• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.566-573
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• 2004

A variable optical attenuator with a bending-sensitive fiber (BSF) that can be used in optical networks is developed. The proposed BSF consists of inner core, outer core, center dip and cladding. The proposed BSF is also very sensitive to mechanical perturbation, such as bending and pressure, making the light propagating in the BSF easily controlled and attenuated. The fabricated fiber-type variable optical attenuator using the proposed BSF (VOAFB) consisted of the BSF in a rectangular rubber ring with a fixed bend radius (BR) in a steady state. The variable optical attenuator using the proposed BSF (VOAFB) was able to attenuate the optical power by more than about -38㏈ with the gradient -88.4［㏈$.$$cm^{-1}$ /］ at (1540∼1560nm) based m adjusting the mechanical pressure applied to the upper surface of the rectangular rubber ring with the bent BSF. According to the experimental results when using the proposed VOAFB, the optical power was easily controlled by adjusting mechanical pressure and produced an insertion loss of 0.68㏈, polarization loss of 0.5㏈, and return loss of less than -60㏈.

• Electronics and Telecommunications Trends
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• v.15 no.6 s.66
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• pp.45-55
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• 2000

현재 국가별로 진행되고 있는 가입자 접속의 고속화 전략은 각 나라의 통신환경 및 서비스 수요에 따라 다양하게 추진되고 있다. 그러나 선로의 종류에 따라 구분하여 보면, 기존의 동선 전화선로를 이용하는 ‘ xDSL 접속’과 새로운 광섬유 선로를 이용하는 ‘광 가입자 접속,’ 그리고 무선주파수를 이용하는 ‘광대역 무선 접속(BWLL)’ 등 세 가지 형태로 구분할 수 있다. 본 고는 이러한 초고속 가입자 접속기술 중 xDSL기술의 개발현황과 표준화 진행을 분석하여 우리나라의 통신환경에 맞는 기술 방향을 제시하고자 한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1083-1092
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• 2016

In this paper, the performance of the optical code-division multiple access (OCDMA) technology on a plastic optical fiber (POF) access network, which had received much attention due to its low weight, large core diameter, flexibility, easy installation, and especially its high bandwidth, is analyzed. Recently, POF was a very attractive candidate for transmission media in an access network based on OCDMA technology. But the conventional OCDMA system only allows finite units to transmit and access simultaneously according to the number of channels which are restricted by BER, and so, in this paper, to resolve this problem a novel multi-priority reservation protocol is also proposed. By using this reservation scheme and a distributed arbitration algorithm, channel collision and destination conflict could be avoided. And this protocol can efficiently support the transmission of multimedia messages that require the different time-delay. The network throughput and average delay using various system parameters have been investigated by numerical analysis and simulation experiments. These results shows that the multi-priority reservation protocol in this POF access network based on OCDMA technology is valid and efficient.

• Korean Journal of Optics and Photonics
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• v.33 no.3
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• pp.99-105
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• 2022

We have evaluated the performance of an all-optical automatic gain-controlled (AGC) erbium-doped fiber amplifier (EDFA) to suppress the optical signal fluctuation induced by atmospheric turbulence in terrestrial free-space optical communication systems. In our measurements, the input power into the EDFA was set to be -30 dBm and -10 dBm to operate the amplifier in the small-signal and saturation regions, respectively. The fluctuations in the optical signal were emulated with an acousto-optic modulator driven with a sinusoidal voltage. From the measured results, we have found that an all-optical AGC EDFA could suppress the optical signal fluctuation effectively, as long as the EDFA operated in the small-signal region with a high feedback amplified spontaneous emission (ASE) power.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.542-548
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• 2001

A robust, accurate, broad-band, alternating current sensor using fiber-optics is being developed as a part of optical over current protection relay system. The sensor uses the Faraday effect in optical fiber and polarimetric measurements tc sense electrical current. The current sensing coil consists of a length of twisted optical fiber and Faraday rotator mirror to suppress the linear birefringence effect. Due to its single-ended closed path structure, it can not only be easily installed to the target with great isolation from other fields in the vicinity, but the sensitivity can be increased by using multiple turns. This paper reports on the theoretical backgrounds of the sensor design and the preliminary experimental results.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.209-216
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• 2010

Optical Temperature Distribution Sensor Measurement System uses fiber optic sensors itself for temperature measurement is a system which can be measured the Installed surrounding entire temperature as a thousand points by laying a single strand of fiber optic. If there are a lot of measuring points in the distribution Measurement, the cost of each measuring point can be reduced the cost level of existing sensors and at the same time this has the advantage of connecting all sensors as one or two strands of fiber. Generally Optical Fiber is used for communication but Optical Fiber itself can be used for sensor and it has the characteristic of sensor function which can be measured Temperature in the at least each one meter distance. By using these characteristics each sensor and the number of Connection Lines can be reduced. In this paper, we implement a real time temperature monitoring system, which is easy to manage and control for data storage, data management, data storage using a computer and which has the functions of monitoring and correction according to Real-time temperature changes using historical temperature data.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.11
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• pp.1-8
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• 1990

We made a 12-Laser Diode Array consisting of 12 Graded Index Separate Confinement (GRINSCH) InGaAs/Inp Buried Heterostructure 4 Quantum Well Laser Diodes and examined the potential of controlling lasing operation of each laser diode by the voltage to its electroabsorption region. Using Si V-Groove with 12 V-grooves, a 12-Laser Diode Array, and 12 optical fibers, we investigated the various characteristics of each laser diode by changing the voltage to its electro-absorption region. Finally, we thought over the promising way of implementing optical local area communication between electric circuit boards or between subscribers and a central office using a 12-Laser Diode Array, Si V-groove, and optical fibers.

• Electronics and Telecommunications Trends
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• v.7 no.3
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• pp.121-128
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• 1992

광통신 시스팀에서 광선로의 접속에 사용되는 부품으로 광커넥터와 Mechanical Splice 등이 있다. 시스팀 구성에 필수적인 부품으로서 이들 기술의 동향을 파악하여 접속부품의 개발에 응용하고자 광커넥터의 최근 연구분야인 광섬유 후퇴현상과 반사손실특성 향상을 위한 연구내용과 Mechanical Splice 의 기술동향을 기술하였다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.3
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• pp.213-219
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• 2017

Recently, the Internet Protocol Television (IPTV) services have become very common, enabling various Internet-based services as well as watching TV. In the IPTV system, a Set-Top box (STB) plays a key role as a network terminal device that transmits and receives realtime multimedia contents. In addition, the IPTV networks are usually supported by broadband optical fiber-base network such as fiber-to-the-home (FTTH), However, a general IPTV STB is regarded as one of the local area network (LAN)-attached devices while sharing the bandwidth of the LAN (e.g., Ethernet). In order to overcome the limited bandwidth utilization by fully facilitating the broadband bandwidth (e.g., 1 Gbps) of the optical fiber-based network, we propose a new FC (Fiber Channel)-embedded IPTV STB which can be directly attached to the optical fiber network. Then, we verify that the impacts of the proposed FC-embedded IPTV STB by organizing the the FC-AL (Fiber Channel-Arbitration Loop) network equipped with the FC-embedded IPTV We measures the average Start-up Delay, Average Reject Ratio and the Number of Concurrent Users through extensive simulations to investigate the performances of the suggested FC-AL-based IPTV network. Surprisingly, the IPTV network architecture with the proposed FC-embedded IPTV STBs has an excellent average start-up delay of less than 10 msec, an acceptable average reject ratio of less than 3 % as well as a linear increase of the number of concurrent users when extending the architecture. This reveals that the proposed FC embedded STB has a superior impacts on the performance of the entire IPTV network by effectively utilizing the broadband bandwidth of the fiber optic-based network.

• Korean Journal of Optics and Photonics
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• v.5 no.2
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• pp.319-325
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• 1994

The performance of Manchester-coded DPSK optical wavelength division multiplexing (WDM) systems using a stochastic approach is evaluated taking into account the shot noise and the four-wave mixing (FWM) caused by fiber nonlinearities. The result of Manchester-coded system is compared to conventional non-return-to-zero (NRZ) systems for DPSK modulation formats. Further, the dynamic range, defined as the ratio of the maximum input power (limited by the FWM), to the minimum input power (limited by receiver sensitivity), is evaluated. For $1.55.{\mu}m$16 channel WDM systems, the dynamic range of DPSK Manchester coded systems shows a 2.1 dB improvement with respect to the NRZ. This result holds true for both dispersion-shifted fiber and conventional fiber; it has been obtained for 10 GHz channel spacing, 1 Gbps/channel bit rate.t rate.