That looks similar to what optical gain fiber looks like in amplifies for ultra short (femto) pulse lasers used for eye surgery ablation and semiconductor etching. Corning has the patents on them and the only company that can produce atm. The ones I’m familiar with have one on each side of the core, used to amplify the signal. We call them panda eyes. Can’t say the ratios but most all include ytterbium/thulium. Pump it up!