Wen-Shing Tsai

A 20-m/40-Gb/s 1550-nm DFB LD-Based FSO Link

An innovative free-space optical (FSO) link using laser light propagation to achieve transmission rate of 40 Gb/s at a wavelength of 1550 nm is proposed and experimentally demonstrated. Over a 20-m free-space link, brilliant bit-error-rate performance and clear eye diagram are obtained in the proposed 1550-nm distributed feedback (DFB) laser diode (LD)-based FSO links. As far as we know, it is the first time that a 1550-nm externally modulated laser transmitter cascaded with an erbium-doped fiber amplifier and a pair of fiber collimators to successfully set up a 20-m/40-Gb/s FSO link has been employed. Compared with the 680-nm vertical-cavity surface-emitting laser-based FSO link, this proposed 1550-nm DFB LD-based FSO link is attractive not only because it has longer free-space transmission distance but because it supplies higher bandwidth operation as well. Such a 1550-nm DFB LD-based FSO link provides the benefits of optical wireless communications for longer transmission distance and higher transmission rate, which is thoroughly helpful for optical wireless network applications.

A 50-m/40 Gb/s 680-nm VCSEL-Based FSO Communication

A 50-m/40-Gb/s 680-nm vertical-cavity surface-emitting laser (VCSEL)-based free-space optical (FSO) communication employing three-stage injection-locked technique and the afocal scheme is proposed and experimentally demonstrated. The three-stage injection-locked technique, which can significantly increase the resonant frequency of the VCSEL, is expected to provide higher transmission rate in FSO communication. The afocal scheme, which can reduce the beam size of laser beam, is expected to provide longer free-space link in FSO communication. As far as we know, it is the first time that a three-stage injection-locked 680-nm VCSEL transmitter and afocal scheme that will successfully build up a 50-m/40-Gb/s FSO communication has been employed. Such a 50-m/40-Gb/s FSO communication provides the advantages of optical wireless links for longer transmission distance and higher transmission rate, which is thoroughly useful for high-speed light-based WiFi (LiFi) applications.

150 m/280 Gbps WDM/SDM FSO link based on OEO-based BLS and afocal telescopes.

A 150 m/280 Gbps free-space optical (FSO) link based on an optoelectronic oscillator (OEO)-based broadband light source (BLS), afocal telescopes, and wavelength-division-multiplexing (WDM)/space-division-multiplexing (SDM) convergence is proposed. Experimental results show that the transmission distance of FSO links is significantly increased by afocal telescopes, and the transmission rate of FSO links is greatly enhanced by WDM and SDM convergence. With the aid of a low noise amplifier and clock/data recovery, good bit error rate performance and a clear eye diagram are achieved at 150 m/280 Gbps operation. This proposed 150 m/280 Gbps WDM/SDM FSO link is shown to be a prominent alternative not only because of its advancement of indoor FSO communications but also because of the advantages of optical wireless communications for a long transmission distance and high transmission rate.

A 50-m/320-Gb/s DWDM FSO Communication With Afocal Scheme

This paper proposes and presents the experimental demonstration of 320-Gb/s free-space optical (FSO) communication based on dense-wavelength-division-multiplexing (DWDM) technology and afocal scheme. To the best of our knowledge, this is the first one that adopts DWDM technology and afocal scheme to successfully demonstrate 50-m/320-Gb/s FSO communication. Results show that the free-space transmission distance is greatly increased by the afocal scheme and that the free-space transmission rate is significantly enhanced by the DWDM technology. DWDM FSO communication over a 50-m free-space link with a total transmission rate of 320 Gb/s (40 Gb/s/λ × 8λ = 320 Gb/s) is achieved. With the aid of a low-noise amplifier and clock/data recovery at the receiving site, good bit-error-rate (BER) performance and clear eye diagram are obtained at a 50-m/320-Gb/s operation. Such 50-m/320-Gb/s DWDM FSO communication provides the advantages of optical wireless communications for long transmission distance and high transmission rate, which is thoroughly useful for long-haul and high-speed light-based WiFi (LiFi) applications.

16 Gb/s PAM4 UWOC system based on 488-nm LD with light injection and optoelectronic feedback techniques

A 16 Gb/s four-level pulse amplitude modulation (PAM4) underwater wireless optical communication (UWOC) system based on 488-nm laser diode (LD) with light injection and optoelectronic feedback techniques is proposed and successfully demonstrated. Experimental results show that such a 1.8-GHz 488-nm blue light LD with light injection and optoelectronic feedback techniques is enough forceful for a 16 Gb/s PAM4 signal underwater link. To the authors knowledge, this study is the first to successfully adopt a 488-nm LD transmitter with light injection and optoelectronic feedback techniques in a PAM4 UWOC system. By adopting a 488-nm LD transmitter with light injection and optoelectronic feedback techniques, good bit error rate performance (offline processed by Matlab) and clear eye diagrams (measured in real-time) are achieved over a 10-m underwater link. The proposed system has the potential to play a vital role in the future UWOC infrastructure by effectively providing high transmission rate (16 Gb/s) and long underwater transmission distance (10 m).

A hybrid lightwave transmission system based on light injection/optoelectronic feedback techniques and fiber-VLLC integration

A hybrid lightwave transmission system based on light injection/optoelectronic feedback techniques and fiber-visible laser light communication (VLLC) integration is proposed and experimentally demonstrated. To be the first one of its kind in employing light injection and optoelectronic feedback techniques in a fiber-VLLC integration lightwave transmission system, the light is successfully directly modulated with Community Access Television (CATV), 16-QAM, and 16-QAM-OFDM signals. Over a 40 km SMF and a 10 m free-space VLLC transport, good performances of carrier-to-noise ratio (CNR)/composite second-order (CSO)/composite triple-beat (CTB)/bit error rate (BER) are achieved for CATV/16-QAM/16-QAM-OFDM signals transmission. Such a hybrid lightwave transmission system would be very useful since it can provide broadband integrated services including CATV, Internet, and telecommunication services over both distribute fiber and in-building networks.

Optical Single Sideband Modulation Based on Injection-Locked Fabry-Perot Laser

We propose an optical single sideband (OSSB) modulation scheme using injection-locked to achieve OSSB modulation. Driving with 11 GHz RF signal into Mach-Zehnder modulator (MZM), due to the injection-locked, lower sideband of modulated signal is amplified and upper sideband is attenuated as well. After 25 km single mode fiber (SMF) transmission, we could observe good system performances including sideband power ratio (SBPR) > 12.9 dB and phase noise <; -80.07 dBc/Hz measured by an optical spectrum analyzer (OSA) and an electrical spectrum analyzer (ESA).