SILICON | Arnold Gruppe

Start

Photovoltaik

AEPS+

Referenzen

Downloads

Kontakt

DRAW TOWER

Unternehmen

First, the preform is placed in a furnace where temperatures exceed 1900 °C. Under these conditions, the glass becomes viscous and can be drawn into a thin fiber by applying a pulling force. The resulting fiber is then continuously guided downward.

The drawing speed plays a key role here, as it directly determines the fiber diameter. At the same time, process stability is maintained through the use of inert gases, typically argon. This prevents unwanted chemical reactions and helps stabilize the thermal conditions.

After exiting the heating zone, controlled cooling takes place. The fiber is then coated with a protective layer that provides mechanical protection and—depending on the application—can also influence its optical properties. The coating often consists of multiple layers with different material properties.

Measurement and Control Technology

Measurement data—particularly fiber diameter—is continuously recorded throughout the entire process. This data is fed into control loops that allow for adjustments to the drawing speed or other parameters. The goal is to immediately compensate for fluctuations and ensure consistent product quality.

Further inspections are conducted even after coating, for example, to verify the uniformity and centering of the layers. These factors are crucial for preventing optical losses and mechanical weaknesses.

Final Processing and Quality Inspection

At the end of the drawing tower, the finished fiber is wound under a defined tension. At the same time, a mechanical test can be performed to measure tensile strength. This allows material defects to be identified and defective sections to be sorted out.

Process Complexity and Optimization

The production of specialty fibers is characterized by a multitude of interdependent parameters. Different preforms each require customized settings, and even minor deviations can affect quality.

Critical factors include, among others, temperature profiles, gas flows, and the calibration of measurement systems. In addition, practical experience plays a key role, as many fine adjustments cannot be fully automated.

A stable and optimally tuned process is therefore crucial for achieving high yields and consistent product properties.

Manufacture of Specialty Optical Fibers via the Drawing Process

The production of specialty optical fibers is based on the transformation of a relatively compact starting material—known as a preform—into an extremely long, thin fiber. While the preform is usually only about one meter long, the drawing process produces fibers ranging in length from several hundred meters to several kilometers.

The preform’s future properties are specifically determined as early as the manufacturing stage. Controlled doping and precise structuring result in defined optical, mechanical, and chemical properties that must be preserved during the subsequent drawing process. The demands on process control are correspondingly high: In addition to consistently high strength, exact geometric parameters and a high-quality coating must also be ensured.

The System-Wide Nature of the Drawing Tower

A drawing tower can be understood as a complex technical system in which several functional units work closely together. Key components include the controlled feeding of the preform, the high-temperature zone for softening the glass, the drawing or pulling system, and the coating unit.

The key factor here is the interaction between temperature and mechanical tensile stress. These two variables directly influence the viscosity of the glass and, consequently, the shaping of the fiber. In addition, other systems are in place to minimize external influences such as vibrations or contamination from particles and moisture.