Soliton lattice dynamics and applications in communication systems

It has been argued that multiple sub-band pulse-position modulation of soliton pulse trains may well exhibit significantly better digital performance than a conventionally encoded ASK train. This is due to two factors: first, the PPM can be rendered immune by channel design to intersoliton interactions; second, the GH noise saturates in a strongly interacting pulse train. Both of these factors imply that much smaller intersoliton periods may be used for PPM than for ASK. Some disadvantages of the proposed scheme are apparent as well. The sub-bands do not have equal bandwidths, and therefore the Nyquist sampling rate is different for each sub-band. The assembly of the FDM complex from all the sub-bands at the transmitter requires modulation frequencies which are not harmonic multiples of a single frequency. The disassembly of the RF sub-bands at the receiver after optical PPM demodulation requires either complicated filter banks or coherent homodyne detection with nonharmonic local oscillator frequencies. Although this can all be carried out in the RF (microwave) domain using electronic technology which is routine in the field of microwave satellite communications, the PPM scheme is nevertheless significantly more complicated than a simple ASK scheme