A micro-electro-mechanical systems (MEMS) mirror array can be constructed using sub-dies that each includes two or more MEMS mirrors. In some implementations, an optical cross-connect system includes a first MEMS mirror array that includes first mirror units. Each first mirror unit can include a first substrate and two or more first MEMS mirrors supported by the first substrate. Each first substrate can be independent from each other first substrate. The cross-connect system can include a second MEMS mirror array that includes second mirror units. Each second mirror unit can include a second substrate and two or more second MEMS mirrors supported by the second substrate. Each second substrate can be independent from each other second substrate.