Describes a methodology that is recommended for engineering single-mode fiber optic transmission system. The methods address the design of a regenerator section in which the transmitter and receiver come from the same vendor. As an initial step, only laser systems operating in the 1300 nm region over a class IVa (refers to dispersion non-shifted single-mode fibers, this definition is contained in EIA-492) dispersion unshifted fiber are being considered.