Linear dispersion curve of the LCTL. The driving frequency is chosen in the (green) shade area which satisfies the relation P(ω) × Q(ω) > 0 with P(ω) and Q(ω) being the dispersion coefficient and the nonlinear coefficient, respectively. f_c and f_s are the upper and lower boundary frequencies of the (green) shade domain (f_c is also the cutoff frequency of system).