nniicckk78, the fiber mode is a TEM00 vs a TEM01 (it is a solid spot vs. a donut shape). Shooting a mode shot at the head is the best way to tell you what exactly is going on with your beam from the lens - down. These fiber lasers are very picky. ANY dust or debris on the lens or protective...
Currently we have Mitsubishi 4kW fiber lasers in house. Mode shots are taken at the head on 3/8" black acrylic glossy purchased from OEM. No idea what type of acrylic they are, and OEM won;t tell us (playing dumb to sell more I suppose). They are 3/8" x 4" x 4", and are pretty pricey...
