Optical Packet Research Articles

All-Optical Programmable Disaggregated Data Centre Network Realized by FPGA-Based Switch and Interface Card

This paper reports an FPGA-based switch and interface card (SIC) and its application scenario in an all-optical, programmable disaggregated data center network (DCN). Our novel SIC is designed and implemented to replace traditional optical network interface cards, plugged into the server directly, supporting optical packet switching (OPS)/optical circuit switching (OCS) or time division multiplexing (TDM)/wavelength division multiplexing (WDM) traffic on demand. Placing the SIC in each server/blade, we eliminate electronics from the top of rack (ToR) switch by pushing all the functionality on each blade while enabling direct intrarack blade-to-blade communication to deliver ultralow chip-to-chip latency. We demonstrate the disaggregated DCN architecture scenarios along with all-optical dimension-programmable N × M spectrum selective Switches (SSS) and an architecture-on-demand (AoD) optical backplane. OPS and OCS complement each other as do TDM and WDM, which can support variable traffic flows. A flat disaggregated DCN architecture is realized by connecting the optical ToR switches directly to either an optical top of cluster switch or the intracluster AoD optical backplane, while clusters are further interconnected to an intercluster AoD for scaling out.

Integrated optical switch matrices for packet data networks.

Integrated circuit technologies are enabling intelligent, chip-based, optical packet switch matrices. Rapid real-time re-configurability at the photonic layer using integrated circuit technologies is expected to enable cost-effective, energy-efficient, and transparent data communications. InP integrated photonic circuits offer high-performance amplifiers, switches, modulators, detectors, and de/multiplexers in the same wafer-scale processes. The complexity of these circuits has been transformed as the process technologies have matured, enabling component counts to increase to many hundreds per chip. Active–passive monolithic integration has enabled switching matrices with up to 480 components, connecting 16 inputs to 16 outputs. Integrated switching matrices route data streams of hundreds of gigabits per second. Multi-path and packet time-scale switching have been demonstrated in the laboratory to route between multiple fibre connections. Wavelength-granularity routing and monitoring is realised inside the chip. In this paper, we review the current status in InP integrated photonics for optical switch matrices, paying particular attention to the additional on-chip functions that become feasible with active component integration. We highlight the opportunities for introducing intelligence at the physical layer and explore the requirements and opportunities for cost-effective, scalable switching.

Blocking Probability Simulations for FDL Feedback Optical Buffers

Asynchronous optical packet switching seems to a suitable transport technology for the next-generation Internet due to the variable lengths of IP packets. Optical buffers in the output port are an integral part of solving contention by exploiting the time domain. Fiber delay lines (FDLs) are a well-known technique for achieving optical buffers, and various optical buffer architectures using FDLs have been proposed. These are generally classified into two types of structure: feed-forward (FF) or feedback (FB). In the FF buffers, optical packets are delayed at the output ports by passing through step-increasing-length multiple FDLs to avoid contentions, and in the FB buffers, optical packets are delayed by being fed back in re-circulating loop FDLs to avoid contentions. We report the detailed characteristics of optical FB buffers with the Post-Reservation (PostRes) policy and clarify the superiority of the FB buffers through simulations. For comparison, we also show the characteristics of FBSI (FB with step-increasing-length FDLs) and FF buffers. We found that 1) the blocking probabilities in the FB buffer were about 10-2 lower than those in the FF buffer and 2) the blocking probabilities for the deterministic case in the FB buffer sharply dropped at D=1.0, where the packet length was equal to the FDL loop length. We carried out 108 packet simulations. The results can be applied to the design of WDM optical packet switches and networks with the maximum throughput.

Design of an All-Optical Network Based on LCoS Technologies

AbstractIn this paper, an all-optical network composed of the ROADMs (reconfigurable optical add-drop multiplexer), L2/L3 optical packet switches, and the fiber optical cross-connection for fiber scheduling and measurement based on LCoS (liquid crystal on silicon) technologies is proposed. The L2/L3 optical packet switches are designed with optical output buffers. Only the header of optical packets is converted to electronic signals to control the wavelength of input ports and the packet payloads can be transparently destined to their output ports. An optical output buffer is designed to queue the packets when more than one incoming packet should reach to the same destination output port. For preserving service-packet sequencing and fairness of routing sequence, a priority scheme and a round-robin algorithm are adopted at the optical output buffer. The wavelength of input ports is designed for routing incoming packets using LCoS technologies. Finally, the proposed OFS (optical flow switch) with input buffers can quickly transfer the big data to the output ports and the main purpose of the OFS is to reduce the number of wavelength reflections. The all-optical content delivery network is comprised of the OFSs for a large amount of audio and video data transmissions in the future.

An Optical Packet Switch with Recirculation Limited Range Wavelength Converter Groups and Recirculation Optical Buffers

AbstractThis paper focuses on performances of limited range wavelength converters (LRWCs) in resolving optical packet contentions. An optical packet switch is proposed, which uses recirculation LRWC groups and recirculation fiber delay lines (FDLs) to resolve optical packet contentions. In order to make full use of the LRWCs and the FDLs, a control algorithm is also proposed. Packet loss probability of the proposed switch versus the number of FDLs, the wavelength conversion range, and the number of LRWC groups are evaluated in detail.

High-speed Optical Packet Switching for Photonic Datacenter Networks

High-speed Optical Packet Switching for Photonic Datacenter Networks

Huge capacity spacial division multiplexing transmission and integrated optical switching technologies (Invited Paper)

We review the research and development of beyond Pb/s capacity space-division-multiplexed transmission technology using multi-core optical fibers for satisfying the ever-increasing traffic demand. Moreover, we present an optical packet and circuit integrated network technology to improve switching capacity and flexibility in network nodes for the rapid traffic fluctuation and the data service diversification.

Performance evaluation of an AWG based optical router

Data centers are most important and integral part of internet. Now a day’s data centers works in collaborative way to solve large-scale problems. The performance of data centers can be further enhanced using fiber optic technology. Routing of data within data centers can be made possible using wavelength routing. Wavelength routing of data can be accomplished by using components like tunable wavelength converters and arrayed waveguide gratings. In routing and buffering optical packet need to be used. This leads to the development of optical switch. In this paper two AWG based switches are compared in terms of physical and network layer parameters, and it has been found that our design outperforms the other recent published design in terms of both physical and network layer parameters. Moreover our design is comparatively more cost effective.

Selective pumping and spatial hole burning for generation of photon wave packets with ray-wave duality in solid-state lasers

The selective pumping and the spatial hole burning are thoroughly considered to determine the excited transverse and longitudinal eigenmodes. By using the mode locking of the excited eigenmodes, an analytical wave representation is derived to manifest the ray-wave duality of the optical wave packet dynamics in the laser resonator. The derived wave function is employed to extract the parametric formula for the periodic ray orbits that reveal the subtle origin between the hyperbolic caustics and linear trajectories. Moreover, the temporal dynamics of the output beam for the total mode-locked state is theoretically demonstrated by combining with the parametric formula and the derived wave function. More importantly, an experiment based on the self-mode-locked laser is performed to make a comparison with theoretical analysis.

High speed optical 4-bit twisted ring counter using electro-optic effect of Mach-Zehnder interferometer

A 4-bit twisted ring counter is demonstrated utilizing the electro-optic effect of lithium niobate based Mach-Zehnder Interferometer (MZI). The MZI structures working on the principle of electro-optic effect show the powerful ability to switch the optical signal from one output port to the other. The theoretical description along with appropriate mathematical formulation is provided and the proposed device is analysed using beam propagation method. The proposed scheme will be helpful in optical signal processing and packet switching networks.

Novel virtual OCS in OPS data center networks

This paper considers a novel virtual optical circuit switching (VOCS) scheme for data center networks where short flows are transmitted via optical packet switching (OPS), while long flows with reliability requirement are transmitted via VOCS. VOCS preserves the advantage of optical circuit switching (OCS) for reliable communication, while it overcomes the disadvantage of OCS in terms of low link utilization. In the VOCS/OPS scheme, idle periods of the virtual circuits can be used by OPS, which thus enhances the overall performance. Simulations on a six-dimensional torus topology data center network with 4096 (=4$$^6$$6) nodes are conducted for the performance evaluation. We have observed that, compared to OCS, VOCS has much less adverse impact on the performance of OPS. Furthermore, quite a large number (i.e., 2048) of virtual circuits can be set up with little affect on the OPS performance.

Optical packet switch with energy-efficient hybrid optical/electronic buffering for data center and HPC networks

Advanced optical switching architectures, capable of scaling to thousands of ports while achieving low communication latency and reduced power consumption, are becoming a dominant theme for interco...

On Whether OCS Maximizes Application Throughput in All-Optical Datacenter Networks

Packet switching and circuit switching are the two main ways to operate all-optical networks in datacenters (DCs). Although optical circuit switching (OCS) is not a good fit for all scenarios, it is often considered appropriate for managing large flows. On the other hand, options based on packet switching, such as optical packet switching (OPS) or optical burst switching (OBS), are considered suitable mainly for small flows at best due to their lack of random-access buffers to manage packet contention. We accordingly study the throughput that applications can achieve in an all-optical DC network composed of fast all-optical switches, where large flows are managed by OCS and the rest by bufferless OPS. We focus on representative DC networks such as fat-trees, hypercubes, and rings, and take into account empirical application workloads, transport protocols, lack of RAM or fiber delay lines for buffering purposes in OPS switches, and characteristics of the network control plane. Surprisingly, we have found no scenario that requires OCS instead of OPS in order to increase application throughput; this holds even when all flows have unrealistically large sizes of tens of GB or larger. Counterintuitively, bufferless OPS offers much higher throughputs than OCS when managing large flows, and the lack of buffers in the OPS switches is irrelevant in this respect.

Demonstration of 100 Gbps optical packet switching using header processor based on 48-bit longest prefix matching

Wire-rate packet processing and its energy saving for over 100 Gbps speed of line are major issues to be resolved in optical packet switching (OPS) networks. For that purpose, we newly develop a high-speed, deterministic-latency electronic header processor based on longest prefix matching (LPM) for searching optical packet destination addresses (OP-DAs). This paper reports the successful experimental results of electronic header processing based on LPM search of up to 48 bits and optical switching of 100 Gbps optical packets by the use of the header processor. We demonstrate 48-bit LPM-capable optical packet switching. We also demonstrate IP packet transfer and 32-bit LPM-capable optical packet switching. In the latter demonstration, the 32-bit OP-DA of optical packets is directly copied from the 32-bit destination address of Internet Protocol version 4 (IPv4) packets. This result indicates that OPS networks can be deployed with electronic IP networks by the use of integrated network operation between OPS and IP networks.

OPS/Agile-OCS Data Center Network With Flow Management

Modeling and performance analysis of a data center network (DCN) combining optical packet switching (OPS) and agile optical circuit switching (OCS) in a unified platform are presented. Hybrid optoelectronic packet routers which combine optical switching fabric and electronic buffers are used, supporting 100 Gbit/s (25 Gbit/s × 4 wavelengths) optical packets. OCS transmission is implemented by a novel “express path,” (ExP) an instant wavelength path on demand, which enables certain flows following the ExP with no packet contention, whereas ordinary OPS packets are switched with a deflection routing algorithm and buffering for contention resolution. This architecture can support OCS for large and reliability-sensitive data transferring and OPS for latency-sensitive applications. The performance of the network is investigated via numerical simulations of top-of-rack switch (ToR)-to-ToR traffic in an N-dimensional (up to 4096 node) torus topology. We have made the following observations: 1) torus topology results in high throughput and can be scaled out by increasing the dimension; 2) contention resolution between OPS and agile OCS is needed and our proposed strategies enhance the overall performance; and 3) in a lightly to moderately loaded case of OPS traffic, more than 100 ExPs can be supported simultaneously with acceptable affect on OPS.

All-optical switching for 10-Gb/s packet data by using an ultralow-power optical bistability of photonic-crystal nanocavities.

An all-optical packet switching using bistable photonic crystal nanocavity memories was demonstrated for the first time. Nanocavity-waveguide coupling systems were configured for 1 × 1, 1 × 2, and 1 × 3 switches for 10-Gb/s optical packet, and they were all operated with an optical bias power of only a few μW. The power is several magnitudes lower than that of previously reported all-optical packet switches incorporating all-optical memories. A theoretical investigation indicated the optimum design for reducing the power consumption even further, and for realizing a higher data-rate capability and higher extinction. A small footprint and integrability are also features of our switches, which make them attractive for constructing an all-optical packet switching subsystem with a view to realizing optical routing on a chip.

Highly Robust Dual-Polarization Doubly Differential PSK Coherent Optical Packet Receiver for Energy Efficient Reconfigurable Networks

A dual polarization doubly differential phase shift keying coherent optical packet receiver that is robust against frequency offset transients and polarization demultiplexing problems is described in detail for energy efficient reconfigurable networks. Its performance is not affected by large frequency offsets. This leads to greatly reduced waiting times compared with previous coherent optical packet receivers, which in turn can significantly increase throughput in the coherent optical packet switched networks.

Bounded-Reorder Packet Scheduling in Optical Cut-Through Switch

The recently proposed optical cut-through (OpCut) switch holds a great potential in achieving high energy efficiency, as it allows optical packets to cut through the switch in optical domain whenever possible, which avoids power-hungry O/E/O conversion. In the OpCut switch, to ensure in-order transmission, only optical Head-of-Line (HOL) packet of a switch flow, i.e., the stream of packets sharing the same input and output port, is allowed to cut-through the switch, and optical HOL packets are always prioritized over buffered HOL packets to achieve high cut-through ratio, which is measured by the portion of packets cutting through the switch optically. However, under such priority rule, switch flows with buffered packets are at the risk of starvation, and the OpCut switch fails to achieve 100 percent throughput for all admissible i.i.d. traffics due to the unfairness in packet scheduling. To address this two issues, in this paper we propose a delay threshold rule for packet scheduling, in which buffered packets with delays exceeding a preset delay threshold are prioritized over optical packets. In the meanwhile, the cut-through ratio is very low under heavily congested traffic due to maintaining packet order, whereas the Internet is designed to accommodate a certain degree of packet reorder, which is very common in practice due to path multiplicity. In this paper, we design a bounded-reorder packet scheduling algorithm that significantly increases the cut-through ratio of the OpCut switch while allowing a small degree of out-of-order transmission. Our extensive simulation results show that the energy efficiency of OpCut switch can be significantly improved with only a very small degree of packet reordering, which has little adverse impact on the network application performance.

Torus Data Center Network With Smart Flow Control Enabled by Hybrid Optoelectronic Routers [Invited

A torus-topology photonic data center network with smart flow control is presented, where optical packet switching (OPS), optical circuit switching (OCS), and virtual OCS (VOCS) schemes are all enabled on a unified hardware platform via the combination of hybrid optoelectronic routers (HOPR) and a centralized network controller. An upgraded HOPR is being developed with the goal of handling 100 Gbps optical packets with a high energy efficiency of 90 mW/Gbps and low latency of less than 100 ns. The architecture of HOPR and its enabling technologies are reviewed, including a label processor, optical switch, and optoelectronic shared buffer. We also explain the concept and operation mechanisms of both the data and control planes in the hybrid OPS/OCS/VOCS torus network. The performance of these three transmission modes is evaluated by numerical simulations for a network composed of 4096 HOPRs.

Stimulated Brillouin scattering gain bandwidth reduction and applications in microwave photonics and optical signal processing

Stimulated Brillouin scattering (SBS) is one of the most dominant nonlinear effects in standard single-mode fibers and its unique spectral characteristics, especially the narrow bandwidth, enable many different applications. Most of the applications would benefit from a narrower bandwidth. Different methods for the bandwidth reduction of SBS in optical fibers are presented and discussed. A bandwidth reduction down to 17% of the natural gain can be achieved by the superposition of the gain with two losses or the utilization of a multistage system. Furthermore, applications in the field of microwave photonics and optical signal processing like high-resolution spectroscopy of communication signals, the storage of optical data packets as well as the processing of frequency combs including generation of millimeter waves and ideal sinc-shaped Nyquist pulses are presented.