We report on the fabrication and characteristics of a step-index glass-clad polymer optical fiber that uses a novel fluorescent stilbenoid compound for lasing and amplification applications. The compound, 1, 4-bis(4-diphenyl-amino-styryl)-benzene, is specifically designed for the blue region of the spectrum and has a very high quantum yield of 0.85 in a solid-state polymer host and a large Stokes shift. Significant spectral narrowing and superlinear increase of output intensity are observed under photoexcitation at 355 nm, which are indicative of the occurrence of amplified spontaneous emission. By means of gain spectroscopy, a large optical gain of up to 36 cm(-1) at 494 nm has been obtained for the fiber when it is transversely photoexcited at 12 mJ/cm(2) . The waveguide loss has been measured to be 0.7 cm(-1) at 494 nm. The demonstration of high gain and low waveguide loss has favorable implications for the construction of a very compact, tunable coherent light source.