Propagation of intense few-cycle laser pulse in a telecommunication-type   optical fiber: analysis of the error introduced by the unidirectional   approximation
  Propagation of few-cycle laser pulses in optical fiber is investigated beyond the unidirectional approximation. Considered medium parameters include dispersion, Kerr and Raman nonlinearities. High intensities of ~10^10 kW/cm^2 lead to generation of the octave-spanning continuum. The error of the unidirectional approximation is seen in simulations as two pulses propagating forwards and backwards, both remain weak under the considered conditions. Direct analytical estimate of the error is derived and verified numerically. It can be applied to a priory justification of the unidirectional approach. 
Leonid Konev and Yuri Shpolyanskiy
physics.optics