A method includes transmitting optical signals through a heterogeneous
sequence of spans of an all-optical transmission line. Each span has an
optical transmission fiber connected to an optical amplifier. Each
amplifier launches the signals into a sequential remainder of the line.
The transmitting includes launching the optical signals into the highest
loss fibers with substantially equal average optical launch powers or
operating the spans with the highest loss fibers to have substantially
equal quality products. The average optical launch powers are
substantially equal to the inverse of a sum of
(1-T.sub.j).gamma..sub.j/[.phi..sub.NL.alpha..sub.j] over the highest
loss fibers. The parameters T.sub.j, .gamma..sub.j, and .alpha..sub.j are
the respectiveare, respectively, transmissivity, nonlinear optical
coefficient, and loss coefficient of the fiber of the j-th span. The
parameter .phi..sub.NL is the line's cumulative nonlinear phase shift.
Each quality product is the per-span optical signal-to-noise ratio of the
associated span times the nonlinear phase shift of the associated span.