Research On Photonic Network-on-Chips Architectures

With the rapidly advanced technology,a huge number of processors were able to be integrated in a single chip,such as Chip Multi-Processors(CMPs)or Multiprocessor Systemon-Chip(MPSoC).The conventional Electronic Network-on-Chip(ENoC)was the communication infrastructure of these processors.However,with the continuously increasing number of processors in the system and the shrinking size of the chip,the metallic wired ENoC suffered from some serious bottlenecks regarding the unbearable End-to-End(ETE)delay of data transmission,bandwidth,and energy consumption of the chip.Photonic Network-on-Chips(PNoCs)was proposed later on as a new technology to settle these issues and meet the high demands of the on-chip networks such as latency,throughput and power consumption.Since the first appearance of Photonic Network-on-Chip,tremendous research efforts have been done on both the industry and academic level to unleash the full potential of PNoCs.These studies have been focusing on different PNoC building blocks,such as network architecture,routing algorithms and wavelength assignments,etc.because improving them could lead to a spontaneous improvement in the overall performance of the network.In this dissertation,we first focused on the atomic component of PNoC,which is Optical Routers(ORs).Optical routers play a significant role in the data transmission process of the network;thus,they draw a major consideration when designing any photonic network.The major components of constructing an OR are photonic devices.For instance,waveguides,Microring Resonators(MRs),and Photonic Switching Elements(PSEs).The dilemma of increasing the insertion loss and power consumption in the optical router,in particular,and PNoC,in general,is caused by these components.This is because these components decide the Insertion Loss(IL)and crosstalk noise experienced by the transmitted signal within the network.Thus,many studies have been done to eliminate the number of photonic devices used in the optical router architecture and thus decrease the power dissipation.However,most of them cannot guarantee the minimum possible number of photonic devices.Therefore,we developed a method that can provide the least number of MRs in an optical router and reduces photonic devices accordingly.This method uses some shared photonic devices to realize some port-to-port communications and thus decrease the loss within the router.According to the developed method,we proposed a new 7×7 low-loss non-blocking optical router based on the Dimension Order Routing(DOR)algorithm.This optical router has the least possible number of many photonic devices such as MRs,waveguides and Optical Terminators(OTs).The appraisals show that the method proposed can reduce the worst-case insertion loss by almost 8.7%to 41.4%,as well as decrease the Optical Signal-to-Noise Ratio(OSNR)worst-case by almost 27.92%to 88%,compared to their opponents.It also reduces the power consumption by 3.22%to 23.99%.Another problem involving the photonic devices is reliability,which is one of ORs'major challenges.These photonic devices,especially MRs,are prone to breakdowns and failures,due to several reasons such as thermal status of the network or tuning issues,etc.When such component failure occurs,the optical router will not work efficiently,and the entire network will breakdown eventually.Some optical routers and routing algorithms have been proposed to overcome such dilemma.However,these researches can only be applied to few specific applications,which did not serve other applications to maintain the required reliability.Another drawback of some of the proposed designs is that it introduces some blocking or contention problems.Thus,in this dissertation we proposed a universal method that can be implemented in any optical router in order to increase the reliability,without exposing it to additional contention or blocking issues.In this method,we used a Reliable Ring Waveguide(RRW)to provide backup paths for each communication path within the original router.The data transmission within this reliable ring waveguide does not influence the data transmission within the original router.Furthermore,we proposed a simultaneous transmission probability analysis for optical routers to show the feasibility of our method.This simultaneous transmission probability analyses all the possible optical signals that can be transmitted at the same time within the router.The results show that the failure probability of the optical routers based on the proposed method is at most 5.19%compare with FTTDOR which has a failure probability of 5.79%.The simultaneous transmission probability is also improved by at least 10%compared to FT-OXY and at most 46%compared to NRFT.The simulation results using VPIphotonics Design Suite(VPI)shows that the worst-case insertion loss of the original router is increased by-0.5 dB using RRW and the worst-case insertion-loss using the backup path is increased by-1.5 dB.Furthermore,the worst-case insertion loss of our scheme can be reduced by 46.34%compared to other fault tolerant routers.The worst-case crosstalk noise is also reduced by 24.55%,at least,for the default path and 15.7%,at least,for the backup path compared to others.Finally,in the network level,the OSNR is increased by an average of 68.5%for the default path and an average of 15.9%for the backup path compared to FT-Crux default and backup paths,respectively,for the size of 4×4,6×6,8×8,10×10,and 12×12 2D mesh.Finally,this dissertation proposes a new Hybrid Concentrated NoC(HCNoC)as well in order to overcome the vertical transmission issue in 3D architectures.This hybrid NoC incorporates electrical and optical interconnects in the architecture.This architecture benefits from the simple structure of 2D architectures;moreover,reduces the optical devices in the network.The large number of low bandwidth optical links offers high bisection bandwidth with less power dissipation due to lower average optical losses.The electrical interconnections are used to transmit short distance traffic,whereas the optical interconnections are used to transmit signals sent to long distances to overcome their increased latency.This architecture decreases the ETE delay and increases the throughput of the network.The layout analysis show that the number of MRs used in 3D HCNoC is reduced by 53.9%and 66.7%compared to 3D Omesh and 3D MONoC,respectively.Moreover,the diameter of the network is reduced by 27%and 11.1%compared to 3D Omesh and 3D MONoC,respectively.The simulation results using OPNET simulator shows that in terms of network latency and throughput performance,3D HCNoC is better than 3D MONoC and 3D Omesh under different traffic models.