Coupling of single-mode Ti-diffused LiNbO 3 waveguides to single-mode fibers

We report on measurements of the near-field intensity distribution of single-mode T-diffused LiNbO ₃ waveguides and on the alignment tolerances when coupled to a single mode fiber. Coupling efficiencies of typically 77 to 87% are calculated and a value as high as 80% has been measured experimentally for a y-cut substrate and TM-like polarisation. The total insertion loss of 1 cm long single-mode Ti-diffused waveguides ( c-cut) inserted between single-mode fibers was typically 10 dB.