Soliton order ($N_s^2=L_D/L_{\mathrm{NL}}$)

A dimensionless comparison of dispersion and self-phase modulation scales. For the focusing cubic fibre equation with a sech input, $N_s=1$ gives a fundamental temporal bright soliton, and integer $N_s>1$ gives an ideal higher-order temporal soliton. It is a scale parameter for an arbitrary initial pulse, not a theorem that the pulse contains exactly that many separated solitons.