Since the late 70's the Beam Propagation Method (BPM) or Split-Step Fourier Method (SS/FM), has been widely used for solving the nonlinear partial differential equations which describe the propagation of spatial pulses through waveguide structures. By applying the Split-Step technique, the paraxial wave equation can be split in two propagating equations, one involving only linear terms and another including nonlinear ones. These two equations describe diffraction and nonlinear refraction respectively. In the SS/FM, diffraction is integrated by using the Fourier transform. However, the performance of this method is known to be seriously affected when abrupt variations of the refractive index are taken into account [1], and the problem tends to become even worse in the high nonlinear regime [2].

Resumo-Este artigo apresenta os resultados experimentais que validam o nosso método para geração de sinais de microondas multi-nível a partir do uso da técnica de heterodinagem de sinais ópticos. Para tal, é considerada a geração de sinais de micro-ondas quaternários (4-ASK) a partir de duas portadoras ópticas moduladas em amplitude de forma binária (2-ASK). Os experimentos foram realizados utilizando enlaces de até 40 km da Rede Kyatera, que é uma rede óptica real geograficamente distribuída no Estado de São Paulo. Desta maneira, pôde-se analisar a técnica proposta sob condições reais de temperatura, umidade, pressão e vento.

The numerical demonstration of spatial multisoliton emission from a nonlinear waveguide [1] immediately opened new possibilities for the design of nonlinear optical devices. Two of these are particularly notable: the soliton coupler [2] and the soliton scanner [3]. The former, designed with the help of the equivalent-particle theory [2],[4], performs exchange of energy between two waveguides by transfer of solitons. The scanner, on the other hand, makes use of a tapered nonlinear slab which terminates in a nonlinear medium. A spatial soliton excited in the thinner (output) end can follow different routes depending on the power and relative phase of a TE1 beam which is added as a probe to the main TE0 input mode.