Silicon Photonics 4×4 Non-blocking Optical Switch Fabric Based On Cascaded Multimode Interferometers And Packaging

With the continuous increase of the network traffic,the present network technology suffers from the increase of electric power and traffic capacity.Future network technologies should resolve such an energy bottleneck in order to be scalable and sustainable.It should be capable of handling several orders of magnitude larger network traffic with lower power consumption than that of the present.One plausible approach is the use of dynamic optical path networks(DOPN),in which high-port-count,low-cost,non-blocking,N×N optical switches play an essential role.The multimode interferometer(MMI)couplers have been widely applied and been regarded as the key components in integrated optics.They function as efficient splitters and combiners for optical beams,while processing the advantages of low excess loss,low crosstalk,accurate splitting ratio,small device size,and good fabrication tolerance.Furthermore,it can be maintained independent of polarization for operation over a board range of wavelength.Owing to those superior performances,MMI couplers have been utilized as building blocks in more complex devices such as generalized Mach-Zehnder interferometer(GMZI)switches,on which N×N optical switches can be built.As an N×N GMZI switch only has N switching states,it can't achieve non-blocking switching.Therefore,cascaded GMZIs are used to build non-blocking switches.The thesis focuses on the 4×4 non-blocking optical switch fabric based on cascaded GMZIs.The switch fabric studied in the thesis is composed of 4×4,3×3 and 2×2 MMI pairs cascaded in series.The total number of switching states is 4×3×2=24,allowing for non-blocking switching.The optical paths in these switching states are not equal,so the on-chip loss is path-dependent,leading to variation in insertion loss.However,this structure only incorporates 3 GMZI switching elements,and hence it has more compact size and less phase shifters.Experimental results show that the on-chip loss of the switch is 3.7dB~13.1dB,the worst crosstalk of all switching sates is-7.2 dB,and the average thermo-optic switching power consumption is 104.8mW.We also perform optical data transmission experiments using a 25 Gbps On-Off keying(OOK)signal to verify the signal fidelity after switching.The function of optical path switching using this optical switch is thus verified.The thesis also explores the optical package technologies for silicon photonics devices.With multiple experiments,the experimental procedures for optical device package are mastered.By improving the experimental setup and optimizing the experimental procedures,the package is successful,resulting in an ultra-low excess loss of the packaged device.