  Photon counting measurements are analyzed for obtaining a classical phase
parameter in linear Mach Zehnder interferometer (MZI), by the use of phase
estimation theories. The detailed analysis is made for four cases: a) Coherent
states inserted into the interferometer. b) Fock number state inserted in one
input port of the interferometer and the vacuum into the other input port. c)
Coherent state inserted into one input port of the interferometer and
squeezed-vacuum state in the other input port. d) Exchanging the first
beam-splitter (BS1) of a MZI by a non-linear system which inserts a NOON state
into the interferometer and by using photon counting for parity measurements.
The properties of photon counting for obtaining minimal phase uncertainties for
the above special cases and for the general case are discussed.
