An optical fiber alignment unit for the easy precise alignment of optical fibers in and array. In a preferred embodiment the positioning array is incorporated twice in an all optical cross connect switch utilizing MEMS mirrors for cross connecting optical fibers in a first set of optical fibers to optical fibers in a second set of optical fibers. The optical fibers are preferably arranged in rectangular arrays. These arrays include array sizes such as 4.times.8, 16.times.16 and 8.times.16. A preferred embodiment built and tested by Applicants is a modular optical switch in which an input 8.times.16 array of optical fibers from sixteen eight-fiber ribbons are cross-connected into an output 8.times.16 array of optical fibers also from sixteen eight-fiber ribbons.