Active demultiplexer enabled mmW ARoF transmission of directly modulated 64-QAM UF-OFDM signals

Ahmad

Martin

et al. 2021

J. Lightwave Technol.

Self Cite

A novel dual-stage optical frequency comb (OFC) demultiplexer, for use in a photonic millimeter-wave (mmW) generator, is demonstrated. Unlike other demultiplexing techniques, the proposed method features a single optical path for both tones used for the mmW generation, thus eliminating the challenges related to the mismatch of path lengths. In addition, the use of active demultiplexing provides filtering, amplification and data modulation of the comb tones, all in a single device. In this article, we demonstrate the operational principle of the dual-stage active demultiplexer-enabled mmW generation, verify the quality (beat tone width ~13 Hz) and stability (power fluctuation ~0.26 dB) of the generated mmW signal and validate the performance of an A-RoF system employing the proposed device. For the system demonstration, 64-QAM UF-OFDM signals, at frequencies of 29.5 and 38 GHz, are generated and transmitted over 25 km of singlemode fiber. A BER of 3.2e-4 for 29.5 GHz and 1.6e-4 for 38 GHz is achieved without the use of optical amplifiers, showing the great potential of the proposed technique. Finally, a case study of an A-RoF distribution system, employing three different demultiplexing techniques, is presented. We demonstrate that the proposed transmitter, in comparison to other demultiplexing techniques, provides a larger power budget (> 6 dB) that can be used to extend the reach of the system and/or increase the number of remote radio units served using a single OFC.

Section: Phase Noise and Stability Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tunable Mm-Wave A-RoF Transmission Scheme Employing an Optical Frequency Comb and Dual-Stage Active Demultiplexer

Ahmad

Martin

et al. 2021

J. Lightwave Technol.

Self Cite

“…While operations transition towards such high frequencies, efficiency in terms of spectral usage, cost and power consumption will be crucial. Hence, the use of a centralised radio access network (C-RAN) along with analog radio over fibre (A-RoF) is considered to be an attractive solution for 5G+ [2].…”

mentioning

confidence: 99%

“…A-RoF relies on photonic mmW generation schemes, based on coherent heterodyning of two optical tones, and exploits the benefit of using mature, high-bandwidth, low loss, offthe-shelf optical components. There are several methods of generating the optical tones, including the use of an optical frequency comb (OFC) [2]- [4], frequency doubling [5], dualmode fibre laser [6], etc. The use of an OFC allows the generation of high-quality mmW signals (excellent frequency stability and low phase noise) with a potential reduction in cost.…”

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confidence: 99%

Optical Linewidth Tolerant mmW Generation Employing a Dual-Stage Active Demultiplexer

IEEE Photon. Technol. Lett.

Kaszubowska-Anandarajah

Tajammul

et al. 2022

In this letter, we propose a novel linewidth tolerant millimetre-wave (mmW) generation scheme employing a dualstage active demultiplexer and an optical frequency comb (OFC). A unique feature of this architecture is that the two heterodyned tones travel the same path, alleviating the challenges associated with mismatches in the path lengths. We analyse the influence of the path length difference and source linewidth on the purity of the generated mmW signal and verify the tolerance, of the proposed scheme, to the optical linewidth. In addition, an experimental investigation of the performance of a 64 QAM discrete multitone (DMT) analog-radio over fibre (A-RoF) distribution system operating at 37.5 GHz using the proposed architecture, is presented. A BER below the HD-FEC limit is achieved, after 25 km fibre transmission, when employing an OFC with linewidth of ∼30 kHz and ∼3.1 MHz. Moreover, no significant performance penalty (at the HD-FEC limit) is observed due to an increase in the OFC linewidth, highlighting the linewidth tolerance of the proposed system.

“…To overcome this drawback, an active demultiplexing technique based on optical injection locking (OIL) has been widely researched [15]. A detailed characterisation of such a scheme is reported in [16] and a demonstration of the multifunctionality of the demultiplexer (its ability not only to filter, but also amplify and serve as a modulator), is discussed in [17,18].…”

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confidence: 99%

Active Demultiplexer-enabled Directly Modulated DMT Transmission Using Optical Frequency Combs for Data Center Interconnects

Ahmad

Kaszubowska-Anandarajah

et al. 2021

J. Lightwave Technol.

Self Cite

In this paper, we experimentally demonstrate an optical frequency comb (OFC) based transmitter, employing directly modulated active demultiplexers, for data center interconnects. The results validate that the proposed transmitter has the potential to achieve aggregate data rates of 100 Gb/s (8 × 12.5 Gb/s) and 200 Gb/s (8 × 25 Gb/s) for systems employing 4and 16-quadrature amplitude modulated (QAM) discrete multitone (DMT) modulation. An OFC based on an externally injected gain switched laser (EI-GSL) is used, providing excellent stability and flexibility in free spectral range (FSR). The OFC is followed by an injection locked active demultiplexer, which not only filters, but also amplifies individual comb tones, thus alleviating the need for an external optical amplifier to boost the low powered comb tones. Using the proposed configuration, we experimentally demonstrate a successful transmission of 12.5 Gb/s/ 4-QAM DMT and 25 Gb/s/ 16-QAM DMT signals over 40 km and 25 km of SSMF, respectively. In addition, we show that it is possible to filter and modulate comb lines that are 20 dB below the spectral peak, whilst achieving a BER below the hard decision (HD-) FEC limit of 3.8e-3. This gain flattening or comb expansion feature leads to a significant increase in the channel count, which in turn provides a reduction in the energy consumption and the footprint of the transmitter. Index Terms-Active demultiplexer, data center interconnects, direct modulation, discrete multi-tone, optical frequency combs. I. INTRODUCTIONVER the past decade, the global demand for communication capacity has increased exponentially [1]. This enormous growth in data traffic, caused predominantly by the bandwidth-hungry applications, like cloud computing and new web applications, is driving data center networks (DCNs) to the so-called "Zettabyte threshold", as predicted by a Cisco report [2]. As a result, there is an increasing need for highspeed DC interconnects (DCI) [3,4]. To meet the growing demand for bandwidth, DCNs must evolve towards higher performance and throughput, whilst improving the spectral "