This letter first introduces the evolution of the manufacturing technologies for G.657single-mode optical fibers. Then it presents the"Three-Step"preform technology for manufacturing bend-insensitive G.657single-mode fibers and designs and fabricates two types G.657fibers

G657A2and G.657B3.They are tested respectively.When the bending radius of G657A2fiber is 7.5mm

its bending losses at 1 550and 1 625nm wavelengths are 0.063and 0.136dB respectively and its attenuation coefficients at 1 383and 1 550nm wavelengths are 0.272and 0.188dB/km

while when the bending radius of G. 657B3fiber is 5mm

its bending losses at 1 550and 1 625nm wavelengths are 0.067and 0.122dB respectively and its attenuation coefficients at 1 383and 1 550nm wavelengths are 0.276and 0.182dB/km respectively.The test results indicate that the presented technology produces high bend-resistant low-loss small bending-radius single-mode fibers and their key specifications are all better than the ITU-T G.657standard.