Transmission of Mixed 260-Gb/s PDM-16QAM and 130-Gb/s PDM-QPSK over 960-km and 4160-km Dispersion-Managed SSMF Spans

Using pulse shaping and maximum-likelihood detection techniques, we successfully transmit a mix of 260-Gb/s PDM-16QAM and 130-Gb/s PDM-QPSK channels at a 50-GHz channel spacing over 960-km and 4160-km legacy dispersion-managed SSMF spans, respectively.. Introduction With the recent commercialization of 100-Gb/s technologies using polarization-divisionmultiplexed quadrature-phase-shift-keying (PDM-QPSK) and digital coherent detection, the focus of the optical communication industry is moving beyond 100-Gb/s. 16-ary quadratureamplitude modulation (16QAM) with digital coherent detection is considered a promising candidate for such systems [1]-[4]. Compared with QPSK, 16QAM requires higher optical signal-to-noise ratios (OSNRs) and is more sensitive to fiber nonlinearities, which becomes more severe in dispersion-managed (DM) links over legacy fiber infrastructure [5]. Most of the 16QAM system experiments demonstrated so far used dispersion-compensation-fiber (DCF) free transmission links and/or new low loss and low nonlinearity fibers [1]-[4], which requires green field deployments. However, many existing optical networks have DCF inline, and in addition, when upgrading these networks to bit rates beyond 100-Gb/s, channels of different modulation formats and bit rates may co-exist. Therefore it is important to investigate the transmission performance of these systems with 32.5Gb/s