Large Capacity Short Reach Optical Communications For Datacenter Interconnect

The global traffic is witnessing an exponential growth due to the emergy bandwidth-hungry applications,such as Virtual reality,video based social network and Cloud services.Datacenter,where the growing amount of data traffic storage,processing,calculation and transmission are carried out,is becoming essential for the information society.According to the forcast,the bandwidth requirement of whale-scale datacenters will increase 20 folds every 4 years.Such data-hunger posing a big challenge in terms of capacity and energy consumption.As a future-proof technology of high capacity,low loss,and high energy efficiency,fiber optic communication is implemented in different segment of networks,is now extending its application in delivering green transmission solution for datacenters.On the other hand,the networking part in datacetners is still carried out by commercial Ethernet switches.The optical-electrical-optical conversion is not only unefficient in energy consumption,but also causing severe delay,which in turn brings a need for high-capacity and energy-efficient solutions.To address the problems mentioned above,we proposed coupler-based passive optical interconnect(POI)as an energy-efficient solution thanks to the fact that passive optical components are manily used for interconnecting different ports.The broadcast nature of coupler is also suitable for the multi-cast and burstness of the intra-datacenter traffic.However,due to the high insertion loss of the optical coupler,the scalability of such architecture is question marked.To evaluate the scalability of the architecture,we developed a methodology not limited to the insertion loss of devices in the link,but also including the type and bandwidth of receiver,modulation formats and decision threshold.Based on the methodology,the impact of introducing an amplifier for a shared group on cost,energy consumption and scalability was also studied.A cycle-based medium access control(MAC)protocol was proposed for the efficient management of the exchange of the control message and data transmission.We also proposed a dynamic time/wavelengths resource allocation algorithm to evaluate the network performance of the coupler-based POI in terms of average packet delay and packet loss ratio.Equiped with 10 Gbps optical network interface,an average delay of millisecond can be realized.In the meanwhile,the impact factor of the scale of POI,transmission window and tuning time of the transceivers were discussed.We introduced the physical-layer network coding(PLNC)into the coupler-based POI and evaluated the proposed scheme from both the physical-layer and network-layer.From the physical-layer,we experimentally demonstrated the feasibility of the application of PLNC in POI by realizing the all optical PLNC in dense wavelength division multiplexing system with 50 GHz grid using different modulation formats.From the network-layer,the dynamic resource algorithm proposed for the POI was tailored to be fit for the characteristic of PLNC.Simulation was carried out showing that the average packet delay can be reduced by around 100 times by deploying PLNC at POI under high traffic load.Moreover,the packet loss ratio can be also suppressed by using PLNC with unefficient wavelengths resource.Last but not lease,targeting the high-bandwidth and delay sensitive requirement in datacenters,a reali-time 100 Gbps signal transmission over single-mode fiber is demonstrated.Electrical duobianry(EDB)scheme is used to achieved the real-time communication.The generation and the decision of the electrical signal are realized on the EDB transmitter and receiver chipsets respectively.The OEO conversion are realized by the monolithically integrated broadband electroabsorption modulated laser and a PIN photodetector.Any form of digital signal processing is avoided in the demonstration,proving the possibility of time-and power-efficient communication for datacenter interconnect.