UPGRADE TO 100G DP-QPSK CORE NETWORKS WITH THE AID OF ANALOG

摘要

Think network traffic can't get any heavier? Though climbing at a rate of more than 50% annually over the past several years, a data deluge looms on the horizon thanks to the emergence of video-on-demand, fiberto-the-home, 4G wireless, and cloud computing. Carriers around the world are desperate for technologies that enable upgrades from current 10- and 40-Gbit/s to 100-Gbit/s backbone networks.The only practical way to achieve the desired leap in core network capacity is to increase optical data-channel bit rates from 10 or 40 Gbits/s to 100 Gbits/s, a technically challenging task indeed. That's because optical fiber non-idealities such as polarization mode dispersion (PMD) and chromatic dispersion (CD) limit the practical data rate of traditional amplitude-modulated signaling to 10 Gbits/s for core network links.Consequently, advanced phase-modulation techniques such as dual-polarization quadrature-phase-shift keying (DP-QPSK) and novel coherent receivers are required to meet the speed objectives of next-generation networks. This demands creative design techniques and innovative analog solutions for 100-Gbit/s optical transmitters and receivers. DUAL POLARIZATION AND COHERENT DETECTION DP-QPSK holds the key to achieving 100 Gbits/s over the installed base of fiber (and its inherent limitations). Quadraturephase-shift keying (QPSK) is a communication technique that encodes two bits of data into every transmitted symbol. Dual polarization (DP) doubles the capacity of an optical channel by transmitting data on two orthogonal polarizations, an X and a Y polarization, of the same channel.DP combined with QPSK achieves a fourfold capacity improvement relative to standard, single polarization, amplitude-shift-keyed systems. Thus, DP-QPSK transmission minimizes the effects of fiber impairments that would limit 100-Gbit/s signaling.