Optical Launch Power Research Articles

Demonstration of an 800G CDM-SDM coherent PON utilizing weakly coupled multicore fibers with CDM tributary manipulation

In this Letter, we present an experimental demonstration of downstream signaling in a 16 × 50 Gbit/s coherent passive optical network (CPON) using the code and space division multiplexing (CDM-SDM) approach. We realize optical SDM through the utilization of a 4-core weakly coupled multicore fiber (WC-MCF), enhancing the total available optical launch power at the optical line terminal (OLT). This enhancement significantly improves the power budget for CPONs that connect with a large number of optical network units (ONUs). At the second stage of the CPON, four CDM-assigned ONUs are connected to individual cores of the WC-MCF, thereby supporting the connectivity of up to 16 ONUs. Through experiments, we have noted substantial disparities in the downstream signaling performance among individual CDM-assigned ONUs, particularly as the capacity is increased to 800 Gbit/s. To address this issue, we have employed an innovative approach by leveraging space–time coding techniques to manipulate the CDM tributaries, to achieve a balanced reception performance for all ONUs within the CPON. We believe that the proposed CDM-SDM CPON scheme, complemented by the advanced DSP flow chart, holds significant promise for future PON systems characterized by substantial capacity and extensive connectivity.

Meta-Learning Assisted Source Domain Optimization for Transfer Learning Based Optical Fiber Nonlinear Equalization

Transfer learning (TL) has been demonstrated its feasibility on fast remodeling for fiber nonlinearity equalization. It will be very efficient with fine-tuning rather than retraining when the channel parameters have been changed, e.g., the optical launch power and fiber distance. However, the performance is dependent on the highly correlation between the source and target tasks. An improper source domain cannot improve the efficiency or even negative transfer. In this paper, we propose a meta-learning assisted source domain optimization scheme in single- and multi-channel transmissions. We construct the support dataset and query dataset from the information of the inner-task and the across-task to train the neural network so that we can find a unified source domain and efficiently adapt to different tasks with fewer epochs. We conduct an experiment to transmit 120-Gb/s dual polarization (DP) 16-QAM signal over 800-km standard single mode fiber (SSMF). The required epochs for convergence can be significantly reduced and there is slight Q-factor improvement with meta-learning algorithm compared with retraining and conventional TL. We also analyze the TL strategy in multi-channel system. The simulation results show that meta-learning can also help to optimize the source domain with lower complexity.

Experimental Demonstration of Constant-Envelope OFDM to Reduce Intermodulation Impairments and Increase Robustness Against Fiber Nonlinearities

Direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems have been proposed as a well-suited solution for cost-sensitive applications, but also for metro/regional optical links. In this article, we experimentally demonstrate tolerance enhancements of constant-envelope OFDM (CE-OFDM) signals towards Mach–Zehnder modulator (MZM) intermodulation impairments and fiber nonlinear Kerr effects. The additional tolerance is achieved by the reduced peak-to-average power ratio (PAPR) of CE-OFDM signals, unlike conventional OFDM signals that inherently possess high PAPR values and therefore, are prone to distortions induced by the above-mentioned impairments. The experiments show that the transmission of CE-OFDM signals with PAPR <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$=3$</tex-math></inline-formula> dB over 1000 km of dispersion-uncompensated standard single-mode fiber (SSMF) is successfully accomplished. The proper choice of the MZM bias point, as well as the electrical phase modulation index, provides link length enlargements at the same bit error rate. An enlargement around 320 km of SSMF was achieved with an optical launch power of 10 dBm and with a guard-band of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\approx 16\%$</tex-math></inline-formula> of the signal bandwidth when compared to conventional DDO-OFDM systems.

Concurrent Inter-ONU Communications for Next Generation Mobile Fronthauls based on IMDD Hybrid SSB OFDM-DFMA PONs

In PON-based mobile fronthauls, direct inter-ONU communications without passing end-user traffic to the OLT offer a promising solution for fulfilling the stringent latency and bandwidth requirements of 5G and beyond networks. In this paper, with slight modifications to the PON remote node, a concurrent inter-ONU and upstream communication technique is proposed and experimentally demonstrated in 101.6Gbit/s multipoint-to-point hybrid SSB OFDM digital filter multiple access (DFMA) IMDD PONs over 25km SSMFs. Multiple gapless inter-ONU and upstream SSB signals are aggregated by digital orthogonal filtering in each ONU transmitter. A single FFT operation is applied for demultiplex and demodulation in the OLT/ONU receivers. The results show that for both the inter-ONU and upstream transmissions, the optimum length of digital filters is 32, based on which the power penalties due to the fiber transmission and ONU channel interference are 30% improvements in aggregated signal transmission capacity. In addition, detailed experimental investigations are also undertaken of the trade-off between differential ONU optical launch power dynamic range and aggregated signal transmission capacity. An approximately 1dB increase in ONU launch power dynamic range is achievable by reducing the aggregated signal transmission capacity by 5Gbit/s.

Optical Nonlinearity Monitoring and Launch Power Optimization by Artificial Neural Networks

We present a linear-to-nonlinear power ratio monitor based on a shallow artificial neural network and the optical power spectrum. The neural network is trained with experimental pairs of input single-channel optical power spectra and output optimal power corrections, i.e., power amendments that lead to the power level maximizing the performance in terms of the signal-to-noise ratio. The technique is tested and shows the capability of providing up to 1 dB of signal-to-noise ratio gain in the ±3 dB region around the actual optimal power. Furthermore, the neural network does not recommend power variations resulting in a severe signal-to-noise ratio penalty (max −0.12 dB). Here, we extend our previous conference contribution by providing further insight into the theoretical background and some additional technical results in the direction of proving the connection between the optical power spectrum and the optimal power correction, i.e., the linear-to-nonlinear power ratio.

Hybrid SSB OFDM-Digital Filter Multiple Access PONs

The previously reported hybrid orthogonal frequency division multiplexing-digital filter multiple access (OFDM-DFMA) PONs offer promising solutions for seamlessly converging optical and mobile networks for 5G. However, the hybrid OFDM-DFMA PONs based on intensity-modulation and direct-detection (IMDD) convey double sideband (DSB) signals at different sub-wavelengths, this halves the spectral efficiency and signal transmission capacity. In this article, hybrid single sideband (SSB) OFDM-DFMA PONs are proposed and explored, for the first time, where multiple SSB OFDM channels produced without employing the Hilbert transform operation are multiplexed using orthogonal digital filtering in ONUs, and demultiplexed/demodulated by a single FFT operation in OLT without incorporating matching filters. It is shown that similar to the DSB PON, the proposed SSB PON has excellent robustness against digital filter characteristic variations and channel interferences. More importantly, it decreases peak-to-average power ratios (PAPRs) of digitally-filtered OFDM signals by >2 dB, thus leading to >2 dB reductions in optimum signal clipping ratio and >1 bit reductions in minimum required DAC/ADC resolution bits. For fixed spectral bandwidths, the SSB PON almost doubles the maximum upstream transmission capacity without considerably degrading its differential ONU optical launch power dynamic range compared to the DSB PON. While for fixed upstream signal transmission capacities, compared to the DSB PON, the SSB PON not only halves the overall signal transmission bandwidth, but also leads to >2.5 dB (>1.2 dB) improvements in power budget (differential optical launch power dynamic range for ONUs locating at high frequency regions).

ACO–OFDM with Improved Bandwidth Efficiency over Long Haul and MIMO Optical Fiber Communication Systems

Authors propose an improved orthogonal frequency division multiplexing (OFDM) scheme in which the information samples are transmitted in otherwise discarded negative frame of asymmetrically clipped OFDM (ACO–OFDM). ACO–OFDM has two similar positive and negative OFDM envelopes so that clipping does not result in loss of signal information. The flipped polarity negative samples are inserted at the zeros of positive frame or back to back with positive frame, in time-compressed frame such that composite signal has the same frame duration as ACO–OFDM but improved transmission power, bandwidth efficiency. Simulation results for bit error rate with respect to number of subcarriers and optical launch power show that the proposed time-compressed OFDM frames perform better in high-dispersion condition over long distance, high data rate, and high transmission power over single-mode fiber. It has been demonstrated that the proposed time-compressed frame structure also performs well with the 2*2 MIMO setup for multimode fiber link.

Kerr Combs for Stimulated Brillouin Scattering Mitigation in Long-Haul Analog Optical Links

By limiting the optical input launch power, stimulated Brillouin scattering imposes detrimental effects on long haul analog optical links. Utilizing Kerr combs generated from an integrated Silicon Nitride microring resonator, we mitigate Brillouin scattering in a 25 Km sampled analog optical link. Such combs offer reduced footprint, high repetition rates and low power consumption, rendering them attractive for next generation integrated analog photonic links. The distribution of the optical carrier power over multiple spectral lines allows launching higher total average powers, significantly improving the link performance. Operating the link in an externally intensity-modulated direct-detection architecture, we compare link metrics using a soliton or a dark pulse as the sampling frequency comb source. An advantageous aspect of the dark pulse is its high pump conversion efficiency. We find that the Kerr comb pump conversion efficiency has a direct effect on the relative intensity noise and the link noise figure. We show that the spurious free dynamic range using Kerr combs can match that of the well-established electro-optic combs.

Transfer learning assisted deep neural network for OSNR estimation.

We propose a transfer learning assisted deep neural network (DNN) method for optical-signal-to-noise ratio (OSNR) monitoring and realize fast remodel to response to various system parameters changing, e.g. optical launch power, residual chromatic dispersion (CD) and bit rate. By transferring the hyper-parameters of DNN at the initial stage, we can fast response to the channel variation with fewer training set size and calculations to save consumptions. For feature extraction processing, we use amplitude histograms of received 56-Gb/s QPSK signals as the input for DNN at the initial stage, which shows the root mean squared error (RMSE) of OSNR estimation is less than 0.1 dB with the OSNRs ranging from 5 to 35 dB. Then, we change several system parameters and find superior capabilities of fast remodeling and data resource saving with the proposed method. The required training epochs have about four times reduction, and the required training set size is only one-fifth compared to retraining the network without any accuracy penalty. The DNN assisted by transfer learning can save resources and will be beneficial for real-time application on OSNR estimation.

Decision-Feedback Frequency-Domain Volterra Nonlinear Equalizer for IM/DD OFDM Long-Reach PON

A low-complexity third-order decision-feedback frequency-domain Volterra nonlinear equalizer (DF-FD-VNLE) with superior nonlinearity-compensation performance is proposed and experimentally demonstrated for OFDM long-reach PONs. High optical launch power up to 18 dBm is implemented to mitigate the chromatic dispersion induced power fading and increase the power budget. By reconstructing and subtracting the nonlinear noise in frequency domain with the knowledge of the nonlinear channel, the proposed DF-FD-VNLE outperforms the conventional time-domain VNLE (TD-VNLE) and feed-forward FD-VNLE (FF-FD-VNLE), resulting in better received signal-to-noise ratio (SNR) performance. The nonlinearity-compensation performance of the DF-FD-VNLE can be further improved with the usage of a FF-FD-VNLE or more than one iteration. Complexity and experimental analyses show that similar complexity and higher SNR can be achieved by using the one-iteration DF-FD-VNLE with FD linear equalization (FD-LE), compared with that of the FF-FD-VNLE. Compared with conventional TD-VNLE, the required number of real-valued multiplication (RNRM) of the one-iteration DF-FD-VNLE with FF-FD-VNLE (FD-LE) is reduced by a factor of as much as 82.19% (89.61%) at a memory length of 14 and a truncation factor of 3. Based on the one-iteration DF-FD-VNLE with FF-FD-VNLE, around 53.79 Gb/s single wavelength OFDM IM-DD transmission over 60.8-km SSMF is successfully demonstrated at a BER of 3.8 × 10−3 and a received optical power (ROP) of −2 dBm, achieving 15% capacity improvement compared to the conventional TD-VNLE.

Performance analysis and optimization of wavelength routed (WR) and wavelength selected (WS) hybrid optical distributed network (ODN) for next generation passive optical network stage 2 (NG-PON2)

Next-generation passive optical network stage 2 (NG-PON2) supports the wavelength routed optical distributed network (WR-ODN), power splitter optical distributed network or wavelength-selected optical distributed network (WS-ODN) and hybrid of both the architecture configuration. NG-PON2 is world’s first multi-wavelength passive optical network (PON) standard. The fiber dispersion and nonlinearity degrades the performance of NG-PON2 severely. Fiber nonlinearity depends on the optical launch power and fiber reach. This paper focuses on maximizing the network performance and maximizing the number of simultaneous users with error-free performance by optimizing the optical launch power respectively at dynamic reach and differential reach. The optical launch power is optimized to abate the fiber nonlinearity and significantly enhances the performance of NG-PON2 at dynamic fiber reach for Alcatel 6912 Teralight Ultra 1625 commercial fiber specification. Furthermore, precise values of the optimum launch power for the dynamic fiber reach, for different NG-PON2 architecture, under industrial fiber specification is meticulously obtained. It is identified that irrespective of both, WR-ODN and WS-ODN architecture configuration, optimum launch power remains constant. Power budget is calculated for both, maximizing the performance and maximizing the simultaneous number of users at differential reach and dynamic reach of the NG-PON2.

Downstream performance analysis and optimization of the next generation passive optical network stage 2 (NG-PON2)

The increase in the number of users and high end to end demand of massive data-rate directs the attention towards innovative point to multipoint links that satisfy the need for next-generation passive optical network stage 2 (NG-PON2). NG-PON2 architecture has the capability to support power-split and wavelength-split optical distribution network (ODN) as well as a hybrid of two ODNs. Wavelength routing (WR) ODN has adequate low insertion loss than the power splitter (PS) ODN which can fulfill the exponential increase in demand for greater connectivity. The wavelength routing passive optical network (WR-PON) is investigated using the OptiSystem-13 simulation design tool. In this paper, we optimize the downstream transmission of eight channels WR-PON over 60 km and 40 km of standard single mode practical fibers (G.655 and G.652) with 10 Gb/s per channel and compared it with PS-ODN based passive optical network (PON). Both WR-PON and PS-PON are analyzed in detail under the specifications of deployed optical fibers like ITU-T G.652.A fiber, ITU-T G.652.B fiber, Alcatel 6912 Tealight Ultra 1625 fiber, Corning LEAF 1625 fiber, and Lucent True-Wave RS 1625 fiber. Next generation multi-wavelength system performance is limited predominantly due to fiber dispersion and nonlinearities. Fiber nonlinearities and dispersions are mitigated and performance is enhanced by characterizing the system and optimizing optical launch power for both WR-PON and PS-PON. Furthermore, the effect of optical launch power on performance is investigated and evaluated for each practical fiber configuration with common optical modulation formats, return to zero external modulation (RZ-EM) and non-return to zero external modulation (NRZ-EM). Power budget for each configuration is calculated and tabulated.

Multi-band CAP for Next-Generation Optical Access Networks Using 10-G Optics

40-Gb/s/λ multi-band carrierless amplitude and phase (CAP) modulation long-reach passive optical networks were demonstrated using 10-G class transceivers only. A major issue of multi-band CAP is that it is vulnerable to timing error, and this work has offered quantitative analysis about it in detail for the first time. A novel simple timing recovery approach, partial differential quadrature amplitude modulation constellation encoding and decoding schemes together with blind multimodulus algorithm equalization are proposed to address the issue efficiently, enabling zero-overhead signal recovery. Results show that it can offer excellent system tolerance to timing error of at least ±0.1 symbol period even for the highest frequency CAP sub-band. The characteristics of the transceiver are measured, and optimization of critical system parameters is performed including the CAP sub-band count, 10-G Mach–Zehnder intensity modulator operation conditions, optical launch power, and wavelength offset asymmetrical optical filtering. For downlink using erbium-doped fiber amplifier preamplifiers, successful 40-Gb/s multi-band CAP signal transmission over an 80-km (90-km) single-mode fiber is achieved with a link power budget of 33 dB (29 dB) considering a forward error correction threshold bit error ratio of 3.8 × 10−3.

A novel wavelength reused bidirectional RoF-WDM-PON architecture to mitigate reflection and Rayleigh backscattered noise in multi-Gb/s m-QAM OFDM SSB upstream and downstream transmission over a single fiber

A novel m-QAM Orthogonal Frequency Division Multiplexing (OFDM) Single Sideband (SSB) architecture is proposed for centralized light source (CLS) bidirectional Radio over Fiber (RoF) – Wavelength Division Multiplexing (WDM) – Passive Optical Network (PON). In bidirectional transmission with carrier reuse over the single fiber, the Rayleigh Backscattering (RB) noise and reflection (RE) interferences from optical components can seriously deteriorate the transmission performance of the fiber optic systems. These interferometric noises can be mitigated by utilizing the optical modulation schemes at the Optical Line Terminal (OLT) and Optical Network Unit (ONU) such that the spectral overlap between the optical data spectrum and the RB and RE noise is minimum. A mathematical model is developed for the proposed architecture to accurately measure the performance of the transmission system and also to analyze the effect of interferometric noise caused by the RB and RE. The model takes into the account the different modulation schemes employed at the OLT and the ONU using a Mach Zehnder Modulator (MZM), the optical launch power and the bit-rates of the downstream and upstream signals, the gain of the amplifiers at the OLT and the ONU, the RB-RE noise, chromatic dispersion of the single mode fiber and optical filter responses. In addition, the model analyzes all the components of the RB-RE noise such as carrier RB, signal RB, carrier RE and signal RE, thus providing the complete representation of all the physical phenomena involved. An optical m-QAM OFDM SSB signal acts as a test signal to validate the model which provides excellent agreement with simulation results. The SSB modulation technique using the MZM at the OLT and the ONU differs in the data transmission technique that takes place through the first-order higher and the lower optical sideband respectively. This spectral gap between the downstream and upstream signals reduces the effect of Rayleigh backscattering and discrete reflections.

On Probabilistic Shaping of Quadrature Amplitude Modulation for the Nonlinear Fiber Channel

Different aspects of probabilistic shaping for a multi-span optical communication system are studied. First, a numerical analysis of the additive white Gaussian noise (AWGN) channel investigates the effect of using a small number of input probability mass functions (PMFs) for a range of signal-to-noise ratios (SNRs), instead of optimizing the constellation shaping for each SNR. It is shown that if a small penalty of at most 0.1 dB SNR to the full shaping gain is acceptable, just two shaped PMFs are required per quadrature amplitude modulation (QAM) over a large SNR range. For a multi-span wavelength division multiplexing (WDM) optical fiber system with 64QAM input, it is shown that just one PMF is required to achieve large gains over uniform input for distances from 1,400 km to 3,000 km. Using recently developed theoretical models that extend the Gaussian noise (GN) model and full-field split-step simulations, we illustrate the ramifications of probabilistic shaping on the effective SNR after fiber propagation. Our results show that, for a fixed average optical launch power, a shaping gain is obtained for the noise contributions from fiber amplifiers and modulation-independent nonlinear interference (NLI), whereas shaping simultaneously causes a penalty as it leads to an increased NLI. However, this nonlinear shaping loss is found to have a relatively minor impact, and optimizing the shaped PMF with a modulation-dependent GN model confirms that the PMF found for AWGN is also a good choice for a multi-span fiber system.

Spectral Shape Impact of Nonlinear Compensator Signal in LTE RoF System

In this letter, a large scale investigation is carried out, utilizing several spectral shapes as the source for direct modulation based frequency dithering (DMFD). DMFD mitigates the nonlinear effect of long term evolution (LTE) radio-over-fiber (RoF) systems. The dithering signal shapes are; sine, square, saw, sinc and Gaussian with different spectral width characteristics. We show that by varying the dithering signal with increasing spectral width, no additional distortion is introduced in the linear and optimum optical launch power regions, which are dominated by the frequency chirp and chromatic dispersion (CD). Additionally, it is revealed herein that introducing dithering signals with varying spectral widths does not change the nonlinear compensator characteristic towards suppression of nonlinearity. The reason for this is that as long as the optical source linewidth is larger than stimulated Brillouin scattering (SBS) linewidth, the proposed method completely suppresses SBS. Finally, the degree of freedom for the dithering signal is infinite, with an optical power budget improvement of up to 8 dB at an optical launch power of 10 dBm, which can in turn be used towards connecting multiple relay nodes (RNs).

Experimental analysis of fibre non‐linearity on second harmonic optical microwave radio‐over‐fibre system

In this study, the authors propose an optical microwave (MW) radio-over-fibre system in which an integrated dual-parallel Mach-Zehnder modulator (DP-MZM) is biased at the maximum transmission biasing point. A single drive Mach-Zehnder modulator, in series with the DP-MZM, is used to modulate the 1 GHz radio frequency data onto the optical carrier. They characterise the efficiency of the practical system in terms of power penalty and error vector magnitude. Two modulation schemes are investigated, namely binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) over fibre spans of 10 and 25 km of standard single mode fibre. The results show that the second-order sideband of MW has the potential to provide error free transmission for BPSK and QPSK. The error free communication system is achieved for BPSK at 10 and 25 km fibre spans at optical launch power (OLP) of 7 dBm, whereas for QPSK, the OLP is ~11 and ~12 dBm for 10 and 25 km fibre spans, respectively.

Investigation of Optical Modulators in Optimized Nonlinear Compensated LTE RoF System

In this paper, we investigate a nonlinear compensation technique with two different architectures using direct modulation (DM) and external modulation (EM) techniques, termed as DM based frequency dithering (DMFD) and EM based frequency dithering (EMFD). We show that DMFD and EMFD methods operate substantially different in radio-over-fiber (RoF) system by optimizing the dithering technique relative to the LTE technology. The proposed techniques is only applicable if the condition of {f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> <; f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> <; f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> } is met, where f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> represents the dithering boundary limit of 14 MHz, f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> is DMFD signal frequency and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RF</sub> is the RoF carrier frequency. Analysis of the optical launch power for DMFD and EMFD methods reveal that the stimulated Brillouin scattering threshold is above ~6 dBm for the LTE-RoF system. In addition, we also unveil that DMFD and EMFD methods do not introduce additional distortion for the linear and optimum optical launch power regions, which are frequency chirp driven regions. If the given condition is met, the proposed method improves the LTE-RoF system without any shortcoming. Finally, at 10 dBm launch power, DMFD and EMFD methods exhibits an average signal-to-noise ratio gain of ~5.95 and ~7.71 dB, respectively.

Nonlinear limit of alternative method to 2 × 2 MIMO for LTE RoF system

Owing to the limited cell size of eNodeB (eNB), the relay node has emerged as an attractive solution for the long-term evolution (LTE) system. The nonlinear limit of the alternative method to multiple-input and multiple-output (MIMO) based on frequency division multiplexing (FDM) for orthogonal FDM (OFDM) is analysed over varying transmission spans. In this reported work, it is shown that the degradation pattern over the linear, intermixing and nonlinear propagation regions is consistent for the 2 and the 2.6 GHz bands. The proposed bands experienced a linear increase in the error vector magnitude (EVM) for both the linear and the nonlinear regions proportional to the increasing transmission spans. In addition, an optical launch power between −2 and 2 dBm achieved a significantly lower EVM than the LTE limit of 8% for the 10–60 km spans.

Experimental Verification of Optimized LTE-RoF System for eNB Cell Radius Improvement

We propose and experimentally demonstrate the design of seamless integration of the third generation partnership program (3GPP) long-term evolution (LTE) with radio-over-fiber (RoF) for the eNodeB cell extension. The proposed system is optimized for all LTE analogue radio bandwidths (ARBs) namely, 3, 5, 10, 15, and 20 MHz. This letter presents the complete LTE-RoF system design with the optimum modulation region and an optimum optical launch power. The resultant optimized error vector magnitude for the 64-quadrature amplitude modulation-orthogonal frequency division multiplexing modulation scheme across the aforementioned ARBs is ${\sim}{0.99\%}$ , which is much lower than the 8% margin defined by 3GPP.