One major challenge for Grid environments is how to efficiently utilize geographically distributed resources given large communication latency introduced by wide area networks interconnecting different Grid sites. In this paper, we use optical networks to connect four clusters from three different sites: Texas A&M University, University of Illinois at Chicago, and University of California at San Diego to form an optical Grid as an OptIPuter testbed, and execute parallel visualization applications and scientific applications to analyze the performance of these applications on the optical Grid. Our experiments indicate that on-demand scheduling for resource allocation on different Grid sites ensures to run MPI programs on the Grid successfully. We explore the dedicated optical Grid for different purpose of usage with on-demand scheduling to address how the optical Grid impacts the performance of parallel programs. To avoid the large across-site communication latency, the ideal applications for the optical Grid are embarrassingly parallel.