Thanks for additional info and sharing the simulation file.
I understand why the use of movie monitor is challenging in your case. You are performing a 3D simulations with 4 fibers in which one of them is located at the center of the simulation region and the other three are positioned with 120 degrees from one another:
Movie monitor can record transmission only on a 2D plane with normal vectors along x,y, or z axes. This means that you will not be able to watch transmission in all 4 fibres with a single movie monitor and you will need a few of them. If you have any questions regarding setting up the movie monitor, please let me know.
Sometime using profile monitors might be as useful as movie monitors to obtain light propagation with the benefit of reducing simulation time significantly as opposed to movie monitors.
Also regarding your simulation file, I do not think that you can employ any symmetry to your simulation, except maybe along the z-direction. You have a cone shape clad and fibers are located on triangular corners. Also, you need to use PML boundary conditions instead of metal so that light is absorbed at the boundaries of simulation region.
I also recommend to use DFT monitors at the end of each fiber to study transmission on each branch. Once that you obtained reasonable transmission, which indicates that you have set your simulation file properly, you can add movie monitors to study light propagation.
I hope this was helpful, and please let me know if you have further questions.