title: Digital coherent superposition of optical OFDM subcarrier pairs with Hermitian symmetry for phase noise mitigation.
abstract: Digital coherent superposition (DCS) provides an approach to combat fiber nonlinearities by trading off the spectrum efficiency. In analogy, we extend the concept of DCS to the optical OFDM subcarrier pairs with Hermitian symmetry to combat the linear and nonlinear phase noise. At the transmitter, we simply use a real-valued OFDM signal to drive a Mach-Zehnder (MZ) intensity modulator biased at the null point and the so-generated OFDM signal is Hermitian in the frequency domain. At receiver, after the conventional OFDM signal processing, we conduct DCS of the optical OFDM subcarrier pairs, which requires only conjugation and summation. We show that the inter-carrier-interference (ICI) due to phase noise can be reduced because of the Hermitain symmetry. In a simulation, this method improves the tolerance to the laser phase noise. In a nonlinear WDM transmission experiment, this method also achieves better performance under the influence of cross phase modulation (XPM).
authors.forename: Xingwen
authors.initials: X
authors.lastname: Yi
authors.forename: Xuemei
authors.initials: X
authors.lastname: Chen
authors.forename: Dinesh
authors.initials: D
authors.lastname: Sharma
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.forename: Ming
authors.initials: M
authors.lastname: Luo
authors.forename: Qi
authors.initials: Q
authors.lastname: Yang
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Li
authors.forename: Kun
authors.initials: K
authors.lastname: Qiu