This PDF file contains the front matter associated with SPIE Proceedings Volume 11308, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists

The current data center architectures based on blade servers and electronic packet switches suffer from inefficient resource utilization and high power consumption. Therefore, new solutions are needed to handle the increasing capacity demand. Optical networks offering ultra-high capacity and low energy consumption per bit may be able to mitigate these problems. This talk reviews the existing ideas for optical interconnect architectures and discuss different resource allocation options. A passive optical top-of-rack interconnect architecture is introduced, which makes it possible to significantly reduce power consumption. In order to improve the resource utilization rack-scale disaggregated data center DDC architecture is proposed and evaluated.

Optical switching is a promising technology to replace electronic switches and meet the bandwidth and energy requirements of future data center networks. In this talk, we will review InP-based switches designed fabricated using a generic foundry approach. The performance of SOA and hybrid MZI–SOA based switches are described. The scalability of the hybrid switch is assessed using a recalculating loop resulting in the feasibility of an energy-efficient 128×128 switch has been demonstrated. Simulations assess the potential for even higher port counts.

We experimentally demonstrate up to 40 Gbit/s optical wireless communication (OWC) systems made of commercial offthe- shelf components (COTS). The OWC systems use Non-Return to Zero (NRZ) or adaptive Orthogonal Frequency Division Multiplexing (OFDM), do not need active alignment and are designed to provide high-speed wireless connectivity in Data-Centers (DCs) or similar environments.

Following the standardization of 400 Gigabit Ethernet for data center networks (DCN), the industry will need 800 Gigabit or 1.6 Terabit pluggable modules soon after 2020. 200G per lambda directly detected links are very promising solutions to achieve the best trade-off between cost, size, and power. This paper investigates the challenges of 200G per lambda in DCN, due to the component bandwidth and noise limitations, and shows the technical feasibility enabled by advanced modulation formats and digital signal processing.

We demonstrate a 100-Gb/s/λ 4-ary pulse amplitude modulation (PAM4)-QSFP28 transceiver operated under C-temp range (0 °C -70 °C) and 5.87 W power consumption. A receiver sensitivity of -9.6 dBm is obtained at BER=10-12, and an 80-km C-band SSMF transmission can be reached with high chromatic dispersion tolerance.

Technology to apply 53 Gbaud 4-level pulse amplitude modulation (PAM4) to each single wavelength is essential for increasing a transceiver’s communication capacity. An electroabsorption-modulator-integrated laser (EML) having the several merits of high output, a high-speed response, and relatively good chirp characteristics is a promising device to provide such high baud-rate operation. We have demonstrated uncooled 53 Gbaud PAM4 operation at temperatures ranging from 20°C to 80°C using a newly developed TO-CAN EML with a novel lead-pin-less structure. We have also demonstrated 400 Gb/s PAM4 signal transmission over 10 km of single mode fiber (SMF) with no penalty using a compact integrated LAN-WDM EML TOSA that we have developed employing stripline with an aperture on the FPC enabling electrical crosstalk to be reduced. The uncooled TO-CAN EML exhibited a transmitter and dispersion eye closure (TDECQ) for PAM4 of better than 1.4 dB and an extinction ratio of over 4.5 dB at temperatures ranging from 20C to 80C thanks to the introduction of the lead-pin-less structure to the TO-CAN header in order to reduce the impedance mismatch and improve the 3-dB bandwidth. Meanwhile, the 400 Gb/s EML TOSA exhibited TDECQs of better than 2.5 dB and extinction ratios of over 4.8 dB for all lanes, as well as achieving a low crosstalk penalty of less than 0.4 dB. We believe that the uncooled TO-CAN EML and the EML TOSA will become key components for next generation 100 Gb/s and 400 Gb/s transceivers for data center applications.

In order to meet the recent vast demands of ICT bandwidth, high speed transmission systems, such as 100G, 200G and 400G, have been developed and installed with extremely high speed. In these circumstances, the de-fact standardization bodies such as IEEE802.3/OIF have played important roles in the industry in order to lead the proper concepts and designs of the leading-edge high-speed optical transceivers. Reviewing the recent activities of these standardization bodies, the future migration towards beyond Tera transceivers are examined and estimated from the view point of technology and economics.

We propose a cost-effective metro network architecture with fiber-granular routing and path-granular add/drop operations together with its ILP-based design algorithm. The proposal alleviates the impact of filtering impairment while using already deployed OXC/ROADM nodes. Numerical simulations on several real-world metro topologies verify that it increases the spectral efficiency compared to the ideal method for DWDM networks.

Stokes-vector modulation (SVM) formats have recently drawn attention for realizing low-cost and high-capacity optical transceivers. However, SVM transmitters reported so far are still complicated because they are based on optical components employed mainly in coherent systems. In order to reduce the device size, cost and power consumption, a more compact transmitter configuration is desired. In this invited paper, we first experimentally demonstrate transmission of 30-Gb/s 8-ary SVM signal over 50 km using the proposed configuration. Then we numerically investigate system performance of our recently-proposed compact transmitter for the 8-ary SVM format.

We present a Forward Error Correction (FEC) - assisted, 56 Gbaud PAM4 optical link having error free performance with adequate link margin of better than 6 dB. The link was formed by driving a 1550 nm Externally Modulated Laser (EML) with a commercial PAM4 transceiver chip. The optical signal was transmitted over various link lengths of dispersion compensated fiber, fed to a low-noise Linear InGaAs Photoreceiver having Automatic Gain Control (AGC), and routed back to the PAM4 transceiver chip with ADC & DSP capability. Real time bit error rate measurements demonstrate the advantage of employing linear receivers having AGC.

Existing transceiver technology inside data centers will soon reach its limits due to the enormous traffic growth rates driven by new, bandwidth-hungry applications. Efforts to develop the next generation of 800Gbps and 1.6Tbps transceivers for intra-DC optical interconnects have already kicked-off to address the demands in traffic, the exhaustion of the ports at the digital switches and the power consumption limitations inherent to the use of many lower capacity modules. The new generation of optical modules must also provide Terabit capacities at low cost, necessitating the use of high-volume manufacturing processes. TERIPHIC is an EU funded R and D project that aims at developing transceiver modules with up to 1.6 Tbps capacity over 16 lanes in duplex fiber and cost less than 1 € per Gbps for distances up to 2 km, utilizing PAM-4 modulation for 100Gbps per lane and high-volume production compatible transceiver designs. At the component level, TERIPHIC will rely on arrays of high-speed electronics, InP Externally Modulated Lasers (EMLs) and InP photodetectors, and at the integration level it will rely on a polymer photonic platform as a host motherboard, leveraging its flexibility and powerful toolbox. A summary of the progress on the TERIPHIC transceiver modules concept, both at the component level and integration level is presented in this paper.

The information technologies (ITs)-communications infrastructure convergence is key to future optical networks for achieving an automated orchestration of IT, optical and cloud resources. To cope with this challenge, transmission systems need to be agile, programmable, and capable of transmitting large amounts of data, while covering data center and metropolitan networks. This work addresses transmission solutions using coherent detection combined with either direct or external modulation, with special focus on flexible, high capacity and cost/energy-efficient systems. The proposed technological solutions are evaluated in terms of throughput, and programmability and interaction with the control plane.

The introduction of quasi-Nyquist wavelength-division multiplexing (WDM) reduces unused frequency resources and hence attains high spectral efficiency. Applying quasi-Nyquist WDM to optical-path networks using wavelengthselective switches (WSSs) is hindered by two factors: the limited bandwidth resolution of WSS passbands and the significant spectrum narrowing occasioned by WSS traversal. In this paper, we propose a novel quasi-Nyquist WDM network architecture, where the bundle-based wavelength assignment and receiver-side partial-response spectrum shaping are simultaneously utilized so as to resolve the two problems. Extensive computer simulations show that the proposed network architecture increases the maximum attainable node-hop count compared to the conventional transmission systems.

This article provides insight on two of the most relevant applications driving the design of the future MAN: the implementation of 5G by means of C-RAN (Cloud - Radio Area Network) and the deployment of edge computing. The work addresses important questions such as the target latency budget for future MANs, the target bandwidth requirements for 2020-2030 induced by 5G midhaul and fronthaul traffic, and describes how optical and electronics layers can co-operate to meet the QoS targets of C-RAN and edge computing traffic. In the process, we identify the key architectural elements to meet the challenges of these applications in a cost-effective way.

Innovative photonic solutions designed and developed in the H2020 research project PASSION are presented for the future metropolitan area network (MAN) supporting different aggregated data traffic volumes and operating at heterogenous granularities. System performance evaluated both by simulations and experimentation regarding the proposed vertical cavity surface emitting laser (VCSEL) -based modular sliceable bandwidth/bitrate variable transceiver (S-BVT) are shown in realistic MANs organized by hierarchical levels with the crossing of multiple nodes characterized by new switching/aggregation technologies. The capabilities and challenges of the proposed cost-effective, energy-efficient and reduced footprint technological solutions will be demonstrated to face the request of huge throughput and traffic scalability.

To improve the physical-layer data confidentiality in short-reach optical networks, we have proposed an M-ary blockciphered system using an optical code multiplexing approach. In a previous system, each optical code (OC), that corresponds to a frequency subcarrier, was mapped onto one of the log₂M bits, and the computational security is related to the correspondence between the bit-block and the OC, and the number of possible combinations equates M!. However, this system presents two critical issues (1) Computational Security: the number M of OCs that can be generated by an optical arrayed waveguide grating (AWG) is limited, due to the port number and the subcarrier crosstalk. (2) Physical security: a careful differential analysis of the corresponding time waveform, optical power, and/or optical spectrum can be used to identify the symbol pattern.

To mitigate the effects of interchannel interference, we propose a new differential phase-shift keying (DPSK)-based multi-dimensional M-ary block ciphering system, that assigns binary phase difference patterns to adjacent symbols and demonstrate a 16-dimensional 2¹⁶-ary ciphered system. In addition, to increase the M-ary number, without increasing the number of OCs, we consider also a differential quadrature phase-shift keying (DQPSK)-based multi-dimensional M-ary block ciphered system and demonstrate a 16-dimensional 2³²-ary ciphered system.

High bandwidth density silicon photonic interconnects offer the potential to address the massive increase in bandwidth demands for data center traffic and high performance computing. One of the major challenges in realizing silicon photonics transceivers is the integration and packing of photonic ICs (PIC) with electronic ICs (EIC). This paper presents our version one, 2.5D integrated multi-chip module (MCM) transceiver for 4 channel wavelength division multiplexing (WDM) operation, targeting 10 Gbps per channel. We identify five key areas critical to successful integration of MCM transceivers, which we have used in developing our version two MCM transceiver: integration architecture, equivalent circuit model development, PIC to EIC interface modelling, MCM I/O design, and design for assembly.

In this paper, we demonstrate the integration of a SiP switching platform to improve real-world Distributed Denial of Service (DDoS) defense systems. We demonstrate how DDoS mitigation in the optical domain can be transparent to network and application layers, allowing for reconfiguration and tuning. Additionally, we show how optical domain DoS mitigation provides significant cost reduction-with a 1/3 cost reduction-compared to traditional mitigation using electronic counterparts. Our approach is ideal for data-center deployments, and our testbed topology mirrors a standard data center set up.

We report on our recent progress in high-speed and large-capacity silicon-photonics-based integrated device technologies targeting large-capacity transmission in both datacom and telecom networks fields. A 70 Gbaud NRZ operation of all-silicon Mach–Zehnder modulator was demonstrated using forward-biased PIN diodes accompanied by passive equalizers. A clear optical eye opening was obtained owing to a broad electro-optic bandwidth of 37 GHz. We also successfully developed co-package-type 16-channels parallel silicon integrated transceivers and demonstrated simultaneous 400 Gbps operation. A novel demultiplexer capable to resolve phase-error-induced impairments is reported. With a simple control algorithm combining the heaters with monitored powers, crosstalks of as low as -58 to -49 dB have been obtained. This technology enabling temperature insensitivity and high yields drastically improves performance and cost of wavelength division multiplexing (WDM) transceivers.

The performance of Pol-Mux systems is limited by polarization dependent loss (PDL) which mainly exist in the passive components and optical nodes. In coherent systems, the function of PDL mitigation to increase the transmission distance of polarization multiplexed signal is essential for the digital signal processing (DSP) technology. Several precoding technologies have been investigated with the capability of suppressing PDL penalty in a blind manner, so that the monitoring technology is not required. Space-time code is one of the precoding technologies with low processing complexity and better performance. An inverse matrix method was also investigated basing on the Mueller matrix monitor. The experimental demonstration showed good improvement by this method. In this paper, the PDL monitoring and the mitigation technologies will be summarized and well explained in theory.

Short-reach transmission technologies based on multimode sources and fiber infrastructure remain highly attractive and competitive against single-mode solutions. We present here details of a versatile integrated multimode simulation framework targeting the design, analysis, and optimization of such systems. Important aspects that are addressed here are detailed multimode signal representations, mode solvers, models for signal propagation in multimode fibers, multimode VCSEL models, models to calculate the coupling between various multimode devices, and system-level building blocks specifying and measuring the characteristics of the overall system. The multimode VCSEL model, for instance, simulates different emission frequencies of the individual modes, considers their dependence on the bias current and laser temperature, and accounts properly for mode competition. In addition to accurate modeling of signal propagation in multimode fibers, statistical analysis of the link performance can be conducted to account for profile defects altering the fiber and link characteristics. A dedicated coupler model simulates launch conditions of multimode transmitters and assesses power coupling losses at fiber-fiber interfaces with the coupled devices being separated in free space and misaligned relative to each other. Besides discussing device modeling details, we present virtual test benches for measuring typical characteristics, such as the Encircled Flux of the launch system, DMD and EMBc of the multimode fibers, as well as system performance characteristics, to determine whether the simulated system and its individual components meet industry-accepted requirements.

We introduce our studies on optical nonlinearity compensation schemes using artificial-neural-networks (ANNs) for optical communication systems. The ANN-based digital signal processing can compensate nonlinear optical waveform distortion caused by SPM, XPM, and FWM. We employed real-valued ANNs and complex-valued ANNs, and compared their performances. The performances were studied in comparison with conventional Volterra series transfer function (VSTF). Furthermore, we introduce polarization tracking capability of the ANN for polarization-multiplexed optical transmission schemes. We also discuss over-training problem with the ANN and the VSTF.

Space division multiplexing (SDM) technologies are promising to respond to the demands of the increasing transmission capacity. Multicore fiber (MCF) is the one of the major candidate for fibers for future systems. In order to put MCF into practical use, many technologies such as cabling, connectors, fan-out devices are necessity. After installing MCF into field, adoption of SDM amplifier is also important to suppress the increase of power consumption. In this manuscript, several technologies enabling MCF installing in the real systems are summarized.

As bandwidth requirements and integration of photonic components in computing systems increase, the optical micro-ring resonator are becoming an important building block for dense, high-bandwidth interconnects. Ring resonators are small in size and can operate at data rates up to 60Gb/s NRZ,¹ making them well-suited for integrating many rings operating at different wavelengths into a single device. These devices are a promising solution for complex interconnected systems, such as chip-to-chip interconnects.² However, using these rings can be challenging as they are sensitive to fabrication and temperature variations and need constant tuning to lock them to their assigned optical wavelengths.³ This tuning is commonly done by inserting embedded heaters in or above the ring. Existing techniques that tune the rings by the optical power coupled into the rings require extensive characterization and spectrum analysis, or out-of-band signalling, to account for rings drifting across optical channels and fabrication variations. In this work, we use four cascaded micro-rings implemented in a silicon photonic device operating in the C-band. Each ring taps a single wavelength from a bus waveguide. The remaining light in the bus waveguide is then fed into a photodiode, which is used to monitor the tuning of all rings. We show an algorithm that, based only on information about the design of the chip, tunes the rings to the exact desired optical channel. With this algorithm the use of more complex techniques to directly measure a ring's coupled wavelength can be avoided, reducing system complexity.

In the context of standardized 400ZR, we study the adjacent channel power ratio (ACPR) as a measure for quantifying the impact of pluggables in flexible-grid dense wavelength division multiplexing (DWDM) networks. Using Monte- Carlo simulations, the ACPR is calculated under standardized roll-off factors for a dual-polarization 16QAM channel at 59.8GBaud. The ACPR is shown to adequately represent the impact of linear cross-talk as a function of channel spacing and channel power. From 75GHz (DWDM) to 59GHz (Super-Nyquist) optical transmission, we report a universal approach for specifying the penalties of flexible-grid pluggables on a channel’s required signal-to-noise ratio (SNR) and timing recovery.