All-Optical Digital Logic Operations For DPSK Signals

High-speed all-optical logic operations appropriate for advanced modulation formatsignals are the key technique of the large-capacity long-distance all-optical communicationnetwork. As semiconductor optical amplifier (SOA) has good nonlinear and integratablecharacteristics, it is suitable for used to fabricate all-optical logic function device and hashave wide applications. Theoretical and experimental researches on all-optical logicminterms, maxterms and complex logics, such as reconfigurable all-optical full-adder andfull-subtractor at40Gbit/s based on nonlinear effects in ultrafast SOA are presented in thisthesis, supported by the National Natural Science Foundation of China under Grant No.60877056, China National Funds for Distinguished Young Scientists (Grant No.61125501)and the National Basic Research Program of China (Grant No.2011CB301704). The maincontents are listed as follows:(1) The research background and significance of all-optical digital logic operationsespecially for advanced modulation format signals are clarified. The research processes ofhigh-speed logic operations based on nonlinear effects in SOA are summarized. The idea ofutilizing the construction of SOA cascaded with bandpass filter which is based on cross-gainmodulation (XGM) and transient cross phase modulation (T-XPM) effect in SOA to achievelogic operations for DPSK signals is proposed.(2) The theoretical model of ultrafast SOA cascaded with bandpass filter is introduced.Also, the principle and theoretical model of the demodulation processes for DPSK signalsusing Delay interferometer (DI) are introduced. The demodulation processes of DPSKsignals have been simplified simulated. The AB and NOR logic operations of two inputRZ-DPSK signals based on the XGM and T-XPM of SOA are simulated, and the influencesof the power of the input data signal, the filter detuning on the performances of output logicsignals are analyzed theoretically.(3) The concept, characteristics and research significance of the logic minterms andmaxterms are introduced. The generation method of reconfigurable and scalable all-opticallogic units is proposed utilizing the model of SOA cascading detuning filter and theflexibility of DI demodulating DPSK signals. All-optical multi-input reconfigurable all-optical logic minterm and maxterm generations for DPSK signals at40Gbit/s, as well asthe relation between their performances and working conditions are experimentally studiedusing the above scheme. The experimental results show that all the output logic signalsexhibit good quality, which can be used to construct arbitrary and complex logic operations.(4) Two schemes of realizing ultrahigh speed (40Gbit/s) reconfigurable all-opticalfull-adder and full-subtractor are proposed and researched. The sum/difference is realized byXOR gate based on FWM through the first SOA. The carryout/borrowoutis realized bycoupling reconfigurable logic minterms based on XGM through another three parallel SOAsand cascaded logic operations in SOAs, respectively. Above two schemes are experimentallydemonstrated at40Gbit/s. Their good output performances show that all-optical logicminterms are expected to be further used to construct arbitrary logic operation and SOA canbe used for cascaded high speed digital logic operations.