In the last several years, FTTH installation, led by Verizon, has become really hot. But traditionally, there is one big issue where fiber lags behind copper cable: macro bending loss.
Traditionally, fiber cables must be handled and installed very carefully to avoid small bends along the fiber path, which can cause signal loss. This is especially true for indoor installations where contract installers encounter many sharp turns.
Several approaches have been designed to reduce the bend performance of optical fibers.
1. Reducing the mode field diameter
2. Depressing the cladding
3. Adding a low index trench
However, these enhancing options are incremental modifications of existing approaches to process and design, the achievable macro-bend improvements are limited and only incremental as well.
There is another completely different approach which is called hole-assisted fiber (HAF). This is shown below. It has a very different waveguide profile compared to the profiles of legacy fibers that leverage the technology of chemical-doped waveguide fabrication.
4. Adding a ring of symmetric holes within the cladding
While hole-assisted fiber (HAF) produces very bend-insensitive fibers, it is very costly to make in large quantities and long lengths, difficult to connect and not backward compatible with the industry standards. It even is not compatible with existing termination and field procedures.
>> Corning ClearCurve Bend-Insensitive Single Mode and Multimode Fibers
In 2007, Corning announced their new fiber design technology, called nonoStructures. This is a really breakthrough that shows superior bend performance that meet the FTTH requirements and are compatible with large-scale manufacturing and field installation procedures.
This design consists of a germania-doped core and a nanoStructres ring within the cladding. This fiber design consists of engineered features in the range of a few nanometers to several hundred nanometers.
Many industry experts have confirmed that the products is, as Corning claims, a major advance in fiber technology. It has better bending properties and is more forgiving of construction mistakes.