400G and Beyond: Coherent Evolution to High-Capacity Inter Data Center Links

We present circuit implementations of blind phase search (BPS) carrier phase recovery (CPR) for M-QAM coherent optical receivers and highlight some BPS algorithm modifications necessary to obtain efficient VLSI circuits. In addition, we show how three key design parameters (input word length, number of test phases, and type and size of averaging window) affect the resulting implementation. To study design tradeoffs, we develop BPS CPR circuit netlists for a 32-GBaud system, using a 22-nm CMOS process technology: Our implementations reach energy efficiencies of around 1 pJ/bit for 16QAM up to 3 pJ/bit for 256QAM, at an SNR penalty of approximately 0.25 dB at a BER of 10 -2 . Furthermore, we present a circuit implementation of pilot-symbol-aided CPR, reaching 0.38 pJ/bit and 0.34 pJ/bit for 16QAM and 256QAM, respectively, at a slightly higher SNR penalty. The two CPR methods are also evaluated in terms of silicon area and scaling to higher-order modulation formats.

Section: Introductionmentioning

confidence: 99%

VLSI Implementations of Carrier Phase Recovery Algorithms for M-QAM Fiber-Optic Systems

Borjeson

Fougstedt

Larsson-Edefors

2020

“…For more information, see http://creativecommons.org/licenses/by/4.0/ relieving many optical link design constrains. Compared with other bandwidth-scaling approaches like coherent communications [9] or ultra-high speed amplitude modulations [10], [11], DWDM approach along with on-off-key (OOK) modulation at medium data rate per channel, e.g., 10-25 Gb/s, can lead to an overall optimal solution for little latency, energy efficient photonics and driving electronics [12], and possibility to enable a high-radix switch architecture to minimize hops between computing nodes [13].…”

Section: Introductionmentioning

confidence: 99%

Fully-Integrated Heterogeneous DML Transmitters for High-Performance Computing

Liang

Roshan-Zamir

Fan

et al. 2020

Optical connectivity, which has been widely deployed in today's datacenters and high-performance computing (HPC) systems, is a disruptive technological revolution to the IT industry in the new Millennium. In our journey to debut an Exascale supercomputer, a completely new computing concept, called memorydriven computing, was innovated recently. This new computing architecture brings challenges and opportunities for novel optical interconnect solutions. Here, we first discuss our strategy to develop appropriate optical link solutions for different data traffic scenarios in memory-driven HPCs. Then, we present detailed review on recent work to demonstrate fully photonics-electronicsintegrated single-and multi-wavelength directly modulated laser (DML) transmitters on silicon for the first time. Compact heterogeneous microring lasers and laser arrays were fabricated as photonic engines to work with a customized complementary metal-oxide semiconductor (CMOS) driver circuit. Microring lasers based on conventional quantum well and new quantum dot lasing medium were compared in the experiment. Thermal shunt and MOS capacitor structures were integrated into the lasers for effective thermal management and ultra low-energy tuning. It enables a

“…S the requirement for the data rate handled by a single transceiver exceeds 400 Gb/s in the up-coming optical communication networks [1], the deployment of coherent optical communication systems becomes necessary in order to satisfy the ever-increasing demands [2][3][4]. The main obstacle to the transition is the high cost of coherent transceivers, to which the most likely solution is photonic integration, bringing semiconductor lasers, modulators, amplifiers, photodetectors and other photonic devices together on a single platform.…”

Section: Introductionmentioning

confidence: 99%

High-Speed Coherent Optical Communication With Isolator-Free Heterogeneous Si/III-V Lasers

Zhang

Zou

Wang

et al. 2020

Coherent optical communication is considered as an indispensable solution to the ever-increasing demand for higher data rates. To reduce the cost and form factor of coherent transceivers, full integration of photonic devices including lasers, modulators, amplifiers, photodetectors and other components is necessary. However, as fabricating optical isolators on chip remains extremely challenging, optical feedback, which can degrade the coherence of semiconductor lasers, becomes the main obstacle, thwarting large-scale photonic integration. An appealing solution to such a problem is to use semiconductor lasers with intrinsic insensitivity to optical feedback as the integrated light sources. The heterogenous Si/III-V lasers, with their built-in high-Q resonators, are expected to possess a robustness to optical feedback which exceeds by several orders of magnitude compared to commercial III-V distributed feedback (DFB) lasers, which will be validated here. We present data showing that the heterogeneous Si/III-V lasers can preserve their phase coherence under much larger optical feedback and therefore function without severe degradation in isolator-free coherent optical communication systems.