Jeung-Mo Kang

All-optical multiple logic gates with XOR, NOR, OR, and NAND functions using parallel SOA-MZI structures: theory and experiment

The authors have proposed, simulated, and experimentally demonstrated all-optical multiple logic gates using two parallel semiconductor optical amplifier (SOA)-Mach-Zehnder interferometer (MZI) structures that enable simultaneous operations of various logic functions of XOR, NOR, OR, and NAND. The proposed scheme, which is optimized by adjusting the optical gain and phase differences in SOA-MZI structures with creative and systematic method, has great merits to achieve the reshaped output pulses with high extinction ratio and enable the high-speed operation at over 10 Gb/s through performance enhancement of SOAs. Its validity is confirmed through simulation and experiments at 2.5 and 10 Gb/s, respectively

A novel hybrid WDM/SCM-PON sharing wavelength for up- and down-link using reflective semiconductor optical amplifier

A hybrid wavelength-division multiplexed/subcarrier multiplexed passive optical network (WDM/SCM-PON) which shares the same wavelength both up-link and down-link is presented by using a reflective semiconductor optical amplifier (RSOA) as a modulator. We investigated down-link of 622 Mb/s using distributed feedback laser diode with direct modulation and 100-Mb/s up-link using an RSOA as a modulator with 900-MHz SCM signal. In our scheme, a novel efficient and cost-effective WDM/SCM-PON using the same wavelength for down/up-link at each optical network unit is proposed and experimentally demonstrated

Life-time estimation of high-power blue light-emitting diode chips

We have proposed a new concept of metal package by which we can estimate the lifetime of blue light-emitting diode (LED) chips with high accuracy. Components in conventional LED package which may obscure the degradation behavior of LED chip itself were removed or replaced by other materials or components. Three kinds of chips from different manufacturers were analyzed in this study using proposed metal packages. In this paper, the optical and electrical characteristics such as light-output degradation and reverse leakage current of high-power blue LED chip were investigated and analyzed. Also, the relationship between light-output degradation and electrical characteristics of LED chip was described. With aging time of 5000 h, only one kind of blue LED chip shows enough light-output degradation to estimate life-time.

Fabrication and Thermal Analysis of Wafer-Level Light-Emitting Diode Packages

Wafer-level packaged light-emitting diodes (LEDs) are useful for the high-power applications such as back light unit and general solid-state lighting due to the compactness and integrated fabrication process. In this letter, wafer-level packaged LEDs with red, green, and blue multichips were fabricated, and the thermal characteristics of wafer-level packaged LEDs with multichips such as thermal resistance and junction temperature are investigated using both serial and matrix measurement methods.

Linearization of DFB laser diode by external light-injected cross-gain modulation for radio-over-fiber link

A novel linearization technique of distributed-feedback laser diode in analog optical transmitter for radio-over-fiber (RoF) link was proposed. The proposed scheme was based on a light-injection technique using cross-gain modulation effect. According to the proposed idea, a linearized RoF transmitter module was implemented and evaluated. The enhanced performance of carrier-to-noise ratio and spurious-free dynamic range were experimentally demonstrated in a wide range of radio-frequency (RF) applications. The experimental results show that the proposed scheme can be applicable for broadband RF optical transmission applications.

Linearization of RoF Optical Source by using Light-injected Gain Modulation

We presented a novel scheme for linearization of optical source in radio-over-fiber system. The linearization scheme consists of RF attenuator, RF phase shifter, and a different light source for the purpose of reducing the third order intermodulation products (IMD3). We experimentally demonstrated two tone SCM optical links where linearization scheme was applied. With optimizing the phase amount and IMD3 intensity from a different LD source, we obtained optimal condition, which results in reducing carrier to IMD3 ratio of 30dBc.

A Novel Hybrid WDM/SCM-PON using Reflective Semiconductor Optical Amplifier

A hybrid wavelength-division-multiplexed/sub-carrier-multiplexed passive optical network having the same wavelength both upstream and downstream is presented by using a reflective semiconductor optical amplifiers (RSOA) as a modulator. We investigated the down stream of 622.08Mbps using a DFB-LD with direct modulation and the 100Mbps upstream using a RSOA as a modulator with 900MHz SCM signal. In our scheme, a novel efficient and cost effective WDM/SCM-PON using same wavelength for down/up stream at each ONU proposed and demonstrated by BER measurements.

WDM-PON with Broadcasting Function Using Direct ASE Modulation of Reflective SOA

We have proposed and experimentally investigated a novel cost effective WDM-PON system which broadcasts the direct modulated ASE of RSOA for broadcasting signal and re-modulates the broadcasted ASE of RSOA for up-link at the ONU.

Performance variation of preamplifier integrated cross-phase modulation wavelength converter by internal reflectivity of semiconductor optical amplifiers

An analysis of a cross-phase modulation (XPM) wavelength converter integrated with preamplifers for increased input power dynamic range is reported. The performance of the preamplified wavelength converter can be deteriorated by the residual reflectivity of semiconductor optical amplifiers (SOAs) inside the converter. We investigate the trade-off relationship between the internal reflectivity of SOAs and the performance of the XPM wavelength converter with an integrated preamplifier through bit error rate (BER) calculation. The optimal physical and operating parameters of the preamplified XPM wavelength converter are proposed.

Optical network unit based on self-seeded reflective semiconductor optical amplifier for WDM-PON

A novel Optical network unit based on self-seeded RSOA for WDM-PON was proposed. The RSOA was self-seeded by amplified spontaneous emission of itself using fiber Bragg grating (FBG) without additional optical source.