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2.333-Tbit/s bi-directional optical mobile networks using optical wireless communication (OWC)
(2020-11-15)
Wei, Liang-Yu
;
Chen, Shu-, I
;
Yeh, Chien-Hung
;
Liu, Yang
;
Chen, Guan-Hong
We propose and experimentally demonstrate a 2.333-Tbit/s bi-directional optical mobile network using optical wireless communication (OWC). The proposed network architecture is divided into: fronthaul network con-necting between the distributed-unit (DU) and the remote-radio-unit (RRU); and midhaul network connecting between the central unit (CU) and the DU. At the midhaul, an aggregated 2.333-Tbit/s transmission is achieved using wavelength division multiplexed (WDM) infrared (IR) based invisible light communication (IVLC). For the link between the RRU and user-equipment (UE), 2.7 Gbit/s white-light visible-light-communication (VLC) transmission is achieved for indoor 1.5 m transmission. It can provide communication and lighting simultaneously. A gateway (GW) is also proposed acting as the interface between the IVLC and VLC transmissions. In the proposed architecture, about 400 VLC end-users can be supported.
High-Bandwidth Green Semipolar (20-21) InGaN/GaN Micro Light-Emitting Diodes for Visible Light Communication
(2020-08-19)
Chen, Sung-Wen Huang
;
Huang, Yu-Ming
;
Chang, Yun-Han
;
Lin, Yue
;
Liou, Fang-Jyun
The light-emitting diode (LED) is among promising candidates of light sources in visible light communication (VLC); however, strong internal polarization fields in common c-plane LEDs, especially green LEDs, result in low frequency and limited transmission performance. This study aims to overcome the limited 3-dB bandwidth of long-wavelength InGaN/GaN LEDs. Thus, semipolar (20-21) micro-LEDs (mu LEDs) were fabricated through several improved approaches on epitaxy and chip processes. The mu LED exhibits a 525 nm peak wavelength and good polarization performance. The highest 3-dB bandwidth up to 756 MHz and 1.5 Gbit/s data rate was achieved under a current density of 2.0 kA/cm(2). These results suggest a good transmission capacity of green semipolar (20-21) mu LEDs in VLC applications.
Adaptive and secure VCSEL FSO based on simple dual-polarized architecture for short distance transmission
(2020-09-01)
Yeh, Chien-Hung
;
Yang, Yun-Cheng
;
Hsu, Tzu-An
;
Chen, Yu-Wen
;
Chow, Chi-Wai
In this study, using dual-polarized-multiplexing VCSEL based free space optical (FSO) transmission system is demonstrated experimentally. Two orthogonal polarizers (POLs), a beam splitter (BS) and a reflected mirror (M) are applied in the FSO transmitter (Tx) side to combine dual FSO signals into one for data security without code encryption. In the receiver (Rx) side, two blended FSO channels can be decoded adaptively by applying a POL with properly polarization status. Furthermore, when we add two corresponding POLs with orthogonal polarization in the Rx side, the FSO capacity also can double by the presented dual-polarized FSO architecture. Here, the relationships of the detected FSO powers and rotating angle between two POLs are also experimentally discussed.
Free Space Optical Communication in Long-Reach Unidirectional Ring-Architecture Fiber Network
(2020-01-01)
Yeh, Chien-Hung
;
Chen, Jhao-Ren
;
You, Wei-Yao
;
Lin, Wen-Piao
;
Chow, Chi-Wai
In the work, a ring-constructed wavelength-division-multiplexing (WDM) access system for delivering multiple free space optical (FSO) wireless signals is investigated. To reach the FSO transmission through single-mode fiber (SMF) connection, the optical wireless unit (OWU) and remote OWU are designed in the WDM network. The downstream and upstream WDM FSO channels could be transmitted in unidirectional propagation with the same wavelength. Hence, the presented ring-based WDM network not only can transmit the FSO signal, but also can circumvent the Rayleigh backscattering (RB) interferometric beat noise. In addition, according to the experimental results, the SMF and FSO transmission lengths can reach 50 km and 500 to 1000 m at the forward error correction (FEC) level without using optical amplification and dispersion compensation, respectively, when four WDM wavelengths are exploited experimentally for demonstration.
Use of Same WDM Channels in Fiber Network for Bidirectional Free Space Optical Communication With Rayleigh Backscattering Interference Alleviation
(2019-01-01)
Yeh, Chien-Hung
;
Guo, Bo-Shen
;
Gu, Chong-Sin
;
Chow, Chi-Wai
;
Lin, Wen-Piao
In the paper, we present and demonstrate experimentally a 10 Gbit/s on-off keying (OOK) bidirectional wavelength-division-multiplexing (WDM) free space optical (FSO) communication architecture integrated in fiber network together with 5 m free space transmission length and 25 km fiber link, respectively. To achieve bidirectional FSO link, the all WDM wavelengths can be used simultaneously to serve as the downstream and upstream traffics in the proposed FSO-WDM system. Here, four pairs of line terminations (LTs) and optical wireless units (OWUs) are integrated arbitrarily in fiber access network for confidential and bidirectional FSO connection based on the requirement of practical environment. In the measurement, the relationship of FSO signal performance and detected tolerance are also discussed and analyzed. Moreover, the WDM-FSO transmission can also avoid the Rayleigh backscattering (RB) beat noise in fiber connection.
An Erbium Fiber Laser With Single-Frequency Oscillation and Wavelength-Upconverted Output
(2020-10-01)
Yeh, Chien-Hung
;
You, Wei-Yao
;
Chen, Jhao-Ren
;
Chow, Chi-Wai
;
Lin, Wen-Piao
In this paper, we present experimentally an erbium-doped fiber (EDF) laser system to accomplish the single-longitudinal-mode (SLM) and wavelength-upconverted output by using nonlinear effect. To accomplish the SLM output, a short length of unpumped EDF saturable absorber (SA) is applied inside the EDF laser cavity for filtering densely multi-mode noise. In accordance with the designed EDF laser system, the lasing wavelength can be upconverted to a longer wavelength position. In addition, the output characteristics of output power, optical signal to noise ratio (OSNR), tunability, stability and linewidth in the EDF laser are also discussed.
Visible light positioning (VLP) system using low-cost organic photovoltaic cell (OPVC) for low illumination environments
(2020-08-31)
Hong, Chong-You
;
Wu, Yu-Chun
;
Lin, Yu-Hsiang
;
Liu, Yang
;
Chow, Chi-Wai
We propose and demonstrate a received-signal-strength (RSS) based visible light positioning (VLP) system using a low-cost organic photovoltaic cell (OPVC) receiver (Rx). The OPVC is a passive device without the need of external power supply. It could detect VLC signal and harvest energy. Our developed OPVC has a high power conversion efficiency (PCE) of 9.8%. The VLP system can be operated at a low illumination of 130 lux. The regression machine learning (MIL) algorithm is used to enhance the positioning accuracy. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1.12-Tbit/s PAM-4 Enabled by a Silicon Photonic Transmitter Bridged With a 7-Channel MCF
(2020-08-01)
Tong, Yeyu
;
Chen, Guan-Hong
;
Wang, Yi
;
Zhang, Zunyue
;
Chan, David Weng U.
We demonstrate a high-capacity and ultra-compact silicon photonic transmitter directly coupled to a 7-channel multicore fiber (MCF). The integrated transmitter contains seven GeSi electro-absorption modulators (EAMs) connected with the perfectly vertical grating coupler (PVGC) array. A high port density for spatial-division multiplexing (SDM) is thus enabled by the out-of-plane coupling while not requiring angled polishing of the MCF. Relying on four-level pulse amplitude modulation (PAM-4) and digital signal processing (DSP), each of the EAMs can support a data rate of 160 Gbit/s in the back-to-back system. The obtained bit-error-rate (BER) is below the low-latency 7% hard-decision forward-error-correct (HD-FEC) coding limit. The integrated transmitter has a total data-rate-capacity of 1.12 Tbit/s over the seven spatial channels and a compact footprint of 1.8 mm x 0.45 mm. BER performance of the optimum spatial channel is evaluated at different wavelengths, revealing its potential for possible wavelength-division multiplexing (WDM) by the on-chip wavelength (de)multiplexers in the future.
Analysis of Non-Hermitian symmetry (NHS) IFFT/FFT size efficient OFDM for multiple-client non-orthogonal multiple access (NOMA) visible light communication (VLC) system
(2020-10-01)
Adnan, Assaidah
;
Liu, Yang
;
Chow, Chi-Wai
;
Yeh, Chien-Hung
;
交大名義發表
Orthogonal-frequency-division-multiplexing (OFDM) format is widely deployed in visible-light-communication (VLC) systems due to its high spectral efficiency. To produce real-valued OFDM signal for VLC, Hermitian-symmetry (HS) is needed during the inverse-fast-Fourier-transform (IFFT) encoding process. However the HS requirement doubles the IFFT/FFT size and increase the encoding complexity. Non-Hermitian symmetry (NHS)-OFDM schemes are proposed, but they have different limitations. In this work, we propose and investigate a non-orthogonal multiple access (NOMA) VLC network serving 2, 3 or 4 clients simultaneously using NHS-OFDM IFFT/FFT size efficient (SE) OFDM format. Numerical analysis of signal amplitude effect to the bit-error-ratio (BER) performance for different users are performed, showing that the BER < 7% forward-error-correction (FEC) limit can be achieved as long as the required signal amplitude ratio of each user is fulfilled. We also compare the proposed system with a typical example of HS-OFDM modulation, i.e. direct-current optical (DCO)-OFDM NOMA-VLC system.
Digital Signal Processing for Visible Light Communication Applications
(2019-01-01)
Chow, Chi-Wai
;
Chen, Guan-Hong
;
Peng, Ching-Wei
;
Wei, Liang-Yu
;
Yeh, Chien-Hung
We reviewed our resent works using digital-signal-processing (DSP) techniques to improve visible-light-communication (VLC). A rolling-shutter-effect (RSE) light-panel and CMOS image-sensor based VLC and a visible-light-positioning (VLP) system using machine learning are discussed.

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