Hai-Han Lu

10m/500Mbps WDM visible light communication systems

A wavelength-division-multiplexing (WDM) visible light communiction (VLC) system employing red and green laser pointer lasers (LPLs) with directly modulating data signals is proposed and experimentally demonstrated. With the assistance of preamplifier and adaptive filter at the receiving sites, low bit error rate (BER) at 10 m/500 Mbps operation is obtained for each wavelength. The use of preamplifier and adaptive filter offer significant improvements for free-space transmission performance. Improved performance of BER of <10(-9), as well as better and clear eye diagram were achieved in our proposed WDM VLC systems. LPL features create a new category of good performance with high-speed data rate, long transmission length (>5m), as well as easy handling and installation. This proposed WDM VLC system reveals a prominent one to present its advancement in simplicity and convenience to be installed.

Optical 16-QAM-52-OFDM transmission at 4 Gbit/s by directly modulating a coherently injection-locked colorless laser diode

Coherently injection-locked and directly modulated weak-resonant-cavity laser diode (WRC-FPLD) for back-to-back optical 16-quadrature-amplitude-modulation (QAM) and 52-subcarrier orthogonal frequency division multiplexing (OFDM) transmission with maximum bit rate up to 4 Gbit/s at carrier frequency of 2.5 GHz is demonstrated. The WRC-FPLD transmitter source is a specific design with very weak-resonant longitudinal modes to preserve its broadband gain spectral characteristics for serving as a colorless WDM-PON transmitter. Under coherent injection-locking, the relative-intensity noise (RIN) of the injection-locked WRC-FPLD can be suppressed to ?105 dBc/Hz and the error vector magnitude of the received optical OFDM data is greatly reduced with the amplitude error suppressed down 5.5%. Such a coherently injection-locked single-mode WRC-FPLD can perform both the back-to-back and the 25-km-SMF 16-QAM-52-OFDM transmissions with a symbol rate of 20-MSa/s in each OFDM subcarrier. After coherent injection locking, the BER of the back-to-back transmitted 16-QAM-52-OFDM data is reduced to 2.5 × 10(-5) at receiving power of ?10 dBm. After propagating along a 25-km-long SMF, a receiving power sensitivity of ?7.5 dBm is required to obtain a lowest BER of 2.5 × 10(-5), and a power penalty of 2.7 dB is observed when comparing with the back-to-back transmission.

A 100-Gb/s Multiple-Input Multiple-Output Visible Laser Light Communication System

A 100-Gb/s multiple-input multiple-output (MIMO) visible laser light communication (VLLC) system employing vertical-cavity surface-emitting lasers with 16-quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM) modulating signals is proposed and experimentally demonstrated. The transmission capacity of systems is significantly increased by space-division-multiplexing scheme. With the aid of low-noise amplifier and equalizer at the receiving site, good bit error rate performance and clear constellation map are obtained for each optical channel. A system of eight 16-QAM-OFDM channels over 5-m free-space links with a total data rate of 100 Gb/s (12.5 Gb/s/channel × 8 channels) is successfully achieved. Such a proposed MIMO VLLC system is shown to be a prominent one not only presents its convenience in free-space optical communication, but also reveals its potential for the real implementation.

L-band Erbium-doped fiber laser with coupling-ratio controlled wavelength tunability

By controlling the output coupling ratio, we demonstrate a novel wavelength-tunable L-band Erbium-doped fiber laser (EDFL) with a maximum tuning range up to 58 nm (from 1567 to 1625 nm) by controlling its output coupling ratio between 1% and 99%. The L-band EDFL is configured by using a bi-directionally dual-wavelength pumped EDFA in close-loop with an output coupler of tunable coupling ratio and an air-gap inserted FC/PC connector pair. Such an EDFL exhibits a quantum efficiency of 42% and an ultra-high power conversion efficiency of 37% under optimized pumping scheme, providing the small-signal gain and output power of ~34 dB and 91 mW, respectively. Low variation of <1.2 dB on channel power, power fluctuation of 0.04% and a narrow linewidth of 0.03 nm are obtained.

Fiber optical CATV system-performance improvement by using external light-injection technique

A directly modulated amplitude modulation with vestigial sideband cable television (CATV) erbium-doped fiber amplifier-repeated system that uses an external light-injection technique is proposed and demonstrated. The external light-injection technique greatly enhances the frequency response of the laser diode, and thus improves the overall performance of the fiber optical CATV system.

CATV/radio-on-fiber transport systems based on EAM and optical SSB Modulation technique

A lightwave transport system based on an electroabsorption modulator and optical single sideband modulation technique is proposed and demonstrated. Simultaneous transmission of CATV and microwave signals, good performances of carrier-to-noise ratio, composite second order, and composite triple beat were obtained for CATV signals; low bit-error rate and third-order intermodulation distortion-to-carrier ratio (IMD/sub 3//C), as well as high spurious-free dynamic range values were achieved for radio-on-fiber applications.

Intermodulation distortion suppression in a full-duplex radio-on-fiber ring network

A full-duplex radio-on-fiber (ROF) ring network based on electroabsorption modulator (EAM) low bias voltage, RF amplifier predistorter, wavelength-division-multiplexing (WDM), and optical add-drop multiplexing techniques is proposed and demonstrated. Over a long-haul fiber ring network transmission, low third-order intermodulation distortion to carrier ratio (IMD/sub 3//C) and bit error rate (BER) values were obtained in our proposed full-duplex ROF ring network.

Generation and Transmission of BB/MW/MMW Signals by Cascading PM and MZM

A bidirectional three-band lightwave transport system is proposed and experimentally demonstrated for both fiber-to-the-X (FTTX) and radio-over-fiber (RoF) networks. By cascading a phase modulator (PM) and a Mach-Zehnder modulator (MZM) to generate multiple coherent lightwaves, hybrid 1.25 Gbps baseband (BB), 1.25 Gbps/20 GHz microwave (MW), and 1.25 Gbps/40 GHz millimeter-wave (MMW) downstream signals and a 1.25 Gbps BB upstream signal are simultaneously transmitted. Furthermore, with an assistance of an optical signal-to-noise ratio (OSNR) enhancement circuit, sufficient low bit error rate (BER) values are experimentally achieved for both down-link BB/MW/MMW and up-link BB signals. No additional high-frequency local oscillator, mixers and upstream laser diode are required in both transmitter and receiver sites. Under this architecture, both wire-lined and wireless clients can be simultaneously served without using any extra device/equipment to convert the downstream signals among BB, MW and MMW formats.

Bidirectional hybrid CATV/radio-over-fiber WDM transport system.

A bidirectional hybrid cable antenna television (CATV)/radio-over-fiber (ROF) wavelength-division-multiplexing (WDM) transport system using injection locking technique to suppress the rf power degradation, tunable optical bandpass filter to generate optical single-sideband format for the CATV signal or only one optical sideband format for the ROF one, and photonic crystal fiber to reduce the net dispersion is proposed and demonstrated. Impressive performances of the carrier-to-noise ratio, the composite second-order, the composite triple beat, and the bit error rate were obtained in our proposed systems.

10 m/25 Gbps LiFi transmission system based on a two-stage injection-locked 680 nm VCSEL transmitter.

A 10  m/25  Gbps light-based WiFi (LiFi) transmission system based on a two-stage injection-locked 680 nm vertical-cavity surface-emitting laser (VCSEL) transmitter is proposed. A LiFi transmission system with a data rate of 25 Gbps is experimentally demonstrated over a 10 m free-space link. To the best of our knowledge, it is the first time a two-stage injection-locked 680 nm VCSEL transmitter in a 10  m/25  Gbps LiFi transmission system has been employed. Impressive bit error rate performance and a clear eye diagram are achieved in the proposed systems. Such a 10  m/25  Gbps LiFi transmission system provides the advantage of a communication link for higher data rates that could accelerate the deployment of visible laser light communication.