What do the scratches on the connector look like when magnified 400x?
In the field of fiber optics communications and optical sensing, the Fiber End-face Inspection Microscope is a critical tool used to assess the cleanliness and physical damage (such as scratches, pits, and dirt) on the end-face of fiber optic connectors.
When observed at a magnification of $400$x, the core (diameter approx. 9\ \mu\text{m}) and cladding (diameter approx. 125\ \mu\text{m})