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

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.2
• /
• pp.380-384
• /
• 2015

As an extension of Visible Light Communication, Optical Camera Communications (OCC) will be a promising service for smart devices. Especially in line of sight marketing service and indoor localization application, by using camera which exists in smart devices, small amount of data (url link) can be broadcasted or find direction from the illumination system. This paper introduces the operation of wireless communications technology that transmits optical information from optical light source to camera, called Optical Camera Communications.

• Smart Structures and Systems
• /
• v.12 no.1
• /
• pp.23-39
• /
• 2013

In this article, a smart multifunctional optical system-on-a-chip (SOC) sensor platform is presented and its application for fiber Bragg grating (FBG) sensor interrogation in optical sensor networks is investigated. The smart SOC sensor platform consists of a superluminescent diode as a broadband source, a tunable microelectromechanical system (MEMS) based Fabry-P$\acute{e}$rot filter, photodetectors, and an integrated microcontroller for data acquisition, processing, and communication. Integrated with a wireless sensor network (WSN) module in a compact package, a smart optical sensor node is developed. The smart multifunctional sensor platform has the capability of interrogating different types of optical fiber sensors, including Fabry-P$\acute{e}$rot sensors and Bragg grating sensors. As a case study, the smart optical sensor platform is demonstrated to interrogate multiplexed FBG strain sensors. A time domain signal processing method is used to obtain the Bragg wavelength shift of two FBG strain sensors through sweeping the MEMS tunable Fabry-P$\acute{e}$rot filter. A tuning range of 46 nm and a tuning speed of 10 Hz are achieved. The smart optical sensor platform will open doors to many applications that require high performance optical WSNs.

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.07a
• /
• pp.128-129
• /
• 2003

일반적으로 광학계를 설계하는 데 있어서 몇 가지 단계를 거치게 되는데, 이 중 최종설계의 성공여부를 좌우하는 가장 중요한 단계는 기초설계라 할 수 있다. 기초설계는 최적화에 필요한 초기데이터를 결정하는 것으로써, 현재 다양한 방법이 제안되어지고 있지만, 가장 체계적인 방법으로 생각되는 것은 자이델(Seidel) 3차 수차론을 활용하는 것이다. 자이델 3차 수차론으로부터 수차식들은 설계 변수들이 복합적으로 커플링된 고차방정식으로 표현이 되고, 이를 또한 해석적으로 표현되는 제한조건들과 함께 수치 해석적으로 풀면 기초설계에 필요한 여러 설계 변수들이 결정된다. (중략)

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.1289-1293
• /
• 2010

A slipring or FORJ are usually adopted in order for power supply of Geo-centrifuge and input/output data acquisition. Since using slipring causes quite a lot electrical noise, an optical communication using FORJ becomes more general for data acquisition. Such data acquisition devices, however, require frequent maintenance and replacement due to deterioration by long term usage. DICT has set up a real-time wireless date acquisition system using wireless communication technology instead of FORJ. The system enables a remote measurement at any inertial acceleration field up to 100g level and provides as same performance as FORJ. The priority of this system is to use a normal modem substituting a special FORJ.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.1
• /
• pp.166-171
• /
• 2012

In this paper, short-range underwater wireless communication technique using visible LEDs is proposed. As an alternative to conventional acoustic system, visible LED communications show high quality and high speed data transmission characteristics. We design a frequency modulation-based optical wireless audio transmission system. The CD4046B phase-locked loop device is applied to implement the frequency modulation and demodulation. With a transmission modulation of 100 kHz, audio signal has successfully received at a transmission distance of 30 cm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.1
• /
• pp.29-35
• /
• 2004

When an optical pulse is propagated through the atmosphere space, it is attenuated and broadened by the effect of atmospheric turbulence. This pulse broadening is occurred by the fluctuation in the arrival time of pulse at an optical receiver. In digital optical communication, the attenuation is important factor but the pulse broadening is more important. In this paper, thus, we will find the broadening of pulse propagated through the turbulent atmosphere, present it as the function of the structure constant for the refractive index fluctuation, and simulate it to the turbulent strength and the transmission length.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.6
• /
• pp.688-697
• /
• 2008

In this paper, an analysis method for indoor optical wireless channel properties based on photon model is presented for characterization of communication environment. In contrast to radio waves, optical waves have very short wave-lengths and very high frequencies, so that material properties become important. Channel models including diffuse reflections and absorption effects due to material surface textures make conventional electromagnetic wave analysis methods based on ray tracing consume enormous time. To overcome these problems, an analysis method using photon model is presented that approximates light intensity by a density of photons. The photon model ensures that simulation time is within a predictable limit.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.17 no.5
• /
• pp.71-78
• /
• 2017

Visible light communication (VLC) offers communication function in addition to illumination. Because the signal communication capacity per cable is 1,000 times compared to the power line communication (PLC), optical fiber is being advertised as the basis of the information and communication. Also dimming control of LED is an important component needed to provide energy savings and quality of life. This study configured multi-hop VLC system model in a building using optical fiber and analyzed the power performance of two of modulations using dimming techniques. The transmission power and received power were used to compare the power performance in multi-hop VLC environments.

• Journal of Ocean Engineering and Technology
• /
• v.32 no.2
• /
• pp.143-150
• /
• 2018

In this study, we designed and developed an underwater LED communication system composed of an LED and a photo sensor. In addition, we experimented with video data transmission in a water tank. Two communication modules were installed in the 3 m water tank, and the image data transmission test was successfully performed at a rate of 20 frames per second(FPS), image resolution of $480{\times}272$, and data communication speed of 4 Mbps.