The linear transmission impairments,such as the timing offset(TO),frequency offset(FO),and chromatic dispersion(CD),are major factors of signal degradations in coherent optical fiber communication systems.The estimati...The linear transmission impairments,such as the timing offset(TO),frequency offset(FO),and chromatic dispersion(CD),are major factors of signal degradations in coherent optical fiber communication systems.The estimation and compensation of such impairments play significant roles in the receiver side digital signal processing(DSP)unit.In this paper,we propose to combat the linear impairments systematically(including TO,FO and CD)with a joint timefrequency signal processing by taking the advantage of fractional Fourier transform(FrFT).In view of geometrical analysis,TO/FO induces a shift in time/frequency coordinate and the CD leads to the rotation in the fractional domain.Both mathematical derivations and geometrical interpretations have been established to unveil the relationships between impairments and linear frequency modulated(LFM)training symbols(TSs).By considering a typical coherent optical orthogonal frequency-division multiplexing(COOFDM)transmission system,three kinds of linear impairments have been jointly estimated by simple geometric calculations using appropriately designed TS based on FrFTs.Simulation and experimental results confirmed the feasibility of time-frequency techniques with better accuracy,less complexity,and improved spectral efficiency.展开更多
文摘The linear transmission impairments,such as the timing offset(TO),frequency offset(FO),and chromatic dispersion(CD),are major factors of signal degradations in coherent optical fiber communication systems.The estimation and compensation of such impairments play significant roles in the receiver side digital signal processing(DSP)unit.In this paper,we propose to combat the linear impairments systematically(including TO,FO and CD)with a joint timefrequency signal processing by taking the advantage of fractional Fourier transform(FrFT).In view of geometrical analysis,TO/FO induces a shift in time/frequency coordinate and the CD leads to the rotation in the fractional domain.Both mathematical derivations and geometrical interpretations have been established to unveil the relationships between impairments and linear frequency modulated(LFM)training symbols(TSs).By considering a typical coherent optical orthogonal frequency-division multiplexing(COOFDM)transmission system,three kinds of linear impairments have been jointly estimated by simple geometric calculations using appropriately designed TS based on FrFTs.Simulation and experimental results confirmed the feasibility of time-frequency techniques with better accuracy,less complexity,and improved spectral efficiency.
