  The mechanisms of nonlinear phase-locking of a large fiber amplifier array
are analyzed. It is shown that Michelson phase conjugating configuration with
double passage through array of fiber amplifiers have the definite advantages
compared to one-way fiber array coupled in a Mach-Zehnder configuration.
Regardless to amount of synchronized fiber amplifiers Michelson
phase-conjugating interferometer is expected to do a perfect compensation of
the phase-piston errors and collimation of backwardly amplified fiber beams on
entrance/output beamsplitter. In both configurations the nonlinear
transformation of the stretched pulse envelope due to gain saturation is
capable to randomize the position of chirp inside envelope thus it may reduce
the visibility of interference pattern at output beamsplitter. A certain
advantages are inherent to the $sech$-form temporal envelope because of
exponential precursor and self-similar propagation in gain medium. The Gaussian
envelope is significantly compressed in a deep gain saturation regime and
frequency chirp position inside pulse envelope is more deformed.
