Linear and non-linear coupling of a waveguide coated with a C60 Langmuir-Blodgett film is investigated from 2 to 20 mW using the 514.5 nm line of an argon ion laser. The results show that non-linear coupling occurs when the input power in increased to 6 mW and extends to 14 mW. This property of a lower threshold for non-linear coupling to occur may be used for power limitation or in an optical switch in guided-wave optics.