An optical signal processing apparatus includes at least two mirror array chips mounted on an upper surface of a base in close proximity to each other to form a compound array. Each mirror array chip includes a substrate, and a plurality of spaced-apart mirrors mounted on an upper surface of the substrate. The mirrors are movable in response to an electrical signal. A plurality of electrical leads for conduct the electrical signals to the mirrors, at least a portion of the electrical leads extending at least partially along the upper surface of the base between a lower surface of the substrate and the upper surface of the base.