A fiber amplifier that generates nearly transform-limited sub-picosecond pulses and greater than 100 W average power at 1.3-GHz repetition rate is described. Modest stretching of the seed pulses allows the amplifier to be operated in the linear regime. The amplified and dechirped pulses exhibit excellent beam quality, and can be frequency-doubled to produce green pulses at 65 W average power. Detailed characterization of the performance is presented.