High-Speed, High-Performance DQPSK Optical Links with Reduced Complexity VDFE Equalizers

• Main Authors: Maki Nanou, Christina (Tanya) Politi, Alexandros Stavdas, Kristina Georgoulakis, George-Othon Glentis
• Format: Article
• Language: English
• Published: MDPI AG 2017-02-01
• Series: Photonics
• Subjects: advanced optical transmission techniques; digital signal processing; electronic equalization; dispersion compensation
• Online Access: http://www.mdpi.com/2304-6732/4/1/13

Optical transmission technologies optimized for optical network segments sensitive to power consumption and cost, comprise modulation formats with direct detection technologies. Specifically, non-return to zero differential quaternary phase shift keying (NRZ-DQPSK) in deployed fiber plants, combined with high-performance, low-complexity electronic equalizers to compensate residual impairments at the receiver end, can be proved as a viable solution for high-performance, high-capacity optical links. Joint processing of the constructive and the destructive signals at the single-ended DQPSK receiver provides improved performance compared to the balanced configuration, however, at the expense of higher hardware requirements, a fact that may not be neglected especially in the case of high-speed optical links. To overcome this bottleneck, the use of partially joint constructive/destructive DQPSK equalization is investigated in this paper. Symbol-by-symbol equalization is performed by means of Volterra decision feedback-type equalizers, driven by a reduced subset of signals selected from the constructive and the destructive ports of the optical detectors. The proposed approach offers a low-complexity alternative for electronic equalization, without sacrificing much of the performance compared to the fully-deployed counterpart. The efficiency of the proposed equalizers is demonstrated by means of computer simulation in a typical optical transmission scenario.