| The continuous improvement in computing performance and multi-tasking simultaneous processing capabilities is an inevitable trend of chip development.Along with gradual maturity of manufacturing technology,on-chip devices have been integrated in nano-scale,and multiprocessor systems-on-chip(MPSoCs)has become the mainstream of on-chip design.However,owing to the delay,bandwidth and power consumption issues,the electrical networks-on-chip(ENoCs)already are unable to satisfy for the demands of MPSoCs development.The appearance of optical networks-on-chip(ONoCs)has become a new kind of on-chip multiprocessor interconnection method that can replace the electrical connection and can effectively solve the problems faced by the ENoCs,and it combines both characteristics that uses the electrical interconnect layers to implement arbitration control and optical layer to implement data transfer.Although optical interconnections can make up for many shortcomings of electrical interconnects,the continuous increase of chip data processing and transmission quantity have led to the ONoCs with single wavelength can no longer meet people's requirements for communication quality.Wavelength division multiplexing(WDM)technology applied on ONoCs can expand the capacity of optical links by augmenting the number of multiplexing wavelengths,thus realizing the large-capacity,large-scale and high-rate on-chip data transmission and effectively solving the disadvantage of single-wavelength ONoCs.WDM-based ONoCs has great application prospects in the fields of big data processing and high-speed communications networks,and it has become the focus of the research.Moreover,the continuous innovation of silicon-based optical device structures and continuous improvement of performance have directly promoted the WDM-based ONoCs as the main design mode of on-chip networks.Optical lasers,modulators,optical routers,photodetectors and other devices integrated on a SOI chip are major components of WDM-based ONoCs.Due to the nature of the device material,multiple signals will be affected by loss and crosstalk noise during transmission thus resulting in signal attenuation and distortion.Compared to single-wavelength ONoCs,multi-channel parallel transmission will result in four-wave mixing(FWM)effect,thus signal suffering from nonlinear crosstalk noise will be more serious in WDM-based ONoCs.Moreover,it also aggravate the magnitude of crosstalk noise at the destination node and results in signal distortion,the decrease of optical signal-to-noise ratio(OSNR)and the increase of bit error rate(BER).The main function of WDM-based ONoCs is to efficiently accomplish the data transmission and exchange among multiple cores with a high level of quality,but the main factors affecting network performance is the loss and crosstalk noise,which also determines the network scale.Therefore,this paper will use WDM-based Torus network to propose the theoretical architecture of the loss and crosstalk calculations and network performance analysis method.The main contents of this paper are as follows:1.The theories of WDM-based ONoCs are expounded,and the basic principle of FWM and the calculation method of FWM nonlinear crosstalk noise in the network are analyzed2.Based on the physical structure and principle of SOI microring resonators,the model of WDM-based basic optical switching elements(BOSEs)which is composed of silicon waveguide and microring resonators with different resonant wavelengths are proposed.By analyzing the BOSEs output optical power and crosstalk noise power of each port from different states,the foundation of the network loss and crosstalk noise model are established.3.Based on the analysis of BOSEs,a five-port optical router model that can be applied to the networks is designed,and the exchange mechanism and routing algorithm adopted in the network are proposed.Besides,the loss calculation formulas between different port pairs and the crosstalk analysis model due to the link crossing are summarized and illustrate with a specific example.4.According to the XY routing algorithm,a method for analyzing the power loss,crosstalk noise,OSNR,and BER of a signal from a source node to a destination node is established.Moreover,the theoretical derivation of the worst optical link selection is proposed.5.WDM-based optimized Crossbar and Crux(WOPC,WCX)optical routers are used in the simulation,and the worst-case optical link and maximum network size are obtained.Furthermore,we built a network model using Optisystem and OPNET,and the signal transmission quality,ETE delay and throughput characteristics are analyzed directly.Simulation results show that the network scalability and signal transmission quality are closely related to the loss characteristics of silicon photonic devices and the crosstalk noise power accumulated on the signals.The effective control of power loss and crosstalk noise are the key to increase OSNR and reduce the BER.For example,when meeting the worst case,if the input optical signals power is Odbm,the network size can reach 6÷5 when WCX routers are used,and the average OSNR,signal power and crosstalk noise power are 1.2dB,-32.6dBm and-33.8dBm,respectively.These values are only-6.9dB,-41.4dBm,-34.4dBm when the WOPC routers are adopted in the same condition.The decrease of signal power and the increase of crosstalk noise lead to the reduction of OSNR,and finally have a negative influences on network performance. |
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