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Recent advances in developing nonlinear optical techniques for processing serial digital information at high speed are reviewed. The field has been transformed by the advent of semiconductor nonlinear devices capable of operation at 100 gigabits per second and higher, well beyond the current speed limits of commercial electronics. These devices are expected to become important in future high-capacity communications networks by allowing digital regeneration and other processing functions to be performed on data signals "on the fly" in the optical domain.

We scrutinize the concept of integrable nonlinear communication channels, resurrecting and extending the idea of eigenvalue communications in a novel context of nonsoliton coherent optical communications. Using the integrable nonlinear Schrödinger equation as a channel model, we introduce a new approach-the nonlinear inverse synthesis method-for digital signal processing based on encoding the information directly onto the nonlinear signal spectrum. The latter evolves trivially and linearly along the transmission line, thus, providing an effective eigenvalue division multiplexing with no nonlinear channel cross talk. The general approach is illustrated with a coherent optical orthogonal frequency division multiplexing transmission format. We show how the strategy based upon the inverse scattering transform method can be geared for the creation of new efficient coding and modulation standards for the nonlinear channel.

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In wireless ad hoc sensor networks, energy use is in many cases the most important constraint since it corresponds directly to operational lifetime. Topology management schemes such as GAF put the redundant nodes for routing to sleep in order to save the energy. The radio range will affect the number of neighbouring nodes, which collaborate to forward data to a base station or sink. In this paper we study a simple linear network and deduce the relationship between optimal radio range and traffic. We find that half of the power can be saved if the radio range is adjusted appropriately compared with the best case where equal radio ranges are used.

Mode-locked lasers emitting a train of femtosecond pulses called dissipative solitons are an enabling technology for metrology, high-resolution spectroscopy, fibre optic communications, nano-optics and many other fields of science and applications. Recently, the vector nature of dissipative solitons has been exploited to demonstrate mode locked lasing with both locked and rapidly evolving states of polarisation. Here, for an erbium-doped fibre laser mode locked with carbon nanotubes, we demonstrate the first experimental and theoretical evidence of a new class of slowly evolving vector solitons characterized by a double-scroll chaotic polarisation attractor substantially different from Lorenz, Rö ssler and Ikeda strange attractors. The underlying physics comprises a long time scale coherent coupling of two polarisation modes. The observed phenomena, apart from the fundamental interest, provide a base for advances in secure communications, trapping and manipulation of atoms and nanoparticles, control of magnetisation in data storage devices and many other areas. Light: Science & Applications (2014) 3, e131; doi:10.1038/lsa.2014.12; published online 17 January 2014Keywords: chaos; mode-locked laser; polarisation phenomena; vector soliton INTRODUCTION Vector solitons (VSs) in mode-locked lasers comprise a train of stabilized short pulses (dissipative solitons 1-13 ) with the specific shape defined by a complex interplay and balance between the effects of gain/ loss, dispersion and nonlinearity. The state of polarisation (SOP) of the solitons either rotates with a period of a few round trips or is locked. [4][5][6][7][8][9][10][11][12][13] The stability of VSs at the different time scales from femtosecond to microseconds is an important issue to be addressed for increased resolution in metrology, 14 spectroscopy 15 and suppressed phase noise in high speed fibre optic communication. 16 In addition, there is considerable interest in achieving high flexibility in the generation and control of dynamic SOPs in the context of trapping and manipulation of atoms and nanoparticles, 17-19 control of magnetisation 20 and secure communications. 21 The stability and evolution of VSs at a time interval from a few to thousands of cavity round trips is defined by asymptotic states (attractors) which the laser SOP approaches at a long time scale, viz. fixed point, periodic, quasiperiodic and chaotic dynamics. Soto-Crespo and Akhmediev 1,2 predicted theoretically based on the Ginzburg-Landau scalar model that dissipative solitons can generate strange attractors at the time scale of thousands of cavity round trips. Quantitative characterisation of strange attractors is usually based on the determination of geometric properties such as the fractal dimensionality, entropy and Lyapunov exponents. [22][23][24][25][26] For experimental data obtained in the form of a one-dimensional waveform (output power vs. time), such analysis requires the accumulation of a large amount of low noise data that is very difficult to achieve in systems where...