Po-Yi Wu

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.

An Upconverted Phase-Modulated Fiber Optical CATV Transport System

A fiber optical CATV transport system that employed an upconverted technique and a phase modulation scheme to reduce noise and distortion induced by system is proposed and experimentally demonstrated. In contrast to a fiber optical CATV transport system that used a conventional intensity modulation scheme, excellent performances of carrier-to-noise ratio, composite second order, and composite triple beat are obtained in our proposed systems over a 100-km single-mode fiber transmission. It verifies the feasibility of the proposed systems and reveals an outstanding one with excellent transmission performances.

Hybrid lightwave subcarrier CATV/16-QAM/16-QAM OFDM transmission system

A hybrid lightwave subcarrier CATV/16-QAM/16-QAM orthogonal frequency-division multiplexing (OFDM) transmission system employing light injection/optoelectronic feedback techniques and photonic crystal fiber (PCF) is proposed and demonstrated. Good performance of carrier-to-noise ratio (CNR), composite second order, and composite triple beat were obtained for the CATV band, and high CNR and low bit error rate values were achieved for the 16-QAM and 16-QAM OFDM bands over a combination of 80 km single-mode fiber (SMF) and 2.86 km PCF transport.

Employing injection-locked FP LDs to set up a hybrid CATV/MW/MMW WDM light wave transmission system.

A hybrid cable television (CATV)/microwave (MW)/millimeter-wave (MMW) wavelength-division-multiplexing (WDM) light wave transmission system based on injection-locked Fabry-Perot laser diodes (FP LDs) is proposed and demonstrated. Different from conventional hybrid WDM light wave transmission systems, which need wavelength-selected distributed feedback laser diodes to support various services, the proposed systems employ injection-locked FP LDs to provide multiple applications. Over a 40 km single-mode fiber transport, impressive performances of carrier-to-noise ratio/composite second-order/composite triple-beat/bit error rate are obtained for 550 MHz CATV/20 GHz MW/40 GHz MMW/60 GHz MMW signal transmissions. Such a hybrid WDM light wave transmission system would be attractive for fiber links 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 10-Gbps optical WiMAX transport system

A 10-Gbps optical worldwide interoperability for microwave access (WiMAX) transport system employing vertical cavity surface emitting laser (VCSEL) and spatial light modulator (SLM) with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed. With the assistance of equalizer and low noise amplifier (LNA) at the receiving site, good bit error rate (BER) performance, clear constellation map, and clear eye diagram are achieved in the proposed systems. An optical WiMAX transport system, transmitting 16-QAM-OFDM signal over a 6-m free-space link, with a data rate of 10 Gbps is successfully demonstrated. Such a 10-Gbps optical WiMAX transport system would be attractive for providing services including Internet and telecommunication services. Our proposed system is suitable for the free-space lightwave transport system in visible light communication (VLC) application.

Bidirectional hybrid PM-based RoF and VCSEL-based VLLC system

A bidirectional hybrid phase modulation (PM)-based radio-over-fiber (RoF) and vertical cavity surface emitting laser (VCSEL)-based visible laser light communication (VLLC) systems employing injection-locked VCSEL-based PM-to-intensity modulation (IM) converters and optical interleavers (ILs) is proposed and demonstrated. To be the first one of using injection-locked VCSEL-based PM-to-IM converters and optical ILs in such bidirectional hybrid RoF and VLLC systems, the downstream light is successfully phase-remodulated with RoF signal for up-link transmission. Through a serious investigation in systems, bit error rate (BER) and eye diagram perform brilliantly over a 40-km single-mode fiber (SMF) transport and a 12-m free-space transmission. Such a bidirectional hybrid RoF and VLLC system would be very attractive for the integration of fiber backbone and in-door networks to provide broadband integrated services, including Internet and telecommunication services.

Hybrid cable television and orthogonal-frequency-division-multiplexing transport system basing on single wavelength polarization and amplitude remodulation schemes

A hybrid community antenna television (CATV) and orthogonal-frequency-division-multiplexing (OFDM) transport system is proposed and experimentally demonstrated to transmit multiple CATV channels and bi-directional radio frequency signals on a single optical carrier. By polarization remodulating an optical CATV signal with downstream OFDM signals and then amplitude remodulating upstream OFDM signals with the hybrid CATV/OFDM signals, this architecture can efficiently utilize only one optical carrier to support optical analog/digital CATV transmission and bi-directional wireless broadband services for each client. Good experimental results prove that this architecture provides a proper wavelength utilization scheme for future multiwavelength optical transport systems.

Full-duplex lightwave transport systems based on long-haul SMF and optical free-space transmissions

A full-duplex lightwave transport system employing wavelength-division-multiplexing (WDM) and optical add-drop multiplexing techniques, as well as optical free-space transmission scheme is proposed and experimentally demonstrated. Over an 80-km single-mode fiber (SMF) and 2.4 m optical free-space transmissions, impressive bit error rate (BER) performance is obtained for long-haul fiber link and finite free-space transmission distance. Such a full-duplex lightwave transport system based on long-haul SMF and optical free-space transmissions has been successfully demonstrated, which cannot only present its advancement in lightwave application, but also reveal its simplicity and convenience for the real implementation. Our proposed systems are suitable for the lightwave communication systems in wired and wireless transmissions.

Long term stability of a long intra-cavity saturable absorber external cavity semiconductor laser

A single-mode, ultra-stable, free-running laser based on an external cavity laser with a saturable absorber is presented. We report for the first time the use of external cavity of fully erbium-doped fiber, where the fiber Bragg grating (FBG) and the hyperbolic lens are directly formed on the doped fiber. Thus, the best scenario for dynamic grating performance, initiated via the inband-pumping along the entire cavity can be reached and the high stability of this laser is reported.