A technique for a secondary manual flat polishing of multimode ferrules to correct its geometric parameters for efficient wireless energy transition

This study examines manual polishing methods for optical ferrules to correct geometric irregularities (apex offset, radius deviation, misalignment) and repair in-service damage. The goal is to provide an effective, low-cost solution for situations where expensive equipment is impractical, such as in small-scale production or laboratories. This work is critical for advancing wireless energy transmission, which increasingly relies on high-power laser systems delivered through fiber optics. In such systems, the precision of optical connections is paramount to minimize energy loss and ensure safe, efficient power transfer.

Patch cords were fabricated using standard multimode cable and FC connectors. Initial inspection identified obvious defects. Samples were characterized using a microscope and an optical spectrum analyzer. A separate group of fibers was intentionally damaged through mechanical abrasion. Both the damaged group and samples with geometric deviations were subjected to secondary polishing using various techniques.

The combined polishing method proved most effective for geometry correction. Secondary polishing successfully eliminated damage from excessive wear in most cases. For samples with gluing violations that underwent secondary polishing, 75-80% showed no geometric deviations from the norm. However, physical strength tests revealed that defects originating at the gluing stage often led to eventual failure, and core misalignment caused gradient loss depending on connector rotation.

The study identified key regularities: Correct secondary polishing reduces apex offset from 300 nm to 30-50 nm in 80% of samples. Ineffective secondary polishing usually indicates deeper, uncorrectable defects like cracks or misalignment. These findings are critical for wireless power applications, where such flaws could lead to catastrophic connector failure or significant transmission inefficiency. For reliable quality assessment, it is recommended to complement insertion loss measurements with mechanical tests. Rotating the connection 360 degrees to measure loss stability helps identify axis misalignment and determine the potential reliability of the connection.