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 bidirectional fiber-invisible laser light communication (IVLLC) and fiber-wireless convergence system with two orthogonally polarized optical sidebands for hybrid cable television (CATV)/millimeter-wave (MMW)/baseband (BB) signal transmission is proposed and experimentally demonstrated. Two optical sidebands generated by a 60-GHz MMW signal are orthogonally polarized and separated into different polarizations. These orthogonally polarized optical sidebands are delivered over a 40-km single-mode fiber (SMF) transport to effectually reduce the fiber dispersion induced by a 40-km SMF transmission and the distortion caused by the parallel polarized optical sidebands. To the best of our knowledge, this work is the first to adopt two orthogonally polarized optical sidebands in a bidirectional fiber-IVLLC and fiber-wireless convergence system to reduce fiber dispersion and distortion effectually. Good carrier-to-noise ratio, composite second order, composite triple beat, and bit error rate (BER) are achieved for downlink transmission at a 40-km SMF operation and a 100-m free-space optical (FSO) link/3-m RF wireless transmission. For up-link transmission, good BER performance is acquired over a 40-km SMF transport and a 100-m FSO link. The approach presented in this work signifies the advancements in the convergence of SMF-based backbone and optical/RF wireless-based feeder.
A 64 Gb/s four-level pulse amplitude modulation (PAM4) vertical-cavity surface-emitting laser (VCSEL)-based free-space optical (FSO) link with an external light injection scheme is proposed and successfully demonstrated. Experimental results show that the 11.2 GHz VCSEL with an external light injection scheme is sufficiently powerful for 64 Gb/s PAM4 FSO links. This study is the first one that adopts a 1550-nm VCSEL transmitter with an external light injection scheme in a 64 Gb/s PAM4 FSO link. The link performances of the proposed PAM4 VCSEL-based FSO links have been analyzed in real-time in terms of eye diagrams and offline processed by Matlab in terms of bit error rate (BER) performances. Good BER performance and clear eye diagrams are acquired over a 100-m free-space link. Such a proposed 64 Gb/s PAM4 VCSEL-based FSO link with an external light injection scheme is a promising one for providing high transmission rate and long transmission distance.
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