Research On Reliability Of On-Chip Optical Interconnect

With the increasing demand for high performance computing and the rapid development of semiconductor technology,the number of processor cores integrated in a single chip is increasing.In multi-core system,an efficient communication architecture is critical to system performance.As the number of cores continues to increase,the electrical network-on-chip(No C)cannot continue to balance power,latency and reliability.The on-chip optical interconnect can effectively solve the current problem owing to its low latency,high bandwidth density,low power consumption and low electromagnetic interference.A large number of microring resonators are used in the optical network-on-chip(ONo C).But microring resonators inevitably introduce crosstalk noise and insertion loss because of their imperfection.Moreover,thermo-optic effect will lead to an operation point drift,and ultimately have a serious impact on the signal-to-noise rate(SNR).In this thesis,the reliability of on-chip optical interconnect is studied,and the influence of crosstalk noise and thermal effect on the reliability of on-chip optical interconnect is studied emphatically.Aiming at the problem of SNR reduction caused by crosstalk noise,the thesis proposes a crosstalk-aware wavelength assignment(CWA)method.By analyzing the transmission paths in the mesh-based ONo C which adopted dimension order routing algorithm,the paths can be divided into 8 subsets according to their transmission directions.Different communication wavelengths are assigned to the communication requests in different subsets.Therefore,the intra-channel crosstalk noise is reduced in the optical router and even in the network.In addition,a simple optical router structure is designed to support the CWA method.It can reduce the intra-channel crosstalk noise and insertion loss by decreasing the number of microring resonators in the router structure.The analysis results show reductions in worst-case crosstalk noise power by up to 50% and improvements in worst-case SNR by up to 3 times on average.In order to solve the problem of signal quality degradation caused by thermal effect,the thesis proposes a thermal-aware power allocation model.The model calculates the laser power required by each communication request under different on-chip thermal distribution scenarios to satisfy the minimum SNR requirement in the network.In addition,time division multiplexing technology is adopted to solve the power allocation conflicts and communication path conflicts in the network.In order to minimize the number of slots under the premise of satisfying the enough power supply,the thesis establishes an optimization model for the network with a particular topology.Moreover,a slot allocation algorithm based on genetic algorithm is proposed to solve the model.The simulation results indicate that our proposed scheme can make the communication requests meet the SNR requirement of the network in 4 different on-chip thermal distribution scenarios,while saving an average of 66.7% of the laser power.