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In the last two years the number of optical OFDM papers has grown exponentially, but is this modulation format really a viable candidate for next generation fiber-optic transmission systems? In this paper we review the most significant technologies and aim to evaluate the potential of OFDM for 100 GbE applications.

Carrier boosting at the receiver enables direct detection optical OFDM (DDO-OFDM) to outperform coherent OOFDM in the nonlinear limit. Boosting also improves the effectiveness of nonlinearity precompensation substantially.

In comparison with adaptively modulated optical OFDM (AMOOFDM), AMOOFDM with adaptive cyclic prefix is capable of offering even higher capacity versus reach performance with improved flexibility and robustness over MMF links without requiring extra resources.

We extended a pilot symbol frequency offset estimation scheme and applied it in combination with a pilot subcarrier compensator. Optimum system sensitivity was found up to few 100 MHz frequency offset.

DCT based precoding is proposed for PAPR reduction to improve the performance of optical OFDM at limited precoding complexity. Effective PAPR reduction and the resultant OSNR performance are shown.

We proposed a FEC enhanced data clipped OFDM system to reduce PAPR effect. Numerical simulations indicate >5-dB and 1.5-dB OSNR improvements are observed under high clipping ratio of 6-dB with FEC over 8000-km SMF.

Orthogonal frequency division multiplexing (OFDM) is currently discussed as an attractive format to overcome physical impairments in spectrally efficient optical communication links such as modal dispersion, chromatic dispersion and polarization mode dispersion. This paper reviews recent progress in the field.

Phase estimation is one of the most critical functions in coherent optical OFDM (CO-OFDM) receivers. We present phase estimation and compensation for a CO-OFDM transmission experiment at 8 Gb/s over 1000-km standard- single-mode-fiber without dispersion compensation.

It will be shown that 40Gb/s over 220m and 32Gb/s over 300m AMOOFDM signal transmission with loss margins of about 15dB is feasible in installed worst-case MMF IMDD links having 3-dB effective bandwidths of 150MHz.km.

Orthogonal frequency division multiplexing offers an attractive method of electronically compensating for single-mode and multipath dispersion in optical links and optically-switched networks. This paper reviews recent progress in optical OFDM systems.

Two methods of generating modified optical OFDM signals that give improved receiver sensitivities over NRZ in unamplified and amplified systems are compared using simulations. Asymmetric-Clipped Optical OFDM can compensate intermodal dispersion. Carrier-Suppressed Optical- Single Sideband OFDM can compensate chromatic dispersion.

Self-seeded passive optical networks (PONs) are currently attracting extensive research interest. In this paper, a novel self-seeded PON transmitter is, for the first time, proposed and experimentally demonstrated, which incorporates two face-to-face-positioned reflective semiconductor optical amplifiers (RSOAs) operating at their gain saturation regions: one RSOA directly driven by an upstream electrical signal and the other RSOA biased at a fixed current. Detailed experimental explorations are undertaken of the dynamic performance characteristics of the proposed transmitter. It is shown that, in comparison with previously reported self-seeded transmitters each employing a reflective mirror and a single electrical signal-driven RSOA, the proposed transmitter has a number of salient advantages including, considerably narrowed optical signal spectra, up to 16dB reduction in RINs of intensity-modulated optical signals, and residual intensity modulation crosstalk suppression as high as 10.7dB. The aforementioned features enable experimental demonstrations of real-time self-seeded 10Gb/s optical OFDM (OOFDM) transmitters. In particular, by making use of two low-cost RSOAs having their 3-dB modulation bandwidths as small as 1.125GHz, 10Gb/s over 25km adaptive OOFDM transmissions with power penalties of 0.6dB are experimentally achieved in the simple self-seeded IMDD PON systems.

With careful designs to combat fibre nonlinearity, 4×1.93 Tbit/s 8-PSK DFT-S OFDM transmission over 2240 km SSMF is experimentally demonstrated. The spectral efficiency within each superchannel is 5.6 bit/s/Hz.

Schemes integrating inter-carrier interference (ICI) self-cancellation and common phase error (CPE) compensation for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems are investigated. The purpose of our research is to counteract the impacts of laser phase noise and fiber nonlinearity. We propose two ICI self-cancellation-based CO-OFDM schemes, and adopt a pilot-aided decision feedback (DFB) loop for CPE compensation. The proposed schemes are compared with conventional CO-OFDM schemes at the same spectral efficiency. Simulations show that our schemes can not only enhance laser linewidth tolerance of the CO-OFDM system, but also present strong robustness against fiber nonlinearity.

The wavelength dependent transmission performance of adaptively modulated optical OFDM (AMOOFDM) signals is investigated, for the first time, over optical amplification- and chromatic dispersion compensation-free IMDD SMF systems using semiconductor optical amplifiers (SOAs) as intensity modulators. A theoretical SOA model describing both optical gain saturation and gain spectral dynamics is developed, based on which optimum SOA operating conditions are identified for various wavelengths varying in a broad range of 1510 nm- 1590 nm. Results show that, SOA intensity modulators operating at the identified optimum conditions enable the realization of colourless AMOOFDM transmitters within the aforementioned wavelength window. Such transmitters are capable of supporting >30 Gb/s signal transmission over 60 km SMFs.

The first 107 Gbit/s coherent optical OFDM transmission over optically non-repeated and repeated multimode fibre link is experimentally demonstrated. A record performance of 10 Tb/s·km over multimode fibre has been achieved using centre launching and OFDM equalisation.

We show that the performance of precompensation of fiber nonlinearity in coherent optical OFDM systems operating at up to 60 Gbps/polarization can be improved by electrical filtering the precompensation signal. The optimal filter bandwidth is related to the FWM efficiency spectrum when dispersion is considered.

Transmission performance for 100 Gbit/s WDM systems with coherent optical OFDM is simulated. The simulation shows that the system Q of the WDM channels at 100 Gbit/s is over 15.0 dB for a transmission up to 1000 km of standard-singlemode-fibre without dispersion compensation.

The first experiment of 21.4 Gbit/s polarisation multiplexed coherent optical OFDM transmission over 200 km of multimode fibre is reported. The experiment signifies that multimode fibre may have a role in achieving high spectral efficiency beyond short reach.

The first proof-of-concept experimental demonstration of coherent optical OFDM systems is reported. 128 OFDM subcarriers with a nominal data-rate of 8 Gbit/s are successfully processed and recovered after 1000 km transmission through SSMF fibre without optical dispersion compensation.

A new technique for using orthogonal frequency division multiplexing (OFDM) in optical systems is presented. Clipped OFDM is derived from a bipolar OFDM waveform by setting the negative values to zero. It has an optical efficiency 8 dB better than DC biased OFDM. If only the odd OFDM subcarriers are modulated, the clipping noise is orthogonal to the wanted signal.

In this paper we propose a passive optical network based on hybrid wavelength/space division multiplexing for digitized fronthaul delivery, capable to meet the requirements of the future radio access networks. Besides explaining this specific network architecture, we also discuss the different programmable data plane elements. Additionally, we evaluate and demonstrate the support of an extended version of 5G-NR radio signals.

We propose DFT-spread (DFT-S) OFDM within each sub-band of multiband-CO-OFDM to mitigate fiber nonlinearity. For 1000-km standard-single-mode-fiber transmission at 420-Gb/s, 32-band DFT-S CO-OFDM outperforms conventional CO-OFDM and coherent single-carrier by 1.1 and 0.8 dB, respectively.

[EN] We present a simple architecture for realizing high capacity W-band (75-110 GHz) photonics-wireless system. 42.13 Gbit/s 16QAM-OFDM optical baseband signal is obtained in a seamless 15 GHz spectral bandwidth by using an optical frequency comb generator, resulting in a spectral efficiency of 2.808 bits/s/Hz. Transparent photonic heterodyne up-conversion based on two free-running lasers is employed to synthesize the W-band wireless signal. In the experiment, we program an improved DSP receiver and successfully demonstrate photonics-wireless transmission of 8.9 Gbit/s, 26.7 Gbit/s and 42.13 Gbit/s 16QAM-OOFDM W-band signals, with achieved bit-error-rate (BER) performance below the forward error correction (FEC) limit., The authors would like to acknowledge the support from Tektronix, Agilent Technologies, Radiometer Physics GmbH, Rohde & Schwarz and u2t Photonics. This work was partly supported by the National "863" Program of China (No. 2009AA01A347), an EU project EUROFOS, a Danish project OPSCODER and an EU project FP7 ICT-4-249142 FIVER.

Recent real-time optical OFDM (OOFDM) research progress is reviewed extensively in terms of adaptive transceiver design, intensity modulators, synchronisation techniques and network architectures. Results indicate that OOFDM is feasible for mass deployment in PONs.

openaire: EC/H2020/777222/EU//ATTRACT Visible light communication (VLC) systems should be designed to provide illumination and wireless data services simultaneously. To achieve this goal at a reasonable cost, the use of Phosphor-Converted (PC) LEDs for indirect illumination should be favored to provide a homogeneous and reliable coverage in the whole service area. Unfortunately, PC-LEDs found in the market so far have not been designed for data transmission; moreover, the response of the other (electro-) optical components of the VLC link are far from ideal. In this paper, we estimate the data rate that is feasible with VLC when indirect illumination is used. For this purpose, the end-to-end response of the VLC link is first modeled using actual measurements of the spectral power distribution of a PC-LED lamp and the ceiling reflectance. Then, different power allocation schemes are studied assuming an optical OFDM waveform. As commercial LEDs have a relatively slow time response, the equivalent VLC channel that results has strong frequency selectivity; therefore, notable data rate gains are achievable when waterfilling power allocation is applied.

We study through theoretical analysis and simulate the nonlinearity and dynamic range for both balanced and single-ended receiver. The 0.5-dB Q-penalty dynamic range for single-ended receiver is 12 dB at laser RIN of -160 dBc/Hz

We experimentally demonstrate the best known 16-ary 4-d modulation format at 24.8 Gb/s using coherent optical OFDM, achieving 0.58 dB OSNR gain over PDM-QPSK at a SER of 10-2. With 7% overhead optimal codes, a 0.38 dB gain is theoretically achievable.

In this paper we propose a passive optical network based on hybrid wavelength/space division multiplexing for digitized fronthaul delivery, capable to meet the requirements of the future radio access networks. Besides explaining this specific network architecture, we also discuss the different programmable data plane elements. Additionally, we evaluate and demonstrate the support of an extended version of 5G-NR radio signals., Grant numbers : AURORAS - Autonomic and disaggregated optical networks leveraging edge computing and photonic technologies (RTI2018-099178-B-I00).

Orthogonal Frequency Division Multiplexing (OFDM) is a robust modulation and multiplexing format which is at the base of many present communication standards. The interest of the OFDM application in optical fiber deployments is quite recent. As the next generation of Passive Optical Networks (NG-PONs) is envisioned, targeting greater capacity and user counts, the limitations of TDMA (Time Division Multiplexing Access) approaches to meet the expected increase in requirements becomes evident and therefore new technologies are being explored. Optical OFDMA is an emerging technology which can be a promising candidate. The main goal of this Master Thesis is to study the problem of users multiplexing in access networks, using OFDM as a technology to transmit the user information data. This work has focused in the uplink study of the network, because it is the most challenging part of the network to design. The studies have been conducted both in a theoretical way and also by simulating the targeted environments by means of a fiber optics transmission simulation tool. Virtual Photonics Integrated (VPI) is the software selected for the simulations. This tool is specially designed to simulate optical transmission system environments. The analysis of the Optical Beat Interference, which is a critical impairment in optical carrier multiplexing schemes, is the most important part of the user multiplexing study.

We propose an algorithm for signal-to-signal-beat-noise (SSBN) cancellation in direct detection optical OFDM systems. Experimental results show that by using our proposed algorithm, the OSNR sensitivity can be improved by more than 8 dB.