Ki-Tae Jeong

Fiber-to-the-home services based on wavelength-division-multiplexing passive optical network

It is anticipated that more than 75 Mb/s per subscriber is required for the convergence service such as triple-play service (TPS). Among several types of high-speed access network technologies, wavelength-division-multiplexing passive optical network (WDM-PON) is the most favorable for the required bandwidth in the near future. Furthermore, WDM technologies, such as athermal arrayed-waveguide grating (AWG) and low-cost light source, have matured enough to be applied in the access network. In this paper, the authors propose and implement a WDM-PON system as a platform for TPS. The system employs an amplified spontaneous emission (ASE)-injected Fabry-Pe/spl acute/rot laser diode scheme. It has 32 channels of 125 Mb/s and adopts Ethernet as Layer 2. Multicast and virtual local area network features are used for the integration of services such as Internet protocol high-definition broadcast, voice-over Internet protocol, video on demand, and video telephone. The services were demonstrated using the WDM-PON system.

WDM-PON experiences in Korea (Invited)

Feature Issue on Passive Optical Network Architectures and TechnologiesWDM-PON activities in Korea including research and development were reviewed. The WDM-PON commercialized in Korea is aimed at delivering a 100 Mbits/s dedicated symmetric bandwidth to each home, based on the prediction of a small statistical gain for future video-centric services. The developed 32-channel WDM-PON based on wavelength-locked Fabry-Perot LDs was qualified by Korea Telecom (KT) and was deployed in KTs networks. Many studies have been conducted with the aim of enhancing the performance of the WDM-PON. High-speed data rate per channel, longer reach, narrow channel spacing, and a high split ratio with the help of subcarrier multiple access or time-division multiple access have been demonstrated. A protection method for feeder fiber fault and OSP fault-monitoring methods were also demonstrated. A gradual upgrade solution from the existing time-division multiplexing-PON to WDM-PON has also been proposed.

First Commercial Deployment of a Colorless Gigabit WDM/TDM Hybrid PON System Using Remote Protocol Terminator

Colorless gigabit wavelength-division-multiplexing (WDM)/time-division-multiplexing (TDM) hybrid passive optical network (PON) using a remote protocol terminator is proposed and experimentally demonstrated. The system consists of reflective semiconductor optical amplifier-based WDM-PON and a legacy TDM-PON, combined with a simple and efficient remote node structure in order to provide high-speed fiber-to-the-home service to a large area with a high population density. The demonstrated system can support 512 subscribers with a single feeder fiber. The performance and feasibility of the system were evaluated by transmitting gigabit per second data including the effects of Rayleigh backscattering and 20 km attenuation. The system has been used by Korea Telecom to provide commercial services in Gwangju, Korea, since March 2009, after successfully passing through the benchmark test. This is the first commercial deployment of a WDM/TDM hybrid PON. It can accommodate field-deployed TDM-PON link without any modification and extend the maximum total reach of PON link by the use of remote protocol termination. Number of subscribers and the allocated bandwidth to the subscribers can be designed by simply changing the splitting ratio.

A novel method for fabrication of a PLC platform for hybrid integration of an optical module by passive alignment

A novel fabrication method and structure of a planar lightwave circuit (PLC) platform for hybrid integration of an optical module by passive alignment technology is presented. Precise formation of V-grooves in the PLC platform can be easily obtained by the proposed process. The passive alignments of optical elements, including optical fiber, are achieved in one-mask. LD modules were implemented by the proposed method.

First commercial service of a colorless Gigabit WDM/TDM hybrid PON system

We describe the first RSOA-based WDM/TDM hybrid PON system to enter commercial service. The system, consisting of a 16 × 1.25 Gb/s colorless Gigabit WDM-PON and a legacy TDM-PON with optical-electrical-optical converters, provides the triple-play service using fiber-to-the-home and fiber-to-the-node in a new residential area in Korea.

NAT Issues in the Remote Management of Home Network Devices

Currently, many customer devices are being connected to home networks. For this reason, it is expected that device management capabilities will be a powerful instrument for the service provider to cope with high maintenance costs, security concerns, and management issues related to home networks. Through DM, the service provider could provide valuable services such as auto-provisioning, remote configuration, firmware and software updates, diagnostics, monitoring, scheduling, and fraud management. However, network address translators that are widely deployed in the home network environment prohibit DM operations from reaching user devices behind the NAT. In this article, we focus on NAT issues in the management of home network devices. Specifically, we discuss efforts relating to standardization and present our proposal to deploy DM services for VoIP and IPTV devices behind NATs. By slightly changing the behavior of Simple Network Management Protocol managers and agents and by defining additional management objects (MOs) to gather NAT binding information, we could solve the NAT traversal problem under a symmetric NAT. Moreover, we propose an enhanced method to search for the UDP hole binding time of the NAT box. For evaluation, we applied our method to 22 randomly selected VoIP devices out of 194 NATed hosts in the real broadband network and achieved a success ratio of 99 percent for exchanging SNMP request messages and a 26 percent enhancement in determining the UDP hole binding time.

Novel in-service supervisory system using OTDR for long-haul WDM transmission link including cascaded in-line EDFAs

We propose and demonstrate a novel optical supervisory system for long-haul wavelength-division-muitiplexing (WDM) transmission link including cascaded erbium-doped fiber amplifiers (EDFAs). By employing a modified optical time domain reflectometry technique with a wavelength selective bidirectional EDFA, it was possible to monitor the status of the WDM transmission link and EDFA at in-service states with negligible power penalty. Proof of the concept with a 2.5 Gb/s/spl times/eight-channel WDM transmission system [single-mode fiber, 320 km] shows clear trace of the transmission line loss/gain/reflection map with minimal signal power penalty of 0.3 dB.

Suppression of cladding-mode coupling loss in fiber Bragg gratings by independent control of refractive index and photosensitive profiles in a single-mode optical fiber

A new method to suppress the cladding-mode coupling loss in fiber Bragg gratings, by independent control of the core refractive index profile and the photosensitive profile, is proposed and experimentally demonstrated. Across the core and the inner cladding, a uniform step photosensitive profile was introduced by co-doping GeO/sub 2/ and B/sub 2/O/sub 3/. The core refractive index was selectively raised by further doping Al/sub 2/O/sub 3/ in the core that has negligible photosensitivity at 244 nm. For strong Bragg gratings inscribed on the fiber, the cladding-mode coupling loss was suppressed below 0.3 dB.

Bidirectional wavelength add/drop multiplexer using two separate MUX and DEMUX pairs and reflection-type comb filters

Abstract A bidirectional wavelength add/drop multiplexer (B-WADM) using two separate multiplexer (MUX), demultiplexer (DEMUX) pairs and reflection-type comb filters (RCFs) is proposed and demonstrated. The proposed B-WADM alleviates the formerly stringent requirement on MUX/DEMUX crosstalk characteristics, while suppressing the power penalty induced by Rayleigh backscattering/optical reflection. Two types of RCFs are proposed based on fiber Bragg gratings and a reciprocal wavelength interleaver, respectively. Experimentally, a combination of an array of fiber Bragg gratings and a light absorber was used as an RCF. The measured crosstalk induced by the Rayleigh backscattering was successfully suppressed to a negligible level (−30 dB) while simultaneously achieving a high B-WADM span gain over 25 dB.

Effect of wavelength shift on PLC-type WDM directional coupler by UV irradiation

The UV light of KrF excimer laser, which is used for making fiber gratings, is irradiated on PLC-type WDM directional couplers. After the irradiation, the shift of transmission wavelengths is observed as a function of UV exposure dose. The amount of the effective refractive index change of rectangular silica waveguides is calculated by the coupled mode theory and the measured data.