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The aim of this study was to prepare and characterize the bifunctional catalysts containing copper (redox source) and boron (acidity source) loaded on SBA-15 for catalytic methanol oxidation. Copper and boron species were loaded by sequential impregnation or co-impregnation, and three series of materials were prepared: series Cu-xB with copper loaded prior to boron, series xB-Cu with boron loaded prior to copper, and series xBCu with copper and boron co-impregnated (x designated B/Cu molar ratio; x = 0.5, 1 and 3). The materials were characterized by XRD, N2 physisorption, XPS, UV–vis spectroscopy, and combined H2-TPR/N2O oxidation analysis and were also investigated by test reactions of 2-propanol decomposition and pyridine adsorption combining with FTIR. The results showed that the strength of the interaction between copper and boron was depended on the sequence of incorporation, and that the materials contained only Lewis acid sites with acidity strength weakened with increasing boron amount. The roles of preparation procedure, content of boron, strength of interaction between boron and copper species, strength and number of Lewis acid sites were considered in the context of activity and selectivity in methanol oxidation. The series xB-Cu catalysts showed higher activity for the oxidation of methanol than other two series, and for xB-Cu catalysts the addition of boron lowered the reducibility of copper oxides. The best catalyst was found to be 1B-Cu, which exhibited relatively high activity, high selectivity to methyl formate and formaldehyde, and high stability.

A 56 Gb/s four-level pulse amplitude modulation (PAM4) light-based WiFi (LiFi) transmission based on a 680-nm/5.4-GHz vertical-cavity surface-emitting laser (VCSEL) with a two-stage injection-locked technique is proposed and demonstrated. Experimentally results show that a 5.4-GHz VCSEL with a two-stage injection-locked technique is effective for 56 Gb/s PAM4 LiFi transmissions. To the authors' knowledge, it is the first one to adopt a 680-nm VCSEL transmitter with two-stage injection-locked technique in a 56 Gb/s PAM4 LiFi transmission. A pair of doublet lenses is employed in the proposed PAM4 VCSEL-based LiFi transmissions to enhance the free-space link. The link performances of the proposed PAM4 LiFi transmissions have been analyzed in real time. Good bit error rate performance and three independent clear eye diagrams are obtained over a 20-m free-space link. Such a proposed 56 Gb/s PAM4 VCSEL-based LiFi transmission with two-stage injection-locked technique has the potential to play a significant role in future wireless infrastructure for providing high transmission rate and long free-space transmission distance effectively.

A 103.12-Gb/s wavelength-division-multiplexing (WDM) four-level pulse amplitude modulation (PAM4) transmission based on 850-nm and 880-nm vertical-cavity surface-emitting lasers (VCSELs) with light injection and optoelectronic feedback techniques is proposed and experimentally demonstrated. Results show that two such 7.5-GHz VCSELs with light injection and optoelectronic feedback techniques are potent for 103.12-Gb/s WDM PAM4 transmissions. To the authors' knowledge, it is the first one to successfully adopt two VCSEL transmitters with light injection and optoelectronic feedback techniques in a WDM PAM4 transmission. A total transmission rate of 103.12 Gb/s (51.56 Gb/s/λ × 2 λs) is achieved in the proposed WDM PAM4 transmissions. The link performances of the proposed WDM PAM4 transmissions have been evaluated in real time. Good real-time bit error rate performance and three independent clear eye diagrams are obtained at a 180-m OM4 multimode fiber operation. Such a proposed 103.12-Gb/s WDM PAM4 VCSEL-based transmission has great potential for providing efficient bandwidth in short-reach optical communications.

A bidirectional fiber-wireless and fiber-invisible laser light communication (IVLLC) convergence system that adopts a dual-polarization modulation scheme and a Mach–Zehnder modulator (MZM)-optoelectronic oscillator (OEO)-based broadband light source (BLS) for hybrid cable television (CATV)/microwave (MW)/millimeter-wave (MMW)/baseband signal transmission is proposed and experimentally demonstrated. The MZM employed in the MZM-OEO is operated at the minimum transmission point, which results in the format of optical carrier suppression for the y -axis component of the light. Using a dual-polarization modulation scheme, the optical carrier modulated with CATV signal ( x -polarization) and the optical sidebands modulated with MW and MMW data signals ( y -polarization) are separated and polarized orthogonally automatically. Through an in-depth observation, good carrier-to-noise ratio, composite second-order, composite triple-beat, and bit error rate performances are obtained over a 40-km single-mode fiber and a 10-m RF/100-m optical wireless transport. Such a bidirectional fiber-wireless and fiber-IVLLC convergence system is a notable option; it would be attractive for providing broadband heterogeneous services such as CATV, Internet, and big data services.

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 10Gbps/5GHz 16-QAM-OFDM underwater wireless laser transmission system based on light injection and optoelectronic feedback techniques is proposed and demonstrated. Good bit error rate performance and constellation map are achieved over a 10-m underwater link.

A 56-Gbps PAM4 LiFi transmission based on a 680-nm/5.2-GHz VCSEL with two-stage injection-locked technique is proposed and experimentally demonstrated. Good BER performance and three independent clear eye diagrams are obtained over a 20-m free-space link.

A bidirectional fiber-wireless and fiber-invisible laser light communication (IVLLC) integrated system that employs polarization-orthogonal modulation scheme for hybrid cable television (CATV)/microwave (MW)/millimeter-wave (MMW)/baseband (BB) signal transmission is proposed and demonstrated. To our knowledge, it is the first one that adopts a polarization-orthogonal modulation scheme in a bidirectional fiber-wireless and fiber-IVLLC integrated system with hybrid CATV/MW/MMW/BB signal. For downlink transmission, carrier-to-noise ratio (CNR), composite second-order (CSO), composite triple-beat (CTB), and bit error rate (BER) perform well over 40-km single-mode fiber (SMF) and 10-m RF/50-m optical wireless transport scenarios. For uplink transmission, good BER performance is obtained over 40-km SMF and 50-m optical wireless transport scenario. Such a bidirectional fiber-wireless and fiber-IVLLC integrated system for hybrid CATV/MW/MMW/BB signal transmission will be an attractive alternative for providing broadband integrated services, including CATV, Internet, and telecommunication services. It is shown to be a prominent one to present the advancements for the convergence of fiber backbone and RF/optical wireless 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.

A 45 Gb/s four-level pulse amplitude modulation (PAM4) transmission based on an 850 nm/7.4 GHz vertical cavity surface emitting laser (VCSEL) with light injection and optoelectronic feedback techniques is proposed. Experimental results show that such an 850 nm/7.4 GHz VCSEL with light injection and optoelectronic feedback techniques is powerful enough for a 45 Gb/s PAM4 signal transmission. To the best of our knowledge, this Letter is the first to adopt a VCSEL transmitter with light injection and optoelectronic feedback techniques in a 45 Gb/s PAM4 transmission system. Good bit error rate performance and three independent clear eye diagrams are achieved over a 200-m OM4 multimode fiber transport. This proposed 45 Gb/s PAM4 VCSEL-based transmission system has great potential for providing effective bandwidth in short-reach optical data communications.