Xiongbin Chen

High Bandwidth Visible Light Communications Based on a Post-Equalization Circuit

A research in extending bandwidth of the visible light communication (VLC) system that uses phosphorescent white LED has been reported in this letter. Slow response of the phosphorescent component limits the modulation bandwidth of white LED to the lower MHz range. In this letter, we present a post-equalization circuit that contains two passive equalizers and one active equalizer. With blue-filtering and the post-equalization circuit, a bandwidth of 151 MHz has been achieved in our VLC system, which allows OOK-NRZ data transmission up to 340 Mb/s. The VLC link operates at 43 cm using a single one Watt white LED, and the bit-error-ratio was below 2×10-3, which is within the forward error correction limit.

A 550 Mbit/s real-time visible light communication system based on phosphorescent white light LED for practical high-speed low-complexity application

In this paper, we first experimentally demonstrate a 550 Mbit/s real-time visible light communication (VLC) system based on nonreturn-to-zero on-off keying (NRZ-OOK) modulation of a commercial phosphorescent white light LED. The 3-dB modulation bandwidth of such devices is only a few megahertz. We proposed an analog pre-emphasis circuit based on NPN transistors and an active post-equalization circuit based on an amplifier to enhance the 3-dB bandwidth of VLC link. Utilizing our proposed pre-emphasis and post-equalization circuits, the 3-dB bandwidth of VLC link could be extended from 3 to 233 MHz with blue-filter, to the best of our knowledge, which is the highest ever achieved in VLC systems reported. The achieved data rate was 550 Mbit/s at the distance of 60 cm and the resultant bit-error-ratio (BER) was 2.6 × 10(-9). When the VLC link operated at 160 cm, the data rate was 480 Mbit/s with 2.3 × 10(-7) of BER. Our proposed VLC system is a good solution for high-speed low-complexity application.

An analog modulator for 460 MB/S visible light data transmission based on OOK-NRS modulation

This article describes an analog modulator that contains modulation, a MOSFET drive, and pre-emphasis circuits for a high-speed VLC application system based on a commercial phosphorescent white LED. We propose a small signal modulation model that is implemented by an AC-coupled N-channel MOSFET circuit and present a pre-emphasis circuit to enhance the 3 dB bandwidth of a VLC link. Utilizing our proposed analog modulator combined with blue filtering, the 3 dB bandwidth of a VLC system could be extended from 3 to 175 MHz, which allows OOK-NRZ data transmission up to 460 Mb/s with BER below 10-9 under a 1 m radial distance. With a simple analog modulator based on the simplest OOK-NRZ modulation scheme, a high-speed VLC system could be realized. The VLC link with the proposed analog modulator is a good solution for a high-speed low-complexity and low-cost practical VLC application system.

Design of indoor wireless communication system using LEDs

An indoor wireless communication system using commercial white LED is presented in this paper. OOK (On-Off Keying) modulation is adopted in the transmitter module. Data transmission is realized based on RS-485 protocol. A DC-balanced coding with error check and correction abilities is applied to avoid blinks and improve the performance of the system. The system can keep 10−7 error bit rate within 2.5m reach at a rate up to 115200 bps.

Visible Light Communication System Using Silicon Photocell for Energy Gathering and Data Receiving

Silicon photocell acts as the detector and energy convertor in the VLC system. The system model was set up and simulated in Matlab/Simulink environment. A 10u2009Hz square wave was modulated on LED and restored in voltage mode at the receiver. An energy gathering and signal detecting system was demonstrated at the baud rate of 19200, and the DC signal is about 2.77u2009V and AC signal is around 410u2009mV.

40Gbps Parallel Optical Module Based On an Advanced Structure of Optical Coupling

We propose an advanced structure of optical coupling which realizes high coupling efficiency and simplifying alignment, enabling the application of optical interconnect. A high-efficiency optical transmitter module based on this advanced coupling was fabricated using a VCSEL array. The VCSEL was directly bonded on bracket which is pasted on a holder with two pin used to locate. And there is a dummy club at the middle of the package for laser driver, favorable for cooling and reducing the noise caused by ground return. Coupling component were fabricated. And bending loss was tested. A successful eye diagram at the speed of 3.3Gb/s/ch with 850 nm was accomplished from the VCSEL-directbonded transmitter module.

10 Mbps Ethernet Access for Indoor Personal Local Area Network based on a Phosphorescent White LED

This paper reports a visible light communication application system realizing 10 Mbps Ethernet access for indoor personal area network based on a phosphorescent white LED, operating with high signal to noise ratio (>45 dB).

Channel Arrangement for optical communication subsystems with 12 parallel channels

This paper devoted to report the design and the achievement of an optical communication subsystem with 12 parallel channels in one chip. The system is capable of transmitting 10 Gbps bidirectional date over hundreds of meters. It can provide error detection and correction by using 8B/10B encoding and Cyclical Redundancy Checking (CRC) encoding when only single-channel fails. The design scheme has already passed the simulation in FPGA. This technique is useful to enhance the capability and the reliability of the very short reach (VSR) transmission systems.

An analysis and simulation about conditioned launch for very short reach (VSR-4)

VSR4 links use graded index multimode fibers (GIMMFs) as the transmission medium with operation wavelength 850nm. For cost reasons, VCSEL has been selected as the optical source to VSR4. The minimum bandwidth specification for 62.5um GIMMF in VSR4 is only 400 MHz•km for over-filled-launch (OFL) condition. The distance of 300 meters is limited over transmission rates of 1.25Gbit/s on the basis of this specification. In order to overcome the OFL bandwidth limit by selective excitation of a limited number of modes, conditioned launch technique is investigated. In this paper, based on a comprehensive dispersion theory of GIMMF, a model is built to simulate the transmission of optical signal in GIMMFs and a comparison between OFL and conditioned launch is analyzed. The result can be the guidelines for the best choice of techniques for various LAN and interconnect systems also.

Proposed scheme for parallel 10Gb/s VSR system and its Verilog HDL realization

This paper proposes a novel and innovative scheme for 10Gb/s parallel Very Short Reach (VSR) optical communication system. The optimized scheme properly manages the SDH/SONET redundant bytes and adjusts the position of error detecting bytes and error correction bytes. Compared with the OIF-VSR4-01.0 proposal, the scheme has a coding process module. The SDH/SONET frames in transmission direction are disposed as follows: (1) The Framer-Serdes Interface (FSI) gets 16×622.08Mb/s STM-64 frame. (2) The STM-64 frame is byte-wise stripped across 12 channels, all channels are data channels. During this process, the parity bytes and CRC bytes are generated in the similar way as OIF-VSR4-01.0 and stored in the code process module. (3) The code process module will regularly convey the additional parity bytes and CRC bytes to all 12 data channels. (4) After the 8B/10B coding, the 12 channels is transmitted to the parallel VCSEL array. The receive process approximately in reverse order of transmission process. By applying this scheme to 10Gb/s VSR system, the frame size in VSR system is reduced from 15552×12 bytes to 14040×12 bytes, the system redundancy is reduced obviously.