• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.262-270
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• 2013

In this paper, we propose a modified optical CBC(Cipher Block Chaining) encryption method using optical XOR logic operations. The proposed method is optically implemented by using dual encoding and a free-space interconnected optical logic gate technique in order to process XOR operations in parallel. Also, we suggest a CBC encryption/decryption optical module which can be fabricated with simple optical architecture. The proposed method makes it possible to encrypt and decrypt vast two-dimensional data very quickly due to the fast optical parallel processing property, and provides more security strength than the conventional electronic CBC algorithm because of the longer security key with the two-dimensional array. Computer simulations show that the proposed method is very effective in CBC encryption processing and can be applied to even ECB(Electronic Code Book) mode and CFB(Cipher Feedback Block) mode.

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.248-249
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• 2004

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.4
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• pp.326-334
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• 1991

We propose an optical Asynchronous Transfer Mode(ATM) switching system using free-space optics and an output buffer memory. The distributor system in the switching fabric was analyzed using the Huygens-Fresnel principle and lens transformation. For monochromatic illumination, a pattern similar to the Fourier transform of the input distribution was observed across the output plane. A spatially broadened intensity distribution across the the output plane can be expected when the system is illminated with a partially coherent, quasimonochromatic beam. Spatially coherent pulses as short as 100fs can propagate through the distributor without severe spatial broadening.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.396-400
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• 2006

We present a weather-insensitive optical free-space communication method supporting optical packet channels. It operates optical fiber amplifiers in gain-saturation regions. When the propagation loss gets too high, it decreases the average packet rate, or the average packet length, or both, to increase the optical power level launched into the free-space. As a demonstration, we transmit $8{\times}10$ Gigabit Ethernet channels over a terrestrial distance of 2.4 km. One gain-saturated free-space optical repeater is used at the halfway point.

• 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.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.32-33
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• 2000

최근 디지털 정보 처리 기술의 획기적인 발전과 함께 저가의 반도체 레이저의 개발로 말미암아 광기록 장치(optical pickup device) 및 고속 광통신(optical fiber communication)분야에 응용을 위한 레이저 광학 시스템에 대한 연구가 활발하다. 광신호의 커플링(coupling) 및 스위칭(switching)을 기반으로 하는 이러한 광학 시스템은 일반적으로 광신호의 변조를 위한 광학 요소와 광학 요소의 공간적 제어를 위한 정밀 구동기로 구성되는데, 기존의 상용 시스템의 경우에는 독립적으로 기 제작된 광학 요소와 정밀 구동기를 사후에 조립하는 방법으로 소기의 목적을 달성하였다. 이와 같은 경우 제작에 많은 노력과 비용이 요구되며, 성능의 획기적인 향상을 기대하기 어려우므로 최근에는 Optical MEMS 혹은 MOEMS(Micro-Opto-Electro-Mechanical System)로 대변되는 마이크로머시닝기술(micromachining technology)을 이용한 초정밀 광학계의 제작 기술을 통하여 기존 시스템의 한계를 극복하고자 하는 노력이 다각도로 모색되고 있다. (중략)

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.333-340
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• 1996

We have implemented a planar integrated optics for the fractional Fourier transform (FRT) which has recently been developed as a generalized form of the conventional Fourier transform. FRT optical systems provide versatile tools for analyzing signals and designing hardwares, but require high accuracy and stability in the arrangement of optical components because of their shift-variant characteristic. The planar optical FRT setup composed of free-space optical components integrated on a single glass block makes the FRT of 2-dimensional(2-D) input patterns through the 3-D glass-space. Therefore, taking advantage of the compactness, easy alignment and thermal/mechanical stability, the planar optics can provide a useful approach to realizing an optical fractional correlation system in a practical way. In the experiment, we have obtained accurate FRT results by using the planar integrated optics with 4 different fractional orders of 0.25, 0.5, 0.75, and 1.0.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.238-239
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• 2002

본 연구에서는 굴절율이 서로 다른 경계면 근처에 원자가 놓여있는 경우, 조건 변화에 따른 원자의 자발방출의 변화에 대해 다루었다. 굴절율이 작은 쪽의 경계에 있는 원자간 여기상태에 있는 경우, 양쪽 매질로 자발방출이 가능하다. 굴절율이 작은 방향으로의 자발방출은 자유공간에서의 자발방출과 별 다를바가 없다. 그러나 굴절율이 큰 방향으로의 자발방출의 경우에는 원자가 에바네슨트 파와 상호작용하여 방출하는 경우가 나타나므로 전자와는 다르게 접근해야 한다. (중략)

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.328-332
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• 1996

We have developed a combined binary-phase hologram (CBPH) consisting of two binary phase holograms. The CBPH can be effectively used for optical interconnection and image processing by suppressing unwanted images of a conventional binary-phase hologram. The theory and properties of the CBPH and experimental results are presented.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.230-236
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• 2019

We propose and demonstrate a searching and autoalignment method for indoor optical wireless communication, using a cost-effective retroreflective sheet and a microelectromechanical system (MEMS) mirror. We use an extremum-seeking method for a single axis and beam steering with a MEMS mirror to maintain a line of sight (LOS) with the optical link. This autoalignment method shows a receiver sensitivity of -31.87 dBm for a bit rate of 2.5 Gb/s over a 7 m communication link.