Invariants of counterinteraction of femtosecond light pulses

In this paper, we obtain invariants of counterinteraction of femtosecond light pulses in a nonlinear medium. In the process of interaction, the harmonic amplitude at a frequency determined by the dispersion of nonlinear response of the medium oscillates along the propagation path with spatial frequency that is also determined by nonlinearity dispersion. The result obtained must be allowed for, in particular, during the computer modeling of interaction between counterpropagating light pulses.