Research And Optimization On Communication Reliability Of Optical Networks-on-chip

Driven by the explosive growth of application demand in the information age,the realization of the super information processing system with high reliability and computing performance is an inevitable trend for the development of system-on-chip.As the significant progress in complementary metal oxide semiconductor(CMOS)technology,multi-core processors system,which integrates hundreds to thousands processor cores on a single chip,has been realized.In the multi-processor systems-on-chip,due to the parallel processing of multi-tasks and the frequent exchange of massive data between processing cores,an efficient communication architecture is urgently needed to realize the high-performance information processing of the system.Thanks to the rapid development of silicon photonics technology which is compatible to CMOS,it gives optical networkson-chip(ONo Cs)the capacity to effectively solve the problems of high latency,high loss,bandwidth limitation,and low communication efficiency caused by traditional electrical interconnections.With powerful parallel computing capability,excellent resource utilization,and wonderful scalability,ONo Cs have broad application prospects in the fields of ultra-high-speed optical communications,supercomputer systems,and computer architecture design.Furthermore,the application of wavelength division multiplexing technology to the ONo Cs can meet the needs of wide communication bandwidth for ultra-high speed and ultra-large capacity.However,the communication reliability of the on-chip multi-core optical networks cannot be effectively guaranteed nowadays.On the one hand,due to the material properties of the silicon-based photonic devices and the imperfections of the current manufacturing process,the optical signal will inevitably suffer from inherent physical loss and crosstalk noise during the transmission process,it results in the decrease of optical signal-to-noise ratio(OSNR)and the increase of bit error rate(BER)of multi-hop communication in network.On the other hand,silicon-based optical switch components are very sensitive to the variation of temperature and deviation of manufacturing process.Slight changes in temperature and manufacturing process will cause the shift of the optical switch resonant wavelengths.As a result,the physical performance of optical communication link becomes worse,which has a negative impact on the communication performance and reliability of the system.Especially for the ONo Cs utilizing wavelength division multiplexing(WDM)technology,the reduction in data communication reliability caused by the above-mentioned problems is more serious.Therefore,in this doctoral dissertation,relevant researches have been carried out on how to improve the communication reliability of ONo Cs,and the following research results have been obtained:1.Aiming at the crosstalk characteristics in the multi-wavelength ONo Cs,the angle optimization(60°/120° waveguide crossing)method is applied to the optical router layer and the optical network layer with WDM technology to improve the physics performance of the optical communication link and reduce the BER of signal transmission in the optical network.First,the complete analysis models of insertion loss and crosstalk characteristic in optical component level,optical router level,and optical network level are constructed hierarchically.Secondly,the architecture of optimized Crossbar and Crux optical router are proposed based on the angle optimization method and theoretical analysis model.The positive influence of the angle optimization method on the crosstalk characteristics of the optical router and the performance of the OSNR of each port is analyzed.Finally,the angle-optimized optical routers are applied into the optical network layer,and the numerical simulation analysis of the optical network layer is carried out based on the ONo Cs with Mesh and Torus topology.According to the simulation results,the angle optimization method can improve the average OSNR by about 1.5 d B under the parameters used in this doctoral dissertation.The OSNR and BER performance of multi-wavelength on-chip optical routers and ONo Cs is effectively improved.Therefore,the lower BER transmission can be realized and the reliability of data communication can be improved.2.The channel coding technology is applied to ONo Cs,the all-electrical,all-optical,and optical-electrical hybrid group counting encoders based on micro-ring resonators are designed with strong error detection ability of the group counting coding method.Based on the simulation software Interconnect,the correctness and feasibility of the proposed optical-electrical group counting encoder are verified.Its error detection efficiency,energy consumption,and area overhead are also analyzed and evaluated in detail.The analysis results show that the error detection efficiency of the group counting coding mechanism can reach 88.2%,which is 36.6% higher than the parity check coding mechanism.The energy consumptions in worst case of all-electrical,all-optical,and optical-electrical hybrid group-counting encoder are 0.260 f J/bit,56.000 f J/bit and 30.386 f J/bit respectively.In addition,the area of the optical group counting encoder accounts for a very small proportion of the entire chip.When the Mesh and Torus ONo Cs scales increase to10×10,the area overhead of optical group counting encoder accounts for less than 0.15%.3.A novel high-reliability communication system which is suitable for ONo Cs is proposed and designed.It has error detection and data retransmission functions,which can effectively ensure the correctness of the data received by the destination node.On this basis,in order to reduce the influence of crosstalk on the communication reliability,the retransmission mechanism is optimized,which further improves the reliability of data retransmission.With the help of the simulation software Opti System,the feasibility and effectiveness of the optical group counting mechanism which can achieve a reliable optical communication system are visually demonstrated and the proposed optical communication mechanism is verified to improve the reliability of data communication in ONo Cs.In addition,the commonly used parity check mechanism is selected as a comparison,and the power consumption and time delay overhead of this reliable on-chip optical communication system are comprehensively evaluated through comparison between different communication mechanisms.The analysis results show that due to the addition of the laser sources,coding and calibration circuits,the reliable transmission of 4 bits data using the group counting mechanism requires an additional 26.4% power consumption compared with the direct transmission without error detection.And it consumes 16.3%power consumption more than the parity check mechanism.Moreover,compared with the data transmission only with parity check mechanism,the zero-load end-to-end delay of the data errors retransmission with parity check is more than about 35%,and data errors retransmission with group counting mechanism is about 39% more than data transmission only with group counting mechanism.The reliability improvement technology proposed in this doctoral dissertation is feasible to implement in current chip integration and can effectively improve the reliability of data communication in the multi-core ONo Cs.It has potential applications in the field of optical communication and large-scale ONo Cs.It provides a theoretical basis and technical reserve for the realization of reliable on-chip optical communication systems.