- 1990 Texas A&M University (Ph.D. – Electrical Engineering )
- 1981 Seoul National University (M.S. – Electronics Engineering )
- 1979 Hanyang University (B.S. – Electronics Engineering )
- 2003 – 2005 Department Chair of Information and Communications, gist
- 2000 – Present Professor, Optical Communications Laboratory, gist
- 1991 – 2000 Principal member of technical staff, ETRI
- 1987 – 1990 Research Assistant, Engineering Research Center in Texas A&M University
- 1982 – 1987 Senior member of technical staff, ETRI
- Optical communicaton system technology
- Optical internet technology
- Microwave photonics technology
- Wired and Wireless Communication Systems LaboratoryThe Wired and Wireless Communication Systems Laboratory at Gwangju Institute of Science and Technology is doing researching on the development of high-speed optical communication systems and networks. The works being conducted in this lab are divided into three parts as optical communication system technology , optical internet technology and microwave photonics technology. For optical communication system technology, we are researching technologies related to implement efficient optical communication system such as SDH/SONET system, WDM system, Optical amplifier, Optical Add-drop Multiplexer(OADM) and Optical Cross-Connect (OXC). For optical internet technology, we are researching technologies related to realizing IP over WDM such as burst mode reiver, dynamic wavelength allocation, optical routing and optical packet switching. Finally we are doing about application area for appling microwave photonics technology. As studying each part work, the ultimate objectives in our laboratory are research and development of optical communication systems and networks with the better performance, and their applications into the real fields. Optical Commmunication System TechnologySDH/SONET system designSONET and SDH are a set of related standards for synchronous data transmission over fiber optic networks.SONET is short for Synchronous Optical NETwork and SDH is an acronym for Synchronous Digital Hierarchy.They have been one of the more significant events in the telecommunication industry in recent years.
WDM system design
The WDM (Wavelength-Division Multiplexing) is the technology of combining a number of wavelength onto the same fiber. The application of WDM has been to upgrade the capacity of existing point-to-point fiber optic transmission links.
Long-haul/Short-haul Transmission Technology
The world has a insatiable appetite for bandwidth, and optical communication provides the means to deliver and manage almost unlimited capacity.
Today’s single-mode optical fibers can provide a huge transmission bandwidth of 25 THz in third windows(1550 nm wavelength region), which is to meet the requirements of todays multimedia telecommunications. In long-distance networks, DWDM has increased the capacity of existing fiber routes could experience increases in capacity by a factor of 80 and perhaps up to 128 as considering optical nonlinear effects.To reduce the cost of installing, many works have been done. Also the fit of optical networking with existing network topologies with multiprotocols, it is natural to expect long/short-haul networks to evolve to an optical networking having wavelength-based facility providing, management, and restoration using optical cross-connects.
Optical amplifiers does play role in currently optical communication, especially third windows communication. But, when several channels are suddenly added/dropped from the networks, the output power from the EDFA for each surviving channel will change to keep the total power constants at the output of the saturated EDFA. Such power transients will occurs on us time scales, dramatically affecting the performance and bit-erro-rate (BER) of the surviving channels. Now we should consider the performance of a physical system related to dynamic fluctuation as adding/droping a few channels as well as carrying packet-signals in optical internet networks.
Optical Add-drop Multiplexing Technololgy
Add/Drop multiplexers are needed for WDM networks in which one or more channels need to be dropped or added while preserving the integrity of other channels. One can think of such a WDM device as a demultiplexer-multiplexer pair since its operation requires demultiplexing of the input WDM signal, changing the data content of one or more specific wavelength channels and then multiplexing the entire signal back again.
Optical Cross-connect Technology
The development of wide-area WDM networks requires dynamic wavelength routing that can reconfigure the network while maintaining its nonblocking nature. This functionality is provided by an optical cross-connect(OXC) which performs the same function as that provided by electronic digital switches in telephone networks. The use of dynamic routing also solves the problem of a limited number of available wavelengths through the wavelength-reuse technique.
2) Optical Internet Technology
IP over WDM As WDM
As WDM technology matures, IP over WDM multicast becomes a mew challenging topic. IP over WDM technology is the method that IP packet is transmitted through WDM network. IP over WDM has been envisioned as the winning combination due to the ability of the IP to be the common revenue-generating convergence sublayer and WDM as a bandwidth-rich transport sublayer. Various important concerns still need to be addressed regarding IP-WDMintegration. These include lightpath routing and resource management protocols, survivability provisioning, framing/monitoring solutions, and others.
Conventional receivers are not suitable for burst mode operation because they cannot instantaneously handle the different arriving packets with large difference in optical power and phase alignment. Therefore, it is necessary to design receivers which can adapt to the variation in optical power and phase alignment on a packet by packet basis. This type of receivers are being studied and will be assemble as a transmission system.
Dynamic Wavelength Allocation
A WDM all-optical network employing wavelength routing consists of optical routing nodes interconnected by optical links. Each link is assumed to be bidirectional and actually consists of a pair of unidirectional links. An optical routing node is capable of routing each wavelength on an incoming link to any outgoing link. However, the same wavelength on two incoming links cannot be routed simultaneously onto a single ougoing link.If each node does not have a wavelength allocation capability, establishing a lightpath may require a wavelength which is commonly idle at all links on its routing path. Therefore, the dynamic wavelength allocation is very important in WDM networks.
WDM technology is used to accomodate several wavelength channels on a fiber. This technology could enhance the line capacity of network. In wavelenth routing, data signals are carried on a unique wavelength from a source node to a destination node passing through nodes where the signals are optically routed and switched without regeneration in the electrical domain. When the physical network and required connections are given, RWA(Routing and Wavelength Assignment) is the problem to select a suitable path and wavelength among the many possible choices for each connection such that no two paths using the same wavelenth pass through the same link.
Optical Packet Switching
A WDM optical packet switch consists of four parts: the input interface, switching
fabric, output interface, and control unit. The input interface is mainly used for packet
delineation and alignment, packet header information extraction and packet header removal. The switch fabic is the core of the switch and is used to switch packets optically. The output interface is used to regenerate the optical signals and insert the packet header. The control unit controls the switch using the information in the packet headers.
3) Microwave Photonics Technology
Microwave Photonics application technology
Rapid advances in both microwave and optical technologies make it possible to merge them together to form a new class of devices that can perform high speed and high frequency electronic functions. This research area has many applications, such as antenna remoting,optically controlled phase arrays, microwave signal processing or mm-wave communication systems and photonic analog to digital conversion etc.
Especially, Optical link technologies for micro and millimeter wave systems are being studied.
Millimeter Wave over Fiber
Microwave photonics can be broadly defined as the interaction between optical signals and high-frequiency(>1 GHz) electrical signals. Typical studies in microwave photonics include basic optical-microwave interactions (e.g., radio-frequency(RF) signal generation and high-speed probing), photonic devices operation at microwave frequencies, photonic control of microwave devices, high-frequency transmission links, and the use of photonics to implement various functions in microwave systems. These include antenna remoting, long delay llines, true time-delay array beamforming, remoting or wireless systems, spectrum analysis, frequency conversion, high-performance oscillators, and analog-to-digital conversion. Continued progress in photonic components and technology applicable to microwave and millimeter-wave sysems sustains great interest in this cross-disciplinary field and expanding acceptance of photonics for microwave systems