Tuneable optical filter

A tuneable optical filter includes a moveable filter plate and an associated optical region for filtering an input radiation beam to provide corresponding filtered output radiation. The optical region has spatially varying filtration properties. Piezoelectric actuating elements are provided for moving the filter plate and its associated optical region relative to the beam for selecting a portion of the optical region for use in filtering the beam and thereby tuning the filter. The actuating elements are operable when driven by electrical signals to repetitively engage or be in repetitively slidable contact and thereby impart a lateral force to a surface of the filter plate for moving the optical region relative to the beam in at least one dimension. The filter is especially suitable for use in optical communication systems where there arises a need for occasional system reconfiguration involving retuning optical filters of the system.