Electronic post-compensation of WDM transmission impairments using coherent detection and digital signal processing

Abstract

A universal post-compensation scheme for fiber impairments in wavelength-division multiplexing (WDM) systems is proposed based on coherent detection and digital signal processing (DSP). Transmission of 10 x 10 Gbit/s binary-phase-shift-keying (BPSK) signals at a channel spacing of 20 GHz over 800 km dispersion shifted fiber (DSF) has been demonstrated numerically.

Nonlinear penalties in long-haul optical networks employing dynamic transponders

“…One such challenge is associated with the nonlinear transmission impairments which strongly link the achievable channel reach for a given modulation format and symbol-rate [7,8]. Compensation of many of the linear and nonlinear fibre impairments can be achieved by employing electronic signal processing using digital back-propagation (DBP) [9][10][11]. Although the future potential of nonlinear impairment compensation using DBP in a dynamic optical network is unclear due to its significant computational burden and limited access to the full dense wavedivision multiplexing band, simplification of nonlinear DBP algorithm using single-channel processing at the receiver has already commenced [12,13] In such a dynamic network, there is a large range of options to provide the desired flexibility including symbol rate [14], sub-carrier multiplexing [15], network configuration [16] and signal constellation [3].…”

Digital Postcompensation Using Volterra Series Transfer Function

“…In order to implement digital BP using Volterra theory, we must find an inverse VSTF (IVSTF) capable of describing the reverse propagation of signal in fiber, which is modeled by the reverse NLS equation given by [2], [3], (1) where is an abbreviation of describing the slowly varying complex envelope of the optical field at time and position , is the attenuation coefficient of the fiber, accounts for the group velocity dispersion and is the nonlinear coefficient accounting for the Kerr effect.…”

“…where represents the complex conjugate of , is the inverse linear kernel, (3) and is the inverse third-order nonlinear kernel, (4) When input power is high, the VSTF method has serious energy divergence problems, limiting its practical application. In order to solve this issue, a modified VSTF (MVSTF) method is presented in [8], based on a phase correction of the output optical field.…”

“…Recently, a digital postcompensation technique based on backward propagation (BP) has been proposed for the joint mitigation of both linear and nonlinear impairments in fiber [2], [3]. This technique requires high computational power in order to numerically solve the inverse nonlinear Schrödinger (NLS) equation.…”

“…This technique requires high computational power in order to numerically solve the inverse nonlinear Schrödinger (NLS) equation. So far, digital BP has been preferably implemented using either a split-step Fourier (SSF) method [2], [3] or a split-step finite-impulse response filter (SS-FIR) [4]. While the first relies on an hybrid time and frequency-domain approach, the later is entirely implemented in the time-domain.…”