• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.2
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• pp.238-246
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• 2024

Modern military operations rely heavily on broadband communication and data transmission. Recently, the rising use of intelligent unmanned technology necessitates more frequencies. Free-space optical(FSO) communication can offer high-data-rate communications with high security and no need for licensing. Therefore, the FSO communication holds significant interest and potential in the defense industry. In this paper, we present design of a FSO communication terminal taking Korean domestic weather conditions into account. The domestic atmospheric attenuation is analyzed using several models and two-year meteorological information for a city in Korea, and this analysis is utilized to design the FSO communication terminal. The design results were verified using an FSO communication test bed, and we achieved an Ethernet bandwidth of approximately 1.86 Gbps at a distance of 1.3 km with the optical amplifier output power of the test bed set to about 20 dBm.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.3
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• pp.329-337
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• 2024

Free-space optical communication technology enables the high-speed data transmission and excellent anti-jamming security. We conduct research on satellite-to-ground free-space optical communication links for high-speed transmission of large-capacity surveillance and reconnaissance data. Since the satellite continues to move along its orbit while the optical signal is transmitted between the satellite and the ground, the pointing angle of the beam from the ground terminal needs to be corrected by Point Ahead Angle(PAA) so that the transmitted light reaches the expected location of the satellite. In this paper, we present the algorithm for PAA estimation and control.

• Korean Journal of Optics and Photonics
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• v.33 no.3
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• pp.113-121
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• 2022

We analyze the link availability of satellite-to-ground free-space optical (FSO) communication systems in South Korea. Using ten-year meteorological data for five major cities (Seoul, Busan, Daegu, Daejeon, and Gwangju), we theoretically predict the link availability from the power losses induced by absorption, scattering, aerosols, and scintillation in the atmospheric channel. For accurate but conservative estimation of the link availability determined by cloud cover, we propose a loss model based on the maximum value of cloud droplet concentration. The results show that the link availability ranges from 45% to 70% when a single ground station is placed in a major city in South Korea and a 20-dB link budget is allocated for atmospheric loss. However, the availabilities improve to 90% and 97% when 3- and 5-site diversities are employed, respectively.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.425-430
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• 2013

Robust and high speed underwater communication is severely limited when compared to communications in terrestial. In free space, RF communication operates over long distances at high data rates. However, the obstacle in seawater is the severe attenuation due to the conducting nature. Acoustic modems are capable of long range communication up to several tens of kilometers, but it has low data-rate, high power consumption and low propagation speed. An alternative means of underwater communication is based on optics, wherein high data rates are possible. In this paper, the characteristics of underwater channel in the range of visible wavelength is investigated. And the possibility of optical wireless communication in underwater is also described. The LED-based transceiver and CMOS sensor module are integrated in the system, and the performance of image transmission was demonstrated.