Compared to the direct OVD deposition on a core rod, using the RIC process allows for the core rods to have a lower initial cladding. While direct deposition is a wet process, the RIC process is a dry process. The core rod’s cladding layer is preventing defects to affect the light guiding core. For the OVD process, this protective inner cladding needs to be sufficiently thick to prevent the diffusion of Hydrogen into the core, which would result in unwanted attenuation. As the RIC process is using electric furnaces to collapse the cylinder onto the core  there is a very limited risk of Hydrogen contamination and the core rod’s undoped portion can be thinner.

As the core rods usually are stretched from a mother core rod, the fiber equivalent per deposition machine can be increased, if the core takes up a larger portion of the mother preform.

Preforms for optical fiber production have for a long time been made of a core rod that was sleeved using a silica tube as additional cladding (so called jacketing tubes).

The size of the jacketing tubes has increased over the years. In 2002 Heraeus has offered precisely machined pure silica cladding cylinders as an even larger jacketing product. The Cylinder had an outer diameter of 150 mm. Heraeus has increased the outer diameter of these so called “RIC cylinders” to 180 mm and further to 200 mm today.

Process Description

Generally, the process is the locally heating and collapsing of a cylinder onto a core rod. It can be done online on a draw tower and offline in a separate process that yields a preform for fiber draw. Heraeus offers to do the offline process for you.

Offline RIC® process

The core rod is put into the hollow pure silica cylinder. These two glass pieces plus a handle and a start piece form a so-called assembly. Vacuum is applied to the void between the inner diameter of the hollow cylinder and the core rod. The assembly is then locally heated to the softening point of fused silica, so that the cylinder collapses onto the core rod. The heat source traverses along the length of the assembly, until the cylinder is fully collapsed. The produced preform is then inspected and prepared for drawing. Heraeus offers to do this process for you as a service.

Online RIC® process

This process starts the same way as the offline process, with the manufacturing of the assembly. This assembly is then brought to the draw tower. The fiber draw furnace heats the glass to melting, due to the applied vacuum the cylinder collapses onto the core rod and the glass is directly drawn to the fiber draw. This avoids the forming of the preform, saving the cost of the additional hot forming step.

Saving costs

In the past decades, the price for single mode fibers for telecommunication decreased from a few hundred dollars per km to under ten dollar per km today. One key contribution to save cost, is the economy of scale. The more volume a producer can manufacture every year, the lower the overhead cost per unit.

It also proved beneficial to increase the individual batch size; the km of fiber drawn from a preform. Many processes need to be done independent of the size of the preform, transportation from storage to draw furnace for example. The cost might increase a little, as the preform gets heavier but that is offset by the number of processes saved.

For example, five 90mm preforms yield the same volume of fiber as a single 150mm preform. While it may take one hour to set up the draw and get fiber draw started for a 90 mm preform, it may take two hours for a 150 mm preform. For the same production volume 3/5th of the setup time is saved.

Outsourcing cladding

Outsourcing not only saves on capex, but the capacity can be expanded quicker than, if new machines for cladding production would need to be set up. This reduces the time to market.

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