Jacket Tubes

Rod-in-Tube technology (RIT)

The RIT process used to overclad core rods has significant benefits compared to other techniques, especially in terms of purity. Since the RIT process does not introduce hydroxyl groups (OH) onto the interface between core rod and outer cladding, the cladding can be very close to the core region of the fiber, resulting in a low b/a ratio. In contrast, outside vapor deposition of cladding material introduces an OH layer at the interface between core rod and cladding material (see graph). The low b/a value achievable with RIT optimizes our customers' core rod production both in terms of efficiency and overall quality. In the case of single mode fiber, typically more than 90% of the total fiber cross-sectional area is composed of Heraeus jacket tube material.

Large variety of tube geometries enables flexibility in preform and fiber design

Jacket tubes are drawn from large cylinders of the highest purity synthetic fused silica without the use of forming dies. This proprietary process ensures high geometric precision and tube surfaces free of contamination. As a result, optical fiber manufacturers can achieve excellent fiber strength. Industry wide, typical optical fiber break rates for our products are below 10 breaks per 1,000 km of fiber when proof-tested at 100 kpsi. The Heraeus tube drawing process allows for very heavy wall single mode as well as thin walled multimode jacket tubes. The outside diameter and wall thickness of the jacket tubes can be precisely controlled to meet customer preform and fiber design requirements.