• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.250-253
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• 1997

The effect of dispersion in optical transmission system changes according to chirp and SPM. Chirp depends on the modulation condition of an external modulator. SPM is proportional to signal power. In this paper, we analyzed the pulse broadening due to SPM and chirp in the system with dispersion by using Split Step Fourier Method and calculated the optimum chirp parameter for 400 km transmission system. Experimental results are presented also.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1136-1142
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• 2010

In this paper, we reduced the optical noise interference using the ASK modulation with optoelectronic feedback in a wireless optical system in which a lighting LED is used as a light source. The carrier frequency of 70 kHz was generated internally by the oscillation in the optoelectronic feedback circuit, and the output light was ASK modulated at a data rate of 9.6 kbps by opening and shortening the feedback loop with the input signal. In an environment with adjacent noise lights, the ASK modulation with optoelectronic feedback improved the signal to noise ratio by about 25 dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1A
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• pp.8-18
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• 2011

Visible light communication (VLC) using optical sources which can be simultaneously utilized for illumination and communication is currently an attractive option for wireless personal area network. Improving the data rate in optical wireless communication system is challenging due to the limited bandwidth of the optical sources. In this paper, we design the singular value decomposition (SVD)-based multiplexing multi-input multi-output (MIMO) system to support two data streams in optical wireless channels. In order to improve the spectral efficiency, the rate adaptation using multi-level pulse amplitude modulation (PAM) is applied according to the channel condition and we propose the method to allocate the optical power, the offset and the size of modulation scheme theoretically under the constraints of the nonnegativity of the modulated signals, the aggregate optical power and the bit error rate (BER) requirement. The simulation results show that the proposed allocation method gives the better performance than the method to allocate the optical power equally for each data stream.

• Korean Journal of Optics and Photonics
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• v.34 no.4
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• pp.151-156
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• 2023

We propose to implement cost-effectively a high-speed short-haul interconnect by transmitting a 200-Gb/s/λ two-channel optical time-division-multiplexed signal generated by a carrier-suppressed optical pulse, which improves the robustness of the multiplexed signal to chromatic dispersion. The multiplexed 200-Gb/s signal is generated in the transmitter by combining two 100-Gb/s 4-level pulse-amplitude-modulated signals (generated using the optical pulse and two Mach-Zehnder modulators). After the signal is transmitted over a fiber, it is amplified by a semiconductor optical amplifier and detected by a photodiode. The amplified spontaneous emission noise is eliminated by an optical band-pass filter. The transmitted signal is reconstructed by a 2 × 2 multiple-input multiple-output equalizer, which compensates for crosstalk. Due to the use of the carrier-suppressed optical pulse, the 200-Gb/s signal can be transmitted over fiber with a chromatic dispersion of 40 ps/nm.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.178-179
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• 2001

무선 통신망의 수요가 급격히 증가하여 기존의 무선통신 대역이 조만간에 포화될 것으로 예측됨에 따라, 새로운 밀리메터파 대역 통신에 대한 연구 관심이 높아지고 있다. 광 밀리메터파 발생 및 전송 시스템은 밀리메터 반송파 발생이 용이할 뿐만 아니라 밀리메터파 광중계기 구현에 그대로 적용되기 때문에, 차세대 밀리메터파 통신 시스템 구현의 핵심기술로서 연구관심의 대상이 되어왔다. 광 밀리메터파 발생 방법으로는 두 개의 레이저를 이용하는 광파 혼합과 외부 변조기로 직접변조하는 방법 등이 있다. (중략)

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.659-664
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• 2020

In this paper, we propose a silicon-based electro-optic (EO) modulator which can modulate a sign of a topological charge number l of |l|=1 orbital angular momentum (OAM) mode. The proposed EO modulator consists of position-dependent doped Si waveguide core and undoped SiO2, cladding, which enables control of the effective index and propagation loss of two OAM constitutive eigenmodes. The modulator functions as OAM mode maintaining waveguide at -0.33V and as topological charge sign inverter at 10V. The output OAM mode purity is calculated through electric field distribution, showing high purity of |l|>0.92 in both cases.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1992.10a
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• pp.342-345
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• 1992

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.11 s.353
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• pp.14-18
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• 2006

Optical interferometer is used for various optical measurement fields in optical metrology and biomedical measurements. In an optical interferometer, optical delay line has to change the optical path length of a reference arm to match with that of a sample in and it's speed was limited by reference arm movement speed. In this paper, we proposed an all-fibered RSODRapid Scanning-speed Optical Delay) without any mechanical movement, and we applied this system to optical interferometer. Experimental setup is consist of pulse laser source (center wavelength 1304nm, pulse width 30ps, repetition rate 10GHz), two phase modulators and dispersive shifted fiber. As experimental results, we obtain the maximum time delay of 11ps at 10MHz repetition rate, and it is easily tuneable the time delay by modulation frequency and modulation voltage.

• Journal of the Korean Society of Radiology
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• v.5 no.6
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• pp.357-361
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• 2011

In this study, the liquid-crystal optical modulation X-ray detection system using a CdS which is a family of II-IV compound semiconductor was proposed. The system consist of the detector, the signal processing part, the liquid-crystal driving parts, microcontroller, and I/O parts, and was designed to be suitable for miniaturization and portable. In addition, the system can measure a wide range X-ray by using the detecting range selection. In order to evaluate the performance of the proposed system, the CdS sensor's output characteristics were confirmed in accordance with changes of dose, and excellent correlation was determined. And also, the optical penetration ratio was discussed in accordance with changes of the applied voltage by measuring the change of the liquid-crystal in accordance with changes of the applied voltage. Through these results, the characteristics of the liquid-crystal optical modulation system such as the excellent reproducibility and the noise immunity were confirmed. And we considered that the CdS cell-based liquid-crystal optical modulated portable X-ray detection system could be applied to compact, low-cost, portable system.

• 전기의세계
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• v.42 no.6
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• pp.32-37
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• 1993

광통신 기술은 지난 25년간 비약적인 발전을하여 이미 세계적으로 2.4Gb/S시스템의 실용화, 해저 광케이블 포설 등이 이루어졌으며 고속 광변조 기술, 광폭증 기술, 광 FDM기술 등 핵심기술의 개발에 따라 10Gb/s이상의 초고속 광통신 시스템의 실용화가 가시화 되고 있으며, 또한 차세대 정보통신 서비스인 B-ISDN서비스에의 응용을 가능하게 하고 있다.