• Korean Journal of Optics and Photonics
• /
• v.5 no.2
• /
• pp.326-332
• /
• 1994

Performance of soliton based long-haul optical communication system with in-line optical amplifier repeaters are evaluated numerically. To reduce the optical amplifier noise, the amplifier gain is increased and the post amplifier loss is included. By theoretical calculation with 1480 nm co propagating pump, 7 dB amplifier gain and operating the amplifier 1 dB in compression, the spontaneous emission factor can be reduced from 2.37 to 1.45 by increasing the pump power from 3.71 to 11.53 mW and increasing the post amplifier loss from 0 to 10 dB. Then, power penalty can be reduced from 4.09 to 1.20 dB for 8,000'km transmission and the maximum transmission distance is 14,890 km. ,890 km.

• Korean Journal of Optics and Photonics
• /
• v.17 no.2
• /
• pp.143-148
• /
• 2006

A new method of measuring the Brillouin gain spectrum of optical fiber is proposed and demonstrated. Unlike existing methods, both the pump light and the counter-propagating probe light are generated from a single laser diode whose optical frequency is directly modulated by injection current modulation. The frequency difference between the pump and the probe is scanned continuously through optical frequency chirp occurring when the injection current is modulated with a square wave. The measured Brillouin gain spectrum of telecom single-mode fiber agrees well with that shown in other literature.

• Proceedings of the KIEE Conference
• /
• 2007.07a
• /
• pp.2048-2049
• /
• 2007

광섬유 온도센서를 이용하여 밀폐형 폐쇄배전반 내부에 설치된 진공차단기(Vacuum Circuit Breaker: 이하 VCB)의 접촉부 및 부싱부 이상 온도변화를 상시 감시할 수 있는 On-line 온도 감시 시스템을 개발하였다. 본 시스템은 온도변화를 측정하는 광센서부, 광신호의 이동 통로역할을 하는 Optical Head부, 변환된 전기신호를 신호처리하고 상위 시스템으로 통신을 수행할 신호처리장치의 세 부분으로 구성되어 있다. 구현한 시스템은 측정 범위가 $-25\;{\sim}\;200^{\circ}C$인 희토류 원소가 첨가된 광섬유 온도센서를 사용하였고, 시스템의 측정 범위는 $-20\;{\sim}\;150^{\circ}C$, 측정 정밀도는 Full Scale의 ${\pm}2\;%$, 측정 주파수는 0.1 Hz이었다. 검출된 온도 값은 Modbus Protocol을 이용하여 상위 시스템으로 송신하도록 구현하였다.

• Journal of the Korean Society for Railway
• /
• v.16 no.3
• /
• pp.189-195
• /
• 2013

Recent trains have broadband train communication networks to improve train operation safety and to provide passengers with multimedia services. Compared to glass optical fiber, plastic optical fiber (POF) has a large diameter; it also provides the good durability and maintainability necessary to railway applications. This paper suggests an All-IP broadband train communication network that connects all devices in the train through a POF interface. Performance tests according to Korean railroad standards shows that this POF interface is usable in the range of vibration and temperature conditions encountered in trains. A dedicated Layer-2 switch with the POF interface is developed for the construction of the All-IP train communication network. A prototype 1Gbps train communication network was set up in a trial-run of train on a metro line using the developed Layer-2 switch and POF. On-track tests indicated the feasibility of the POF train communication network. POF has an additional advantage of economic feasibility, and it is expected to start a trend toward broadband train communication networks using POF.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.10
• /
• pp.1854-1862
• /
• 2006

The numerical methods of finding out the optimal position of optical phase conjugator (OPC) and the optimal fiber dispersions are prosed, which are able to effectively compensate overall channels in $8{\times}40Gbps$Gbps WDM system with non zero - dispersion shifted fiber (NZ-DSF) as an optical fiber. And BER characteristics in the system with two induced optimal parameters are compared with those in the system with the currently used mid-span spectral inversion (MSSI) in order to confirm the availability of the proposed methods. It is confirmed that the applying two induced optimal parameters into WDM system contribute to reduce power penalty to 4 times than that of WDM system with the conventional MSSI. Thus, the methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which generates a serious problem if it was not made but it is the condition in the case of applying the OPC into multi-channels WDM system.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.10
• /
• pp.2293-2302
• /
• 2012

New optical transmission links technique for compensating of the distorted wavelength division multiplexed (WDM) signals due to group velocity dispersion (GVD) and self phase modulation (SPM) in single mode fiber (SMF) are proposed. The proposed optical links have optical phase conjugator (OPC) placed at nearby WDM transmitter or receiver and repeater spans with artificial distribution of SMF length and residual dispersion per span (RDPS). It is confirmed that optimal link configuration expanding effective launching power range and effective net residual dispersion (NRD) by improving system performance is that having OPC closely placed at WDM receiver and the gradually descended distribution of SMF length and RDPS of each repeater spans, related with the gradually increased optical link length. And, it is also confirmed that NRD is controlled by postcompensation in optimal optical link with OPC closely placed at WDM receiver.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.12
• /
• pp.2953-2960
• /
• 2014

In the field of image recognition, circle detection is one of the most widely used techniques. Conventional algorithms are mainly based on Hough transform, which is the most straightforward algorithm for detecting circles and for providing enough robust algorithm. However, it suffers from large memory requirements and high computational loads, and sometimes tends to detect incorrect circles. This paper proposes an optimal circle detection and approximation method which is applicable for inspecting fiber optic connector endface. The proposed method finds initial center coordinates and radius based on the initial edge lines. Then, by introducing the simplified K-means algorithm, the proposed method investigates a substitute-circle by minimizing the area of non-overlapped regions. Through extensive simulations, it is shown that the proposed method can improve the error rate by as much as 67% and also can reduce the computing time by as much as 80%, compared to the Hough transform provided by the OpenCV library.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2006.05a
• /
• pp.361-364
• /
• 2006

The numerical methods of finding the optimal position of optical phase conjugator (OPC) and the optimal fiber dispersions are proposed, which are able to effectively compensate overall channels in $8\times40$ Gbps WDM system with non zero - dispersion shifted fiber (NZ-DSF) as an optical fiber. And BER characteristics in the system with two induced optimal parameters are compared with those in the system with the currently used mid-span spectral inversion (MSSI) in order to confirm the availability of the proposed methods. It is confirmed that the applying two induced optimal parameters into WDM system contribute to reduce power penalty to 4 times than that of WDM system with the conventional MSSI.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.14 no.5
• /
• pp.571-577
• /
• 1989

In this paper, the double-refractive index profile, which is generalized a trapezoidal index profile, is proposed to study the characteristics of a optical fiber in the wave length 1.55um. Being compared with a triangle profile, it has many advantages over an optimum core radius, the minimum refractive index difference and the change of chromati dispersion characteristics with wavelength. Though the value of a varies from 2 to infinite, the same results are approximately obtained. Therefore, in fabrication of a fiber, the step part of trapezoidal index profile can replace the profile of a-power refractive index. Because the refractive index presented in this paper varies with a, it can be applied to multiple cladding fiber or segmented core fiber. And it is expected that the characteristics of the fiber are obtained.

• The Science & Technology
• /
• v.17 no.7 s.182
• /
• pp.23-26
• /
• 1984

불붙은 미,일의 선기술 경쟁 / 동케이블 통신위성은 사양길로 / 일본, 광집적회로개발 7천5백만불 투입 / 광섬유의 2대 이점 / 새연결 장치로 각광받는 단일모드형 / 연속생산 기대되는 VAD법 / 잠수함 탐지용으로도 이용