Coupling of fibers to Ti-diffused LiNbO(3) waveguides by butt-joining

The optical losses due to butt-joining a single-mode optical fiber to a 32-microm wide Ti-diffused LiNbO(3) waveguide have been investigated. Measurements of the total insertion loss as a function of waveguide length show that the waveguide attenuation is 1.25 dB/cm and that coupling losses as low as 0.5 dB can be achieved. The coupling loss has been calculated by a numerical evaluation of the overlap integral of the fiber and waveguide mode profiles, and the results agree with the measured loss.