Optical Interconnects In Datacenters Based On WDM-PON

With the growing scale of the datacenters and the increasing performance of the servers,the datacenter network also has the demand for high bandwidth and low power consumption.The passive optical network(PON),as a technology getting mature in access network,realize an access network with high data rate and low power consumption with passive optical components.So the application of PON in the datacenter network is expected to satisfy the requirements of datacenters.Many architectures of the datacenter network have been proposed.But most of the researches focus on the interconnects between the racks while the switches are still employed in the racks.In the proposed optical interconnects,the optical switch matrix(OSM)and semiconductor optical amplifier(SOA)are mostly used to realize the link switch.Because of the large amount of the active optical devices in these schemes,they usually have high power consumption.And the controls of those active optical devices increase the difficulty of the design of the control plane.The technology of PON is regarded as a solution for this problems.Considering the issues above,we focus our work on the optical interconnects in the datacenters.In this thesis,we proposed three different structures for the intra-rack passive optical interconnects based on WDM-PON between the servers in racks.These structures also offer an up-and down-link for the rack.They employ different wavelength tunable devices and have different characteristics to satisfy different requirements.And we also take a scheme for inter-rack communications based on OSM as example to show the combination of the proposed schemes and the inter-rack schemes.With the calculation of the insertion loss,simulations and experiments,we test and evaluate the transmission performance of the optical links,and prove the feasibility of the proposed shemes.Then we introduce an medium access control protocol which can be employed in the schemes we proposed.With setting a master server in each rack,the protocol can handle the transmission in the rack.The results of the simulations prove that the protocol plays an important role in reducing the delay and improving the performance of the network.And we also calculate the cost and power consumption of the 3 schemes and compare the results with the scheme based on commodity switches.The results shows that the schems have advantage of the power comsuption.Based on data in literatures,we also made a prediction on the cost of the schemes in the future,and analyzed the sensitivity of the total cost to the prices of different components.In this thesis,we also propose passive optical interconnects based on 2-stage cascaded arrayed waveguide grating routers(AWGRs).With the 2-stage AWGRs based structure,we first realize the connection in the cluster.Then with the relay rack,we realize the extension of the structure and make the architecture able to offer the interconnects in the whole datacenter.Considering the impact of the crosstalk in the AWGRs,we propose a crosstalk suppression scheme based on optical power equalization and polarization control.The results of the experiments prove the necessary of the crosstalk suppression scheme and the feasibility of the passive optical interconnects.And we make a research on the circuit switching and packet switching.For the circuit switching,we introduce a scheme based on multiple path and increasing the transceivers,which can reduce the blocking probability.For the packet switching,we proposed a decentralized protocol,which can avoid the collisions and improve the network performance.