Arrayed Waveguide Grating Router Research Articles

Direct Optical Convolution Computing Based on Arrayed Waveguide Grating Router

Direct Optical Convolution Computing Based on Arrayed Waveguide Grating Router

ODRAD: An optical wireless DCN dynamic-bandwidth reconfiguration with AWGR and deep reinforcement learning

The rapid growth of Data Center Network (DCN) traffic has brought new challenges, such as limited bandwidth, high latency, and packet loss to existing DCNs based on electrical switches. Because of its theoretically unlimited bandwidth and faster data transmission speeds, optical switching can overcome the problems of electrically switched DCNs. Additionally, numerous research works have been devoted to optical wired DCNs. However, static and fixed-topology DCNs based on optical interconnects significantly limit their flexibility, scalability, and reconfigurability to provide adaptive bandwidth for traffic with heterogeneous characteristics. In this study, we propose and conduct performance evaluations on a reconfigurable optical wireless DCN architecture based on distributed Software-Defined Networking (SDN), Deep Reinforcement Learning (DRL), Semiconductor Optical Amplifier (SOA), and Arrayed Waveguide Grating Router (AWGR). Our architecture is called ODRAD (which stands for Optical Wireless DCN Dynamic-bandwidth Reconfiguration with AWGR and Deep Reinforcement Learning). A Mininet simulation model is established to further verify the reconfigurability of the ODRAD network for various server scales. Based on experimental verification, ODRAD achieves an average end-to-end server latency of 5.2μs under a load of 99%. Compression results demonstrate a 17.36% improvement in packet rate latency performance compared to RotorNet and a 15.21% improvement compared to OPSquare at a load of 99% as the ODRAD network scales from 2,560 to 40,960 servers. Furthermore, ODRAD exhibits effective throughput across different routing protocols, DCN scales and loads.

Re-routable and Low-latency All Optical Switching Algorithm for Next Generation DCN

Digital infrastructure is now indispensable to the function of society and quality of life of the citizen. All over the world there is leveraging of digital infrastructure that comprises use of data, computerized devices, methods and systems. During COVID-19 pandemic it comes more prominently in front. India being the most popular and populated country in the world, comprises nearly half billion internet users expected to transform the digital ecosystem. With the increasing demand of smartphone application, online activities gigantic amount of data has been generated, so evolution and development of data centers be the high importance not only for India but as well as for the world. Thus, it is the need to promote and create robust data center network infrastructure that supports emerging technologies such as 5G, IoT, AI, machine learning, adaptive manufacturing, smart agriculture, and automation and so on. In this paper we propose an all Optical re-routable, low latency Data Center Network (DCN) architecture using Passive Optical Datacenter Switch (PODS). The PODS consists of an Arrayed Waveguide Grating Router (AWGR) in association with a controller unit. An efficient wavelength assignment algorithm is integrated in PODS, to reroute the packet for congestion avoidance and packet loss.. This feature makes the DCN architecture more scalable, proficient with high throughput, low latency, power efficient under high traffic and bursty traffic conditions. The performance of the proposed PODS-based DCN is compared with existing passive optical DCN architectures PODCA and finds improved characteristics in terms of delay, throughput and blocking probability. Simulation of the framework is done in Python platform and executed on google COLAB in the Windows environment and the result shows 46.3% improvement in latency and throughput in terms of 90% network load compared with PODCA architecture.

Reconfigurable AWGR based on LNOI with a tunable central wavelength and bandwidth used in elastic optical networking.

Elastic optical networking introduces elasticity and adaptation into the optical domain, which highly depends on reconfigurable optical devices. In this paper, a tunable 4×4 arrayed waveguide grating router based on lithium niobate on insulator is designed. By using the electro-optic effect of lithium niobate, we design electrode regions with specific shapes in the array waveguide region to realize the tuning of the routing wavelength and bandwidth of the third output channel. The designed arrayed waveguide grating router (AWGR) has a dense channel spacing of 0.8nm, and the minimum insertion loss is 2.3dB. Experiments show that the tuning range of the central wavelength can reach 3.2nm, and the 3dB bandwidth can be expanded from 0.2 to 0.6nm.

A 51 Gb/s Reconfigurable mmWave Fiber-Wireless C-RAN Supporting 5G/6G MNO Network Sharing

The growing demand for ubiquitous broadband connectivity in 5G/6G Radio Access Networks (RANs) has turned Centralized RAN (C-RAN) and reconfigurable Point-to-MultiPoint (PtMP) network topologies into the mainstream approach for keeping pace with the vastly increasing traffic capacities and connection densities. Relying on an all-passive Arrayed Waveguide Grating Router (AWGR), we propose and demonstrate reconfigurable allocation of multiple parallel Fiber-Wireless (FiWi) millimeter wave (mmWave) analog (Intermediate Frequency over Fiber) IFoF interfaces. The proposed technology provides a framework for the implementation of reconfigurable multiple FiWi backhaul /midhaul/fronthaul (X-haul) connections. The use of AWGR enables wavelength slicing and the co-existence of multiple transport links over the same X-haul network infrastructure. The proposed concept is experimentally validated by two sets of experimental measurements. More specifically a 4λ- Wavelength-Division Multiplexed (WDM) signals modulated by IFoF signals are routed through the AWGR and wirelessly transmitted over the air across a 1m V-band distance by two different pairs of mmWave 60 GHz antennas. In the first experiment, a Phased Array Antenna (PAA) operating at 60 GHz is utilized achieving a 2.5 Gb/s data rate per wavelength and beam pair with an Error Vector Magnitude (EVM) of less than 12.5% and an aggregate 10 Gb/s traffic capacity. The achieved performance meets for the first time the respective 5G Key Performance Indicator (KPI) requirements for EVM quality and peak data traffic while supporting the link reconfiguration wavelength routing and mmWave beam direction. In the second experiment, the PAA is replaced by a point-to-point 60 GHz link utilizing a high-end mm-wave transmitter, thus achieving a data rate of 12.75 Gb/s per wavelength-beam with an EVM of less than 6.5% and an aggregate capacity of 51 Gb/s. To this end, the proposed solution is shown to form a promising roadmap toward flexible and reconfigurable 5G/6G mmWave C-RAN architectures where multiple Mobile Network Operators (MNOs) can share the same network infrastructure and dynamically allocate fiber, antenna beams and wavelengths.

Efficient and fast contention resolution for AWGR based optical data center networks

A packet contention resolution scheme featuring efficient bandwidth utilization (CRSebu) is proposed for arrayed waveguide grating router (AWGR)-based optical data centers (DCNs). Optical bandwidth can be efficiently provided in this proposed scheme to adapt the burst network traffic by flexibly arranging the timeslot and wavelength. Moreover, the CRSebu scheme implements a “Dislocation Pipeline” strategy to prevent the conventional “Request-Grant” scheduling caused extra traffic waiting delay. Experimental investigations prove the CRSebu scheme can completely prevent packet contention and also improves the network performance in terms of packet loss and server-to-server latency due to the high bandwidth utilization. Numerical assessments also validate the excellent scalability of this proposed contention resolution scheme in large-scale AWGR-based DCNs. Compared with the typical OPSquare structure deploying an Optical Flow Control scheme to prevent packet contention, the CRSebu-equipped optical DCN eliminates the retransmission of conflicted packets, which significantly improves the network performance. Experimental investigations prove the proposed CRSebu strategy can completely prevent packet contention. Numerical assessments show that the network deployed with the CRSebu scheme decreases 73.6% packet loss, and 11.9% server-to-server latency compared with the static scheme.

Monolithic silicon photonic 32x32 thin-CLOS AWGR for all-to-all interconnections.

This paper reports the design, fabrication, and experimental demonstration of a monolithic silicon photonic (SiPh) 32×32 Thin-CLOS arrayed waveguide grating router (AWGR) for scalable SiPh all-to-all interconnection fabrics. The 32×32 Thin-CLOS makes use of four 16-port silicon nitride AWGRs, which are compactly integrated and interconnected by a multi-layer waveguide routing method. The fabricated Thin-CLOS has 4 dB insertion loss, < -15 dB adjacent channel crosstalk, and < -20 dB non-adjacent channel crosstalk. System experiments operated on the 32×32 SiPh Thin-CLOS demonstrate error-free communication at 25 Gb/s.

High resolution, high channel count silicon arrayed waveguide grating router on-chip.

A 32×32 100 GHz silicon photonic integrated arrayed waveguide grating router (AWGR) is experimentally demonstrated for dense wavelength division multiplexing (DWDM) applications. The dimension of the AWGR is 2.57 mm×1.09 mm with a core size of 1.31 mm×0.64 mm. It exhibits 6.07 dB maximum channel loss non-uniformity with -1.66 dB best-case insertion loss and average channel crosstalk of -15.74 dB. In addition, in the case of 25 Gb/s signals, the device successfully realizes high-speed data routing. The AWG router provides clear optical eye diagrams and low power penalty at bit-error-rates of 10-9.

Nanosecond photonic integrated multicast switch for low-latency optical wireless data center networks

Optical wireless data center networks (OW-DCNs), featuring no cable complexity, low latency, and high throughput, are highly attractive for the next generation of DCNs, while photonic integration provides a compact, low-power, and low-cost solution. In this Letter, we propose a novel, to the best of our knowledge, OW-DCN architecture using photonic integrated multicast switches (PIC-MCSs) to realize fast optical switching and multicast operation between top-of-the-rack switches (ToRs). By properly turning on/off the transmission channels of a semiconductor optical amplifier (SOA)-based PIC-MCS, the optical signals are directed to different target ToRs via arrayed waveguide grating routers (AWGRs) and free-space links. A 4×2 PIC-MCS with lossless multicast operation has been designed and fabricated. An OW-DCN of 4×4 interconnected racks has been experimentally demonstrated with the chip and a 4×4 AWGR. The results confirm the performance of low-latency switching, dynamic bandwidth reallocation, and WDM multicast transmission. Error-free operation at 10 Gb/s OOK with a power penalty of less than 1 dB is achieved, showing a negligible impact of cross talk on the PIC-MCS.

ReSAW: a reconfigurable and picosecond-synchronized optical data center network based on an AWGR and the WR protocol

The explosive growth of data center (DC) traffic imposes unprecedented challenges on the current electrical switch-based data center networks (DCNs) with the bottleneck of limited bandwidth and high latency. Benefitting from transparency to the data rate and format, optical switching with theoretically infinite bandwidth could overcome the bandwidth bottleneck of electrical switching DCNs. However, DCNs normally deploy multitenant applications with a variety of DC traffic. It is hard to reconfigure the optical interconnections in real-time to provide adaptable bandwidth to the traffic with heterogeneous characteristics. Moreover, to improve the bandwidth utilization, statistical multiplexing is generally deployed in optical DCNs to forward the traffic flow in a time slot, which requires the network time to be precisely synchronized to all network nodes. For fast optical switches with a nanosecond switching configuration time, overall end node times must be synchronized at subnanosecond magnitude. In this paper, we propose and experimentally investigate a reconfigurable and picosecond-synchronized optical DCN (ReSAW) based on an arrayed waveguide grating router (AWGR) and the White Rabbit (WR) protocol. A scheduler based on a distributed field-programmable gate array is implemented in the proposed ReSAW to realize flexible wavelength configuration by controlling the fast laser array based on semiconductor optical amplifiers (SOAs) according to time slot and traffic priority. Moreover, the WR protocol is implemented in optical DCNs for what we believe is the first time to synchronize the time of the distributed top of racks (ToRs). The experimental demonstration validates that ReSAW achieves an average end-to-end latency of 317.44 ns and a precise synchronized time with an average 386 ps skew. When the load is 0.4, the packet loss after ReSAW reconfiguration is less than 1.83 × 10 − 6 , and the network latency is less than 1.73 µs. Based on the experimental parameters and results, the OMNeT++ simulation model is built to further verify the reconfigurability and scalability of the ReSAW network. Results show that the packet loss rate and latency performance increase 8.24% and 12.47%, respectively, at a load of 0.6 as the ReSAW network scales from 2560 to 40,960 servers compared to before the reconfiguration.

Low-Loss Silicon Photonic 16 × 16 Cyclic AWGR Based on SOI Platform

We experimentally demonstrate a low-loss and low-crosstalk 16-channel 200 GHz-channel-spacing arrayed waveguide grating router (AWGR) with a size of 0.67 × 0.37 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , targeting for C-band wavelength division multiplexing (WDM) interconnect routing applications. As a result, the AWGR features a channel spacing of 200±10 GHz, a free spectral range of 25.62 nm and a 3 dB channel bandwidth of 0.9 nm. Based on comprehensive optimal design, the measured characterization revealed 5.55 dB maximum channel loss non-uniformity with 1.13 dB best-case channel insertion loss. Besides, the fabricated device exhibits good cyclic-frequency operation for all 16 × 16 port combinations with channel crosstalk of –15.11 dB.

Monolithically Integrated 8 × 8 Transmitter-Router Based on Tunable V-Cavity Laser Array and Cyclic Arrayed Waveguide Grating Router

A monolithic 8 × 8 transmitter-router chip fabricated on InGaAlAs-InP multi-quantum well wafer for distributed wavelength routing network in the O-band with a channel spacing of 400 GHz is experimentally demonstrated. A tunable V-cavity laser (VCL) array, a cyclic-arrayed waveguide grating router (AWGR) and a semiconductor amplifier (SOA) array are integrated using the quantum-well intermixing (QWI) technique for its fabrication simplicity and cost effectiveness. A 200 GHz-spaced compact-size VCL is demonstrated with a 27 nm tuning range and a side-mode suppression ratio (SMSR) around 40 dB using a single-electrode controlled tuning. The chip output power is 24.6 mW. Measurement results of the transmitter-router chip show that all 64 input-output combinations have cyclic response spectra. After passing through the SOA with 80 mA bias current, an output power of about 9.6 mW and optical signal-to-noise ratio (OSNR) up to 39 dB have been measured. The demonstrated transmitter-router chip is fabricated on the same quantum well structure without requiring multiple epitaxial growth and complex grating fabrication. The characteristics of multi-wavelength and multi-port transmissions enable the distributed optical routing networks with flexible bandwidth allocation, which can find wide application in datacenters and high-performance computers.

RGAIA: a reconfigurable AWGR based optical data center network.

Benefitting from the cost-effective and flexible interconnection between computing nodes and storing infrastructures, various applications and services are deployed in data centers (DCs). These traffic-boosting applications put tremendous pressures on current electrically switched DC networks (DCNs) which suffer the bandwidth bottleneck. Benefitting from the data-rate and format transparency, the optically switched DCN with intrinsic high-bandwidth characteristics is a promising solution to update the hierarchical electrical DCNs with bandwidth limitations. Moreover, the applications deployed in DCNs with mixed traffic characteristics require dynamic quality of service (QoS) provisioning. Optical DCNs thus need to be designed in a flexible topology with the capability of bandwidth reconfigurability to adapt the variety of the traffic. In this paper, we propose and experimentally investigate a reconfigurable optical packet switching DCN named RGAIA, based on flexible top of racks (ToRs) and fast optical switch, where the optical switch is implemented by tunable transceiver combing with arrayed waveguide grating router (AWGR). Under the management of the designed software defined network (SDN) control plane, RGAIA can dynamically distribute the wavelength resource and then reconfigure the bandwidth in real-time based on the monitored traffic characteristics. Experimental assessments validate RGAIA improving performance of 37% and 66% in latency and packet loss, respectively, compared with the network with rigid interconnections at the traffic load of 0.8.

Low-Latency Optical Wireless Data-Center Networks Using Nanoseconds Semiconductor-Based Wavelength Selectors and Arrayed Waveguide Grating Router

In order to meet the massively increasing requirements of big-data applications, data centers (DCs) are key infrastructures to cope with the associated demands, such as high performance, easy scalability, low cabling complexity and low power consumption. Many research efforts have been dedicated to traditional wired data center networks (DCNs). However, DCNs’ static and rigid topology based on optical cables significantly limits their flexibility, scalability, and even reconfigurability. The limitations of this wired connection can be addressed with optical wireless technology, which avoids cable complexity problems while allowing dynamic adaption and fast reconfiguration. Here, we propose and investigate a novel optical wireless data-center network (OW-DCN) architecture based on nanoseconds semiconductor optical amplifier (SOA)-based wavelength selectors and arrayed waveguide grating router (AWGR) controlled by fast field-programmable gate array (FPGA)-based switch schedulers. The full architecture, including the design, packet-switching strategy, contention solving methodology, and reconfiguration capability, is presented and demonstrated. Dynamic switch scheduling with a FPGA-based switch scheduler processing optical label and software-defined network (SDN)-based reconfiguration were experimentally confirmed. The proposed OW-DCN was also achieved with a power penalty of less than 2 dB power penalty at BER &lt; 1 × 10−9 for a 50 Gb/s OOK transmission and packet-switching transmission.

INTREPID program: technology and architecture for next-generation, energy-efficient, hyper-scale data centers [Invited

The INTREPID program is developing power-efficient coherent optics for package-level integration with future switch integrated circuits as a path to realizing higher-radix switches for flatter networks. The link architecture is underpinned by coherent quadrature phase-shift keying (QPSK) polarization-multiplex transceivers at 200 Gb/s per λ , further enhanced with wavelength division multiplexing (WDM) to enable energy-efficient 800 or 1600 Gb/s inter-switch fiber connections. The technology is compatible with conventional three-level data center designs as well as a two-level data center design introduced here, which includes an added layer of passive, arrayed waveguide grating routers (AWGRs) or WDM circuit switches to further improve the cost, energy efficiency, and latency of the network.

Multimedia Encrypted Experiment of Reconfigurable Wavelength Hopping Protection against Eavesdroppers over a Wireless Wavelength Division Multiplexing Network

To enhance the video transmission security of a physical layer over wireless optical communication, an optical switch configured in front of an arrayed waveguide grating (AWG) router is proposed for implementing reconfigurable wavelength hopping configuration over a wavelength division multiplexing network for protection against eavesdropping. In the practical experiment of an AWG/optical-switch-based random wavelength hopping scheme, a simulated pseudorandom noise generator algorithm was designed and embedded into a master&#x2010;slave microprocessor (e.g., Arduino chips) to generate a time series of electrical signals for triggering an optical switch. The path of the optical switch was randomly varied to change the space transmission of the AWG router. Therefore, varying wavelengths were assigned as the carriers of authorized users to realize the AWG/optical-switch-based wavelength hopping scheme. An optical spectrum analyzer and an oscilloscope were used for monitoring measurement. The experimental results indicated that eavesdroppers cannot accurately interpret analog, digital, audio, and uncompressed high-definition multimedia interface signals of 10&#xA0;MHz, 1&#xA0;MHz, 3.125&#xA0;MHz (encoded into 6.25&#xA0;MHz), and 1.485&#xA0;GHz, respectively. According to the experimental results, authorized and unauthorized users are characterized by a large difference in the retrieved energy signal, which ensures the safety and privacy of the proposed AWG/optical-switch-based reconfigurable wavelength hopping scheme over a wireless optical communication network.

Lotus

Machine learning is at the heart of many services provided by data centers. To improve the performance of machine learning, several parameter (gradient) synchronization methods have been proposed in the literature. These synchronization algorithms have different communication characteristics and accordingly place different demands on the network architecture. However, traditional data-center networks cannot easily meet these demands. Therefore, we analyze the communication profiles associated with several common synchronization algorithms and propose a machine learning--oriented network architecture to match their characteristics. The proposed design, named Lotus, because it looks like a lotus flower, is a hybrid optical/electrical architecture based on arrayed waveguide grating routers (AWGRs). In Lotus, a complete bipartite graph is used within the group to improve bisection bandwidth and scalability. Each pair of groups is connected by an optical link, and AWGRs between adjacent groups enhance path diversity and network reliability. We also present an efficient routing algorithm to make full use of the path diversity of Lotus, which leads to a further increase in network performance. Simulation results show that the network performance of Lotus is better than Dragonfly and 3D-Torus under realistic traffic patterns for different synchronization algorithms.

25.6 Tbps Capacity and Sub-µsec Latency Switching for DataCenters Using &gt;1000-Port Optical Packet Switch Architectures

We discuss the challenges and limitations of current electrical DataCenter switches towards scaling beyond the 25.6 Tb/s capacity-era while meeting a low-latency and high-radix envelope. With the high-power SerDes and required DSP interfaces forming critical scaling factors, we discuss the perspectives and challenges of migrating to Optical Packet Switch (OPS) technologies for avoiding the electronically-induced bottlenecks, while exploiting reliable and practical techniques for overcoming well-known OPS problems, like buffering and high-port connectivity. We demonstrate the feasibility of OPS schemes by reporting experimental results of our Hipoλaos architecture towards extending its line-rate to 25 Gb/s per port and enabling 25.6 Tb/s switch capacities through a 1024-radix layout, while still preserving sub-μs latency metrics. Experimental results are presented for both unicast and multicast packets, employing the 1024-radix Hipoλaos architecture in a fully-fledged FPGA-controlled switching Plane, along with a 32 × 32 Arrayed Waveguide Grating Router (AWGR) device. The unicast performance is validated through BER measurements, while optical multicasting to 5 nodes is also experimentally evaluated at 25 Gb/s, along with an evaluation of the broadband multicast capabilities of the switch. Moreover, a mixed-traffic scenario involving both unicast and multicast traffic is demonstrated. Finally, a discussion about the perspectives and challenges of bringing OPS in DC networks is presented.

WDM-Based Silicon Photonic Multi-Socket Interconnect Architecture With Automated Wavelength and Thermal Drift Compensation

A silicon photonic circuit comprising all the building blocks necessary to demonstrate optical communication between two sockets interconnected through an Arrayed Waveguide Grating Router (AWGR) is reported. The article focuses on the robustness of the interconnection scheme to the unavoidable wavelength and thermal fluctuations observed in real datacenter environments. To improve the reliability of the system, a feedback control mechanism, based on contactless integrated photonic probes (CLIPP) and heater actuators, is added to the interconnection to monitor in parallel the working point of each sensitive device and keep it locked in real-time. Experimental results demonstrate successful operations in a 30 Gbit/s data routing scenario at $\text{5}\cdot \text{10}^{-11}$ bit error rate, irrespective of sudden wavelength shifts of up to 200 pm or of iterated thermal variations in a 10 $^\circ$ C temperature range, with a recovery time of around 30 ms. These results prove that AWGR-based interconnections equipped with real-time drift compensation systems can be a viable option in multi-socket layouts even in highly demanding environments.

400 Gb/s Silicon Photonic Transmitter and Routing WDM Technologies for Glueless 8-Socket Chip-to-Chip Interconnects

Arrayed Waveguide Grating Router (AWGR)-based interconnections for Multi-Socket Server Boards (MSBs) have been identified as a promising solution to replace the electrical interconnects in glueless MSBs towards boosting processing performance. In this article, we present an 8-socket glueless optical flat-topology Wavelength Division Multiplexing (WDM)-based point-to-point (P2P) interconnect pursued within the H2020 ICT project ICT-STREAMS and we report on our latest achievements in the deployment of the constituent silicon (Si)-photonic transmitter and routing building blocks, exploiting experimentally obtained performance metrics for analyzing the 8-socket chip-to-chip (C2C) connectivity in terms of throughput and energy efficiency. We demonstrate an 8-channel WDM Si-photonic microring-based transmitter (Tx) capable of providing 400 (8 × 50) Gb/s non-return-to-zero (NRZ) Tx capacity and an 8 × 8 Coarse-WDM (CWDM) Si-AWGR with verified cyclic data routing capability in O-band. Following an overview of our recently demonstrated crosstalk (XT)-aware wavelength allocation scheme, that enables fully-loaded AWGR-based interconnects even for typical sub-optimal XT values of silicon integrated CWDM AWGRs, we validate the performance of a full-scale 8-socket interconnect architecture through physical layer simulations exploiting experimentally-verified simulation models for the underlying Si-photonic Tx and routing circuits. This analysis reveals a total aggregate capacity of 1.4 Tb/s for an 8-socket interconnect when operating with 25 Gb/s line-rates, which can scale to 2.8 Tb/s at an energy efficiency of just 5.02 pJ/bit by exploiting the experimentally verified building block performance at 50 Gb/s line. This highlights the perspectives for up to 69% energy savings compared to the standard QuickPath Interconnect (QPI) typically employed in electronic glueless MSB interconnects, while scaling the single-hop flat connectivity from 4- to 8-socket interconnection systems.