한상국 교수

A novel concept for integrating visible light communications (VLC) with three‐dimensional indoor positioning is presented. A VLC link based on transmitter and receiver characteristics using experimental measurements was modelled. Proposed is a three‐dimensional positioning algorithm using received signal strength indication, which changes based on the angle and distance of the location based service. To reduce inter‐cell interference, the transmitter's location code was sent using different subc

The authors propose a new high‐resolution indoor positioning method based on visible light communication using two light emitting diode (LED) lightings and an image sensor of camera as a receiver. Through the proposed method, the authors can determine position of receiver using the real coordinate of two LED lightings and a captured image. In order to demonstrate the applicability of positioning method, they evaluated the positioning accuracy as changing receiver position. From the experimental

Abstract In this article, we propose an indoor location estimation algorithm that uses the signal extinction ratio distribution of LED‐based visible light communication.To improve the positioning accuracy, we use the received extinction ratio from different LED transmitters. In order to mitigate interference between transmitters, a location code was sent using time division multiplexing (TDM). We verified the feasibility of the proposed position estimation algorithm with an experimental demonstr

Free-space optical (FSO) communication has been studied for next-generation network systems. Because an FSO system establishes point-to-point communication links, maintaining alignment among the transceivers is a critical challenge. In addition, atmospheric turbulence causes significant signal loss in FSO vertical links. Even in clear weather conditions, transmitted optical signals suffer significant scintillation losses due to random variations. Thus, the effect of atmospheric turbulence should

Power limiting in semiconductor-doped glass waveguides in the cw regime is explained on the basis of thermal effects. From the measurement of the temperature dependence of the refractive index and transmission as a function of wavelength, we show that the change in the absorption coefficient that is due to heating of the bulk-glass substrates at high optical powers accounts for the nonlinear behavior of the waveguides. The power limiting observed in planar waveguides was calculated, and excellen

For the first time a narrowband wavelength filter in InGaAlAs/InP is reported. A highly asymmetrical, vertically-coupled directional coupler operating near the band edge is formed by a narrow ridge and a wide strip-loaded waveguide. Operation at a centre wavelength of ~1.5 µm with a bandwidth of 18 Å and transfer efficiency of ~50–70% has been achieved.

We proposed the statistical misalignment model and the power-efficient configuration of transceivers for bi-directional multi-input and multi-output (MIMO) based vertical free space optical (FSO) links. Spatial diversity based MIMO FSO systems could be used to mitigate atmospheric fading issues. However, the increased number of channels can cause additional pointing error in pointing, acquisition and tracking (PAT) systems. The statistical misalignment model for detecting misalignment error is d

The architectures of wired/wireless signal transmission based on RoF access network are proposed and their experimental results are shown. Both a wired and a wireless signals with a same data and heterogeneous data in different schemes are simultaneously generated using an injection locking technique and optical carrier suppression modulation based on a Fabry-Perot laser as a cost-effective WDM optical source. A reflective semiconductor optical amplifier (RSOA) is employed for the purpose of a c