Time-domain equalizer (TDE) is one of the most important modules in high-s peed coherent optical digital receivers.Starting from the implementation need,this paper analyzes and studie s the effect of the feedback delay on the convergence of the time-domain equalizers in details,pro poses a simplified theoretical analysis method,and verifies its effectiveness through simulation results with optical f iber dispersive channels.The theoretical analysis results show that for small iteration step size,the feedba ck delay has negligible effect on the equalizer′s convergence,and the equalizer′s performance after convergence ha s no difference with respect to the ideal case of no feedback delay.However,as the feedback delay increases,the f eedback delay causes the equalizer′s coefficients to oscillate and the equalizer becomes divergent as a result of large feedback delays. Meanwhile,the feedback delay will greatly reduce the maximum allowed step size for the equalizers and slow down the convergence speed.Then,we study the time-domain equaliz ers with optical fiber dispersive channels based on numerical simulations.The simulation results verify the eff ectiveness of the above theoretical method.Based on simulations,the maximum allowed step sizes at different fee dback delays are also obtained,which decrease from 1to 0.1as the feedback dela y increases.