Tunable four-wave mixing in low-mode-number optical fibers.

Partially degenerate four-wave mixing for different pump wavelengths in step-index optical silica fibers with low mode numbers is considered. The frequency shifts that correspond to the phase match and the overlap integrals are calculated for a tunable pump. It is shown that when the interacting waves propagate in some combinations of the modes LP(01) and LP(11), four-wave mixing is possible for tunable pump wavelengths in the region from 0.4 to 0.9 µm, far from the minimum of the material dispersion.