We develop a space-efficient single-mode fiber (SMF) having a cladding diameter of only 82 mu m. This SMF has the depressed-cladding index profile and its mode-field diameter, cutoff wavelength, and macro bending loss are designed to be similar to those of the conventional step-index SMF. We fabricate this reduced-cladding SMF and measure its optical and mechanical characteristics. The results show that this fiber satisfies major specifications of the ITU-T G.654 recommendations. We also fabricate a fiber ribbon by using twelve of these reduced-cladding SMFs. Compared to a commercial fiber ribbon made of twelve standard SMFs having 125-mu m cladding diameter, this fiber ribbon can improve the spatial efficiency by similar to 75%. (C) 2016 Elsevier Inc. All rights reserved.