NetApp TR3548 for MetroCluster shows cabling limits. The limit for a stretch metrocluster can be extrapolated for a controller to the first shelf, but I would open a ticket to confirm support won't have an issue with this.
TR3548 Lists Optical Distances: 270m at 4GB and 500M at 2GB with OM3 (50/125UM) Fiber. This is not shelf to shelf only the optical from fas to the first shelf.
The new DS4243 shelves are all copper cables with a max distance of 5m. I haven't seen an update on metrocluster support for these shelves yet but would be interested in the road map or support planned and if it will use optical transceivers.