Polishing Large Diameter Bare Fibers With SpecPro™

Large diameter bare fiber polishing for laser and source applications requires a process that can deliver stability, repeatability, and a high-quality endface without introducing unnecessary risk of breakage. In this example, KrellTech’s SpecPro™ Polishing System was used to polish a 400/430 µm fiber sample held in our LD/cannula workholder, with in-line inspection performed throughout the process using the SpecVision™ video scope.

The process begins by installing the fiber into the precision V-groove of the workholder, which helps stabilize the fiber during polishing. A spacer is used to maintain consistent fiber protrusion, helping support repeatable results from one sample to the next. For larger diameter fibers, maintaining control over position and pressure is especially important to support endface quality and reduce the risk of damage during processing.

The first polishing step uses a 30 µm silicon carbide film with a 40D rubber disc for a 30-second dry polish. The rubber disc helps absorb the sharper initial impact of the process while beginning to refine the fiber endface. After this step, the CleanTouch™ Stick is used to remove debris from the surface before inspection. Once the debris is cleared, the SpecVision™ video scope is used to inspect the fiber surface. Because inspection is in-line, the fiber does not need to be removed from the workholder. This helps reduce handling, save time, and allow the operator to quickly evaluate polishing progress before moving to the next step.

The second step uses a 9 µm silicon carbide film on a glass disc for another 30-second dry polish. Moving to a glass disc helps produce a flatter polish while continuing to refine the surface finish after the initial material removal step. After polishing, the fiber is again cleaned with the CleanTouch™ Stick and inspected with the SpecVision™ video scope, which engages directly with the workholder for a smooth polish-and-inspect workflow.

The final step uses a 0.3 µm aluminum oxide film on a glass disc in a wet polish process. Only a couple of light sprays of water are needed directly on the film to support the final polish. After polishing is complete, the fiber is dried and cleaned using SkyBrite™ wipes for final inspection.

One of the advantages of this workcell approach is that polishing and inspection are combined into one system. The operator can move through each polishing stage, inspect results in-line, and make adjustments as needed without removing the fiber from the workholder. For teams working with large diameter fibers in laser and source applications, this can help improve process control, efficiency, and overall workflow consistency.

Switching polishing films and discs is also straightforward, making the system practical for both development work and day-to-day production. Multiple discs can be prepared ahead of time when needed, helping maximize throughput and minimize interruption between steps.

KrellTech’s workholder design further supports process consistency. Independently suspended polishing positions and equalized pressure distribution help minimize fiber breakage, while optically aligned polishing positions help precisely control endface geometry. Together, these features make the SpecPro™ system well suited for large diameter bare fiber applications where endface quality, repeatability, and in-line inspection are critical.

For this application, the process used a 30 µm silicon carbide film with a 40D rubber disc for 30 seconds dry, followed by a 9 µm silicon carbide film with a glass disc for 30 seconds dry, and a final 0.3 µm aluminum oxide film with a glass disc for a wet polish. The products used included the SpecPro™ Polishing System, LD/cannula workholder, SpecVision™ video scope, CleanTouch™ Stick, and SkyBrite™ wipes. This example highlights how KrellTech’s SpecPro™ platform supports a streamlined polish-and-inspect workflow for large diameter bare fibers, helping users achieve a flat, refined finish with greater confidence and efficiency.