Serial and parallel convolutional neural network schemes for NFDM signals.

Two conceptual convolutional neural network (CNN) schemes are proposed, developed and analysed for directly decoding nonlinear frequency division multiplexing (NFDM) signals with hardware implementation taken into consideration. A serial network scheme with a small network size is designed for small user applications, and a parallel network scheme with high speed is designed for places such as data centres. The work aimed at showing the potential of using CNN for practical NFDM-based fibre optic communication. In the numerical demonstrations, the serial network only occupies 0.5 MB of memory space while the parallel network occupies 128 MB of memory but allows parallel computing. Both network schemes were trained with simulated data and reached more than 99.9% accuracy.

Synchronised dual-wavelength mode-locking in waveguide lasers.

We present a novel approach to study continuous-wave mode-locking in a waveguide laser in the presence of a gain profile with complex features. We introduce a new simulation approach where we separate the role of gain, nonlinearity, dispersion and saturable absorption elements to provide a better understanding of the interplay between these elements. In particular, we use the simulation to explain synchronised dual-wavelength mode-locking. The results show that despite the existence of dispersion which tends to form separate pulse trains in the laser cavity, the saturable absorber plays a critical role in keeping the different wavelength components synchronised. This work, for the first time, provides insight into existing experimental results. It also demonstrates new methods for studying lasers, especially mode-locking laser, with short laser cavities.

A six-strut suspended core fiber for cylindrical vector mode generation and propagation.

We report fabrication and simulation of an F2 glass six-strut suspended core fiber (SCF) with small effective core diameter of 2.5 µm for cylindrical vector (CV) modes generation and propagation. Simulation results show that the fiber has a large effective refractive index difference in the order of 10-4-10-3 between the first higher-order CV modes, including TE01, HE21even and odd and TM01 modes. TE01 and TM01 were experimentally generated and were evaluated as having high purity of 82 percent and 85 percent, respectively. The results demonstrate that the SCF is a competitive waveguide candidate for selectable CV mode generation and propagation.