Real-time PAM4 fiber-IVLLC and fiber-wireless hybrid system with a parallel/orthogonally polarized dual-wavelength scheme

et al. 2020

IEEE Access

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A 448-Gb/s four-level pulse amplitude modulation (PAM4) free-space optical (FSO) communication through 600 m free-space link was constructed, utilizing polarization-multiplexing injection-locked vertical-cavity surface-emitting lasers (VCSELs) for presentation. When uniting fourwavelength polarization-multiplexing and PAM4 modulation schemes, the transmission capacity of FSO communications is substantially multiplied, with an aggregate transmission rate of 448 Gb/s [56 Gb/s PAM4/wavelength × 4 wavelengths × 2 polarizations (x-and y-polarizations)]. The results show that four 1.55 µm VCSEL transmitters with injection locking technique are sufficiently powerful for 448 Gb/s PAM4 signal transmission. Adopting a tunable optical band-pass filter and a polarization beam splitter for wavelength filtering and polarization de-multiplexing, the polarized wavelengths are effectually filtered and de-multiplexed in each polarized state. As the polarization state is well preserved in the scenario over 600 m free-space transmission, a sophisticated polarization tracker is not required in this proposed FSO communication. High bit error rate performance and accepted PAM4 eye diagrams are attained through 600 m free-space transmission. The four-wavelength polarization-multiplexing PAM4 FSO communication established here reveals the prominent benefits of high aggregate transmission capacity and long-distance free-space link.

Section: Resultsmentioning

confidence: 99%

A 448-Gb/s PAM4 FSO Communication With Polarization-Multiplexing Injection-Locked VCSELs Through 600 M Free-Space Link

et al. 2020

IEEE Access

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“…Given that each polarisation only has one sideband, the SSBI will not emerge. Regarding cross-beating, considering the orthogonality of x -polarisation and y -polarisation, the cross-beating will be trivially small 27 . Thus, the BER performance will not be degraded by SSBI and cross-beating terms.…”

Section: Resultsmentioning

confidence: 99%

“…However, the downstream data rate/FSO link of 20 Gbps/100 m 6 , 30 Gbps/10 m 22 , 30 Gbps/50 m 26 , and 20 Gbps/100 m 7 are significantly less than the corresponding values of 128-Gb/s/200-m adopted in this proposed PDM-based bi-directional fibre-FSO integration. In addition, a real-time PAM4 fibre-FSO and fibre-wireless hybrid system with parallel/orthogonally polarized dual-wavelength scheme was presented 27 . Yet, it is difficult for a practical implementation in real networks due to uni-directional transmission.…”

Section: Introductionmentioning

confidence: 99%

A PDM-based bi-directional fibre-FSO integration with two RSOAs scheme

Huang

et al. 2019

Sci Rep

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A polarization-division-multiplexing (PDM)-based bi-directional fibre-free-space optical (FSO) integration with two reflective semiconductor optical amplifiers (RSOAs) scheme to efficiently wipe off the modulated data for upstream modulation is proposed and successfully demonstrated. For downstream modulation, a high-speed 128 Gb/s vestigial sideband (VSB)-four-level pulse amplitude modulation (PAM4) fibre-FSO integration is feasibly established. The transmission capacity is increased up to four times through PDM operation and VSB-PAM4 modulation. For uplink transmission, a 10 Gb/s non-return-to-zero fibre-FSO integration with two RSOAs scheme to effectually erase the downstream modulated data is practically constructed. The upstream performance exhibits noticeable enhancement by using of two RSOAs scheme to wipe off the modulated data clearly. Such illustrated PDM-based bi-directional 128 Gb/s (downstream)/10 Gb/s (upstream) fibre-FSO integration is shown to be prominent not only due to its enhancement in the convergence of fibre backhaul and optical wireless reach extender but also because of its benefit in bi-directional transmission for affording high transmission capacity with long-reach optical wireless link and improved upstream performance.

“…The polarization domain has been examined substantially for optical wireless communications. Parallel/orthogonally polarized dual-sideband operation is greatly matched with two-way free-space optical (FSO) communications [6]- [8]. Verticalcavity surface-emitting laser (VCSEL) has excellent optical characteristics including low operation current, single longitudinal mode operation, and large modulation bandwidth.…”

Section: Introductionmentioning

confidence: 99%

Centralized-Light-Source Two-Way PAM8/PAM4 FSO Communications With Parallel Optical Injection Locking Operation

et al. 2019

IEEE Access

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For the first time up to our knowledge, a centralized-light-source two-way eight-level pulse amplitude modulation (PAM8)/four-level pulse amplitude modulation (PAM4) free-space optical (FSO) communication with parallel optical injection-locked vertical-cavity surface-emitting laser (VCSEL) transmitter is practically demonstrated. With the assistance of parallel optical injection locking, injection locking in the polarization sideband causes a simultaneous generation of the free-running orthogonal polarization sideband to form a centralized-light-source scheme. With the centralized light source, additional light source or wavelength reuse component, such as Fabry-Perot laser diode or reflective semiconductor optical amplifier, is not needed at the receiver side. It is very attractive because it enables the receiver side to share the light source remotely located at the transmitter side. Based on the centralized-light-source scheme and parallel optical injection-locking operation, the injection-locked parallel polarization sideband is used for downlink transmission, and the induced free-running orthogonal polarization sideband is transmitted and used as the optical carrier for uplink transmission. Over a 200-m free-space link, good bit-errorrate (BER) performance, the qualified PAM8, and PAM4 eye diagrams are obtained for two-way FSO communications. This proposed centralized-light-source two-way FSO communication provides a practical choice for two-way high transmission capacities and considerably develops the scenario characterized by parallel optical injection locking.