120nm, respectively. A moderate lifetime of the thermally coupled upper manifolds of ${\sim}212{\pm}10{\mu}s$ together with a high stimulated emission cross-section of ${\sim}(3{\pm}1){\times}10^{-20}\;cm^2$ promises to be useful for $1.6{\mu}m$ band fiber-optic amplifiers that can be pumped with an existing high-power 1480 nm laser diode. Codoping $Er^{3+}$ enhances the emission intensity by way of a nonradiative $Er^{3+}:\;^4I_{13/2}\;{\longrightarrow}\;Pr^{3+}:\;(^3F_3,\;^3F_4)$ energy transfer. The Dexter model based on the spectral overlap between donor emission and acceptor absorption describes well the energy transfer from $Er^{3+}$ to $Pr^{3+}$ in these glasses. Also discussed in this paper are major transmission loss mechanisms of a selenide glass optical fiber.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.862-867
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• 2016

In this study, the embroidery textile conductive wire of conductive yarn was designed into the wearable integrated clothing for sensing the infant's body temperature. To develop a high quality of the stable fiber-based textile conductive wire, firstly the five types of conductive yarns were twisted or covering polyester yarns and the coated conductive fiber with silver(Ag) or iron(Fe). As a result of comparative conductivity in conductive yarns of yarn processing, the 250 denier of conductive yarns with $0.74{\Omega}$/1~5cm were proposed and used for the integrated embroidery textile conductive wire for sensing. During experiments using the proposed embroidery textile conductive wire, measured resistance of thermistor according to the body temperature was correctly delivered to amplifier module, and showed feasible reliability of temperature sensing. As a wearable application, conductive yarns which takes forms of embroidery textile conductive wire would seems to be reliable as a conductive wire and could be replaced by the conductive metal wires.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12C
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• pp.249-254
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• 2001

A receiver ASIC for fiber optic modules of STM-1 optical communication has been fabricated with 0.65 $\mu\textrm{m}$ CMOS technology. The ASIC has a limit amplifier circuit for the 155.52 Mbps data reshaping, and a clock extraction circuit for the 155.52 MHz clock recovery. The ASIC has an acquisition aid and LOS monitoring circuit for properly operation with near 155.52 MHz clock frequency in case of the data loss due to transmission line open or data transfer fail. Measured results show that the circuit reshapes data from 5 mV to 1 V wide range of input voltage condition, add it recovers system clock with stable on any condition.