High-power (620 W) and high-gain (28 dB) amplification was achieved by a rhodamine B (RB)-doped GI polymer optical fiber amplifier (POFA) with a 1-m length. A theoretical analysis of the amplification in the RB-doped GI POFA was carried out using the rate equation for the fast three-level system. The calculated gain behavior reasonably fit the experimental data. The possibility of higher power (more than 620 W) and higher gain (more than 28 dB) amplification covering a wide range in the visible region is shown from the calculation. Absorption and emission cross sections of RB in poly(methyl methacrylate) bulk were determined and used in the calculation. The values of the cross sections (σα max = 3.4 · 10-20 m2, σe max = 3.4 · 10-20 m2) were approximately 10,000 times larger than those of Er3+ in GeO2 -SiO2 glass.
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