A data input apparatus having at least one transmit element coupled to a source of light of a predetermined wavelength, at least one light receive element and a detection device to detect interruption of beams of the light of said predetermined wavelength extending from said transmit element to said receive element wherein at least one of said transmit element and said receive element comprises at least one waveguide having a light transmitting core and a non-core portion and one or more discontinuance means adapted to reduce transmission of stray light within the non-core portion. The discontinuance is adapted to scatter, absorb, divert or block stray light and can be applied to one or more of the upper cladding, lower cladding, substrate or common base.