Pump-linewidth-tolerant optical wavelength conversion for high-order QAM signals using coherent pumps
; Albuquerque, A.
; Puttnam, B. J.
; Sakamoto, T.
Drummond, M. V.
; Kanno, A.
; Shinada, S.
; Wada, N.
; Kawanishi, T.
Optics Express Vol. 22, Nº 5, pp. 5067 - 5075, March, 2014.
ISSN (print): 1094-4087
Journal Impact Factor: 3,488 (in 2014)
Digital Object Identifier: 10.1364/OE.22.005067
Optical wavelength conversion (OWC) is expected to be a desirable function in future optical transparent networks. Since high-order quadrature amplitude modulation (QAM) is more sensitive to the phase noise, in the OWC of high-order QAM signals, it is crucial to suppress the extra noise introduced in the OWC subsystem, especially for the scenario with multiple cascaded OWCs. Here, we propose and experimentally demonstrate a pump-linewidth-tolerant OWC scheme suitable for high-order QAM signals using coherent two-tone pumps. Using 3.5-MHz-linewidth distributed feedback (DFB) lasers as pump sources, our scheme enables wavelength conversion of both 16QAM and 64QAM signals with negligible power penalty, in a periodically-poled Lithium Niobate (PPLN) waveguide based OWC. We also demonstrate the performance of pump phase noise cancellation, showing that such coherent two-tone pump schemes can eliminate the need for ultra-narrow linewidth pump lasers and enable practical implementation of low-cost OWC in future dynamic optical networks.