A method and an apparatus for calibrating a MEMS actuator of a hybrid MEMS-PLC optical switch or router is described. Two calibrating waveguides, embedded monolithically adjacent to the waveguides that provide the PLC output functions, are used for referencing a MEMS mirror tilt angle by maximizing optical coupling of light, reflected off the MEMS mirror, into one or each of the two calibrating waveguides. The input light is provided by either a waveguide carrying a live optical signal, or by a special input waveguide, coupled to an LED, for providing a calibrating light. Two emitting waveguides, embedded monolithically adjacent to the waveguides that provide the PLC input functions, can be used.