Change in the Singlemode Cable portfolio to SMF-28® Ultra Fiber

As one of the first German cable manufacturers, LEONI Fiber Optics included Corning® SMF-28® Ultra Fiber into its singlemode cable portfolio.

It meets the requirements of fibers with the lowest attenuations according to ITU-T G.652.D and at the same time features excellent bending characteristics of the well-known ITU-T G.657.A1 fibers. This provides you with the opportunity of realizing projects with both fiber types using only one fiber, and even to successfully link difficult applications.

Since September 1, 2015 we produce all buffered fiber types that are ordered with G.652.D fibers with the SMF-28® Ultra Fiber.

In doing so, we offer our customers essential advantages in areas that require

  • bending insensitivity
  • low optical attenuations
  • compatibility as well as
  • cost benefits

With its mode field diameter of 9.2µm and its high bending resistance, this fiber, made of ultrapure fused silica, solves the permanent conflict between compatibility, costs and bending insensitivity.

Specifications of the fiber types compared (non-wired):

AttributeSMF-28® Ultra FiberITU-T G.652.DITU-T G.657.A1
Attenuation @ 1310 nm≤ 0.32 dB/km≤ 0.4 dB/km≤ 0.4 dB/km
Attenuation @ 1383 ± 3 nm≤ 0.32 dB/km≤ 0.4 dB/km≤ 0.4 dB/km
Attenuation @ 1550 nm≤ 0.18 dB/km≤ 0.3 dB/km≤ 0.3 dB/km
Attenuation @ 1625 nm≤ 0.20 dB/km≤ 0.4 dB/km≤ 0.4 dB/km
Macrobend Loss, 1 turn x 10 mm radius @ 1550 nm≤ 0.50 dBNot specified≤ 0.75 dB
Macrobend Loss, 1 turn x 10 mm radius @ 1625 nm≤ 1.5 dBNot specified≤ 1.5 dB
Macrobend Loss, 10 turns x 15 mm radius @ 1550 nm≤ 0.05 dBNot specified≤ 0.25 dB
Macrobend Loss, 10 turns x 15 mm radius @ 1625 nm≤ 0.30 dBNot specified≤ 1.0 dB
Macrobend Loss, 100 turns x 30 mm radius @ 1625 nm≤ 0.01 dB≤ 0.1 dBNot specified
Mode Field Diameter @ 1310 nm9.2 ± 0.4 μm8.6-9.5 ± 0.6 μm8.6-9.5 ± 0.4 μm
PMD Link Design Value≤ 0.04 ps/√km≤ 0.20 ps/√km≤ 0.20 ps/√km
Maximum Individual Fiber PMD≤ 0.1 ps/√kmNot specifiedNot specified


For many years, singlemode fibers of the ITU-T G.652.D standard - last amended in 2005 - were used. Apart from low attenuation values especially in a wavelength range of 1,383 nm, fibers of all manufacturers were characterized by leveling off at a mode field diameter of 9.2 µm with a tolerance of +/-0.4 µm within the standard range. New, challenging applications of the cables, like miniaturization or installation of cables under difficult space conditions, required the development of new, bend resistant fibers.

In 2009 the ITU-T G.657 standard was therefore adjusted. Within this standard, different categories of bending resistance were defined, including ITU-T G.657.A1, ITU-T G.657.A2, ITU-T G.657.B2 and ITU-T G.657.B3. The categories ITU-T G.657.A1 and ITU-T G.657.A2 were supposed to feature improved bending properties and be fully compatible with fibers of the ITU-T G.652.D standard. Therefore, for these fibers the same range of the mode field diameter nominal value of 8.6 µm to 9.5 µm applied. Within the range of the nominal diameter, though, only fibers were available which had a mode field diameter at the lower range of the standard requirements, and therefore had a smaller mode field diameter than the usual singlemode fibers.

Despite the advantages of the bending resistance according to ITU-T G.657.A1 standard, these fibers could not establish in the market as their smaller mode field diameter created problems connecting them to already installed ITU-T G.652.D type fibers. Even at a good splice, great attenuation losses appeared during the splice loss measurement from one side, and apparently signal amplifying when measured from the other side. This disadvantage largely reduced the users’ acceptance of this bend resistant fiber, and, among others, large telecommunication providers decided not to use G.657A.1 fibers any longer.

The new fiber now offered by LEONI Fiber Optics GmbH is characterized by a mode field diameter of 9.2 +/- 0.4 µm at 1,310 nm in order to avoid coupling losses when connecting to existing ITU-T G.652.D type singlemode fibers, but still being bend resistant. The requirements of the ITU-T G.652.D standard as well as the ITU-T G.657.A1 standard are therefore fulfilled.

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