Ching-Hung Chang

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.

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.

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.

A broadband ASE light source-based full-duplex FTTX/ROF transport system

A full-duplex fiber-to-the-X (FTTX)/radio-over-fiber (ROF) transport system based on a broadband amplified spontaneous emission (ASE) light source is proposed and demonstrated for rural wide-spread villages. Combining the concepts of long-transmission transmission and ring topology, a long-haul single-mode fiber (SMF) trunk is sharing with multiple rural villages. Externally modulated baseband (BB) (1.25 Gbps) and radio-frequency (RF) (622 Mbps/10 GHz) signals are successfully transmitted simultaneously. Good bit error rate (BER) performance was achieved to demonstrate the practice of providing wire/wireless connections for long-haul wide-spread rural villages. Since our proposed system uses only a broadband ASE light source to achieve multi-wavelengths transmissions, it also reveals an outstanding one with simpler and more economic advantages.

Simplified radio-over-fiber transport systems with a low-cost multiband light source

In this Letter, low-cost radio-over-fiber (ROF) transport systems are proposed and experimentally demonstrated. By utilizing a laser diode (LD) and a local oscillator (LO) to generate coherent multiband optical carriers, as well as a self-composed wavelength selector to separate every two carriers for different ROF transport systems, no any other dedicated LD or electrical frequency upconverting circuit/process is needed in the central station (CS). Compared with current ROF systems, the required numbers of LDs, LOs, and mixers in a CS are significantly reduced. Reducing the number of components not only can simplify the network structure but can also reduce the volume and complexity of the relative logistics. To demonstrate the practice of the proposed ROF transport systems, clear eye diagrams and error-free transmission performance are experimentally presented.

Direct CATV modulation and phase remodulated radio-over-fiber transport system

A novel transport system, with directly modulating community antenna television (CATV) signal downstream and phase-remodulating radio-over-fiber (ROF) signal upstream, is proposed and experimentally demonstrated. By modulating multi-carriers CATV signal in amplitude domain and ROF signal in phase domain, a single optical wavelength is able to serve these two applications simultaneous. To be the first system of communicating CATV signal downstream and phase remodulating radio signal upstream, the performances of transmitting CATV and radio signals over 20 km single-mode fiber (SMF) were experimentally verified. Good performances of carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) were obtained for CATV applications as well as high extinction ration (ER) and low bit error rate (BER) values were measured for ROF transmission.

A Hybrid CATV/16-QAM-OFDM In-House Network Over SMF and GI-POF/VLC Transport

This letter proposes and experimentally demonstrates a hybrid cable television (CATV)/16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) in-house network over a combined 40 km single-mode fiber, 1.43 km photonic crystal fiber, and 30 m graded index-plastic optical fiber/5 m visible light communication transport. Good performances of carrier-to-noise ratio, composite second-order, and composite triple-beat are obtained for the CATV signal. A low bit error rate value is achieved for the 16-QAM-OFDM signal.

A Hybrid WDM Lightwave Transport System Based on Fiber-Wireless and Fiber-VLLC Convergences

A hybrid wavelength-division-multiplexing (WDM) lightwave transport system for millimeter-wave (MMW)/microwave (MW)/baseband (BB) signals that are transmission based on fiber-wireless and fiber-visible laser light communication (VLLC) convergences is proposed and demonstrated. A broadband light source with an optical signal-to-noise ratio enhancement scheme in a hybrid lightwave transport system is employed. Light is optically promoted from a 5-Gbps/15-GHz RF data signal to 5-Gbps/60-GHz MMW and 5-Gbps/30-GHz MW data signals in fiber-wireless convergence. Light is also optically demoted from a 5-Gbps/15-GHz RF data signal to a 5-Gbps data stream in fiber-VLLC convergence. Over a 40-km single-mode fiber and a 4-m RF wireless/a 10-m free-space VLLC transmission, bit error rate performs impressively for 60-GHz MMW, 30-GHz MW, and 5-Gbps BB signal transmission. Such a hybrid WDM lightwave transport system could have practical applications for fiber-wireless and fiber-VLLC convergences to provide broadband integrated services.

RoF transport systems with OSNR enhanced multi-band optical carrier generator

A combination of an economic multi-band optical carrier generator and a novel optical signal to noise ratio (OSNR) enhancement circuit is proposed and demonstrated for radio over fiber (RoF) transport systems. Different from normal RoF transport systems which a central station (CS) needs multiple dedicate wavelength laser diodes (LDs) to support various base stations (BSs), the proposed scheme can employ a single LD to provide multiple optical carriers for various BSs. To verify this scheme, 8 coherent optical carriers are firstly generated using a single LD and a local oscillator (LO). Subsequently, their OSNR values are optimized by the developed OSNR enhancement circuit. An up to 15 dB OSNR enlargement in those optical carriers is experimentally achieved. To demonstrate the practice of the proposal, a pair of those optical carriers is employed to experimentally achieve frequency up-conversion process in a RoF transport system. Clear eye diagram and error free transmission reveal that with a proper carrier selector the proposed scheme can be employed to support multiple RoF transmissions. Furthermore, this proposal also presents a high possibility to achieve 60 GHz RoF transmission using a 10 GHz LO, a LD and a low frequency external modulator.

A hybrid CATV/OFDM long-reach passive optical network architecture

A hybrid CATV/OFDM long-reach PON architecture is proposed and experimentally demonstrated. By multiplexing the OFDM and CATV signals in different frequency bands, the overall network structure is simplified and the available bandwidth for the OFDM signals is increased. Furthermore, by carefully adjusting the driving voltage of the employed CATV transmitter, the overall transmission performance can be optimized by eliminating a large amount of unwanted distortions. Unlike the current fiber optical CATV transport system in which the CATV signals need to be amplified in every 30 ~40 km transmission span, the proposed architecture has successfully extended the transmission span to 60 km. This can practically remove the needs of electrical power provisioning and monitoring between the central office (CO) and each local exchange (LE). Good transmission performances of carrier-to-noise ratio (CNR), composite second-order (CSO), composite triple beat (CTB) and bit error rate (BER) were obtained for the transmitted CATV and OFDM signals. All of these experimental results prove the practice and efficiency of the proposed architecture in providing simplicity and extended reach services to customers.