The system performance of optical buffing is investigated based on fiber delay lines in asynchronous optical packet-switched networks. The queuing model here is different from other papers in that the interval of optical packet arrival is defined by Weibull distribution, which has been demonstrated to be a suitable traffic model for WWW service. Through numerical analysis, conclusions show that the system performance of optical buffering, such as packet loss possibility, the average waiting time, can be optimized by the proper design of the delay unit and the buffering depth for given traffic load.