Sang-Kook Han

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

An Indoor Visible Light Communication Positioning System Using a RF Carrier Allocation Technique

We propose a new indoor positioning system utilizing visible light communication. Intensity modulation/direct detection and carrier allocation methods are utilized in the proposed system. Simultaneous three channel transmissions were applied to calculate the receivers position. The characteristics of the proposed positioning system were investigated through simulation based on the experimental results, and the feasibility of the proposed system was verified by experimentation. The experimental result shows that the average error of estimated positions is reduced to 2.4 cm using adjustment process by normalizing method, which is compared with 141.1 cm without adjustment process.

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

Reflective SOA-Based Bidirectional WDM-PON Sharing Optical Source for Up/Downlink Data and Broadcasting Transmission

We proposed and experimentally demonstrated the reflective semiconductor optical amplifier (RSOA)-based wavelength-division-multiplexed passive optical network (WDM-PON) scheme where not only up/downlink data services but also broadcasting service could be provided using a single optical source. In the proposed scheme, the digital signal and subcarrier multiplexing (SCM) signal for downstream were simultaneously modulated by a single distributed feedback laser diode and RSOA in optical network unit remodulated downstream source as an upstream. Without performance deterioration of digital signals both in up- and downstream, the proposed WDM-PON scheme can stably offer the SCM signal for broadcasting service. In the experiment, 1-Gb/s digital signals both for up- and downstream and 20-Mb/s SCM signal at 2.2 GHz for broadcasting were demonstrated in 10-km bidirectional link

Three-Dimensional Visible Light Indoor Localization Using AOA and RSS With Multiple Optical Receivers

A novel concept is proposed for integrating optical wireless visible light communications with 3-D indoor positioning using a single transmitter and multiple tilted optical receivers. We modeled a channel link, which was based on the transmitter and receiver characteristic data obtained in this experiment. The proposed 3-D positioning algorithm is based on gain difference, which is a function of the angle of arrival and the received signal strength. Our demonstration shows that the proposed algorithm can determine accurate positions, including height, without intercell interference.

Indoor Location Estimation Based on LED Visible Light Communication Using Multiple Optical Receivers

An novel concept for integrating visible light produced by LEDs with indoor positioning using multiple optical receivers is presented in this study. We propose an algorithm using the received signal strength indication (RSSI), which changes by on transmission distance and angle. In order to estimate the position, the transmitters location code was received using multiple optical receivers. The validity of the proposed scheme was demonstrated by determining the local position using distances between the transmitter and receivers, and the relative position between receivers.

Mitigation of dispersion-induced effects using SOA in analog optical transmission

A novel technique to improve an analog optical transmission performance by reducing both the nonlinearity and chromatic dispersion induced carrier suppression has been proposed. The intrinsic nonlinear distortion component of Mach-Zehnder modulator (MZM) was reduced by gain saturation characteristics of semiconductor optical amplifier (SOA). The composite triple beat (CTB) of MZM was reduced as much as 9 dB at the quadratic bias point and the following enhancement of dynamic range by 4.5 dB was obtained. The RF carrier suppression for the transmission length and operating frequency was reduced by a negative chirp characteristic of semiconductor optical amplifier (SOA) and the enhancement of CTB after transmission were also achieved as a result of the linearization using SOA.

1.25-Gb/s Wavelength-Division Multiplexed Single-Wavelength Colorless Radio-on-Fiber Systems Using Reflective Semiconductor Optical Amplifier

A wavelength-division multiplexed colorless radio-on-fiber (RoF) system based on a reflective semiconductor optical amplifier (RSOA) is proposed in this paper. This scheme has a colorless and simple base station (BS), because an RSOA playing the role of amplification and modulation is used at the BS, irrespective of the wavelength. The spurious-free dynamic range, gain, and noise figure of both the downlink and uplink are presented to verify the suitability of the scheme for an RoF system. Error-free transmissions for both uplink and downlink wireless signals of 1.25 Gb/s are demonstrated. From the experimental results using an RF subcarrier of 3 GHz as a wireless signal, it is held that the performance of this scheme will change only slightly when using a millimeter-wave signal (> 30 GHz).

Optical single sideband signal generation using phase modulation of semiconductor optical amplifier

An optical single sideband (OSSB) generation method using phase modulation in semiconductor optical amplifier (SOA) is proposed to overcome the dispersion-induced carrier suppression problem which limits available fiber frequency range in analog optical link. The OSSB generation was achieved by phase variation in SOA which results /spl pi//2 phase difference between the amplitude and phase terms of modulated optical signal. A 21-dB difference between two sidebands was experimentally observed. From the transmission experiment up to 100 km over single-mode fiber, we confirmed that the generated OSSB signal is good enough to remove the radio frequency signal degradation due to chromatic dispersion.

Outdoor Visible Light Communication for inter- vehicle communication using Controller Area Network

In this paper, we implemented the outdoor Visible Light Communication (VLC) system based on Controller Area Network (CAN) which is normally used in a car, plane, ship, product line control system, medical device and industrial device. For vehicle to vehicle (V2V) or indoor vehicle communication, we used common use device such as head light and back light. We made an application circuit and explained the principle. Also, we found an outdoor VLC problem which is sun light noise and photo detector (PD) saturation problem. Circuits pulse features were demonstrated by signal. Total communication distance was 20 m in the daytime outdoor condition and its experimental transmission performance is presented.