Research On Reducing IFFT/FFT Complexity In Optical Orthogonal Frequency Division Multiplexing System

Optical Orthogonal Frequency Division Multiplexing(O-OFDM)technology combines the advantages of fiber-optic communication technology and Orthogonal Frequency Division Multiplexing(OFDM)technology,it has gradually become a new type of optical transmission technology with a wide range of applications.With the rapid development of Field Programmable Gate Array(FPGA)technology and the maturity of its devices,FPGA-based O-OFDM research has drew extensive attention.Due to the requirement of transmission rate,the dual-band O-OFDM system can better meet the demand for high transmission rate and large capacity.However,the system complexity and FPGA logic resource utilization brought by the dual-band O-OFDM system is much higher than the baseband system.In particular,IFFT/FFT is the core module of the dual-band O-OFDM system,which mostly depends on the logic resource utilization of the system.Therefore,in order to reduce the logic resource utilization of IFFT/FFT in a dual-band O-OFDM system,a conjugate transform algorithm can be employed.In the dual-band O-OFDM system,the algorithm can reduce a pair of IFFT/FFT,so that the dual-band system is similar to the baseband system,and only a pair of IFFT/FFT operations to achieve dual-band signal transmission.In this thesis,the focus is to propose and study a FPGA-based conjugate transform dual-band Optical OFDM system.After the IFFT/FFT conjugate transformation,the higher transmission rate can be achieved while reducing the complexity of the dual-band system and the utilization of FPGA logic resources.Firstly,a baseband system and a common dual-band system are designed through the circuit respectively,and the respective advantages are obtained by comparing these two systems.The baseband system is simple and the PFGA logic resource utilization is about half lower than the dual-band system,whereas the dual-band system has a higher transmission rate.In order to combine the advantages,it is proposed to use the conjugate transform for optimizing the core module IFFT/FFT and reducing the logic resource utilization of the dual-band system.Then through Matlab modeling and simulation,and Quartus design circuit and simulation waveform,the feasibility of the algorithm is verified when applied to hardware circuits.Finally,the conjugate transform of IFFT/FFT is applied to 32-point and 64-point dual-band O-OFDM systems,compared with 32-point and 64-point common dual-band O-OFDM systems.Then calculating the mean squared value of the error and the FPGA logic resource utilization.Verifying the correctness and feasibility of dual-band O-OFDM systems based on conjugate transformation.In addition,compared to common dual-band systems,FPGA logic resource utilization can be reduced by 40%-50%.