Overcoming degradation in spatial multiplexing systems with stochastic nonlinear impairments

Single-mode optical fibres now underpin telecommunication systems and have allowed continuous increases in traffic volume and bandwidth demand whilst simultaneously reducing cost- and energy-per-bit over the last 40 years. However, it is now recognised that such systems are rapidly approaching the limits imposed by the nonlinear Kerr effect. To address this, recent research has been carried out into mitigating Kerr nonlinearities to increase the nonlinear threshold and into spatial multiplexing to offer additional spatial pathways. However, given the complexity associated with nonlinear transmission in spatial multiplexed systems subject to random inter-spatial-path nonlinearities it is widely believed that these technologies are mutually exclusive. By investigating the linear and nonlinear crosstalk in few-mode fibres based optical communications, we numerically demonstrate, for the first time, that even in the presence of significant random mixing of signals, substantial performance benefits are possible. To achieve this, the impact of linear mixing on the Kerr nonlinearities should be taken into account using different compensation strategies for different linear mixing regimes. For the optical communication systems studied, we demonstrate that the performance may be more than doubled with the appropriate selection of compensation method for fibre characteristics which match those presented in the literature

Space Division Multiplexing in Optical Fibres

Optical communications technology has made enormous and steady progress for several decades, providing the key resource in our increasingly information-driven society and economy. Much of this progress has been in finding innovative ways to increase the data carrying capacity of a single optical fibre. In this search, researchers have explored (and close to maximally exploited) every available degree of freedom, and even commercial systems now utilize multiplexing in time, wavelength, polarization, and phase to speed more information through the fibre infrastructure. Conspicuously, one potentially enormous source of improvement has however been left untapped in these systems: fibres can easily support hundreds of spatial modes, but today's commercial systems (single-mode or multi-mode) make no attempt to use these as parallel channels for independent signals.Comment: to appear in Nature Photonic

Implementation complexity of constellation expansion

Constellation expansion and iterative demodulation and decoding are advanced coded modulation techniques that can potentially outperform traditional system based on soft-decision FEC. In this paper we show that they can be implemented with off-the-shelf components at a surprisingly moderate complexity

Analytical OSNR formulation considering nonlinear compensation

We develop the analytical OSNR formulation to predict Q-factor improvement with nonlinear compensation. Fiber with Aeff of around 130 µm2 is found to be optimum for transpaci¿c submarine digital coherent systems upgraded with nonlinear compensatio

Method and device for monitoring distortion in an optical network

A method and a device for monitoring of distortion in an optical network are provided, wherein at least one reference signal and at least one data signal are conveyed via an optical link and wherein a distortion of the at least one data signal is determined based on the at least one reference signal. Also, a corresponding transceiver and a communication system comprising any such device are suggested

On the nonlinear tolerance of 42.8-Gb/s DPSK with co-propagating OFDM neighbors

The nonlinear tolerance of 42.8-Gb/s DPSK is investigated with co-propagating OFDM neighbors. It is found that the XPM that is generated by co-propagating OFDM neighbors is significantly stronger than DPSK and furthermore dependent on the spectral width of the OFDM signal

Method and device for transmission and reception of a polarization multiplexed optical signal

A method and a device for transmission and reception of a polarization multiplexed signal in an optical network are provided, wherein a first carrier of a first polarization and a second carrier of a second polarization are provided at different frequencies. Furthermore, a communication system is suggested comprising said device

Reduced complexity back-propagation for optical communication systems

In this work, a significant reduction of the computational complexity of the back-propagation algorithm applied tp dispersion managed links is proposed, without degrading the system performanc

Impact of interleaving on SD-FEC operating in highly non-linear XPM-limited regime

We experimentally investigate the behavior of two SD codes in a 100G-PDM-DQPSK system with high-power 10G-OOK neighbors. We show that in the presence of sufficient interleaving the input-output BER relationship of both codes remains unaffected