The crosstalk problem is introduced by an optical multistage interconnection network, which is caused by coupling two signals within a switching element. To avoid this crosstalk, a time domain approach is used, which is to partition the set of the connections into several subsets such that the connections in each subset can be established simultaneously in the network without crosstalk. Since we want to partition the messages to be sent to the network into several groups, we have to use a window method that is used for finding the conflicts among all the messages to be sent. In this paper, we proposed two parallel window method algorithms called unbalanced parallel window method (UPWM) and balanced parallel window method (BPWM) algorithms. The UPMW algorithm reduced the execution time approximately 79%, whereas the BPMW algorithm reduced 85% of the time compared to the sequential algorithm if we use seven processors.