Volterra-Assisted Optical Phase Conjugation: A Hybrid Optical-Digital Scheme for Fiber Nonlinearity Compensation

Abstract

Mitigation of optical fiber nonlinearity is an active research field in the area of optical communications, due to the resulting marked improvement in transmission performance. Following the resurgence of optical coherent detection, digital nonlinearity compensation (NLC) schemes such as digital backpropagation (DBP) and Volterra equalization have received much attention. Alternatively, optical NLC, and specifically optical phase conjugation (OPC), has been proposed to relax the digital signal processing complexity.In this work, a novel hybrid optical-digital NLC scheme combining OPC and a Volterra equalizer is proposed, termed Volterra-Assisted OPC (VAO). It has a twofold advantage: it overcomes the OPC limitation in asymmetric links and substantially enhances the performance of Volterra equalizers. The proposed scheme is shown to outperform both OPC and Volterra equalization alone by up to 4.2 dB in a 1000 km EDFA-amplified fiber link. Moreover, VAO is also demonstrated to be very robust when applied to long-transmission distances, with a 2.5 dB gain over OPC-only systems at 3000 km.VAO combines the advantages of both optical and digital NLC offering a promising trade-off between performance and complexity for future high-speed optical communication systems.

Optical Phase Conjugation With Complex-Valued Deep Neural Network for WDM 64-QAM Coherent Optical Systems

“…In such a case, optical phase conjugation (OPC) as an NLC scheme operated in optical domain, outperforms other digital NLC schemes. Compared with digital NLC schemes, OPC can be rapidly operated over large optical bandwidths to compensate for the deterministic inter and intra nonlinearity [21][22][23]. Thus, OPC can not only increase the launched power into fiber, but also alleviate the wavelength competition in the optical network by the attached wavelength conversion.…”

Probabilistic Shaping for the Optical Phase Conjugation Channel

“…Combination of OPC with other nonlinearity compensation techniques, e.g. digital back-propagation in [38] and Volterrabased equalization in [39], [40], has been recently explored, showing that the digital and optical techniques can supplement each other. Ultimately, they aim at compensation of the same effects and are thus not complimentary.…”