title: Phase noise mitigation of QPSK signal utilizing phase-locked multiplexing of signal harmonics and amplitude saturation.
abstract: We demonstrate an all-optical phase noise mitigation scheme based on the generation, delay, and coherent summation of higher order signal harmonics. The signal, its third-order harmonic, and their corresponding delayed variant conjugates create a staircase phase-transfer function that quantizes the phase of quadrature-phase-shift-keying (QPSK) signal to mitigate phase noise. The signal and the harmonics are automatically phase-locked multiplexed, avoiding the need for phase-based feedback loop and injection locking to maintain coherency. The residual phase noise converts to amplitude noise in the quantizer stage, which is suppressed by parametric amplification in the saturation regime. Phase noise reduction of ∼40% and OSNR-gain of ∼3  dB at BER 10(-3) are experimentally demonstrated for 20- and 30-Gbaud QPSK input signals.
authors.forename: Amirhossein
authors.initials: A
authors.lastname: Mohajerin-Ariaei
authors.forename: Morteza
authors.initials: M
authors.lastname: Ziyadi
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Chitgarha
authors.forename: Ahmed
authors.initials: A
authors.lastname: Almaiman
authors.forename: Yinwen
authors.initials: Y
authors.lastname: Cao
authors.forename: Bishara
authors.initials: B
authors.lastname: Shamee
authors.forename: Jeng-Yuan
authors.initials: JY
authors.lastname: Yang
authors.forename: Youichi
authors.initials: Y
authors.lastname: Akasaka
authors.forename: Motoyoshi
authors.initials: M
authors.lastname: Sekiya
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Takasaka
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Sugizaki
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Touch
authors.forename: Moshe
authors.initials: M
authors.lastname: Tur
authors.forename: Carsten
authors.initials: C
authors.lastname: Langrock
authors.forename: Martin M
authors.initials: MM
authors.lastname: Fejer
authors.forename: Alan E
authors.initials: AE
authors.lastname: Willner