Free space optical (FSO) communication has established a reputation for itself as a next-generation network capable of delivering high-speed data services. In light of the upcoming launch of 5G services, this paper aims to evaluate the performance of the FSO system for the implementation of 5G technology in diverse geographical locations of India. The proposed 16 × 10 $\text{Gbps}$ wavelength division multiplexing (WDM) based FSO link uses orthogonal frequency division multiplexing (OFDM) and digital signal processing (DSP) module to mitigate channel-induced limitations. Additionally, the proposed FSO design also employs Erbium-doped fiber amplifier (EDFA) with optimized gain characteristics. Using the data sourced from the Meteorological Department of India, the link analysis reveals that due to weak fog events in coastal areas effective link range of up to 10.75 $\text{km}$ can be achieved while maintaining bit error rate of $10^{-9}$ . Despite dominant foggy conditions in hilly, plains and desert areas, the proposed FSO link significantly limits the degrading effects of channel. Hence, in pursuit of futuristic smart city models, a heterogeneous combination of FSO and 5G infrastructure can conveniently cover diverse geographical locations of India to support high-speed data connectivity.

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Design and Analysis of High-Speed Free Space Optical (FSO) Communication System for Supporting Fifth Generation (5G) Data Services in Diverse Geographical Locations of India

A bi-directional fiber-free-space optical (FSO)-fifth-generation (5G) millimeter-wave (MMW)/5G new radio (NR) sub-THz convergence with intensity-modulated downlink 40 Gbit/s/100 GHz 5G NR sub-THz signals ( x - and y -polarizations), and phase-modulated uplink 10 Gbit/s/28 GHz and 10 Gbit/s/24 GHz 5G MMW signals is established practicably, by adopting a parallel/orthogonally polarized dual-carrier mechanism, phase modulators, and remote injection locking distributed feedback laser diodes (DFB LDs) for demonstration. It is a pioneering work to realize a bi-directional fiber-FSO-5G MMW/5G NR sub-THz convergence for providing high downlink/uplink traffic capacity with accepted transmission performance. Through 20 km single-mode fiber transmission, 500 m free-space link, and 1 m/4 m RF wireless transport, impressively low bit error rate of 10−9 and accepted PAM4/NRZ eye diagrams are acquired. Such established bi-directional fiber-FSO-5G MMW/5G NR sub-THz convergence accelerates a feasible solution that can afford high traffic capacity with qualified transmission performance, and develops the state achieved by the incorporation of optical fiber network with FSO-5G MMW/5G NR sub-THz convergence. It discloses a brilliant convergence developed for bi-directional high-speed and long-reach transmission with given transmission performance.

Bi-Directional Fiber-FSO-5G MMW/ 5G New Radio Sub-THz Convergence

This letter presents results of an experimental measurement campaign involving the deployment of combined radio over the fiber and radio over free space optics (FSO) technology in the cloud-based fifth generation (5G) fronthaul network operating in the millimeter wave (mmW) area. For this purpose, we have used 10 km of optical fiber, 50 m long outdoor FSO link and 1 m long antenna seamless radio frequency transmission at 39 GHz. The results show excellent performance in terms of the phase noise and the signal-to-noise (SNR) ratio. The error vector magnitude performance depends on the modulation format and are below the standard limits for the 5G new radio signals, with 400 MHz QPSK and 64-QAM showing almost identical results for SNR of up to ~19 dB whereas 256-QAM signal offering the best spectral efficiency. Moreover, we investigate the received mmW signal deterioration due to the atmospheric conditions in the FSO channel.

Performance Evaluation of Seamless 5G Outdoor RoFSO Transmission at 39 GHz

Simultaneous transmission of fifth-generation (5G) millimeter-wave (MMW) and sub-THz signals through a fiber-free-space optical (FSO)-5G new radio (NR) converged system is successfully achieved. It is an inventive demonstration that utilizes a cross medium of optical fiber, optical wireless, and RF wireless to enhance the aggregate transmission rate to 60 Gb/s. We transmitted 20 Gb/s in the 50-GHz MMW, 100-GHz sub-THz, and 150-GHz sub-THz bands at the same time through the seamless fiber-FSO-5G NR convergence, comprising 20-km single-mode fiber (SMF), 500-m optical wireless, and 2-m (50-GHz MMW)/1-m (100-GHz sub-THz)/0.5-m (150-GHz sub-THz) 5G wireless transmissions. Sufficiently low bit error rate (< forward error correction criterion of 3.8×10<sup>−3</sup>) and error vector magnitude (<third-generation partnership project limit of 12.5%) are attained to satisfy the requirements of 5G NR communications in MMW and sub-THz bands. This newly-built fiber-FSO-5G NR converged system shows promise for the development of long-haul wired-wireless transmissions with wider service areas and higher access data rates.

Simultaneous Transmission of 5G MMW and Sub-THz Signals Through a Fiber-FSO-5G NR Converged System

We report the implementation of a full optically-powered 5G new radio (5G NR) fiber-wireless (FiWi) system based on power-over-fiber (PoF) and radio-over-fiber (RoF) technologies. Our approach enables the simultaneous transmission of a 5G NR signal at 3.5 GHz with bandwidth up to 100 MHz and a 2.2-W optical power signal employing dedicated fiber-optics links. The optical-wireless data link consists of a 12.5-km single-mode fiber (SMF) optical fronthaul followed by a 10-m wireless propagation environment, which is the longest wireless reach reported in literature up to now, regarding optically-powered FiWi systems. The proposed PoF system is able to deliver stable electrical power up to 475 mW, by means of using a 100-m multimode fiber (MMF) link, with the purpose of optically powering a 5G NR remote antenna unit (RAU). An overall power transmission efficiency (PTE) of 23.5% is experimentally demonstrated in a real 5G NR system. Furthermore, the FiWi system performance is investigated in accordance with the <inline-formula><tex-math notation="LaTeX">$3^{\mathrm rd}$</tex-math></inline-formula> generation partnership project (3GPP) Release 15 requirements, in terms of root mean square error vector magnitude (<inline-formula><tex-math notation="LaTeX">${\mathrm EVM}_{\mathrm RMS}$</tex-math></inline-formula>). The proposed optically-powered 5G NR FiWi system provides 500 Mbit/s throughput with <inline-formula><tex-math notation="LaTeX">${\mathrm EVM}_{\mathrm RMS}$</tex-math></inline-formula> as low as 3.9%, employing 64-quadrature amplitude modulation (QAM) without using optical amplification.

Implementation of a Full Optically-Powered 5G NR Fiber-Wireless System

The fifth-generation of mobile networks (5G) claims for a radio access network (RAN) update in order to support the enormous incoming wireless data traffic. In this context, we experimentally evaluate two distinct hybrid architectures applied to 5G New Radio (NR) FiWi systems based on different optical fronthaul approaches. The first architecture operates in non-standalone (NSA) mode, defined by the 3rd generation partnership project (3GPP), for simultaneously transmitting 4G and 5G technologies through an unique FiWi system. The three considered waveforms are as follows: a filtered orthogonal frequency division multiplexing (F-OFDM) signal at 778 MHz with 10 MHz bandwidth from our 5G flexible-waveform transceiver; a long-term evolution-advanced (LTE-A) signal with five 20 MHz sub-bands centralized at 2.24 GHz; a 5G NR signal at 2.35 GHz with 100 MHz bandwidth. On the other side, the second architecture employs radio over fiber (RoF), free space optics (FSO), and wireless technologies converged into a heterogeneous network (HetNet). The additional multi-standard and multiband optical-wireless network is based on a 10-MHz bandwidth F-OFDM signal at 788 MHz, a 100-MHz bandwidth 5G NR signal at 3.5 GHz, and a 400-MHz bandwidth M -QAM signal at 26 GHz. Throughput up to 3 and 1.4 Gbps are demonstrated for RoF/FSO and RoF/FSO/Wireless transmission, respectively.

Whebert Damascena Dias

Papers

Non-Standalone 5G NR Fiber-Wireless System Using FSO and Fiber-Optics Fronthauls