Video: Fiber stripping process in slow-motion with a mid-IR fiber laser from Femtum

Manufacturing processes are constantly evolving and the complexity of the devices to be produced continues to grow. In the microelectronics, medical and photonics industries, most devices include a stacking of various layers made of different materials. Each layer must be processed individually to ensure a good performance of the device. This is where selective laser processing in the mid-IR comes into play!

Selective laser processing enables to process only one layer of material without affecting the underlying layer made of a different material.

explanation of selective laser processing
Figure 1: Standard vs Selective laser processing

Why fiber optic stripping ?

In this first article of selective laser processing, we concentrate on a process known as fiber optic stripping because this simple process can be time-consuming and still causes major headaches to the world’s largest fiber optic manufacturers. These manufacturers are subjected to ever increasing tolerances in most of the industries they serve. In telecommunication, fiber components are used in harsh environments and must have excellent mechanical properties. In the high-power fiber laser industry, these fiber components must hold very high optical powers and temperatures. For example, fiber components that require high quality stripping are fiber pump combiners, ribbon fiber cables and fiber Bragg gratings (FBG).

schematic of an optical fiber
Figure 2: Schematic of a stripped optical fiber

Problems with the current stripping techniques

An optical fiber is generally made of a core and a clad composed of glass material (mostly silica) that are protected by polymer coatings (see fig. 2). One of the most critical part when comes to the manufacturing of fiber-based components is the removal (stripping) of the polymer coatings. Current stripping techniques (mechanical tweezers or chemical solvents) damage the fiber or affect the stripping edge quality. These issues can cause unwanted burning or breaking of the fiber components later on the production line or directly in the field once the device has been deployed.

On the other side, laser stripping of optical fibers is a great, touchless and consumable-free alternative. However, current laser strippers rely on CO2 or UV lasers that are strongly absorbed by polymers and glasses in general. Such lasers can thus easily ablate the polymer coating, but they also affect the glass underneath or delaminate the polymer coating, leading to a reduction of the mechanical strength and power handling of the optical fiber.

Improve fiber optic laser stripping with a mid-IR fiber laser

Mid-IR fiber lasers can emit short nanosecond pulses around 2.8 µm, a wavelength where silica glass transmits, but polymer coating (like acrylate) strongly absorbs. Laser selectivity is thus a major advantage in this spectral range. Mid-IR fiber lasers can selectively ablate the polymer in a precise manner without affecting the glass underneath. The video below clearly illustrates this new laser stripping process (in slow motion).  The stripping process does not affect the mechanical property of the fiber and preserves very clean edges without delamination.

Polyimide fiber stripping

Various types of polymers can be stripped with this technique, including polyimide coated fibers that are difficult to strip with standard techniques. If you want to test your own fiber, send us your sample.

picture of polyimide fiber
Figure 3: Polyimide fiber stripped by a Femtum laser

Fiber optic stripping using a Femtum laser can be adapted to several geometries of fibers and polymer coatings. If you want to test your fiber first before considering this approach, please contact us. For more information about selective processing in the mid-IR and Femtum fiber lasers, visit our industrial applications page.