New single-mode fiber collimator arrays (FCAs) were designed, assembled, and tested at a wavelength of 1550 nm. For FCAs using an 8-channel GRIN planar microlens array with a pitch of 250 μm and a focal length of 0.7 mm, the insertion loss was 0.5 dB with uniformity of 0.12 dB, at a collimator separation of 10 mm. The crosstalk from the other channels was less than -45 dB and the return loss of each channel was > 60 dB. For FCAs using a 6-channel lens array by fixing GRIN rod lenses into a V-groove array, the insertion loss was less than 0.5 dB at a collimator separation of 100 mm. By analyzing formulas for calculating Gaussian beam propagation for the design, some simple and useful formulas were introduced for calculating the size and position of the beam waist from those of its image, and for calculating the maximum collimator separation with efficient coupling.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.