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The RIC® cylinders

The RIC® cylinders have largely enabled the strong volume growth of the optical fiber market in the past two decades. It is an industry standard for the cladding section of the optical single-mode fiber and about 1 billion kilometers of fibers have been produced using this product.


The RIC® process provides a versatile, highly productive and cost-efficient way to manufacture single-mode optical fiber.

  • Versatility:

RIC® cylinders can be combined with other functional components, like Fluorine-doped tubes and different types and sizes of core rods, to manufacture different types of optical fibers, including bend-insensitive fibers like G.657.A2 or G.657.B3. Ideally, the components (core rod, Fluorine-doped tube and RIC® cylinder) are assembled in the fiber draw factory and drawn into the final fiber without additional collapsing steps.

  • Productivity:

    With a batch size of more than 200 kg, or more than 7000 km of fibers, the RIC® cylinders are the largest cladding batches in the world. By exploiting this economy of size, relative handling times are minimized and productive machine times are maximized.
  • Cost-effectivity:

Using the RIC® process, all components (Core rods, Fluorine-doped tubes, RIC® cylinders) arise from “dry” processes where glass is never exposed to OH-rich atmosphere when at high temperatures. This way, OH-incorporation at the core rod outer layer is negligible. Compared to alternative technologies like the soot-on-core-rod technology, this enables core rod designs with much less cladding glass in the core rod. The result is that the fraction of the more expensive core-rod glass in the final fiber can be very low (below 5 %) without significant OH-induced attenuation penalty.

In addition to the immediate effect on direct glass cost in the fiber, this also provides a significant increase in core rod equipment productivity (more fiber km can be yielded per kg of core rod).

  • Fiber performance / yield:

RIC® cylinders are made from high-purity synthetic quartz glass. We monitor purity of our materials using mass spectroscopy and typically do not find any trace elements above the ppb-detection limits. This way, detriments to the fiber draw process are minimized. In addition, RIC® cylinders come with machined surfaces that provide uncompared geometrical precision that no competing high-volume cladding technology can deliver. RIC® cylinder customers hence benefit from highest geometrical precision of the yielded fiber as well.

Technical data:

Typical cylinder dimensions

  RIC® cylinders
Outer diameter (OD) 200 mm, 230 mm possible, small ODs upon request
OD max - OD min ≤ 0.6 mm
Inner diameter (ID) tol +/- 0.5 mm
Length 3,000 mm
Ovality ≤ 0.1 mm
Siding ≤ 1 mm
Bow ≤ 0.5 mm/m

RIC® process

The Rod In Cylinder process is a large volume production process for the manufacturing of single-mode optical fiber. Since its development by Heraeus in 2002 this process has paved the way and defined the speed of the volume growth of optical fiber production.


Before 2002, 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 and reached feasible boundaries of efficient tube manufacturing processes. In 2002 Heraeus has offered precisely machined pure silica cladding cylinders as an even larger jacketing product. The RIC® cylinder at that time had an outer diameter of 150 mm, scaling the batch size by almost a factor of 5. After that, Heraeus has increased the outer diameter of the RIC® cylinders in various steps to 200 mm and 230 mm today. This size-scaling path increased the amount of producable fiber per batch all the way to 7000 km for RIC® 200 or even 10 000 km for RIC® 230. What’s more is that at the same time the required size of the core rod per batch did almost not grow, which gave a tremendous boost to the productivity of core rod plants when measured in fiber km per machine hour.

More information on the production of optical fibers

More information on fused silica tube

More information on silica cladding cylinders

Process Description

Online RIC® process

A core rod is inserted into the central hole of the RIC cylinder, (and optionally a Fluorine-doped tube if a trench-assisted fiber design is the target) This assembly is then brought to the draw tower. The fiber draw furnace heats the glass to melting, and vacuum is applied vacuum to the void between the RIC cylinder and the core rod and the assembly is directly drawn to the final fiber.

Offline RIC® process

As an alternative for fiber draw factories with limitations e.g. in preform size, Heraeus can offer to apply a similar process with the components that are used in the assemble and collapse all components to a solid optical preform. Sizes (outer diameters and lengths) of the yielded preforms are very flexible and can be defined by the customer. Customers then received solid glass preforms that are optimized to the needs of their facility.

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