Research On All-Optical Programmable Logic Array Based On Canonical Logic Units

The development of all-optical logic goes through from single logic function to reconfigurable logic functions.Recently,with the upsurge of artificial intelligence,the intelligent signal processing technology,which are applied to all-optical communication networks and optical computing,has gradually become a research hotspot.The realization of all-optical programmable logic operation can not only take an important step towards intelligence,but also help the logic system to achieve performance improvement in practical applications.Programmable logic array(PLA)is a further development of reconfigurable logic operation.By improving the flexibility of output logic functions with programmable selection,PLA can meet users' definition.Besides,by setting multiple programmable control points,PLA can also output diverse logic results.This dissertation focuses on investigation of the computing capacity expansion and integration of all-optical PLA.On the one hand,the methods of expanding the computing capacity of PLA are analyzed systematically,and the general structure of the expanded PLA is proposed and experimentally demonstrated.On the other hand,the integrated all-optical PLA is designed and experimentally demonstrated.The main achievements are listed as follows.(1)The general structure of the expanded PLA is studied theoretically.Comparing with operation in electric domain,operation in optical domain has the advantages of operation speed and the parallelism of light.Attributing to the parallelism of light,a variety of logic functions can be realized simultaneously in different spatial channels and different wavelength channels in only one logic device.Therefore,based on the ideas of increasing the output ports and the canonical logic units(CLUs)wavelength channels of the logic device,we propose three feasible methods to expand the computing capacity of the PLA: the first is introducing bidirectional structure of the logic device,the second is the wavelength multicasting of the four-wave mixing(FWM),and the third is using several nonlinear effects simultaneously.Based on these methods,we propose the general structure of the expanded CLUs-PLA,and analyzed the computing capacity of the structure quantitatively.The conclusion is that,comparing with the standard CLUs-PLA,the computing capacity of the expanded CLUs-PLA will be significantly enlarged,with the increasing number of wavelength channels of different types of CLUs.(2)Two-input and three-input expanded PLAs based on highly nonlinear fiber(HNLF)are experimentally demonstrated.Firstly,the numerical analysis of the expanded CLUs-PLA scheme based on four-wave mixing is carried out.The influence of wavelength location and wavelength spacing of the input signals,and the HNLF length on the FWM efficiency is analyzed.The conclusion is that the FWM conversion efficiency will reach the maximum,when the pump wavelength is red-shifted from the zero dispersion wavelength by 1.6 nm.When the HNLF length is reduced from 1000 m to 300 m,the FWM conversion bandwidth will increase from 3.2 nm to 6.4 nm.Then,based on the methods of bidirectional structure and FWM multicast,we experimentally demonstrate the two-input CLUs-PLA with capacity expansion of 4 times,the two-input CLUs-PLA with capacity expansion of 10 times and three-input CLUs-PLA with capacity expansion of 7.5 times,respectively.Finally,on the one hand,we theoretically analyze the quality of the output signals in the experiment.On the other hand,we analyze the feasibility of the integration of the proposed schemes in the active or passive platform,and it is concluded that the expanded CLUs-PLA has the potential to be realized in the active or passive platform.(3)The integrated all-optical PLA based on semiconductor optical amplifier(SOA)at 40 Gb/s is studied systematically.We design and manufacture an integrated all-optical PLA chip,which mainly includes delay interferometer(DI)and SOAs with different lengths.DI acts as the input circuit,whose role is to demodulate differential phase shift keying(DPSK)signals to produce complementary data streams.The longer SOAs are used as nonlinear mediums to realize FWM or cross-gain modulation(XGM)process.The shorter SOAs are used as switches array to select the proper minterms to output.Firstly,we experimentally demonstrate the function of the input circuit,the CLUs generation of the CLUs array and the switching function of the switches array,when the PLA works in the two modes of FWM and XGM,respectively.Then,we numerical analyze the different influences of the parameters of the DI on the logic results in different working modes.Finally,we discuss the extensibility of the integrated PLA from three aspects of wavelength correlation,working speed,and computing capacity,then we draw conclusions: 1)the wavelength flexibility of the PLA can be improved by adding a phase shifter in one arm of the DI;2)the integrated PLA has the potential to work at higher speed using FWM or XGM;3)the integrated PLA has the potential to expand the computing capacity by increasing the wavelength channels of CLUs,and the two-input PLA can also expand to multiple-input PLA by increasing the number of input signals.