  We present full phase stabilization of an amplified Yb:fiber femtosecond
frequency comb using an intra-cavity electro-optic modulator and an
acousto-optic modulator. These transducers provide high servo bandwidths of 580
kHz and 250 kHz for frep and fceo, producing a robust and low phase noise fiber
frequency comb. The comb was self-referenced with an f - 2f interferometer and
phase locked to an ultra-stable optical reference used for the JILA Sr optical
clock at 698 nm, exhibiting 0.21 rad and 0.47 rad of integrated phase errors
(over 1 mHz - 1 MHz) respectively. Alternatively, the comb was locked to two
optical references at 698 nm and 1064 nm, obtaining 0.43 rad and 0.14 rad of
integrated phase errors respectively.
