Permanent attachment of single-mode fiber arrays to waveguides

We report on coupling arrays of SM fibers in silicon
V
- grooves to waveguides. Arrays with up to 12 fibers have been permanently attached to waveguides with an average excess loss of 0.3 dB per interface. We discuss a subtle, heretofore unreported effect of polarization on fiber-waveguide insertion loss and we describe the first measurements of waveguide-mode position as a function of polarization. In general, the modes of a Ti:LiNbO
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waveguide peak at different positions. This results in different optimum positions for coupling and thus leads to an unavoidable excess loss when attaching fibers. For low-loss waveguides, we predict a minimum excess loss of 0.25 dB per interface.