Corning's HI 1060 Flex fiber was specially designed to make fused fiber 980/1550nm WDM couplers. The HI 1060 Flex fiber has very low splicing loss with fibers for 1550nm (such as SMF-28e fiber, or standard G652.B, G652.D fiber), and also has low splicing loss with fibers for 980nm (HI 980, HI 1060 or PM 980 fibers). It can be spliced to Erbium doped fiber with low loss. The bending loss for 1550nm wavelength is also very small. These features are desirable for EDFAs, especially EDFAs with compact size.

OFS ClearLite 980 16 fiber (BF05635-02 fiber) is another popular fiber to make fused fiber 980/1550nm WDM couplers. BF05635-02 fiber was once called 980nm Coupler Fiber. The numerical aperture of OFS BF05635-02 fiber is slightly lower than that of the HI 1060 Flex fiber (0.16 vs. 0.20). The mode field diameter at 980nm is 5micron, and that is 7.5 micron at 1550nm. Those numbers are 4.0micron and 6.3micron for the HI 1060 Flex fiber. Based on those numbers, OFS fiber looks like to have slightly lower splice loss with 1550nm or 980nm fibers, while it can have higher bending losses than the HI 1060 Flex fiber.

The WDM couplers made from either type show no obvious difference on performance.