If you want to run a time division multiplexing simulation, you will have to run it a little differently. The Optical Delay used here is more of a simulation tool. Since all components need an input before they can simulate, you need to run the simulation for multiple iterations and for the first iteration the delay component will emit a null signal.
This tutorial probably explains it better than I can in a quick reply:
Lesson 5: Bidirectional Simulation — Working with Multiple Iterations
Regards