Optical buffering is known to significantly improve the performance of optical packet and burst switched networks and a number of useful analytic models for the case of Poisson traffic have been proposed previously. In this paper, we propose an approximate analytic model for generally distributed arrivals, specifically treating Gammadistributed interarrival times, and show that the variance of the traffic has a significant impact on performance. The analysis is formulated in terms of virtual traffic flows within the optical switch from which we derive expressions for burst blocking probability, fibre delay line occupancy and mean delay. Emphasis is on approximations, by way of momentmatching techniques, that give good numerical efficiency so that the method can be useful for formulating dimensioning problems for large-scale networks. Numerical solution values from the proposed analysis method are compared with results from a discrete-event simulation of an optical burst switch. © 2011 ACADEMY PUBLISHER.