  Optical communication systems, operating in C-band, are reaching their
theoretically achievable capacity limits. An attractive and economically viable
solution to satisfy the future data rate demands is to employ the transmission
across the full low-loss spectrum encompassing O, E, S, C and L band of the
single mode fibers (SMF). Utilizing all five bands offers a bandwidth of up to
$\sim$53.5THz (365nm) with loss below 0.4dB/km. A key component in realizing
multi-band optical communication systems is the optical amplifier. Apart from
having an ultra-wide gain profile, the ability of providing arbitrary gain
profiles, in a controlled way, will become an essential feature. The latter
will allow for signal power spectrum shaping which has a broad range of
applications such as the maximization of the achievable information rate X
distance product, the elimination of static and lossy gain flattening filters
(GFF) enabling a power efficient system design, and the gain equalization of
optical frequency combs. In this paper, we experimentally demonstrate a
multi-band (S+C+L) programmable gain optical amplifier using only Raman effects
and machine learning. The amplifier achieves >1000 programmable gain profiles
within the range from 3.5 to 30 dB, in an ultra-fast way and a very low maximum
error of 1.6e-2 dB/THz over an ultra-wide bandwidth of 17.6-THz (140.7-nm).
