We fabricated polymer optical fiber (POF) amplifiers operating between 440 and 480 nm, using POFs doped with a series of fluorene oligomers, including tri-, penta-(9,9-dioctylfluorene) and hepta-(9,9-dihexylfluorene). The gain properties of pure oligofluorene films demonstrate gain coefficients on the order of 250 dB/cm and amplified spontaneous emission thresholds between 1 and 8 μJ cm-2, significantly lower than other fluorene gain media. The optical and morphological characteristics of PMMA thin films doped with the oligomers demonstrate that the oligomers are largely isolated within the PMMA. The optical and gain properties of POFs produced using an adapted preform-drawing technique and doped with the oligofluorenes provide gain values on the order of 0.07 dB for 2 mm of doped POF. The oligofluorenes are largely isolated within the POFs, paving the way for all optical gain-switching.