Experimental Characterization of 10 x 8 GBd DP-1024QAM Transmission with 8-bit DACs and Intradyne Detection

We experimentally investigate the transmission of 10 × 8 GBd DP-1024QAM over full Raman amplified low-loss fiber spans. For multicarrier systems using 8-bit DACs, a record achievable information rate of 15.7 bit/symbol is observed after 200 km using standard intradyne detection

デジタルコヒーレント光伝送における超多値信号の高精度歪み補償に関する研究

Tohoku University中沢正隆課

Advanced Digital Signal Processing Techniques for High-Speed Optical Links

L'abstract è presente nell'allegato / the abstract is in the attachmen

Investigation into Information Capacity of Nonlinear Optical Fibre Communication Systems

The optical fibre is a ubiquitous transmission medium since it is able to provide both high speed and low loss. Optical fibre transmission systems carry 99% of the world’s telecommunication traffic. The emergence of new services and Internet applications gives rise to the exponentially increasing demand for higher transmission data rates, motivating the search for new methods to enhance the capacity of optical fibre systems. However, due to the presence of power-dependent signal degradation effects (the optical Kerr effects) together with bandwidth limitations constrained by the low-loss region of the fibre, the current optical fibre communication infrastructure is unable to cope with the ever-growing demand for data rates. The capacity of an optical fibre channel remains unknown and is an open research question. The PhD research described in this thesis aimed to theoretically investigate the capacity of the nonlinear optical fibre channel using information-theoretic tools with the view to improving information data rates of optical fibre networks. The first part of the thesis is concerned with a comprehensive study of Kerr nonlinearity-compensated dispersion unmanaged ultra-wide bandwidth optical fibre communication systems. The bounds on information rate, based on the proposed model, which takes into account the fundamental limitations due to nonlinear interactions between optical signal and amplifier noise, were accurately estimated. The second part deals with the application of the so-called integrability property (the general ideas based around nonlinear Fourier transform (NFT)) of a lossless and noiseless nonlinear Schrödinger equation (NLSE). A new non-Gaussian channel model for soliton-based transmission, in which data is assumed to be embedded into the imaginary part of the nonlinear discrete spectrum was proposed for the first time. New asymptotic semi-analytic approximations for non-decaying capacity bounds have been derived. The theoretical results of this research can be considered as an important first step towards the ultimate capacity limits of nonlinear optical communication links

Maximising Achievable Rates of Experimental Nonlinear Optical Fibre Transmission Systems

It is generally expected that the demand for digital data services will continue to grow, placing ever greater requirements on optical fibre networks which carry the bulk of digital data. Research to maximise achievable information rates (AIR) over fibre has led to increasing spectral efficiency, symbol rate and bandwidth use. All of these contribute to transmission impairments due to the nonlinear nature of the optical fibre. This thesis describes research performed to investigate the effects of nonlinear impair- ments on the AIRs of experimental optical fibre transmission. To maximise throughput, the entire available optical bandwidth should be filled with transmission channels. An investigation into large bandwidth transmission through the use of spectrally shaped amplified spontaneous emission noise (SS-ASE) was con- ducted. The enhanced Gaussian noise model is used to analytically describe this tech- nique, and SS-ASE was experimentally shown to provide a lower bound on the AIR. Nonlinear interference (NLI) was modelled from an inter-symbol interference (ISI) model to characterise the noise and was experimentally verified. This new understand- ing helps quantify potential gain available from nonlinearity mitigation. Multicore fibres offer an alternative route to improve AIR, and are susceptible to another noise source known as crosstalk. This inter-core crosstalk can be controlled by suitable design of the fibre, hence in the limiting case, NLI rather than crosstalk will limit AIR. Nonlinearity compensation was, for the first time, experimentally demon- strated in the presence of crosstalk in a homogeneous 7-core fibre and shown to provide an increase in AIR. The results of this thesis can be used to evaluate future transmission systems for maximising information rates. It was shown that experimentally, SS-ASE is a viable transmission tool to evaluate system performance, NLI can be characterised using an ISI model and nonlinearity mitigation is possible in MCF systems limited by crosstalk

Bismuth-doped Fibre Amplifiers for Multi-band Optical Networks

Fibre-optic networks are the backbone of the global communications infrastructure that made possible modern Internet, providing a multitude of online services and a digital economy. The development of novel approaches for further increasing capacity of optical communication systems is in the focus of research around the world due to the constantly growing data traffic and the corresponding bandwidth demand. Arguably, the most practical technique is multi-band transmission which utilises a huge spectral bandwidth of the existing fibre base that has not previously been used. Unlike spatial division multiplexing, multi-band transmission does not require a new fibre deployment. However, it involves a significant upgrade of current networks with novel amplifiers in the O-, E-, S-, and U- optical bands that are yet to be developed and optimised. In this thesis, E- and S-band bismuth-doped fibre amplifiers (BDFAs) are demonstrated. The following record characteristics of BDFAs are achieved: 40 dB gain, 4.5 dB noise figure, and 38% power conversion efficiency. In total, three BDFAs have been developed, characterised and optimised using pump laser diodes at different wavelengths. Two modelling techniques of BDFAs are proposed: one based on conventional rate equations, and another one based on a neural network "black box" approach. Both of these methods are analysed and their challenges are discussed. A big part of the thesis is devoted to data transmission demonstrations supported by developed BDFAs in E- and S-bands. The experiments include both IM/DD and coherent signal transmissions through various lengths of single mode fibre including record E-band transmission through 160 km of single mode fibre. In addition, a multi-band transmission experiment in E-, S-, C-, and L-band is performed with an in-line amplifier based on combined bismuth-doped fibre and discrete Raman amplification. The total signal bandwidth is 195 nm and the total number of transmitted channels is 143. The obtained results pave the way towards commercial implementation of multi-band transmission enabled by BDFAs in E- and S- optical communication bands

Enabling Technology in Optical Fiber Communications: From Device, System to Networking

This book explores the enabling technology in optical fiber communications. It focuses on the state-of-the-art advances from fundamental theories, devices, and subsystems to networking applications as well as future perspectives of optical fiber communications. The topics cover include integrated photonics, fiber optics, fiber and free-space optical communications, and optical networking

Machine Learning for Multi-Layer Open and Disaggregated Optical Networks

L'abstract è presente nell'allegato / the abstract is in the attachmen