  We study the photo-assisted noise generated by time-dependent or random
sources and transmission amplitudes. We show that it obeys a perturbative
non-equilibrium fluctuation relation that fully extends the lateral-band
transmission picture in terms of many-body correlated states. This relation
holds in non-equilibrium strongly correlated systems such as the integer or
fractional quantum Hall regime as well as in quantum circuits formed by a
normal or Josephson junctions strongly coupled to an electromagnetic
environment, with a possible temperature bias. We then show that the
photo-assisted noise is universally super-poissonian, giving an alternative to
a theorem by L. Levitov {\it et al} which states that an ac voltage increases
the noise. Restricted to a linear dc current, we show that the latter does not
apply to a non-linear superconducting junction. Then we characterize minimal
excitations in non-linear conductors by ensuring a poissonian photo-assisted
noise, and show that these can carry a non-trivial charge value in the
fractional quantum Hall regime. We also propose methods for shot noise
spectroscopy and for a robust determination of the fractional charge which is
more advantageous than those we have proposed previously and implemented
experimentally.
