We design and fabricate digital thermo-optic switches using low-loss photocuring fluoroacrylate polymers. We use both modeling and experimental design-rule studies to elucidate the contributions to loss and cross talk of the various important building blocks that comprise a Y-branch digital optical switch (YDOS). We present the results of these studies as well as the achieved performance for 1×2, 2×2, and 4×4 switches fabricated with these designs. Average fiber-to-fiber chip- level insertion loss (IL) values for the three designs are 1.1, 1.5, and 2.8 dB, respectively, for 1550-nm illumination. Switching times in every case are below 3 ms. Polarization-dependent loss is less than 0.1 dB at 1550 nm. Fully packaged permanently pigtailed versions of the 2×2 and 4×4 switches are also constructed. For these packaged devices, average insertion losses of 2.0 and 3.3 dB are achieved, and cross talk is maintained at a value less than –45 dB. Recent advances in materials performance have now allowed the insertion loss performance to be further improved, with chip-level IL being reduced to 1.0 and 2.2 dB for 2×2 and 4×4 switches, respectively.