Soliton trains can be parametrically generated in fiber loops wherever an incoming soliton train interacts with a cw pump in the nonlinear loop. The phase-conjugated signal may either copy or multiply the incoming repetition rate, depending on whether the corresponding cavity harmonic is exactly matched or differs by an amount equal to an integer fraction of the longitudinal mode spacing. It is also shown that the phase relationship between adjacent solitons in the multiplicative conditions continuously evolves on propagation. This effect limits the range of potential application of multiplicative loops.
