• Journal of the Institute of Convergence Signal Processing
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• v.14 no.4
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• pp.261-269
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• 2013

This paper describes the design and development of VSI (VLBI standard interface) optical adapter for transmitting VLBI(Very long baseline interferometry) observation data with optical signal. VSI cable comprised of 80-line is being used for observed data transmission with maximum length of 5-meter between playbacks (Mark5B, VERA2000) and raw VLBI data buffer (RVDB), RVDB and VLBI correlation subsystem (VCS) in Daejeon correlator. It has a plan to conduct the data processing for 16-stations and introduce the 14 RVDB systems in near future. And data loss frequently occurred because of trouble of VSI cable MDR80 connector. By considering the data loss by connector error of VSI cable, RVDB system extension plan, effective space usage and long distance data transmission(e-VLBI), the VSI optical adapter was proposed and developed for effectively transmitting and receiving VLBI data through optical signal. In order to confirming the performance of developed VSI optical adapter, the experiments for data transmission was conducted between playback and RVDB system, and confirmed that data transmission was clearly done without any data loss.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.2
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• pp.1-8
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• 2004

This paper describes the design of monolithic optical transceiver circuitry being used as a part of the fiber optic modules. It has been designed in 0.6 ${\mu}{\textrm}{m}$ 2-poly 3 metal silicon CMOS analog technology and operates at 155.52 Mbps(STM-1) data rates. It drives laser diode to transmit intensity modulated optical signal according to 155.52 Mbps electrical data from system. Also, it receives 155.52 Mbps optical data that transmitted from other systems and converts it to electrical data using photo diode and amplifier. To avoid noise and interference between transmitter and receiver on one chip, layout techniques such as special placement, power supply separation, guard ring, and protection wall were used in the design. The die area is 4 ${\times}$ 4 $\textrm{mm}^2$ and the estimated power dissipation is less than 900 ㎽ with a single 5 V supply.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.11-17
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• 2004

This paper describes the implementation of monolithic optical transceiver circuitry being used as a part of the fiber optic modules. It has been fabricated in 0.6 ${\mu}{\textrm}{m}$ 2-poly 3-metal silicon CMOS analog technology and operates at 155.52 Mbps(STM-1) data rates. It drives laser diode to transmit intensity modulated optical signal according to 155.52 Mbps electrical data from system. Also, it receives 155.52 Mbps optical data that transmitted from other systems and converts it to electrical data using photo diode and amplifier. To avoid noise and interference between transmitter and receiver on one chip, layout techniques such as special placement, power supply separation, guard ring, and protection wall were used in the design. The die area is 4 ${\times}$ 4 $\textrm{mm}^2$, and it has 32.3 ps rms and 335.9 ps peak to peak jitter on loopback testing. the measured power dissipation of whole chip is 1.15 W(230 mW) with a single 5 V supply.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.5
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• pp.502-508
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• 2012

Heliostat, as a concentrator to reflect the incident solar energy to the receiver, is the most important system in the tower-type solar thermal power plant since it determines the efficiency and ultimately the overall performance of solar thermal power plant. Thus, a good sun tracking ability as well as a good optical property of it are required. Heliostat sun tracking system uses usually an open loop control system. Thus the sun tracking error caused by heliostat's geometrical error, optical error and computational error cannot be compensated. Recently use of sun tracking error model to compensate the sun tracking error has been proposed, where the error model is obtained from the measured ones. This work is a development of heliostat sun tracking error measurement and compensation method using BCS (Beam Characterization System). We first developed an image processing system to measure the sun tracking error optically. Then the measured error is modeled in linear polynomial form and neural network form trained by the extended Kalman filter respectively. Finally error models are used to compensate the sun tracking error. We also developed the necessary image processing algorithms so that the heliostat optical properties such as maximum heat flux intensity, heat flux distribution and total reflected heat energy could be analyzed. Experimentally obtained data shows that the heliostat sun tracking accuracy could be dramatically improved using either linear polynomial type error model or neural network type error model. Neural network type error model is somewhat better in improving the sun tracking performance. Nevertheless, since the difference between two error models in compensation of sun tracking error is small, a linear error model is preferred in actual implementation due to its simplicity.

• Current Optics and Photonics
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• v.1 no.3
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• pp.186-195
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• 2017

Obtaining accurate visibility measurements is a common atmospheric optical problem, and of vital significance to civil aviation. To effectively evaluate and improve the accuracy of visibility measurements, an outdoor atmospheric simulation chamber with dimensions of $1.8{\times}1.6{\times}55.7m^3$ was constructed. The simulation chamber could provide a relatively homogeneous haze environment, in which the visibility varied from 10 km to 0.2 km over 5 hours. A baseline-changing visibility measurement system was constructed in the chamber. A mobile platform (receiver) was moved from 5 m to 45 m, stopping every 5 m, to measure and record the transmittance. The total least-squares method was used to fit the extinction coefficient. During the experiment conducted in the chamber, the unit weight variance was as low as $1.33{\times}10^{-4}$ under high-visibility conditions, and the coefficient of determination ($R^2$) was as high as 0.99 under low-visibility conditions, indicating high stability and accuracy of the system used to measure the extinction coefficients and strong consistency between repeated measurements. A Grimm portable aerosol spectrometer (PAS) was used to record the aerosol distribution, and then Mie theory was used to calculate the extinction coefficients. The theoretical results were found to be consistent with the measurements and exhibited a positive correlation, although they were higher than the measured values.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.2
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• pp.1-8
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• 1999

We analyze the transmission performance of WDM system based on cascaded optical add/drop multiplexers. The considered factors degrading the performance in this paper include the intra-channel corosstalk caused from space switches and demultiplexers/multiplexers, the amplified spontaneous emission noise, and the extinction ratio. To ensure the power penalty within 1dB, the extinction ration more than 13dB, the switch corosstalk less than 39dB, and the demultiplexer/multiplexer crosstalk less than 20dB are required. Under the assumption of switch corosstalk less than 30dB, performance degradation due to the ASE noise is dominant compared to the crosstalk. With the fixed decision threshold in an optical receiver, the maximum number of cascaded nodes reduces to a half compared to the case of the optimum decision threshold.

• Korean Journal of Optics and Photonics
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• v.27 no.4
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• pp.133-142
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• 2016

This paper presents the design and simulation of a three-dimensional pixel-by-pixel scanning light detection and ranging (LIDAR) system with a microelectromechanical system (MEMS) scanning mirror and direct sequence optical code division multiple access (DS-OCDMA) techniques. It measures a frame with $848{\times}480$ pixels at a refresh rate of 60 fps. The emitted laser pulse waves of each pixel are coded with DS-OCDMA techniques. The coded laser pulse waves include the pixel's position in the frame, and a checksum. The LIDAR emits the coded laser pulse waves periodically, without idle listening time to receive returning light at the receiver. The MEMS scanning mirror is used to deflect and steer the coded laser pulse waves to a specific target point. When all the pixels in a frame have been processed, the travel time is used by the pixel-by-pixel scanning LIDAR to generate point cloud data as the measured result.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.11
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• pp.79-85
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• 1995

In this paper, an epi layer and a device structure for InP/InGaAs p-i-n/HBT OEIC is designed for a receiving frontend of high speed optical communications. A 3 stage transimpedance circuit using the p-i-n/HBT device is also designed by SPICE simulations for a high sensitivity including ISI noises at a given bit rate. Our simulations show that the Personick's assumption which is not commonly satisfied have estimated a photoreceiver sensitivity too high, so thus we have to also consider ISI noises in OCIC receiver designs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2941-2956
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• 2013

In this paper, we propose an effective fragile image watermarking scheme for tampering detection and content recovery. Cover image is divided into a series of non-overlapping blocks and a block mapping relationship is constructed by the secret key. Several DCT coefficients with direct current and lower frequencies of the MSBs for each block are used to generate the reference bits, and different coefficients are assigned with different bit numbers for representation according to their importance. To enhance recovery performance, authentication bits are generated by the MSBs and the reference bits, respectively. After LSB substitution hiding, the embedded watermark bits in each block consist of the information of itself and its mapping blocks. On the receiver side, all blocks with tampered MSBs can be detected and recovered using the valid extracted reference bits. Experimental results demonstrate the effectiveness of the proposed scheme.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.5
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• pp.737-746
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• 1990

Ga0.47In0.53As PIN photodiodes(PD) having various areas have been fabricated by liquid phase epitaxial techniques. Ternary melt has been baked out at 675\ulcorner in H2 atmosphere for 20 hours before growth, which resulted in reduction of background carrier concentration of grown epi-layer. Also, lattice mismatch has been controlled within 0.01%. The room temperature performance of 10**-4cm\ulcornerarea PIN PD at a bias voltage of -5V were` quantum efficiency(with no antireflection coating)=60% for 1.3\ulcorner light source, dark current\ulcorner5nA, and capacitance\ulcornerpE. Frequency response measurement of packaged PIN PD has shown that cut-off frequency (f-3dB) was 961MHz. This PD has shown a good eye pattern when it was incorporated in a 565Mbps optical receiver.