Characterization of a multifunctional active demultiplexer for optical frequency combs

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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: A Operational Principlementioning

confidence: 99%

Section: B Generation Of the Mmw Signalmentioning

confidence: 99%

Section: System Deployment Scenariosmentioning

confidence: 99%

Section: Introductionmentioning

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

Lakshmijayasimha

Ahmad

Martin

et al. 2021

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“…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

Lakshmijayasimha

Kaszubowska-Anandarajah

et al. 2021

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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 "

Injection Locking Properties of an Dual Laser Source for mm-Wave Communications

Gonzalez-Guerrero

Guzmán

Ali

et al. 2022

We for the first time, the optical injection locking (OIL) to a frequency comb of a hybrid InP-Si 3 N 4 dual laser source for high-purity mm-wave generation through optical heterodyning. Key performance parameters of the comb line demultiplexing functionality provided by this source under OIL -such as adjacent-comb-line side mode suppression ratio (SMSR) and locking range -are reported. It is also shown that the amount of free-running drift exhibited by the hybrid lasers (which should be as little as possible to keep them within the locking range) can be minimized by reducing the amount of bias level applied to the heater-based phase actuators present in such lasers. According to the measured drift, locking range and SMSR, these lasers have potential to achieve continuous locking with SMSR levels of more than 45 dB at comb line separations higher than 9 GHz. Successful carrier generation at 93 GHz is demonstrated by locking the two lasers to an optical frequency comb achieving an ultra-stable International Telecommunication Union (ITU)-compliant signal. Both real-time and DSP-aided data transmissions are demonstrated at this frequency achieving data rates of 12.5 and 28 Gbit/s, respectively.