The present invention relates generally to optical waveguides for the transmission of electromagnetic energy. The present invention relates more particularly to optical couplers for coupling optical fibers, and methods for making them. One aspect of the present invention is an optical coupler for use with a polarization-maintaining input optical fiber and a polarization-maintaining output optical fiber. The coupler includes: a tube having a wide end, a narrow end having an end face, and a taper therebetween; a polarization-maintaining feed-through optical fiber having a first end having an end face and a second end, the polarization-maintaining feed-through optical fiber being disposed within the tube from the wide end to the narrow end, at least the narrow end of the tube being fused around a first length of the polarization-maintaining feed-through optical fiber including the first end of the polarization-maintaining feed-through optical fiber to form a coupler end face comprising the end face of the tube and the end face of the first end of the polarization-maintaining feed-through optical fiber. In one aspect of the invention, the polarization-maintaining feed-through optical fiber has an outer diameter no greater than about 200 μm in the region in which the tube is fused around it. In another aspect of the invention, the polarization-maintaining feed-through optical fiber has an outer diameter at the coupler end face no greater than about 75% of the diameter of the polarization-maintaining input optical fiber.